Conservative settings

[xychix]

I've tested my lifepo4 230Ah batteries and they delivered as expected (or even better).

Now i'm down to 3.00v per cell (ish)

JDB BMS is now set to trigger at:
LOW 2.5v (reset 3.0v)
HIGH 3.65 (reset 3.45v)

I really don't need 230Ah, it was just the cheapest cell / kwh ratio at that point.

What are good conservative working boundaries? (The pack might do more shelf live than actual use! It's a recreational battery for weekends away)
LOW 2.9 (reset 3.1)
HIGH 3.55 (reset 3.45v)

balancing while charging above 3.3v

Does this make sense?

 

[ArthurEld]

If you want to be conservative, do it with the charge controller.
Set it to something like low=3.1, high=3.35 (convert to 12, 24 or 48V)

Try it and if that gives you what you need then you should be good.

The BMS protects the battery if something goes wrong with a single cell. Either of those BMS settings should be fine.

 

[xychix]

Thanks, unfortunately is the wall charger I use now (Victron blue power charger 12/30) a fixed program charger.

On 12v (Li-ion setting) it will charge to 14.2v (absorption) before dropping to 13.5 (float/storage). No way to set this, Only thing I can do is use the BMS to get Soc and roughly time a 80% charge and disconnect the charger.

 

[ArthurEld]

You are likely to harm your battery with that charger.
I imagine someone else has done what you are trying to do.

 

[Short_Shot]

You shouldn't use the bms to do this, but rather with charge settings.

Ideally you should never hit those cutoffs if everything is sized properly for your needs.

14.2v is not a 100% charge on a lifepo4 battery anyways as long as the absorption time is not too excessive (its 3.55/cell) so you'll be fine, and 13.5 float is only 3.375v per cell.

If you try to use the bms to limit the top you'll trigger it during charging which could be problematic, and unnecessary.

Raising the bottom cutoff on the other hand isn't always a terrible idea, though something like 3v per cell is enough to keep you out of the discharge knee at least.

If I were you I'd just raise the low voltage to that 3v cutoff and leave the rest alone.


Last, I don't think I'd put balance that low, preferring to keep it operating only in the charge/top knee while doing so. This helps ensure you are not dipping too low into the flat part of the discharge curve and unbalancing the pack accidentally while under load.