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Battery SOC monitor from reliable source

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nctnico:

--- Quote from: boB on March 01, 2024, 10:37:20 pm ---Most of this depends on the BMS itself which sometimes gives you SOC%.  I assume that some times it is even accurate.

--- End quote ---
A well designed battery should have a way more accurate SOC as this is typically also tuned for the cell chemistry used by the battery. You can't match that with a generic, external counter.

Siwastaja:
Well, what do you expect? As usual, solutions to complex engineering problems are:
1) Aliexpress crap which is easy to buy and cheap, but does not work,
2) Properly engineered stuff which is difficult to buy and expensive, and still might not work, but at least you'd get support.

The key takeaway is, battery charge level indication is not a trivial problem.

Besides, usually all of the battery management is integrated in one management system. What is the existing solution on the pack, and does it properly measure cell voltages, does it properly control the charger and the loads, and does it do balancing? If yes, does it really lack SoC estimation? If the answer is yes, instead of gluing two BMS's which both do partial job, one option is to replace the whole BMS with something better.

(Elithion was just one random example I know of, no affiliations and have not personally used it.)

Simon:
Well they won't want to go the two expensive route. I think the ebay one has been OK but the main issue is that they come with different shunt resistors every time so the metalwork has to be changed. It is also possible that the specs of the unit itself change without notice.

SiliconWizard:
I've used the MAX17048 with li-ion batteries, which I found worked quite well. The MAX17049 is a 2-cell version.
They have newer parts, and some for LiFePO4 batteries. But I don't think they have anything that could work with 48V. A 48V LiFePo4 pack is probably an arrangement of many cells in parallel and series, and unfortunately, I don't think any of these battery gauge ICs are available for such arrangements. You'd have to design the SOC monitor yourself and it'll be quite a bit more complex than just a single-chip solution.

Properly evaluating the SOC of a single cell is already not trivial (but those ICs do the job fairly well), but doing so for a series-parallel arrangement of many cells is yet another level of complexity.
Yes, it's probably going to be integrated in a balancing circuit as well. There's no way you can find something cheap, off-the-shelf and working properly. :-//

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