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Old 01-08-2022, 07:31 AM
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Quote:
Originally Posted by ndutton View Post
Edward, a thought:
If gasoline is difficult to source in the Bahamas, especially the Exumas (the reason for not relying on the engine for recharging), what about sourcing LiFePO4 batts or the associated management components in an exotic destination if (when?) a failure occurs?
Neil,

I must admit that this is one of the thoughts that weighs heavily on my mind during this planning process. As Joe pointed out, I'm trying to design as redundant a system as possible. The better option might be two independent, paralleled banks with two separate BMSs, but this would get more expensive. Re-configuring underway from a 2P4S configuration to a 1P4S configuration would suck but would be possible.

As for unavailability of stuff in the Exumas, I'm already in that "boat" Gel Cells are also impossible to source in the Bahamas. Hell, they're difficult to source in the US!

My ultimate fallback would be to temporarily replace them with a pair of cheap flooded Lead-Acid batteries. The highly programmable charge controllers would have no trouble accommodating that.

Before our first trip, I thought long and hard about what engine spares to bring. There isn't enough space to bring everything, so I tried to confine myself to critical things I couldn't repair. This included a spare alternator (with its own regulator), a spare starter, and a spare EI module.
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Old 01-08-2022, 09:00 AM
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Exactly Edward. If you can't get 'em, you'll have to carry spares. For a more accurate spelling, make that $pare$.

I've not cruised but I did build and outfit a boat for long distance cruising before the divorce from Hell quashed that dream so I've been through much of the analyses and planning. That was 35 years ago and things were comparatively primitive in terms of tech. Regarding this discussion, Faster charging has been of interest to cruising sailors for several decades. When I was building my Westsail the hot ticket was manually adjustable regulators with a giant panel knob (looked like a variac) that allowed the user to increase the charge voltage for faster charging regardless of their State of Charge. I recognized the liabilities immediately so it was never a consideration on my boat but the cruisers went ape[feces] over it. How well did it work? When was the last time you saw or even heard of one of those? I can't even find a picture of one on the internet to add to this post.
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Old 01-08-2022, 09:40 AM
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Quote:
Originally Posted by ndutton View Post
Exactly Edward. If you can't get 'em, you'll have to carry spares. For a more accurate spelling, make that $pare$.

I've not cruised but I did build and outfit a boat for long distance cruising before the divorce from Hell quashed that dream so I've been through much of the analyses and planning. That was 35 years ago and things were comparatively primitive in terms of tech. Regarding this discussion, Faster charging has been of interest to cruising sailors for several decades. When I was building my Westsail the hot ticket was manually adjustable regulators with a giant panel knob (looked like a variac) that allowed the user to increase the charge voltage for faster charging regardless of their State of Charge. I recognized the liabilities immediately so it was never a consideration on my boat but the cruisers went ape[feces] over it. How well did it work? When was the last time you saw or even heard of one of those? I can't even find a picture of one on the internet to add to this post.
You are thinking of the Mac/Automac and variants of it. You can still find them used.
They were the first step from the old fixed-point regulators to modern multi-stage regulators. The first ones had a timer that would full-field the alternator for as long as the timer was set for and then revert to normal regulation. The timer was the old twist-knob type, so the actual device looked the same as the one shown below. They could hugely improve the time to charge a big battery bank, but they also could cause huge amounts of damage if not carefully watched. The ONLY safety mechanism involved was the human operator.
The next step was the Automac that had a rheostat to control the field instead of always full-fielding the alternator and a cutoff voltage. When the battery reached the cutoff setting, it would disengage the Automac and revert to internal regulation.
By the time I was doing this work for a living in the mid 90s these were already considered obsolete, the first generation of smart regulators were out. We never did install any of these and did remove a few. They were a good idea at the time if you were VERY careful.
Knowing HOW they work is important, you can make these from parts on your boat as an emergency get-home device. Full-fielding the alternator just needs a jumper wire and "regulating" the alternator just needs a couple jumpers and various light bulbs. I discovered a running light bulb gave me a decent voltage when my regulator crapped out, it held about 12.9 volts.
See this thread on the DIY emergency regulator: https://www.moyermarineforum.com/for...tor+light+bulb
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Old 01-08-2022, 10:09 AM
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Quote:
Originally Posted by edwardc View Post
Neil,

I must admit that this is one of the thoughts that weighs heavily on my mind during this planning process. As Joe pointed out, I'm trying to design as redundant a system as possible. The better option might be two independent, paralleled banks with two separate BMSs, but this would get more expensive. Re-configuring underway from a 2P4S configuration to a 1P4S configuration would suck but would be possible.

As for unavailability of stuff in the Exumas, I'm already in that "boat" Gel Cells are also impossible to source in the Bahamas. Hell, they're difficult to source in the US!

My ultimate fallback would be to temporarily replace them with a pair of cheap flooded Lead-Acid batteries. The highly programmable charge controllers would have no trouble accommodating that.

Before our first trip, I thought long and hard about what engine spares to bring. There isn't enough space to bring everything, so I tried to confine myself to critical things I couldn't repair. This included a spare alternator (with its own regulator), a spare starter, and a spare EI module.
Most commercially available lithium batteries can be connected in parallel, I don't see any reason you can't make two batteries with two BMSs. Speaking of, are you SURE you have a good source for cells? I looked into that and it seems a crapshoot at best, apparently almost all cells are rejects that Renogy and the rest of the battery companies didn't want.
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Old 01-08-2022, 07:00 PM
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Quote:
Originally Posted by joe_db View Post
Most commercially available lithium batteries can be connected in parallel, I don't see any reason you can't make two batteries with two BMSs. Speaking of, are you SURE you have a good source for cells? I looked into that and it seems a crapshoot at best, apparently almost all cells are rejects that Renogy and the rest of the battery companies didn't want.
SURE? No. Fairly confident, yes.

I’ve spent the last year reading all the reviews (and I mean real technical reviews, not “fanboy” stuff) particularly those who have bought large quantities of cells from multiple vendors. With enough time and data points, some trends started to appear. I did this because about a year ago, I tried to order some cheap cells for testing, direct from China. After waiting for them for 8 weeks, I had the vendor put a trace on them, and the shipping company reported them as “lost”. (But I did get a quick full refund).

At the present time, the Chinese company “Doucan”, while not the cheapest, seems to have a reputation for delivering quality product. Their sales rep Jenny Wu in particular, has a rep for never lying and delivering what was promised. And best of all, they can deliver LiFePO4 cells out of their warehouse in Houston!

So, on Jan 2 I took the plunge and ordered eight 280ah cells from them.
FIVE DAYS LATER, they were sitting on my living room floor!! They arrived well packaged in thick foam liners, two to a box, sealed up watertight.

Initial inspection all looked good, every cell showing no signs of terminal scratching or bulging, both of which are signs of previous use. Every cell had the OEM QR code laser etched on it. I decoded a mfg date of Jun 2021. A more detailed evaluation and measurement is in progress. Wish me luck!
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Old 01-08-2022, 08:18 PM
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Do you need to clamp these together to keep them from bulging and getting ruined?
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Old 01-08-2022, 08:49 PM
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Hi all.

Just this year I put together an e-bike with lithium-ion battery and also got a camper with AGM house battery,
What an education!

Everything said here was discovered by myself as I got up to speed on these technologies.
upshot for me is:
  • Hi-tech lightweight batteries for fun on the bike,
  • Heavy tolerant systems for the camper and boat.
A telling consideration is found in this ironic question:
Why would one care about weight savings in a boat with 5,000 lbs of lead in the keel?

I agree with Neil; gotta keep these systems from running our lives, but we do need to keep the beer cold.

Cheers,

Russ
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Old 01-08-2022, 11:05 PM
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Quote:
Originally Posted by joe_db View Post
Most commercially available lithium batteries can be connected in parallel, I don't see any reason you can't make two batteries with two BMSs. Speaking of, are you SURE you have a good source for cells? I looked into that and it seems a crapshoot at best, apparently almost all cells are rejects that Renogy and the rest of the battery companies didn't want.

SURE? No. Fairly confident, yes.

I’ve spent the last year reading all the reviews (and I mean real technical reviews, not “fanboy” stuff) particularly those who have bought large quantities of cells from multiple vendors. With enough time and data points, some trends started to appear. I did this because about a year ago, I tried to order some cheap cells for testing, direct from China. After waiting for them for 8 weeks, I had the vendor put a trace on them, and the shipping company reported them as “lost”. (But I did get a quick full refund).

At the present time, the Chinese company “Doucan”, while not the cheapest, seems to have a reputation for delivering quality product. Their sales rep Jenny Wu in particular, has a rep for never lying and delivering what was promised. And best of all, they can deliver LiFePO4 cells out of their warehouse in Houston!

So, on Jan 2 I took the plunge and ordered eight 280ah cells from them.
FIVE DAYS LATER, they were sitting on my living room floor!! They arrived well packaged in thick foam liners, two to a box, sealed up watertight.

Initial inspection all looked good, every cell showing no signs of terminal scratching or bulging, both of which are signs of previous use. Every cell had the OEM QR code laser etched on it. I decoded a mfg date of Jun 2021. A more detailed evaluation and measurement is in progress. Wish me luck!
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Old 01-09-2022, 10:22 AM
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Quote:
Originally Posted by lat 64 View Post
Hi all.

Just this year I put together an e-bike with lithium-ion battery and also got a camper with AGM house battery,
What an education!

Everything said here was discovered by myself as I got up to speed on these technologies.
upshot for me is:
  • Hi-tech lightweight batteries for fun on the bike,
  • Heavy tolerant systems for the camper and boat.
A telling consideration is found in this ironic question:
Why would one care about weight savings in a boat with 5,000 lbs of lead in the keel?

I agree with Neil; gotta keep these systems from running our lives, but we do need to keep the beer cold.

Cheers,

Russ
Weight savings is not why I would get lithium batteries, the vastly longer lifespan would be.
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Old 01-09-2022, 03:24 PM
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Weight savings is not why I would get lithium batteries, the vastly longer lifespan would be.
That, and greater total energy storage in the same volume.
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Old 01-11-2022, 11:34 AM
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Ed - are you using contactors or the BMS itself for switching?
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Old 01-12-2022, 08:42 AM
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I had been leaning towards the REC Active BMS, which is set up for driving contactors, but nothing is cast in stone yet.

Other contenders were the Orion, and Stuart Pittaway's DIY BMS project.

The thing that gives me pause with the REC Active is that it wants to be both the BMS and the central charge controller. Seems like too many eggs in one basket. I like the redundancy of a federated architecture, where each charge source is responsible for its own regulation.
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Old 04-25-2022, 03:23 PM
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Any progress reports?
My batteries are shot, so I need to do SOMETHING real soon. I can physically fit a 300ah battery, so that would be say about 275ah or so of usable capacity at something like 3,000 cycles. The same package gets me 200ah of lead-acid capacity, at only 100ah usable for long life and probably 200-400 cycles if I use about 150 out of the 200.
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Old 04-25-2022, 04:50 PM
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The only progress I've made is deciding to stay with deep cycle lead acid for now. Lithiums clearly aren't ready for the uneducated masses, of which I am a member. I'm not ready to fuss with all the details at this point.
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Old 04-26-2022, 02:48 PM
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Thanks for the nudge.

To refresh, I have eight EVE 280AH LiFePO4 prismatic cells.

I ended up ordering the Rec Active BMS. The manufacturer was very quick to reply to my questions, and I now understand how to configure the BMS to operate as part of a distributed system.

In addition to the BMS, I ordered a pair of 500A contactors, one for the charge bus and one for the load bus, and the WiFi adapter so I could configure and monitor the BMS without needing the Windows-only software package (I'm a Mac guy).


Initially, I strapped all the LiFePO4 cells in parallel, and hooked them to a regulated supply. I brought them up to full charge in steps. For instance, I initially set the supply to 3.0V and limit it to 4.5 amps (Its only a 5A supply), and let this sit until the current dropped off to ~100 mA. (this took a LONG time (days) due to the MASSIVE AH capacity of eight paralleled cells, 2240AH!). Then I would bump it up a few tenths of a volt and repeat. Each cycle took less time. By the time I was pushing all the cells up into their fully-charged state, the last cycle took just over an hour. This process "top balances" all the cells.

I next rewired all the cells in a 2P4S (2 parallel 4 series) configuration to create a 12V 560AH battery pack. I wired up the bms sense leads to each of the 4 series cell-groups, connected the charge and load contactors to the appropriate drive leads from the BMS. The charge bus was connected to my supply (now setup for the correct charge voltage) and the load bus was connected to a 1000W inverter. The inverter was connected to a small heater and a collection of incandescent light bulbs to bring the total up to around 900W. This would produce a DC load current of around 75A.

I since setting all this up had brought the battery pack down below full charge, I first tested the high limit charge cutoff. Turned on the supply and let it charge. As soon as the pack reached the charge max voltage that I had set, the Charge contactor shut down as designed. Keep in mind that this is NOT the normal charge voltage, but the "Never Exceed" voltage for the pack. In normal operation, this should never happen. Its just a protection to keep a failure elsewhere from overcharging and destroying your batteries. Meanwhile, the load contactor remained connected, which would allow you to drain the pack down to a safer level.

Next test was a crude capacity test. With the supply turned off, I activated the inverter. The idea was to see where the pack capacity was (according to the BMS monitor) when the load contactor cut off. This test was a reasonable success. It ran about 7 1/2 hrs. The problem was that the inverter shut down due to low voltage before the pack was down to what the BMS considered the 0% State-of-Charge for the pack. This inverter cutout happened within a few Amp-Hours of of the spec value of 560AH, so I considered the capacity test to be a success. The BMS monitor showed all the cells individual voltages stayed within the proper amount, so it looks like the cells I received are reasonably matched.

After a few minutes of sitting, the pack voltage "rebounds" some. This allowed me to temporarily reconfigure the low voltage cutout to a higher voltage than the point where the inverter cuts out. Turned the inverter back on, and this worked perfectly, shutting down the Load contactor, but leaving the Charge contactor on.

So far, I'm satisfied with my purchases. Still need to configure a relay to cutoff the Balmar alternator controller in case of a BMS shutdown of the charge contactor and test that for all cases.

After that, the next step is to start creating a new battery box area in the boat. The old battery location is effectively in the engine compartment, and gets too hot for the LiFePO4's max operating temp of 140 deg F.
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Old 04-28-2022, 12:55 AM
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Quote:
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Thanks for the nudge.

To refresh, I have eight EVE 280AH LiFePO4 prismatic cells.

Ed, what is the normal voltage of each cell? I've seen some 100Ah 'lithium' batteries popping up on web advertisements that look like normal 12v batteries, like Dakota and Renogy, and I think are designed as 'drop in', from a form factor anyway, replacements for 12v lead acid. But I doubt that is the case. Trying to begin getting educated on the subject.
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Old 04-28-2022, 08:21 AM
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Ed, what is the normal voltage of each cell? I've seen some 100Ah 'lithium' batteries popping up on web advertisements that look like normal 12v batteries, like Dakota and Renogy, and I think are designed as 'drop in', from a form factor anyway, replacements for 12v lead acid. But I doubt that is the case. Trying to begin getting educated on the subject.
*There is no such thing* as "drop in" lithium batteries no matter what the ad says. The lithium batteries do work in 12 volt systems, so in a sense you could just install them and see what happens. The most likely result of that would be ruined batteries, a burned up alternator, or both. They have some unique issues you need to deal with for a successful installation. I'll post my idea for a lower budget install soon, but the first thing to remember is the BMS (battery management system) does NOT actually manage the batteries the way you might think it does. It takes care of cell balancing, but other than that the charge and discharge disconnects are emergency last-ditch ways to save the battery. It does not do anything like manage charging voltages for a correct charge.
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Old 04-28-2022, 10:25 AM
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This is my idea of a lower cost system. The Victron DC-DC charger is configurable to charge lithium batteries correctly.
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Old 04-29-2022, 02:04 PM
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Ed, what is the normal voltage of each cell? I've seen some 100Ah 'lithium' batteries popping up on web advertisements that look like normal 12v batteries, like Dakota and Renogy, and I think are designed as 'drop in', from a form factor anyway, replacements for 12v lead acid. But I doubt that is the case. Trying to begin getting educated on the subject.
Shawn,

The LiFePO4 chemistry has a nominal cell voltage of 3.2v per cell. Thus, a pack of 4 series cells has a nominal voltage of 12.8V

But this is slightly misleading. The cells have an almost FLAT charge/discharge curve (see attachment), pushing up to a max of 3.65v/cell right at the end of safe charging, and dropping down to 2.5v/cell right at 0% State-of-Charge. This corresponds to pack voltage limits of 14.6V and 10V respectively, which is close enough to typical lead-acid limits.

Keep in mind that these are the "never exceed" limits, and normal pack operation will not see them unless there is a failure somewhere. For example, I will set my chargers limits around 13.2V (3.3V per cell). Because of the "S" shaped charge/discharge curve, I'm only sacrificing a few percent of theoretical storage capacity at the top, but research has shown that this extends the cell's cycle life. More on LiFePO4 charging in a later post.

So, from a purely voltage perspective, the packs look like "drop-in replacements" for lead acid. But that's before you consider the possible actions of the Battery Management System (BMS). At any time, for one of many reasons (over voltage, undervoltage, over temp, under temp, over current), the BMS can abruptly disconnect the battery from the rest of the system in order to protect it. This can cause havoc with the rest of the electrical system unless there are features specifically designed in to handle it. For example, if your alternator is charging at full capacity and the BMS disconnects, its just like flipping the main battery switch off while the engine's running. The output of the alt will try to spike up to infinity, blowing the alt's diodes and potentially every bit of (expensive) electronics that's turned on at the time.

This is the biggest problem with these "drop-in" packs. They have a BMS that's sealed up inside the case, with no way to communicate with the outside world. The more expensive packs, such as Victron, have outputs, such as relays or CANBus, that can be used to signal external chargers of a disconnect so that they can be gracefully shut down.

Another problem with these inexpensive packs is that they use a BMS that uses inexpensive MOSFET switches to disconnect the pack. This often limits them to relatively small charge and discharge currents (50A), which negates one of the advantages of LiFEPO4 batteries.

So, in order to successfully use LiFePO4 in a boat, you either have to design a system using raw cells and an external BMS that can disconnect the chargers when necessary, buy an expensive single-vendor fully integrated system from a company (such as Victron or Mastervolt) that understands and handles these issues, or design a system (such as Joe's low-cost example) that never allows the alternator to become un-loaded while in operation.

Since I have the necessary electronics knowledge, and am an incurable DIY'er, I chose the first approach. YMMV
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Old 04-29-2022, 04:11 PM
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One more reason I am looking at the DC-DC charger is a big lithium bank can look like a dead short and be very hard on alternators.
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Old 04-30-2022, 10:57 AM
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I guess the first thing I'd change is the old Moto Alternator. They just don't put out much output. You can buy a delco 70amp for about $65 online.

I added a small solar panel on my dodger that does a good job of topping up my batteries while at anchor. The only issue is that it needs to be mounted somewhere where it can't be shaded. But for a racer, there's little weight added.

I had a starting battery in reserve (I have 2x Group 27 flooded) that I ditched when it went bad and just carry a lith starting pack for emergency starts if all goes bad.

Jack
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Old 05-01-2022, 02:30 PM
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LiFePO4 Charging

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Originally Posted by joe_db View Post
One more reason I am looking at the DC-DC charger is a big lithium bank can look like a dead short and be very hard on alternators.
Quite true. My Balmar 612 alternator regulator has a feature called "Belt Manager". It lets you dial back the maximum output of the regulator. It was intended to stop belt squeal when dumping full output into a highly discharged lead acid bank, but it is just the thing for keeping lithium batteries from cooking your alternator.

And this provides a great excuse to segue into a discussion of LiFePO4 charging.

One of the downsides of Lithium batteries is that they are extremely sensitive to over (and under) charging. A single episode can destroy your expensive investment. This is why the selection of a reliable, programmable, and "bulletproof" BMS is essential.

On the plus side, the charging protocol is much simpler than lead acid. It almost entirely consists of what would be called "Bulk" charging in Lead Acid. In this phase, you let the charge source provide as much current as it can until the cell voltages come up to the "knee" on the charge curve, around 3.35V per cell (this is why its important to have matched and top-balanced cells, so they all arrive there at the same time). At this point, the cells are within a few percent of being fully charged. Technically, you could go through a brief "Absorption" phase at this point until the charging current drops off to a low value, But its really not necessary, and skipping forcing the cells up to that last few percent will increase their cycle life.

And then you simply STOP CHARGING. No "Float" mode! Keeping Lithiums at a float voltage will greatly decrease their cycle life!! This is why you need a highly programmable charger, as many of the smart chargers' preset LiFePo4 mode has a float voltage programmed! If float can't be disabled, you can set it to a lower voltage than Bulk so it will never be a problem. This allows the charger to still carry some of the loads without charging the battery further.

The only tricky point then is to select a point to "Re-Bulk". Because of the almost flat charge/discharge curve, voltage does not provide a reliable indication of State-of-Charge (SOC). You need something that does "Coulomb counting" (Amp-Hours) to properly select when to go back into bulk.

And there isn't one stock answer for this. It depends on your use-case. From the standpoint of absolutely maximizing battery lifetime, a re-bulk point of 50% SOC or less is probably right, as Lithiums kept at 50% experience very little degradation.

On the other hand, when used as a "standby" power source that needs to be "at the ready" at full capacity, a value closer to 80% or 90% is probably indicated.

Sailboat usage is neither of these cases exactly, so I need to do more research to come up with a good re-bulk target.

My Balmar 612 can do some, but not all, of these algorithms. In particular, it uses voltage combined with simple timers instead of coulomb counting to determine when to end various phases. The WakeSpeed 500 is the only alt regulator I've found that includes a current shunt for doing current (and Amp-Hour) based calculations. And as a bonus, it includes a CANbus input, and The REC-Active BMS I have knows how to talk to it, including instructing it to shutdown gracefully in the face of an impending BMS disconnect.

Stay tuned for further developments.
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Last edited by edwardc; 05-02-2022 at 12:23 AM.
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Old 05-09-2022, 11:20 AM
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Looking through Amazon's offering, you get kind of a matrix.
BMS max current is 100 amps or 200 amps.
Some have low temp cutoff, some don't, and some say they do and don't.
Some have heaters and some don't.
Some have a bluetooth connection to the BMS.
Some have a plug in data link to the BMS.
Some have both and some have neither.
All of them will need Sawzall surgery to extract the cells if the BMS ever dies.
Some of them have USA based distribution and some don't.

Right now I am not even thinking about 100 amp max batteries nor ones without connection to the BMS.
My other cheap-ish play is to buy Doucan (sp?) cells and a decent BMS. That at least allows for a BMS swap if needed and a way to bypass the BMS in extremis.
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Old 05-09-2022, 01:41 PM
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Joe,

That's a pretty accurate summary of most of my last year's research. It's why I chose the raw-cells/external-BMS path.

There's one other item for the list that Rod Collins (Mainesail) thought was pretty important. Some (most) BMS's use MosFets for switching, and others drive an external contactor. The MosFets tend to limit the currents to 50-100 amps, and are the weak link due to heating. The contactor versions can easily handle up to 500 A without breaking a sweat.

I selected the REC Active BMS because it tics almost all of these boxes. In addition, it is in a water-resistant housing with a water-resistant single connector. This makes it very simple to swap out with a spare in case of failure. And as a bonus, the manufacturer has been very helpful answering questions, responding within a day in understandable english despite being in Postojna, Slovenia. And the US distributor has a fairly active users forum, and also responds quickly.
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Great Explanation

[QUOTE=edwardc;127610]Wow, a subject that's near and dear to my heart! I'm in the middle of what's turned into a years long project to convert our boat to Lithium batteries. Its a DEEP rabbit-hole!

That was a very helpful explanation of why i can't use a Lithium battery as a replacement in my car or my boat. Requires an entirely new system.

Thank you!
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