DALY over-discharge didnt work, bad BMS or bad setup?

[Xiphiar]

I have a 5kwh 14s battery using a Daly 14s 100A common-port BMS. I accidentally left an extra load on one night that drained the battery, woke up to my 14s battery at 25v. The BMS should have a low voltage disconnect, could a few watts of solar charging on the common port could allow enough output to drain the battery?

I'm really trying to figure out the best way forward to protect my battery, not sure if I need to replace the BMS (potentially with a separate-port model), or look into an external solution to prevent over-discharge. Any insight or advice is appreciated!

 

[sunshine_eggo]

I have a 5kwh 14s battery using a Daly 14s 100A common-port BMS. I accidentally left an extra load on one night that drained the battery, woke up to my 14s battery at 25v. The BMS should have a low voltage disconnect, could a few watts of solar charging on the common port could allow enough output to drain the battery?

No. The outflow of current is blocked.

Did you attach directly to the battery and bypass the BMS? I've seen it done.

I'm really trying to figure out the best way forward to protect my battery, not sure if I need to replace the BMS (potentially with a separate-port model), or look into an external solution to prevent over-discharge. Any insight or advice is appreciated!

Hopefully, it's not actually destroyed. I would check all your cells and confirm there isn't something amuck.

 

[Xiphiar]

Both charge and load are connected to the P- lead on the BMS, the only thing connected directly to the battery is the BMS.
Every cell is within 0.005V of eachother (most cells currently measure at 3.985 and a few at 3.980-3.983).

 

[burgerking]

woke up to my 14s battery at 25v

Where exactly did you measure this? it contradicts this:

Every cell is within 0.005V of eachother (most cells currently measure at 3.985 and a few at 3.980-3.983).

A diagram would be most helpful.


Maybe what you measured 25V is residual voltage with the BMS disconnected to load (which should be fine).

 

[sunshine_eggo]

Where exactly did you measure this? it contradicts this:


A diagram would be most helpful.


Maybe what you measured 25V is residual voltage with the BMS disconnected to load (which should be fine).

This is a very good point. Did you directly measure or query the cells when the battery measured 25V? Many BMS report an arbitrary voltage when in protection mode.

 

[HRTKD]

I use the Victron Battery Protect to prevent loads from draining my LiFePO4 battery bank too far. The Battery Protect is NOT used to feed the inverter. The inverter has its own low voltage disconnect and you're not supposed to use a Battery Protect in an inverter circuit anyhow.

 

[mikefitz]

14 s BMS won't be LFP cells.