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Friday, September 28, 2018

Lithium-based Power System

There is so much to say on this topic that I struggle with where to begin.  It's been an exercise in drinking from a fire hose, and everywhere I turn there is another hose blasting away.  So I'll just pick a starting point, and describe what our plans are for 6837, and how I'm proceeding from here to there.  That should set out the context, and I can write other articles later digging into particular aspects of Lithium power systems.  Make sure you have read this Lithium Battery Backgrounder before reading this article, or some of the terms and concepts may not make sense.  I'm hardly an expert, but learning fast, and my goal will be to distill it down to something more digestible, without at the same time dumbing it down.   So here goes...

First a little personal background. I'm a retired electrical engineer/computer science person, turned exec, but still a geek at heart. Our boating is long distance/remote cruising with extended periods of time away from civilization, so dependable systems are vital, and repair/workaround essential when the inevitable issues arise. We are building another Nordhavn and the plan of record is to use LFP,  but before pulling the trigger on LFP for the boat, I'm building a proof project in a slightly less demanding environment to test and assess LFP viability for the boat.

Now I already need to pause and explain something.  You are probably wondering what "LFP" is.  It's short hand for a particular type of lithium battery, specifically LiFePO4.  There are many different types of lithium batteries, and LFP is the only on that I (and most other people) consider suitable for use on a boat, mostly for safety reasons.  Some other time I'll dig into the different types and their characteristics, but not now.

I mentioned a test project, and that will be to build an LFP system for an off-grid house. In nearly every way the requirements are the same as the boat, but less consequential if there is a failure, and a lot easier to get parts etc when needed. If nothing else, the shipping address isn't changing all the time :-)

With that preamble, here's my current thinking for the LFP sub-system:

- I am building the system myself. It's not that I object to the available pre-engineered BMS (Battery Management Systems) systems, but I'm very concerned about the long term viability of nearly all of the companies and products. When some part fails in 3 or 5 or 10 years, I think there is a good chance that any given company I might choose will be gone, and I'll have to buy a whole new BSM. Victron is about the only company that I think has long term staying power, but the cost puts LFP into a price range where it isn't worth it to me. I want something that is long term repairable and supportable and will live the life of the batteries. So the plan is to an industrial Programmable Logic Controller (PLC) with off-the-shelf modules for monitoring and control.  Pretty much everything in the modern world is run by PLCs.  Manufacturing, lighting controls, building environmental controls, elevators, and many of the control systems on larger ships.  They are made by many very large companies, have highly standardized interfaces and protocols, are incredibly robust and reliable, and are relatively inexpensive.  And best of all, a lot of much bigger, much more important customers will be complaining way ahead of me if there are problems.

- The PLC "BMS" will be a monitoring and fail safe system, but not a balancing system. Instead, I'll follow the approach of operating the batteries away from their SOC end points, or "knees" in the voltage curves. When monitoring suggests an imbalance, I will have to respond manually to re-balance.

- For batteries I am using CALB CA180s. CALB seems to be the most reliable vendor, but it's admittedly a low bar, and I am open to alternatives. The 180 cells seem to be the largest that are readily available. Bigger cells means less paralleling, few interconnections, etc. The 400s are appealing, but don't seem to be available

- I'm planning on 360AH of LFP capacity operating at 48V, so about half of the FLA usable capacity that I currently have. That will last me 1.5 to 2 days without sun. If the batteries get too low, the generator will start and recharge in a little over 2 hrs. The generator may run more frequently, but for a lot less time in each run, and less in total. Right now, a full recharge of the FLA batteries takes just under 6 hrs.

- The battery configuration will be paralleled pairs of cells, wired in series for 320ah @ 48V.   Short hand for this configuration is 2P16S.  That's "blocks" of 2 batteries in parallel, designated by "2P".  Then 16 of those "2P" blocks are wired together in series, designated by "16S".  Put it together and you have 2P16S indicating 2 parallel battery groups, wired 16 in series, for a total of 32 batteries.

The other battery wiring option is two 48V strings of single 180Ah batteries (16S), with isolation switches for each string. So two strings - effectively 16S2P - totaling 360Ah at 48V. This later arrangement would be to provide for string isolation for diagnostics, and to be able to run on one string if the other is out of service.  I might convert to this arrangement later on, and it might be the preferred arrangement for the boat for increased fault resilience.

- For monitoring, I plan to instrument voltage and temperature on each battery, or pair of batteries if they are paralleled. Absolute values, and differences in values will lead to various warnings, alarms, and fail safe actions.  All of the thresholds are are adjustable so I can fine tune as I learn.  It will also let me start out with very conservative operation, then expand a little bit at a time while monitoring how everything works.

- I only have two charge sources to contend with at the house, and both are programmable. I plan to program each to essentially be a two stage charger, with a bulk voltage to perform charging, followed by a float voltage down at the battery resting voltage. There will be no absorb stage, with an immediate transition from bulk to float. I expect float will require some tweaking to prevent excess battery cycling and get solar to carry the loads once batteries are charged, but while solar power is still available.

- The only fail safe I'm currently planning is a main disconnect contactor that will be controlled by the PLC.  The only time the batteries will disconnect is after all alarms have been triggered, and if the situation remains uncorrected and the batteries are facing imminent damage because of over charge or under charge.  This should never happen under any sort of normal operation.

- I'll also have to adjust the Automatic Generator Start (AGS) stop/start.  The start voltage will be adjusted to match LFP voltages, but starting will probably have to happen more quickly once the low voltage point is reached.  LFP battery voltage drops very quickly when they reach their fully discharged range, and it will be important to get the generator running and charging started before the batteries plummet.  With the FLA batteries currently, I look for a low voltage level lasting for 15 minutes, or maybe even 30 minutes (I can't remember exactly).  With LFP I'll probably trigger a start after 15 seconds of low voltage.  It takes 45-60 seconds to get the generator on line, so that should be enough.

There must be more, but that's all I can think of right now.

Next up will be a bunch more detail on the BMS that I have built so far.

I welcome comments and suggestion?

Wednesday, September 26, 2018

Lithium Battery Backgrounder

I started writing about the lithium power system we are planning for the new Nordhavn 68, and quickly realized that it's incomprehensible without some basic back ground.  So here is my attempt at a lithium battery summary.

Not all Lithium Batteries are the Same

First, there are lots of different types of lithium batteries, and different types of lithium-ion batteries, and they behave quite differently.  It's really important to understand some of the distinctions or you can reach a lot of incorrect conclusions.

For example, it's hard to mention lithium-ion without someone bringing up the Boeing 787 battery fire issue.  All batteries pose fire risks, but it varies quite a bit between different battery types.  The type of batteries we use on boats is different, and doesn't have the same fire characteristics as those used in the 787.  Those were lithium-cobalt-oxide (LiCoO2), and are subject to thermal runaway under certain fault conditions.

787 Burned Batteries

It also doesn't take long for someone who paid attention in chemistry to note that lithium burns violently when exposed to water.  Yikes, that sounds really bad for a boat, doesn't it?  But it's lithium metal that burns in water, not the lithium-ion substances used in rechargeable lithium-ion batteries.  It's like the hydrogen that's in water (H2O, remember?)  Hydrogen is highly explosive, but water isn't.  It's the same with lithium metal vs it's form in a battery.

Lithium Metal in Water

Some other time I'll dig into the different types of lithium ion batteries, but for now let me say that Lithium Iron Phosphate, or LiFePO4, or LFP for short, is the preferred battery type for boats.  It is by far the safest type with excellent fire resistance, and no run-away fire if it does get going.  And any released substances are far less toxic than with other types of batteries.  So for boats, we use LFP batteries.

CALB Lithium-Iron-Phosphate (LFP) battery

Characteristics of Lithium Batteries

Charging, discharging, and general management of LFP batteries is quite different from lead acid batteries (LA for short).  To really get your head around LFP,  you need to forget most everything you know about battery management, because it's all steeped in LA.

For example:

- LA batteries need to be brought back to full charge on a regular basis.  Not true for LFP.  In fact, it's fine to never bring them back to full charge.

- LA batteries shouldn't be too deeply discharged, with 50% as a typical limit.  Not true with LFP.  It's fine to drain them down to to near zero, but never all the way to zero.

- LA batteries should be stored at full charge.  Not true for LFP.  They should be stored in the 40-60% range.

- LA batteries need temperature compensation for their charge voltages.  Not true for LFP.  You need to turn temp compensation off or you can damage them.

- LA batteries should be left on a constant "float" trickle charge.  Not true for LFP.  Continuing to charge them once full will ruin them very quickly.

- LA batteries can be degraded if they are discharged too low.  For LFP, this is harsher.  They will be irreparably damaged if over discharged.

- LA batteries can tolerate a wide range of temperatures.  LFP batteries are less tolerant of temperature extremes.

All this may seem daunting, but it doesn't have to be.  Charging batteries within these constraints is common place in electronic devices, and can be done just as well on a boat with a bit of thought and planning.  But it also means that the idea of a "drop-in" LFP battery is a compromise at best.  We have the luxury of starting from a clean sheet of paper on our boat, so will be building a power system with all the necessary controls and safeties.

Battery Management Systems

Speaking of the controls and safeties, these are commonly referred to as a Battery Management System, or BMS.  A BMS is just some sort of system that monitors the batteries, controls chargers, and controls loads to be sure the battery operates within safe limits.  And if something starts to get outside of safe limits, it starts setting off alarms, shutting things down, and ultimately disconnecting the batteries completely to keep them from getting ruined.

The simplest BMS can be found in the mirror.  It's you, and lots of early adopters of LFP do all this themselves.   With appropriate knowledge and attention, it works fine.  Others want a more automated BMS that can operate without constant attention, and while you are away from the boat, and this has given rise to a variety of packaged BMS systems.

The basic functions of a BMS are:
  • Monitor individual cell voltages and alarm or take action if too high or too low.
  • Monitor cell temperature and alarm or take action if too high or low.
  • Provide a control signal to tell chargers when it's OK to charge, and when it's not
  • Provide a control signal to tell loads when they can draw from the battery and when they should stop.
  • Control of a fail-safe switch to disconnect the batteries as a protection of last resort.
Some BMSes also provide cell balancing.  With LA batteries, it's good practice to regularly over charge the batteries in a modest way.  Typical float charging does this to some extend, and periodic equalization does it to a larger extent.  This overcharging forces lower cells to catch up with more charged cells.

But with LFP, overcharging is instant death, so another means of balancing is needed.  If one cell is more charged than the others,  a good BMS will stop charging when the highest cell is full.  If it keeps charging while the others catch up, the more fully charged cell will get overcharged and ruined.  Similarly, when discharging, the loads need to be stopped when the lowest cell reaches it's lower limit.  Because charging stops when the highest cell is full, and loads stop when the lowest cell is empty, if the cells are too far out of balance the overall battery bank will end up operating over a narrower capacity range than is actually available.  To address this, many BMSes have circuits on each cell that redirects charge power away from higher cells and towards lower cells to bring them into balance.

Building an LFP Power System

To build up an LFP power system, there are a few different approaches:

1) The simplest and lest expensive is to buy batteries, and manage them yourself.  And if you don't charge them too high, and don't discharge them too low - in other words, stay away from either end of the charge range - they seem to work very well.  Lots of people report excellent results with this approach.
2) The next approach would be to buy batteries, plus a piece-part BMS.  These piece-part BMSes typically consist of a module that connects to each cell, plus a central brain that talks to the individual cell modules and controls everything.  These can also typically be connected to charge devices to control them.  They also include an emergency disconnect, but the idea is that with proper control of chargers and loads, an emergency disconnect should never happen in normal operation.  When you think about a boat and it's reliance on the DC power system, you REALLY don't want the battery to disconnect, EVER.  So these other controls to head things off well in advance are really important.

3) The last approach is to buy a fully integrated system of batteries, BMS, and controls.  Companies like Victron offer this with battery packs with integrated BMS modules, cables to link them together, and a BMS brain to connect them to.  Plus they offer ways to control their chargers and inverters, and ways to control other chargers and loads.

Fully Integrated LFP System

Charging LFP batteries

Given all the differences between LA and LFP batteries, just how should one charge an LFP battery bank?  Conceptually, there is a change of roles between all the devices in a power system, when you switch to LFP.  With LA, each charger controls itself, looking only at it's own voltage and current.  This is imperfect with lots of overcharging, but good enough since LA batteries are very tolerant of over charging.

With LFP, the batteries are very sensitive to overcharging, so a little role reversal helps a lot.  Instead of the chargers deciding things, you really want the battery to decide things, telling chargers when to turn on, and when to turn off.  Only the battery knows it's real state of charge, so it's in the best position to conduct charging activities.  Now this is great in theory, but in practice we need to work with chargers that can't be told what to do, or have limits on what you can tell them to do.  So any system today is likely a compromise and combination of different types of controls.  The trick is to make sure they all work together in a reasonable way.

Since LFP batteries can be irreversible damaged very quickly if over discharged or over charged, it's really important to avoid both things.  In fact, there are some good arguments for never dropping below around 10-20% state of charger (SOC), and not charging above 80-90%.  There isn't much capacity to be gained by going all the way to the limits, and the risk of damage goes up rapidly.  There also are a variety of studies that show that LFP life is a lot longer if you do not operate to the extremes.  "How much is too much" remains an unanswered question.  For example, there is a study that shows significantly improved life discharging to 50% SOC vs 0% SOC.   But it's unclear what happens at 40%, 30%, 20%, or 10% SOC.  So there is a bunch of guessing, but many people are having success operating in the 10-20% to 80-90% range.  And remember, unlike lead acid batteries, it's fine to operate LFP batteries at a partial state of charge indefinitely.

Another characteristic of LFP batteries is that they very quickly transition from charging, to full.  It's totally different from lead acid batteries that soak in absorption charge at a constant voltage for hours.  LFP batteries will be taking full charge rate, then bang, they are full.   The result of this is two fold.

First, because LFP can accept full charge rate right up until they are full, you can get them recharged much faster than LA batteries.  LA will charge at full rate up until about 80% SOC, then sit at a constant voltage for hours.  As a result, you really can't get an LA battery full in anything less than 3-4 hours, and sometimes longer.  And it doesn't matter how fast you charge them, because the absorption at the end still takes hours.  And if you don't fully recharge them every several days, you will slowly destroy them, reducing their capacity as the sit at partial charge.

LFP works differently, and in a way that is very, very favorable for a boat.  In short, you can fully charge them in 1 to 3 hours depending on the charge rate.  This is incredibly useful for boats that need to run a generator or other engine to recharge batteries because you can be done much faster.  And, because LFP batteries don't care if you fully charge them or not, you can run the generator for less time and only partially recharge with no harm.

For those interested, here's a quick side bar about why charging is so much faster.  A battery's capacity is rated in amp-hours, or Ah.  That's the number of amps you can draw out, times the length if time before it's empty.  So a 100 Ah battery can, in theory, provide 100 amps for 1 hour, or 50 amps for 2 hrs, or 5 amps for 20 hrs.  All multiply out to be 100 Ah.  This capacity is referred to as "C" for a battery.  If you further look at a battery's specifications, it will tell you how fast you can charge the battery, and how fast you can discharge it.  So a battery may allow for charging at up to 0.5C (50A for our example 100 Ah battery), and it may allow for discharge up to 1C (100A for our 100 Ah battery).

Back to charging LFP, most batteries specify a "normal" charge of 0.25C to 0.3C, and a fast charge of 1C.  That means you can charge the 100 Ah battery at anywhere from 25A to 100A, and that will take a corresponding time of 4hrs to 1hr.  So even at the lowest charge rate, you can be done in 3-4 hrs, and a fast charge can be done in an hour.

I could go on and on for ever, but think this is a reasonable stopping point.  Later on I'll try to dig into a bunch of this in more detail.

Wednesday, September 12, 2018

Tanglewood N6062 has Sold

They say the happiest two days of boat ownership are the day you buy and the day you sell.  We closed on the sale of Tanglewood N6062 today, and I only kind of agree.  It's definitely not a happy day, but it's certainly a load off my mind.  A boat sitting is a boat breaking, and I'm glad Tanglewood didn't sit for too long, and now it's ready for more adventures with her new owners.

It's exciting to be building a Nordhavn 68, and I'll get going soon blogging about that, but it's also worth a look back on our time on N6062.  I have to start calling it N6062 since our 68 will also be named Tanglewood, and things will get confusing otherwise.

N6062 took us to many new and incredible locations, all along the west coast of North America.  We explored the Pacific Northwest which remains our favorite area so far.  We cruised year round, and spent 3 seasons in Alaska, including one in Prince William Sound.  On that trip we hit our furthest point north (61 deg, 13' N) in College Fjord.  Prior to that, our furthest point north was rounding the Gaspe Peninsula in the Gulf of St Lawrence in Quebec.  And we reached our furthest point west (149 deg 26' West) in Resurrection Bay on the Kenai Peninsula.  By the way, Resurrection Bay is only about 5 degrees east of Hawaii, just to put it in perspective.  We also hit our furthest point south (22 deg, 50' N) rounding the Baja Peninsula in Mexico, with our prior record in the Atlantic at the Exuma Islands in the Bahamas.

N6063 in Prince William Sound, Alaska

We put about 2200 hours on the boat, and traveled about 20,000 miles, all in the comfort and security of a Nordhavn.  It's a bit sad to leave that behind, but exciting to think about where we will go next as N6837 starts to take shape.

N6837 in the Mold

Thursday, March 29, 2018

Where Has All My Power Gone?

Anyone who anchors out a lot like we do, and doesn't run a generator all the time, really cares about power consumption.  The less power you consume, the longer your batteries last, the more effective solar power becomes, and the less you need to run your generator.  And every bit of power you consume turns into heat which, depending on your climate, makes the boat harder to cool.  On the other hand, I don't want to be camping when we are on the boat.  We want all the comforts and conveniences of home.

The goal is to have your cake and eat it too, and that means being mindful of power consumption, and making sure every watt consumed is serving you well.  This is front and center in our minds since we are now on day 55 without plugging into shore power.  Since leaving La Paz at the end of February, we haven't plugged in once.  We have spend a couple of weeks at the marina in Puerto Escondido, but the power is under construction and we have not had any for our whole stay.

It's along time without shore power, but everything is working just fine, and we honestly don't miss it.  We recharge, do laundry, and make water while underway, or we run the generator if we are not underway.  During the day most of our power needs are covered by our solar panels.  This is all possible because we have paid close attention to appliance selection and electrical system design to minimize wasted power, while at the same time not giving up any of the conveniences that we want.  With a little attention, we have our typical battery draw down to around 20A on average, when other boats of the same model are more typically in the 30-40A range.

One thing that has been really interesting over the past couple of years, and the subject of this article, is looking at where all our power goes.  Some of it you might expect, but I'll bet there are some surprises as well.

Below is a table in rank order of the primary power consumers while we are at anchor going about our daily business.  It is essentially the daily background load, but does not include any form of cooking, laundry, or any number of other things.  So it's not an exhaustive study - just a snapshot of a bunch of things that are on pretty much all the time.

Device Watt-hrs per day Notes
KVH V3ip 3360  
Sub Zero Fridge 930  
Ships Network 864
Bosch Dishwasher 770 1 full wash cycle
N2K network 593  
Water pump 486  
Panel meters 432 12 meters total
Ship's Mac 406  
Nav Mac 406  
SeaFire 300  
LPG 250 On
AIS 246  
NavPixel Monitor 234 Full dim
Nav network 234  
FCV627 Fish finder 180  
Peplink Balance 20 134  
Watermaker 96 Standby
Wifi Ext 62  
Netgear wifi stations 62  
LPG 37 Off

I think if you ask most boaters what the biggest power consumer is on their boat, they would say it's refrigeration.  And they would probably be right, unless they have a KVH sat device.  Our KVH V3ip Sat phone and data system consumes 140W continuously which is three and a half times more daily power than the fridge which is the next high runner.  Wow, what a pig.  After discovering this, I turn it off at night to save power.

The fridge consumes a bunch of power, but considering it's a full size fridge and freezer, it's actually not bad at all and comparable to any other quality marine fridge.

The next big one is the boat's network switch.  We have a 24 port gigabit ethernet switch, and because it's on all the time, it's power draw really adds up.  I have been working on putting the commonly used things on a smaller, lower power switch, and only using the big switch when specifically needed.  Turning it off would be almost like turning off the fridge from a power draw perspective.

Next is the dishwasher.  We typically run it once a day, and the chart shows the power consumption for a full wash cycle.  It's a lot, but we clearly get something in return.

Our N2K network adds up over 24hrs as well.  It would be nice to get it down lower, but we use most of it for tank monitoring, weather, anchor watch, and alarming, so there isn't much we are willing to give up.

The water pump is a lot, and I think it's higher than it needs to be because of the way our Headhunter Mach 5 pump works.  Most pumps cycle on when pressure drops below some level, run until pressure builds back up, then shut off.  The Headhunter does the same, but it keeps running as long as there continues to be water flow.  So, for example, it will run the whole time you are taking a shower.  It has the benefit of maintaining constant high pressure the whole time rather than pressure that cycles up and down, but I'd estimate that it runs twice as long as a conventional pump doing the same thing.

A couple of other surprises are the power panel meters, the SeaFire engine shutdown system, and the LPG system if you leave the gas enabled.  Down at the very bottom of the list you can see how much the LPG control power drops if you just turn off the gas when not in use, which you should do anyway....

Although they are not in the chart above, here are a few things you may want to watch out for on your own boat:

- A lot of entertainment electronics, especially older models, don't really turn off when you turn them off.   They may go dark, but many keep drawing the same or nearly the same amount of power as when turned on.  Cable and satellite TV boxes are particularly offensive in this regard, and can often be one of if not the largest power consumer in your house or boat. 

- TVs have improved significantly in the past 5 years with respect to power consumption.  First, to get an Energy Star rating, they have to actually stop consuming power when you turn them off, or at least drop down to a very low level.  If you look at the EPA ratings, it will tell you what the standby power draw is.  It should be less than a watt.  And LED TVs are much lower power than older LCD TVs.  So if you are looking an excuse to get a new TV, this might help.

- Some things may not be as bad as you imagine.  Take a microwave oven.  Yes, they draw a lot of power when on, but you typically only run them for a short time.  If you run a 1000W microwave fro 5 minutes a day, that's only 83 watt-hrs per day, and would rank near the bottom of the list above.

- Refrigeration can be bad, or not so bad at all.  A lot of people dump on sub-zero for being a power hog, but our particular model really isn't that bad, and is actually comparable with the most efficient alternatives of a similar size.  On the other hand, I helped a friend who was having battery trouble on his boat, and his fridge was consuming eight times as much power as ours.  In his case, I'm quite sure there was a problem with his fridge, but just looking at the EPA ratings you will quickly see that there can be significant variation in the performance of similar sized units, both for fridges and freezers.

- LED lighting makes a huge difference.  Most 12V and 24V bulbs can be swapped for LEDs, and LED bulbs for 120VAC fixtures are readily available too.  Our lighting power load is so low that I simply pay no attention to it at all anymore.

- As a corollary to LEDs, florescent lights do use a lot of power.  Our engine room lights draw several hundred watts, and if left on are worse than the KVH.  They are excellent candidates for replacement with LEDs.

If you are interested in digging into your own boat (or home) to see where the power goes, there are a few tools that will help.

First is a Kill-O-Watt meter which simply inserts between any plug-in appliance.  It shows instantaneous power figures, and also totals up the power consumption over time which is particularly handy for things that cycle on and off like a fridge or water pump.

The next is a clamp-on ammeter.  These are commonly available for AC power, but less common for DC power.  If you want to measure the power for any DC device, you will need one that can measure DC current.

And for major appliances, I have found the EPA EnergyStar guides to be quite accurate.  They have accurately predicted the power consumption for several refrigerators and freezers that we have had over the years, and at a minimum provide a good comparative guide.

Friday, March 9, 2018

Voltage Sensing for Balmar MC624 Regulators

When charging batteries, the charge voltage really matters.  Being off by one or two tenths of a volt can result in batteries that never get fully charged, lose capacity, and serve a shorter life.  Most charge controllers have a remote battery sense to address this.  The sense wires carry essentially no current, so experience no voltage drop along their length and can accurately sense the voltage.  You can connect them directly to your batteries, or to your battery bus bar, and get a really accurate reading that isn't impacted by the load or charging current in or out of the batteries and through the main battery cables.

Balmar makes a good voltage regulator for engine alternators, and there are 12V and 24V versions.  The 12V version (MC-612) has a remote voltage sense, but for some reason the 24V version (MC-624) does not.  Instead, it senses the battery voltage through its main power and ground wires.  This creates some interesting challenges in getting a good battery voltage reading.

The diagram below shows a typical regulator installation.  In this example, the batteries are in the laz about 15' away from the main engine and alternator, and the regulator is mounted in close proximity to the alternator.  While underway with electronics running, ventilation fans running, and other power loads, the alternator current can be 100A or more, even as the batteries approach full charge and are not accepting much charge current.  The regulator senses voltage at the alternator, but even with 4/0 cable as shown, there will be a 0.2V or larger drop to the batteries, which is too much for accurate charging.  It really should be a tenth of a volt or less.

Typical regulator installation near engine and alternator

One way to solve this problem is to wire the MC-624's power and ground wires directly to the battery or battery bus bar.  This brings the battery voltage directly to the regulator.  On the surface this would seem like a good solution, but you actually end up with the same problem, just in a different way.

The diagram below shows an installation with the regulator power wired directly to the battery.  But the power wires both sense the voltage and carry the current to power the regulator itself, and more importantly, it's the source of power for the field wire that causes the alternator to product power.  In this example the regulator is drawing 10A, 1A of which powers the regulator, and 9A of which power the field on the alternator.

The power wires need to cover the 15' distance to the batteries, and when you run the calculations to figure out what wire size is required to carry 10A with no ore than 0.1V loss, it's #4 wire which is pretty darn big wire.

But there's another way to solve the problem.  Rather than bring the battery voltage to the regulator, you can instead bring the regulator to the batteries.  Instead of mounting the regulator next to the alternator, mount it right near the batteries or battery bus bar.  That makes the power wires to the regulator very short, yielding excellent voltage sensing with the 12 ga wires supplied with the regulator.  Then make the longer 15' run back to the alternator with the Ignition, Field, and Stator/Tach wires.  Of the three wires, only the Field wire carries much current (9A in our example), and it is relatively insensitive to voltage drop.  Even with a half volt drop in the Field wire, there is no noticeable reduction in alternator output.  I have been using 14 ga, 3 conductor cable and it works great with no loss of alternator output.

Regulator relocated to DC power panel and bus bar
Short wiring distance to DC bus bar

Tuesday, February 27, 2018

Water Maker Media Filter

I have had two water makers, one operated primarily in New England waters, and  one operated primarily in the Pacific Northwest.  Both areas have very nutrient-rich waters, and this tends to plug up the water filters on a water maker.

The sea water has to be carefully filtered before being run through the reverse osmosis membrane at very high pressure (around 800 psi).  This typically happens in three stages, each with progressively finer filtration.
  • The first stage is a simple sea strainer to keep out large debris, jelly fish, etc. 
  • The second stage is a standard 2.5" x 10" cartridge filter using a 20 micro fabric filter element.  
  • The third and final stage is a similar cartridge filter, but with a 5 micron element
I was typically only able to get 8-12hrs of run time before needing to change the filters.  The filters can be cleaned and reused a few times, but we were always changing filters, cleaning filters, and buying more new ones.  The good news is that the filters were doing their job, but all the filter maintenance sure was a deterrent to making water.
Standard 2.5" x 10" 20 and 5 micro filters
On our last boat I replaced the standard 2.5" x 10" filters with larger 4" x 10" versions.  These worked much better because the larger filter elements can hold more material before plugging up, but were still not what he hoped for.

Talking to people and doing some research suggested two additional things we could do.  The first is a plankton filter which is like the standard cartridge filters, but uses a fine mesh stainless steel basket.  What's plugging up the filters is microbial life in the sea water, and the plankton filters do a much better job of catching it.  And the stainless basket can be rinsed clean and doesn't need replacement.  That sounded like a big improvement, but it still sounded like I was going to be opening sea strainers and cleaning them all the time which is not something I was looking forward to.

The other alternative sounded even better, and involved adding a media filter.  A media filter is a very simple filter that runs the water through some sort of "media" like sand or gravel.  Whatever is in the water gets trapped in the sand, and clean water comes out the other side.  This is exactly the principal that makes ground water safe to drink when surface water is not.  The ground water starts out on the surface, but gets filtered as it soaks through the ground.  Media filters are used for pool filtration, and a wide range of drinking water filtration.  They work equally well for filtering sea water for a water maker.

One of the best parts about a media filter is the way you clean it.  All you need to do is back flush it, which is simply running water through it in the reverse direction, and dumping the outflow overboard.   The reverse flow dislodges all the trapped crud and flushed it away.  There are no filters to open, baskets to clean, and no sea water getting splashed around inside the boat.  It's just a matter of switching a valve and running the flush pump.  Not THAT sounded appealing, so this is the direction I went.

At the Seattle Boat show I came across a vendor who had just the sort of filter I was looking on display, so I arranged to buy it from him at the end of the show at a discounted price, with "some assembly required".

Media Filter

With filter in hand, the next question was what to use for filter media.  Everyone I talked to said to use "pool filter sand", whatever that is.  I couldn't find anything that actually described how fine the sand should be, or what size material it would filter out.  As best I could tell, I should expect to filter out particles anywhere from 20-100 micron in size.  I honestly didn't know how much that would help the 20 micro filters already in place, but figured it could only help.  I called around and found a pool supply shop that despite it being February, was open and could sell me "pool filter sand", whatever that is.

The media filter is an 8”x30” fiberglass filter cylinder with control valve.  The valve has 3 plumbing ports; one for incoming sea water, one for waste discharge, and one for filtered water outlet.  The valve also has three control positions:

  1. Forward Filter:  This is the normal operation position.  Water enters the inlet, flows through the filter media, then out the outlet to the rest of the water maker.   As material is filtered out and collects in the media, there is an increasing pressure drop across the filter, and eventually it needs to be cleaned with a back flush.
  2. Back Flush:  In this position, water enters the inlet, but flows through the media in the reverse direction such that is dislodges the trapped material.  And the outflow is directed out the waste outlet and overboard.   All you need to do is run the filter in back flush for 15-30 minutes, and it cleans itself.  That's my kind of maintenance.
  3. Forward Flush:  When you are back flushing, you do so with sea water.  As sea water is flowing through and flushing our previously trapped material, that same seawater is being filtered by the media as it flows through in the reverse direction.  Much less material is captured because it only runs for maybe 30 minutes, but there is still some.  When you resume normal operation for forward water flow, you are now essentially back flushing what you trapped during the backwash.  Make sense?  This is what Forward Flush is for.  It runs water through in the normal forward direction, but direct the outflow out the waste port and overboard.  So after a back flush, you do about 1 minute forward flush to clear out anything trapped during the back flush and get a clear forward flow.

Media Filter with Top-mounted Control Valve
In my quest for better filtering for the water maker, I was of a mind to hit things with the largest hammer I could find.  That was part of the thinking behind using a media filter rather than a plankton filter, and it also drove me to replace the 2.5" cartridge filters with the larger 4" x 10" cartridges.  I also wanted to relocate them below the water maker control unit to keep salt water away from it.  So I got two filter canisters and mounted them up in their new location where they had nothing but the floor drain to drip on.

New, Larger Cartridge Filters

And remember that large hammer that I've been swinging around?  Well, another frustration throughout my water maker ownership had been figuring out which filter or filters are plugged and which are not.  It's always been a guessing game, and has made if very difficult to figure out how to fix the filtration problems.

The solution was to add pressure sensors between each filtration stage so I could see exactly what the pressure drop is across each filter, and hence which filters were plugging up and which were fine.  I did this using our existing Maretron monitoring system, and pressure transducers.

Pressure Transducers

Getting back to back flushing.... to get a good back flush, there needs to be enough water flow to agitate the media to shake loose all the trapped material.  With too little flow, the media doesn't really get cleaned.  From the reading I could find, a back flush rate of 3-5 times the forward filtering rate is what was required, and I honestly didn't know if the pump that came with the water maker could adequately back flush, but figured I'd give it a try and see.

I ran for a year with this new setup, and wow, what a difference. The original 2” filters were only good for about 8hr of run time before cleaning was required. With the media filter and the big blue filters, I only changed the fabric filters as part of annually scheduled maintenance.   They never plugged up.  I back flush the media filter about every 8hrs of run time, and it’s really easy to do.  Just move the filter control valve to back flush, and turn on the pump.  I installed an “Auto/Manual On” switch for the boost pump that gets switched to “Manual On” to run the pump for back flush, and is left in Auto for normal operation.  I typically back flush for 15-30 minutes. You can hold a light up to the back side of the media filter and see the cloud of crud when you start the back flush, and see it clear over time.

This all worked very well, however by the end of the season I was having more and more trouble back flushing, so went back to the drawing board researching filter media and back flush flow rates.  The good news is that with the pressure gauges, I could tell that the problem was the media filter and not the fabric filters.  I was catching all the microbial material, but wasn't getting rid of it.

In my research I found a filter material called Micro-Z that is now part of Parker's product line. The material provides filtering down to 5 microns, and is much easier to back flush requiring only 1x the forward flow. So I gave it a try, and that was the key to success. I’ve been running for 3 years now with the stuff, and it still filters and back flushes great with the Spectra boost pumps.

Schematic of final system

Another challenge is fresh water flush. After running a water maker, you flush it with fresh water.  With the media filter, plus the big blue filters, there is a much larger volume to flush.  The flush water is first run through a charcoal filter to remove any chlorine which will otherwise ruin the water maker.  For proper filtering, run can only run water through this filter at a limited rate, and that constrains how fast you can flush the water maker.  What I discovered that there is a limit to the flush time in the Spectra controller, and it is actually too short. Even at max flush time, I was still getting salt content readings that were too high. So instead I set the flush time to 1/2 what’s needed, and after the automatic flush at the end of making water, I just manually trigger a second flush to finish the job.  It's not ideal, but works.

I would love to get Spectra to increase the allowed flush timer, and their new controller system may be able to do it.  I'm waiting for confirmation as I write this.

Saturday, February 24, 2018

Into Prince William Sound

June 13, 2017

After giving up on getting our packages, we decided it was high time to move on to Prince William Sound.  After all, that’s what we came to do.  So on the morning of the 13th, off we went to Fox Farm Bay on Erlington, Island, just at the entrance to PWS when approaching from the west.  We had a nice overnight, then continued on to Squire Island, now well inside the western part of the sound.  Then next to Mallard Bay on Knight Island, followed by Herring Bay, again on Knight Island.  Then to West Twin Bay on Perry Island, then to Bettles Bay, back on the Kenai Peninsula side.  All this to be staged for a run up Harriman Fiord, and College Fiord to see the College Glaciers.

Harriman came first, and what a trip.  There are actually eight different Glaciers that flow into Harriman Fiord.  We were able to get by all of them, and ended up at the biggest, the Harriman Glacier which is still tidal and actively calving.  After poking around for a while, we found a spot that was deep anchoring, but seemed acceptable so decided to stay the night in front of the Glacier.  Throughout the night you could hear rumbles of thunder that was actually ice calving off the glacier.  The next day we did some kayaking around the glacier, and decided to stay another night.


Then we caught a glimpse of an unexpected sight – people walking on the shore.  Where the heck did they come from?  We paddled closer, which took a while, and realized they were in kayaks.  Then we remembered that we weren’t that far from Whittier, and that in fact our own daughter had done a sea kayaking trip out of Whittier some number of years earlier.  We had a quick visit, and off they went.  Over the next several days we saw a number of other kayak groups poking around various areas.

After Harriman, we moved to Hobo Bay which is a little closer to College Fiord, then Bettles Bay, then made a day trip up College Fiord and back to Hobo.  College Fiord has nine Glaciers named after Harvard, Yale, and the “Seven Sisters”.  It's pretty ironic to view these colleges in their historic context as strictly men's and women's institutions, depicted in front of us as ancient glaciers.

College Fiord with Harvard Glacier in the distance.

Holyoke Glacier

Vassar Glacier

Here are Vassar, Bryn Mawr, and Smith leading up to Harvard.

Here’s a close up of the Harvard Glacier.  Those are 12,000’ and 13,000’ peaks in the background.

And then, as we get closer, we can’t get any closer.  Lots  of ice.

The Yale inlet forks off and leads to  - you guessed it – the Yale Glacier.  Here we are heading up the inlet.  This picture was "Miss January" for the Nordhavn 2018 calendar.

Yale Glacier

Then we moved in as close as we could to the Harvard Glacier until once again blocked by ice.

Next stop, Siwash Bay on Unakwik Inlet.  The next day we ran up to the head of the Unakwik Inlet to the face of the Meares Glacier, with plenty of big chunks of ice along the way.

After Unakwik, we started towards the Columbia Bay and the Columbia Glacier.  We were warned that getting close to the Columbia was unlikely because of the large quantities of ice coming down the inlet, and as we got closer, sure enough, the ice got bigger and more frequent.
First stop was Eickelberg Bay as a staging location, then the next morning we headed up Columbia Bay.  But we didn’t get vary far.  There is a bar a few miles up the inlet and huge amounts of ice ground on it making somewhat of a wall.  And even if you can get through it, there is risk of it closing up so you can’t get back out again.  So we poked around the bar for a while, then moved on.

After the Columbia Inlet, we started working our way east and south towards the Hinchinbrook Entrance to stage for our crossing back to SE Alaska.  We crossed the Valdez Channel and rounded the famous Bligh Reef where the Exxon Valdez ran aground and dumped millions of gallons of crude oil into Prince William Sound.  From there we tucked into Landlocked Bay and hung out for two days waiting for weather, then relocated to Garden Cove in Port Etches just inside the entrance, ready to depart the next AM to cross back to SE AK.

July 2, 2017 we departed through the Hinchinbrook Entrance and ran direct back to Sitka, docked at 12:00 on July 4th, just in time for the parade!

Rose Point Navigation's Nemo Interface

I've been using Rose point Navigation's Nemo interface for 2 years now, initially as an Alpha/Beta test customer, then as a full paying customer.  And I continue to test new releases since I seem to have special skills when it comes to breaking things...

- Nemo is essentially the interface to all your marine electronics. It connects to your marine electronics using the two standard interfaces (NMEA 2000 and NMEA 0183), and connect to your computer via ethernet.

- Because it connects to your computer via ethernet and not USB or serial ports, it actually works reliably. No drivers are required, which is the source of most evil in Windows.

- The NMEA 0183 interfaces are correct RS-422 interfaces, not RS232 which so many people use. The two are NOT the same, and are NOT compatible by design and by specification. Using RS232 to interface to marine electronics is just asking for a flaky, unreliable system.

- It supports four 0183 inputs, so you can bring in data from a number of sensors without requiring external multiplexers. This reduces complexity, reduces the number of failure points, and reduces cost.

- It supports two 0183 outputs. This lets you directly control an autopilot via 0183, and other devices as well.

- In addition to interfacing all your data to Coastal Explorer, Nemo also sends the data on ethernet using a de-facto UDP standard. Other devices on your network can pick up and use this data, like iPad apps, Coastal Explorer running on a laptop, etc.

- It has excellent NMEA 2000 support including superior source data selection. With N2K, all data from all sensors is on the network at the same time. As a result, it's up to each listening device to decide which sensors it wants to use. This is referred to as Source Selection, and some vendors do it a lot better than others. The simplest devices will automatically pick one of each sensor type, and typically they will fail over to another if the first fails. But you have no control over which it picks.

Better devices present you with a list of available devices and let you pick which you want to use. At least this lets you ensure the system is using the best of each device type that you might have. If the selected sensor fails, some will automatically switch to something else, where others require you  make a new choice.

The best devices present you with a list of available sensors and let you prioritize their use, picking which you want to be primary, which is secondary, and so fourth. Coastal Explorer and Nemo do this better than anyone else, allowing you to prioritize any arbitrary number of devices. The only other product I've encountered that comes close it the Furuno NavPilot which let's you prioritize up to three devices for each data type.

- Nemo passes "native" N2K data back and fourth between Coastal Explorer and the N2K network. This means that the actual N2K messages pass through to Coastal Explorer and it processes and interprets them. And Coastal Explorer sends N2K messages which nemo relays to the N2K network. LOTS of other N2K interfaces don't do this, but rather translate between N2K and 0183, communicating with the computer only via 0183. Translation between the two is NOT 1 for 1, and can sometimes be quite messy. Plus you lose all ability to do source selection for your N2K sensors. Nemo does this correctly.

- Nemo can also translate between its 0183 and N2K interfaces. This provides a bridging function between the two that otherwise requires dedicated converter devices. And it does this translation MUCH better than any other device that I've used, allowing you to select individual sentences/PGNs that you want translated, selecting the update frequency, and of course using proper source selection. I have not seen any other device that can do this.  With this translation function, I have eliminated four dedicated converters from my electronics suite.

- Nemo might seem expensive (list price $699), but when you look at what it replaces, it's a real bargain. First, if you are going to add proper RS-422 data interfaces to your PC, it's going to cost you.  Yes, you can get RS-232 USB adapters for about 5 cents each, but remember, they are not compatible with NMEA 0183, and although they will probably appear to work, it will be unreliable. I used one once in a pinch, and all seemed to work OK. But when I looked at the actual sentences being received by Coastal Explorer, a significant portion of them were corrupted. Enough made it through OK for things to mostly work, but do you really want corrupted data running around you navigation system? I sure don't.

Anyway, an ethernet-connected 4 port RS-422 interface can cost $300-$500. So right there is probably 60% of the cost.

Then an N2K interface will cost another $200 or so, and they are all USB connected. That means they only work with the computer they are plugged into, and you have the associated driver nightmares. Nemo gives you the same capability, plus more. The data is on the network, so any Coastal Explorer  (or other) systems can see it. And you are spared the windows driver fiasco. At this point you have pretty much covered the cost of Nemo.

Oh, and because Nemo puts the data on the network, it eliminates the need for one of the many devices that do that as a dedicated function. There's another couple hundred $$ saved.

Then, if you have any data translation conversion required between N2K and 0183, then you really start coming out ahead with Nemo. I have already replaced four $200 converters, and expect to replace two more. That's $800 worth of converters eliminated

- And in good Rose Point fashion, the product is reliable, simple to use, easy to update over the internet, etc.

When you consider what you get for the $$ you spend a dedicated chart plotter, or how much more software like MaxSea costs, and how it solves none of the data interfacing problems, I think Coastal Explorer + Nemo is a real bargain, and one of the best performing products I have used in a long time.

Adding 240V Inverter Service

As discussed in more depth in this article, we wanted to be able to do laundry while underway without running our generator.  Laundry can take hours, and it's not really enough load by itself for the generator.  To run it off the main engine alternator required two things; 1) 240V inverter power, and 2) more alternator capacity to handle the steady increased load.  The alternator update was covered in this article, and this current article covers the inverter service upgrade.

I went around and around in circles on how to add 240V inverter service.  As a retrofit, I had to work within the context and constraints of the existing boat, creating the following considerations:
  • Any new equipment needs to fit somewhere, preferably with minimal relocation of existing equipment.
  • Minimize long, fat wire pulls.  This means any large DC cables need to be confined to the laz near the batteries.  And wire runs from the laz to the main AC breaker and distribution panel in the pilot house should be kept to a minimum.  It's a long, circuitous route with very little extra space for fat cables.
  • There should be minimal (preferably none) increase in idle background power loads.  There is a certain amount of wasted power in an inverter, and I wanted to keep that to a minimum.  Also, transformers consume power and I wanted to keep that to a minimum.  These losses are inevitable to some extent when actually powering a device, but when the device is turned off, I ideally wanted all those losses to stop completely.
  • Our existing 120V inverter system is capable of 7kw, so if there is a way to leverage that equipment, it would help solve a number of problems.
  • If new inverters were required, it was desirable to have them be the same make/model as our existing inverters.  This makes sparing easier, and utilizes the existing control panels.
  • The amount of rework of our breaker panel should be minimized.  We had a single 240V service to begin with, and the idea was to split it into two separate circuits, one powered only from shore power or generator, and the other powered by 240V inverter service.  Also part of this was dealing with the circuits that are 120/240 split phase, vs those that are pure 240V.
Like I said this sent me around in circles for a while considering different alternative.  Here are some of them:
  1. Add a separate, dedicated inverter for 240V service.  I could leave the existing 120V inverter service unchanged which was good.  It would also be an inverter that I could completely turn off when not used, so no background power drain.  But I would have to find space for the new inverter, necessitating fabrication of some sort of power panel in the laz.  Large DC cables would have to be run with fuses and disconnects.  And two 10/4 cables would have to be pulled from the laz to the pilot house (one for shore/gen input power, and one for output power), plus probably a control panel cable.
  2. Reconfigure my 120V inverters for 120/240 service.  This initially seemed very attractive.  I could reuse the existing inverters so no new equipment would be needed, and no new large DC cables would be needed.  But it created complications elsewhere.  In their 120V configuration, one of the inverters goes into standby when power loads are low, thereby reducing the background power loss.  When configured for 240V service, both inverters would be on all the time, roughly doubling the background power loss.  Also, both the AC input and output cables would have to be replaced.  The existing input cable didn't have a neutral conductor, and the output only had one line conductor.  But the worst part was the subsequent need to rearrange the 120V power panel to balance it across two split phases.
  3. Add an auto-transformer to create 240V off the existing 120V inverter service.  This seemed promising.  There would be additional power loss in the transformer which I wasn't thrilled about, but it would be limited to the 240V loads.  And as long as it could be turned off with a breaker, the losses would not be there all the time.  There would be no need to rewire the 120V panel, and if I could fit the transformer behind the pilot house console, there would be no need to pull wires back to the laz.  The only hang up was figuring out how to have breaker space for a master-disconnect for the auto-transformer and 240V service.
I ended up going with approach #3, using a 6kw auto-transformer from Outback Power, the same people who make my inverters.

Here is a before of the 240V breaker panel.  You can see all the 240V devices as part of a single service.

And below you can see the after picture.  The only things on the 240V Ships service are the water heater, battery charger, dive compressor, and input power to the inverter.  To the right is the 240V Inverter service with main disconnect at the top, and the load breakers below.  The washer, dryer, and oven can now be run while underway, or while on 50hz shore power.

And here's a wiring diagram.

So far we are really happy with the results.  It's great to be able to do laundry while underway without the generator, and the loads are comfortably within the capacity of the main alternators.