DIY Lifepo4 on 39' Privilege Cat (with Boat Rewire)

[manly]

This thread is for logging the journey of installing a DIY lifepo4 bank on our 39' cat which I'm fitting out to be off-grip electrically. As far as builds go, this is fairly vanilla. But perhaps it will be of interest to someone and, in any extent, I can refer back to it in the future.

This post will recap what has been done so far and give an introduction to my philosophy.

First, why DIY? Why not drop-ins? Cost is definitely an issue. But more than that, even if drop-ins were handed to me (which in fact they were, Qty 10 perfectly good Battle Borns are in the boat now which I'm replacing), I still would prefer my DIY pack. Because I want to know how it works and is setup. What assumptions went into the battery builds. And I can check the cell health of each cell. Even more importantly, at the end of this project I'll be far better equipped to troubleshoot and fix a problem when/if it arises. If I'm off-grid in a remote island chain and my drop-in batteries give me trouble, I won't have the skills, knowledge, or even tools to be equipped to fix them. Additionally, I would like the batteries to have internal heaters which mine currently do not.

It is unfortunate that LiFePo4 is so finicky. The Pros in why they are advantageous, and for what I'm trying to do on 12v, pretty much essential. (i.e. run air conditioning, piston pump water maker, washing machine, hot water heater, etc.) However, the cons are increased complexity to manage (temperature, over/under voltage protection, etc). Complexity is never good on a boat. But if we must have it, at least I want to understand it as much as possible.

Ok, onwards to the details:

I purchased 16 cells of the supposed Grade A variety from AliExpress. From the LiitoKala&VariCore Flagship Store, to be precise. These were 280ah 3.2v cells [note: in future posts I discover they actually shipped me 240ah cells]. Cost with shipping to Florida was $1754.50. Took about 3 months to arrive (purchased 2021), but they were well packaged and I didn't see any damage. So the bank is 1,120 amp-hours. My initial capacity tests show the batteries are not pulling the full rated 280ah each. I'm going to re-test with a Renogy shunt and try to get more definitive numbers. However, if I only end up with 1,000 amp hours, that is still an adequate bank for us.

I will say that sending $1700 to China via AliExpress for batteries is heartburn inducing. And waiting 3 months for them to arrive... definitely felt like a gamble.

The BMS's I'm using are Overkill Solar. Qty (4) of the 12v as I'll be making 4, 12v batteries. Cost of these BMS's with shipping was $607.76. The upside of Overkill BMS's is they appear exceedingly robust and conservative in design. One downside is the 12v model only supports 120amps current (charge or discharge) per BMS. This would be a deal breaker if I only had 1 or 2 batteries. But with 4, that yields 480 Ah discharge capacity, which is more than enough. And charging will be under 200 amps, so no issue there.

I toyed with the idea of 24v system, and even originally bought the Overkill Solar BMS's for 24v. But in the end, I wanted to keep things as simple as possible, so sold those and bought the 12v ones.

 

[manly]

Battery Case And Location:

The case has been a topic of much thought. In the end, I'm going with the plastic battery boxes from AliExpress. Their outside dimensions are 345x245x190mm. Still waiting for those to arrive as I ordered them recently. Cost for 4 with shipping was $250.32. These have come down in price, I'm assuming as DIY has become less popular now that prices have really come down on out-of-the-box solutions.

I've gone back and forth on cell compression. I would prefer to wrap the 4 cells together with Kapton tape and be done with it. This is controversial, but I noticed even SOK batteries, which are regarded well by Will, are not compressed. So though my batteries may not last as long, the setup is simpler and the footprint can be smaller. However, being subjected to loads while sailing, I understand it is important for the installation to be solid.

Planning for each battery to have an internal heater. Though I'll mainly be in Southern latitudes the next few years, I'm hoping this battery bank to last 10+ years, and in that timeframe I very well may cruise North.

The batteries will be mounted in the starboard engine room. That is where the current batteries are. There is lots of chatter about how heat is bad for these batteries and the engine room is not an ideal place for LiFePO4 batteries. That is certainly true, but my cat is a sailboat and besides that, most the time it is at anchor. So time the engines are being run is very little in the grand scheme of things. And when the engines are running the blower will be on to circulate air through that space. The bigger issue in my mind is the additional vibration in the engine room. But that is the most logical place for the electrics to go, so that's where they're going.

For reference, here is an informative article on marine LiFePO4 installations: https://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/

 

[manly]

Battery Posts & Tools:

Some nitty gritty. For the battery posts, here is hardware used:

Hardware for Battery Posts	Cost / Ea	Qty	Total	Link
M6 Lock Washers (pack of 100)	$11.14	1	$11.14	https://www.mcmaster.com/97079A103/
M6 Set Screws (pack of 10, 20mm long) 92029A260	$4.26	4	$17.04	https://www.mcmaster.com/92029A260/
M6 Nuts (pack of 50)	$9.39	1	$9.39	https://www.mcmaster.com/94150A345/
M6 Washers (pack of 100)	$6.00	1	$6.00	https://www.mcmaster.com/98690A113/
T-Handle for 3mm 6954A22	$4.70	1	$4.70	https://www.mcmaster.com/6954A22/
Loctite 263	$15.33	1	$15.33	https://www.mcmaster.com/91458A610/

I went stainless steel. Some on here recommend copper screws, and that may have been preferred. However, I've also seen other use stainless without any ill effects. I've loctighted in the studs on all 16 cells without issue.

There were some tools invested in for the project:

Crimping Tool (Heavy Duty)	$148.79	1	$148.79	https://www.amazon.com/dp/B00HJYY5G...a18deb7e56ed3bf2474e50a3e2a23e&language=en_US
Battery Capicity Meter	$54.00	1	$54.00	https://www.amazon.com/MakerHawk-El...battery+capacity+tester&qid=1669350971&sr=8-5
Klein Current Meter	$81.96	1	$81.96	https://www.amazon.com/gp/product/B07P323914/ref=ox_sc_act_title_2?smid=ATVPDKIKX0DER&psc=1
DC Power Supply	$71.99	1	$71.99	https://www.amazon.com/gp/product/B082HXVRNF/ref=ox_sc_act_title_1?smid=A2KV19AYUKS3X0&psc=1
Cable Stripping Knife	$16.33	1	$16.33	https://www.amazon.com/gp/product/B00BMUDIGA/ref=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1
Crimpers / Wire Cutters	$12.99	1	$12.99	https://www.amazon.com/gp/product/B07RZ66XZF/ref=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1

I already had a number of electrical tools (wire strippers, voltmeter, soldering gun, etc) but now I'm even more prepared.

 

[manly]

Charging sources for the LiFePO4 Bank:

Boat is currently equipped with 1920 watts of solar that charge the house bank via 4 separate Victron charge controllers. These are already installed. Additionally, I'm adding a 30 amp DC-DC Orion from the starter battery to the LiFePo4 house bank that will run when the alternators are running (boat is equipped with 2 70 amp stock alternators on 30hp engines). Alternators will go to the starter battery only. I'm NOT planning to have a combiner switch for starter and house banks. There is one now, but I'm taking it out. I want to keep the banks totally separate for simplicity (except the Orion charger). If for some reason my starter battery dies, I'll rig up jumper cables from the house battery. Also, for charging sources, the 30 amp charger from the alternators is kind of a joke, since with such a large bank it would take over 24 hours to charge by alternator alone. However, as an emergency backup, I like having this option. And the 30 amps shouldn't tax the alternators much, even if I'm only running one engine to conserve fuel.

The last charging source I'm thinking of adding in the future is a wind turbine. This one: https://store.marinebeam.com/marinekinetix-mk4-marine-wind-generator/

Of note, I'm not planning to have a diesel or gasoline generator on board. A built in generator takes valuable room (our Cat is only 39' so space is precious). A gasoline generator, such as the Honda 2000, may be a valuable backup piece of kit (and I may succumb), but as of now I don't want it. It must be stored, maintained, I would need to carry additional gas (already carrying too much gas for the dinghy), and there is the increased danger of carbon monoxide poisioning. If the solar is not cutting it, instead of throwing $ at a Honda generator, I plan to throw $ at a wind generator instead.

Finally, on charging, it goes without saying that I am not factoring in marina shore power. Though I do have a shore power hookup that goes through Victron Multiplus 3000, I'm intending to keep this boat off-grid indefinitely.

 

[manly]

Current Project Status as of 11/25/22:

I've had the battery build project on the back burner for over a year. I'm finally getting back to it. So far I've top balanced 3 of the batteries, and am working on the 4th.

Concurrently with this project, I'm also re-wiring the Cat and replacing breaker panels. I'm using Paneltronics breakers: 6 DC panels with 8 breakers each, and one AC panel with 5 breakers. Additionally, 3 Sea-Dog switch panels used in various spaces. And a plethora of fuse boxes and terminal strips located around the boat. I may post some of that on this thread as well, if anyone is interested.

The entire project sounds complicated, but once it is all done the layout will be quite straightforward. And I'm documenting everything, so fairly easy to troubleshoot in the future. I want the electrical system to be as simple and robust as possible, with redundancy and, as much as possible, running in a closed system on renewable energy sources.

 

[manly]

Battery Specs:

My cells are supposedly Lishen. And, for future reference, here are the specs from the AliExpress listing:

Product name:	lithium iron phosphate cell
Shell Material:	Aluminum
Nominal capacity:	280Ah
Minimum capacity:	280Ah
Internal impedance:	0.1 ~ 0.3mΩ
Nominal voltage:	3.2V
Discharge end voltage:	2.5 v
Recommend constant current:	280a (1c)
Recommend constant current:	140a (0.5c)
Charging voltage:	3.65 v
Maximum continuous discharge current:	280a (1c)
Life cycle (80% dod):	4000 cycles
Charging temperature:	-5 60 60 ° c
Discharge temperature:	-30 60 60 ° c
Dimensions (l*w*h):	205*174*72mm

 

[JoeHam]

You can look up your cells here if you’re curious :

LiFePO4 Cells QR Codes Decoder : GobelPower.com

GobelPower.com : LiFePO4 Cells QR Codes Decoder - China Lithium Battery Distributor and manufacturer, Offers LiFePO4 Battery, 18650 Battery, 12V/24V/48V/72V Rechargable Lithium Battery for Home Solar Energy Storage, Electric Bikes, Scooters, Forklifts, Sweepers, Mowers and Boats.

www.gobelpower.com

 

[manly]

@JoeHam My batteries don't appear to have legit barcodes. There is a barcode but it just goes to varicore.com. See attached.

By the barcode there is also a "scratch-off" area revealing a long string of numbers. I don't know how to interpret these numbers, and when I plugged it into your link above it didn't recognize the format.

See attached.

So I guess this means I have Grade B cells?

 

[manly]

I just peeled up under the black top part and saw what looks like the original barcodes.

However, the numbers still don't work for me on that website link.

Here is what I read:

17Q712A0356565
CATL 6IH3L7
3.2V - 768 Wh

The 768 Watt-hour solves a mystery though. I've been pulling slightly over 240 amp-hours on capacity tests (like 242). It says on the side they are 280amp-hours, and they were advertised as such, but in fact they are 240 amp-hour batteries.

I just reached out to the vendor to see what they say.

With these lifepo4 builds, you don't know what you don't know.

 

[manly]

*** Battery Boxes ***

Received 2 out of 4 battery boxes. The other 2 should arrive soon. Pretty excited to finally see these in person. I've thought about a lot of DIY options for boxes, but these seemed like a good solution. They are sturdier than I was expecting. A year ago when I first received my cells these were going for about $150/ea. I bought these for $62.50, so the price has really come down. Still, it's nerve racking buying anything AliExpress. For one thing the ads are confusing about which size will or will not fit. These are the 345x245x190mm size and fit my 240 ah fine. Also they work with 280 ah.

*** Battery Capacity Testing after 1 year ***
It's been over a year since I received my 16 cells and capacity tested them in 4 batteries, 12v each. The 4th battery I never got around to even touching.

Most of the last year they were on my boat in the forward locker which got very hot in the Florida sun through this past summer. Not an ideal place for storage.

Also, these were left mostly full. Not 100%, but 70% or so.

I feared there may be significant degradation if I re-capacity tested them now. So I went ahead and re-tested all 4 batteries. And... I was pleasantly surprised they still seem in great shape. 3 of the 4 pulled 240 ah (and I stopped the test when they hit capacity). The only one that didn't was Battery #2 that I tested last and, out of curiosity, didn't do a top balance first (the other 3 I top-balanced and then tested). However, battery #2 had been top balanced a year ago. It only pulled 238 ah. I'm recharging it now and will top balance it again and re-capacity test it to see if it pulls the 240.

			Capacity Result	End V	Final Voltages
Battery #1	Completed Top Balance & Capacity Test 12/3/22		240 ah	11.04	(#1: 2.801, #2: 2.838, #3: 2.703, #4: 2.704) Delta .135v
Battery #2	Completed Capacity Test 12/6/22		238.2 ah	10.86	(#1: 2.803, #2: 2.573, #3: 2.662, #4: 2.830) Delta .257
Battery #3	Completed Top Balance & Capacity Test 11/27/22		240 ah	10.95	(#1: 2.842, #2: 2.793, #3: 2.703, #4: 2.618) Delta .224v
Battery #4	Completed Top Balance & Capacity Test 11/30/22		240 ah	11	(#1: 2.874, #2: 2.829, #3: 2.801, #4: 2.895) Delta .094v

Looking forward to getting these put together and finally having actual batteries to work with.

 

[manly]

Completed a top balance on Battery #3 and then immediately started another battery capacity test. The result was 239.0 ah. Still 1ah shy of rated capacity. But that's still 99.5% of rated capacity, so not bad after over a year of calendar aging in a hot compartment.

Final results:

			Capacity Result	End V	Final Voltages
Battery #1	Completed Top Balance & Capacity Test 12/3/22		240 ah	11.04	(#1: 2.801, #2: 2.838, #3: 2.703, #4: 2.704) Delta .135v
Battery #2	Completed Top Balance & Capacity Test 12/8/22		239 ah	11.2	(#1: 2.853, #2: 2.720, #3: 2.740, #4: 2.889) Delta .169
Battery #3	Completed Top Balance & Capacity Test 11/27/22		240 ah	10.95	(#1: 2.842, #2: 2.793, #3: 2.703, #4: 2.618) Delta .224v
Battery #4	Completed Top Balance & Capacity Test 11/30/22		240 ah	11	(#1: 2.874, #2: 2.829, #3: 2.801, #4: 2.895) Delta .094v

 

[manly]

I've been working on getting the circuit breakers together for the boat. One step closer.

Also, the other two battery boxes came in from China, so now I have all four. They were all damage free and arrived in 2 weeks. The seller was Dongguan Teswatts Batteries Store from AliExpress. Came with Qty (8) bolts but I would like 16 so I can bolt from the bottom and the top. I need to figure out the threads.

I've been working on making a mounting plate system in CAD that will fit in the spare area of the box and hold the BMS and also "squeeze" the pack enough to keep it in place and not shift, even if turned upside down.

 

[curiouscarbon]

labels look great!! ??

 

[CB-OTB]

Do you have a link to the case?

 

[manly]

Here is the link to the battery case. This was the best deal I could find on AliExress. Some looked cheaper but the shipping was higher. I bought 4, shipped to my door for $250.32. 2 weeks delivery. Looks like these fit a number of cases in the 200-300 ah range. I bought the ones with the M8 screws. But they only come with 2 per box, and you need 4 per box. 2 to screw in underneath and 2 to screw in on top. These are about 12mm long bolts (apx 0.5") and there are enough threads to screw in from top and bottom. So about 1" of threads.

https://www.aliexpress.us/item/3256804216551609.html?spm=a2g0o.order_list.order_list_main.5.19891802GB8Vga&gatewayAdapt=glo2usa&_randl_shipto=US

 

[MisterSandals]

Battery #1

Completed Top Balance & Capacity Test 12/3/22

240 ah

11.04

(#1: 2.801, #2: 2.838, #3: 2.703, #4: 2.704) Delta .135v

I have a question about using that tester. I have the same one from Amazon.
When testing a single cell, starting at 3.4V and discharging at 20A, the tester immediately shows voltage drop to ~3.1V (DMM still measures ~3.4V).
So tester displayed volts when discharging about .3V low. I set my test stop voltage to be 2.7V so my tests actually stop when cell voltage is about 3.0-3.1V.

Are you seeing voltage differences/ issues like this?

I am getting about 260Ah out of 280Ah cells and that seems about right discharging to 3.1V. But some cells vary a lot, 3.05V to 3.2V at the end so thinking tests are inconsistent and invalid.

 

[Dr.Maro]

Thank you very much for sharing all this info and detales. I'm also planning to do big remake of my electricity on Sun Odyssey 49, with also 16 cells of EVE LF280K and its great to be able to learn from your experiance. Keep posting .

 

[manly]

@MisterSandals yes, I see a smalle rvoltage at the chinese capacity tester compared to the battery. I assume that is because of the resistance in the wire.

Attached is a picture with voltages circled in blue. You can see the capacity tester measuring 12.8 volts while the Renogy battery monitor mesaures 13.0 volts.

I haven't tested cells individual, only 4 in series. As an aside, I've been running the tester about 10 amps. When I go higher it gets too hot for my comfort.

Besides the voltage issue, the amps is really what gets me. Nothing seems to match. See the attached picture where I have the amps circled in red. The chinese tester reads 10.3 amps discharge, the Renogy battery monitor reading 10.2 amps, and a Klein meter between the shunt and the capacity tester reads 9.99 amps. I'm not a "sparky," so don't understand why the disparity.

But regardless, I've found the chinese capacity tester and the Renogy battery monitor agree within 1-2 amp-hours over the 240 amp-hour test of my batteries. Renogy monitor usually shows 1-2 amps less capacity than the chinese capacity tester. I take this as confirmation that my batteries are pulling close to their rated capacity and the system works well enough for my needs.

My goal is to put this battery into service and get a 10 year life from it. Not planning to sell the boat in the next 10 years.

@Dr.Maro Glad this is helpful to you. The Sun Odyssey is a nice boat, also French like mine. Have you purchased cells yet?

 

[Dr.Maro]

For last 2 weeks going around different cell suppliers and comparing all, so as the regulated battery chargers and meaters etc
So Believe to start all in Januray / Feb.

 

[manly]

Am resuming the project... the distribution part of the project is starting to come along. Just laying out how all the wiring on the boat is going to go took quite a bit of thought / time.

I installed 5 circuit panels at the nav station. These are all DC 8-position panels made by Paneltronics. You can buy them a number of places, I got most of mine from Defender.com. They are $120 each. I have these 5 (pictured below mounted at the nav station) as well as 3 more located elsewhere. Only 1 of the 8 is an AC panel, the rest are DC. These panels have negative busses on the back, which for me was a plus as I'm running all the wiring directly to the panel. I know it's not recommended to do that, but to instead go to terminal strips that in turn run to the panel. However, I have excellent access to the back of my panels, so for simplicity I'm just going straight to the panels.

These Paneltronics are about half the price of the equivalent product by Blue Sea Systems. I'm impressed with the build quality.

Besides all those, I'm also distributing loads with 3 Sea Dog panels located in various rooms. Attached is a picture of those as well. I mounted them in project boxes (10.4" x 7.2" x 3.7", $20 at Amazon here).

Also using a number of Blue Seas Systems fuse blocks as well, as well as a host of terminal strips.

This boat has quite a few systems.