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16s LiFePo4 280ah battery (48v), is there a "reliable" BMS option?

Messier11

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Dec 26, 2021
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Sweden
Hi everyone,

I am looking at setting up an off-grid system in our cabin which we spend a lot of time at during the summers and also around Christmas. I am a newbie at this, but have spent a lot of time trying to educate myself and I still have about 5 months to "launch" (my summer vacation).

Background
Things can change, but right now I am looking at a system fundamentally based on:
Victron Multiplus II 48/5000
Victron Energy SmartSolar MPPT MC4 250V 60 Amp 148-Volt Solar Charge Controller
16 x LiFePo4 280ah batteries from China
And 4-8 "24v" solar panels.

The BMS and its reliability
So watching all these videos on how to build a DIY Off-Grid solution, it seems like issues with the BMS is very common. Since my cabin will be unsupervised for months at the time and at other points only used by family (my mom, sister, aunt), I would like to get the most reliable BMS option. Efficiency definitely comes second in priority.

Anyone have any input on how I should think when choosing a BMS against the above background?
 
Good question. It seems like we have similar goals in mind with our two posts. Watching with interest.
 
Good question. It seems like we have similar goals in mind with our two posts. Watching with interest.
Perfect! :)

This seem to be on fairly often recommended solution (albeit expensive, around 500 USD in Sweden):

But again, I don't know if its over the top or very reliable. Perhaps a more passive solution would fit me/us.
 
Jbd are the most popular with the least amount of issues. I have sold alot of the jbd with no issues
 
JBD BMS' are popular and there is a large selection of options. JK-BMS' are also popular and have some good features & functions. On that point, I am in process of changing my battery bank (5 packs) and 3 utility packs over to JK-BMS with 2A Active Balancing, Bluetooth etc. These are FET Based BS without Relays or Contactors. If you have loads / needs that require "a more serious" handling the there are a few like QUCC, Charger & Others which have Relays or Contactors.

If budget is no concern, Batrium, Rec and other high-end BMS are available. It really depends on what kind of features, functions, interactivity you want. For a user friendly simpler system a moe inter-connecter interactive system is better... ie having the battery interact with the inverter & SCC and temp management of course if applicable.
 
I'm looking much the same. Mine will have capable people around, and be 16s2p, so theoretically there's some redundancy as well, so a failure isn't necessarily immediately fatal, just annoying. Spent quite a while looking and started spinning my wheels on it.
 
A 13kWh LFP battery bank should do pretty well for a small place with a smaller top-freezer fridge. "24V panel" means almost nothing. Watts output is a much more useful metric. Plan them to give you 1.5-1.8kWh on all but the very worst days and you'll probably have more than enough power.
 
I've had a 1280W PV system with ~12kWh lead acid bank, feeding a big French door fridge with slide out freezer, electric ignition/clock stove, small ethernet switch, piano heater bar, and some lights. Samlex EVO 2224 running 24x7. It mostly works, but stretches of poor days drain the battery.
 
For a complete off-grid setup, I don’t consider the “premium” Batrium, REC, EMUS, etc. to be all that costly, especially for things that should be ideally purchased once in 10-30 years. I am happy to pay the ~$500 (single string) to ~$5000 (large system) cost for that. It’s a small price to pay to protect the battery investment. The frustrating part for me is that as a prospective customer, pre-purchase product support is quite lacking, for each and every one of these companies, in my experience trying to decide on one over the past few months.
 
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I suspect the larger companies are not all that motivated to deal with the diy community. For the smaller companies, I suggest reading the Overkill manual. I read it and was impressed with the info and detail.
 
How important is the BMS’ balancing capacity?

I saw one example of an entire system struggling pretty much because one cell probably wasn’t balanced properly. So that shouldn’t be an issue early if the cells are properly balanced, but might they age differently? 6-8 years in?

The Daly 16s BMS and a few other cheaper ones only has a discharge currency/balancing capacity of 0.15-0.25 Amps. While the Rec’s discharge capacity is 1.3A (at “3.9 ohms”, whatever that means in practice?), Batrium’s cellmate K9 at 0.5A (cellmate is the best name for sure), and Emus’ Mini3 also is at 0.5A.
 
BMS balancing capacity importance varies with factors like battery age (cells can age a little differently), battery capacity, and especially cell quality and initial match. A very good initial match and top balance leaves the BMS very little to do. In theory a well-matched and balanced pack won't need the BMS to do anything. In practice, a small current flow helps with the tolerances that inevitably creep in.

I noted the same, Bluedog. Leaves me considering the source quite suspect.
 
BMS balancing capacity importance varies with factors like battery age (cells can age a little differently), battery capacity, and especially cell quality and initial match. A very good initial match and top balance leaves the BMS very little to do. In theory a well-matched and balanced pack won't need the BMS to do anything. In practice, a small current flow helps with the tolerances that inevitably creep in.

I noted the same, Bluedog. Leaves me considering the source quite suspect.
What is the experience with these Chinese 280ah LiFePo4 DIY batteries, is it easy to assemble 16 of them into a battery that function well without a good BMS?

I am just afraid that I won’t nail all connections etc and they will discharge differently, causing problems.
 
If you have loads / needs that require "a more serious" handling the there are a few like QUCC, Charger & Others which have Relays or Contactors.

JK has a high current contractor option as well (you have to add your own).

For what it's worth, I've been running JK's on my 2x16s 280Ah for over a year and a half now 24/7. I haven't had to touch them since I installed them.
 
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