New SOK Battery Dead :(

[meetyg]

This can be easily checked by measuring the voltage between the battery negative (before the BMS) and the positive terminal.
If you get anything lower than 10v (for a 4s pack), then yes, some or all cells have reached lower than 2.5v.
I think some BMSs (JBD/OVERKILL ?) have a hardware cutoff voltage which should power off the BMS when reached. That's why it's not possible to just charge them up, the BMS needs to awakened after slightly charging the battery.

 

[cs1234]

Yes, the BMS does protect the cells, but there is also the factor of self-discharge of the cells with a micro-draw coming from the BMS itself. We're talking very little draw here, but the curves are very steep at this end of the spectrum.

That's what I meant, the BMS is what drew down the power the rest of the way. What defense do the cells have against the BMS itself once the power level is that low.. does that BMS completely shut off at some point and not draw any power whatsoever until it's hit with power from a charger? If not, then eventually all the batteries would die horribly if not maintained with some charge over a long period of time. The would die without a BMS anyway from the cells on discharge rate anyway.. just faster if the BMS never stops sucking some power.

 

[Bluedog225]

I guess if I were writing the programming, the BMS would shut down completely. And require hitting some sort of reset button to fire it back up. And leave enough voltage in there to carry the batteries without damage for a year or so.

 

[HighTechLab]

That's exactly what happened here. First the voltage got too low and the Discharge MOSFETs (D-MOS) turned off, then over time it continued to get so low that the BMS turned off the C-MOS to further reduce it's self-consumption. Self-discharge took it the rest of the way down.

To have a year of reserve, we would need the BMS software to de-rate the cell capacity at least 10-15%...but who wants to carry 10-15% more weight for a corner case when you can just fully charge the batteries then disconnect the loads before storage?

 

[cs1234]

That's exactly what happened here. First the voltage got too low and the Discharge MOSFETs (D-MOS) turned off, then over time it continued to get so low that the BMS turned off the C-MOS to further reduce it's self-consumption. Self-discharge took it the rest of the way down.

To have a year of reserve, we would need the BMS software to de-rate the cell capacity at least 10-15%...but who wants to carry 10-15% more weight for a corner case when you can just fully charge the batteries then disconnect the loads before storage?

I agree, it seems a bit much for an edge case. However, I'm wondering if batteries with BMS, or even batteries in general, should come with a large warning sticker on them that says what state of charge to put them away in for storage with a rough estimate of how much time you have before self destruction / damage at that charge level.

I don't have any statistics for what level of edge case this is, but the OP might not have done something so ignorant if they had known / been warned. Not everybody enjoys following battery technology and care procedures as much as we do.

 

[HighTechLab]

FYI, from GanFeng's specs:

 

[Alkaline]

Does anyone have the datasheet to the cells SOK is using? 1.8v seems very low, in all previous literature I have read this is you have damaged your cell voltage.

 

[HighTechLab]

Does anyone have the datasheet to the cells SOK is using? 1.8v seems very low, in all previous literature I have read this is you have damaged your cell voltage.

Yes. Post 26