Lithium battery system thoughts

[Dave Neptune]

Again

Mark, my boat was close on power for a single night & day then the power would begin to drop. I added a 300 watt solar per my design & research. This worked quite well but my batteries were still lower than I liked in the morning and she would still start the diesel with just the house side. I switched out to 2 Grp 31 AGM's and I'm still good after a few cloudy days. The other advantage of AGM's is you can hide the batteries away as there is little maintenance other than checking connections annually.

To change over all I needed to do was flip 3 switches the shore charger, the Baldor regulator and the Victron controller. I even added a switch to kill the alternator so when motoring on a sunny morning the engine worked less, the alt did nothing but keep the belt turning the water pump and old sol would top off the batteries. The solar ran the fridge, the freezer, the nav stuff, the stereo and Ray the steersman in a box.

I like Neil's comment as to the KISS rule and I always try to implement it.

I had a couple of buddies with power boats and some money who decided to convert to LiFeP04. After many dollars and many "electrical guys" they both went back to LA and replaced some fried electronics. It wasted a season for both. A complete from the ground up system is fine but piecing one together is really a nasty task.

Dave Neptune

[joe_db]

Your two choices:
1. Pay a professional to set up a high dollar system like Mastervolt.
2. DIY keeping in mind you are a pioneer and you will need to be constantly on top of the system.

I enjoy this kind of challenge, but many do not and #2 is not a good option if you don't like electrical experiments.

[edwardc]

Good point about system cost of ownership.

One thing I have found in my research, and confirmed by personal experience (I know, that's only one data point) is that Lead-Acid batteries, even Gel Cells, only have about a 600 cycle lifetime when cared for and charged properly. If I'm only going on day sails and weekends, they will last me a decade. But when I'm cruising full time, that only comes to less than two years!!!

LiFePo4 batteries, when charged and discharged properly, have anywhere from a 2000 to 6000 cycle life, depending on which manufacturer's data you believe. At one cycle per day, that comes to anywhere from 5 1/2 to 16 years, giving a MUCH longer time to amortize the higher initial cost.

And those lifetime figures are for full charge-discharge cycles at high current (1C to 4C). For shallow discharge cycles at fractional C rates (the norm on a sailboat), the results tend towards the higher end of that range.

So right now, I'm looking at the following approximate costs for LiFePO4 conversion:

$800 REC Active BMS, cables, contactors
$600 Wakespeed WS500 Alt regulator w/canbus
$500 Victron 40 A LiFePO4 charger
$1200 Eight 280AH LiFePO4 cells (for a 560AH/12V bank)
-----------------------
$3100 Aprox. total cost (will probably go higher)

Since my purpose in doing all this in the first place was to double (or more) my AH capacity so that I could go at least two sunless days without running the engine, my alternative to LiFePo4 is to replace my existing two (dead) Group31 97AH Gel Cells with four of them. At $400/battery this comes to

$1600 Four Deka 8G31DTM batteries


This means that the LiFePO4 installation has to last at LEAST two times as long (4 years) as the Gel Cells (2 years) in order to have a better cost-per-year. Given that 4 years is about 1500 cycles, this seems completely doable.

[edwardc]

Your two choices:
1. Pay a professional to set up a high dollar system like Mastervolt.
2. DIY keeping in mind you are a pioneer and you will need to be constantly on top of the system.

I enjoy this kind of challenge, but many do not and #2 is not a good option if you don't like electrical experiments.

Absolutely true. But I would never put a system in my boat that I didn't thoroughly understand or that I wasn't capable of maintaining. Its just my OCD nature. I have a really hard time paying someone else to work on my boat. Its not so much the money as I want to know exactly how it was done.

One of the (many) reasons I love my A4!

[msmith10]

Thanks, Joe and Ed. I think I need to forget about Li for a while. I can fix anything that has moving parts but solid state electronics is a black box as far as I'm concerned. I can wire a house to code, but I really don't want to have to fiddle with things that aren't ready for prime time yet.
I will look into AGMs. For my purposes alternate charging systems aren't really viable.

[joe_db]

Thanks, Joe and Ed. I think I need to forget about Li for a while. I can fix anything that has moving parts but solid state electronics is a black box as far as I'm concerned. I can wire a house to code, but I really don't want to have to fiddle with things that aren't ready for prime time yet.
I will look into AGMs. For my purposes alternate charging systems aren't really viable.

FYI - Gels have a higher cycle life than AGMs.

[edwardc]

FYI - Gels have a higher cycle life than AGMs.

Agreed. That's why I've stayed with them up till now. But be aware that Gel Cells have a different charging profile than either Flooded or AGMs. They need somewhat lower voltages. And they are more sensitive to overcharging. Tenths of a volt count! All your chargers (shore, alternator, solar, wind) must have a specific Gell Cell setting. Otherwise, you'll cook them.

One more comment on cycle life. Batteries are considered End-Of-Life (EOL) when they can hold only 80% of their original rated capacity. But they are still usable to a certain extent. My batteries had reached this point, and were ready for replacement, just as the pandemic began. As a result of the pandemic, and other issues, our cruising plans got put on hold, and the most we've done is an overnight in that time. If we used the generator to keep them topped-up until we went to bed, the batteries still had enough "juice" to keep our refrigeration running overnight at anchor without getting too low. But by the end of this past season, this was no longer true. I then used a capacity tester and did a full 24-hr capacity test (the most accurate way) and found that the batteries were down to 64%!!!

I think it's time to replace!

[ndutton]

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?

[joe_db]

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?

ANYTHING besides for rum is a huge PITA to get in the Exumas!

[joe_db]

Speaking of spares, by far the most likely thing to go out is the alternator. I absolutely would have a spare onboard for this trip. Even my Balmar - not a cheap alternator - needed a visit to the alternator shop. A4s are a worst-case for alternators, turning slower than usual makes them hotter than usual.
* I just put on an alternator temp sensor for this reason

I also might think about a cheaper standby BMS. You will have "spare cells" if you think about it, just make one string of 4 instead using 8 if one dies.

[edwardc]

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.

[ndutton]

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.

[joe_db]

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

[joe_db]

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.

[edwardc]

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!