Can recharge battery after accidental discharge

[psychonurse]

Hi, guys wondering if I have totaled my 36volt 15 a.h. battery. I accidentally left switch on. Drained battery for several weeks. Now when I put on charger all I get is a flashing red light on charger. Battery now won't take a charge. I have heard something about "awakening" a sleeping battery. Any help or suggestions appreciated.

 

[psychonurse]

Hi guys, I left the off/on switch ON for several weeks by accident. Drained the 36volt 12 a.h. battery completely. I put the charger on and it now red light just flashes instead of usual solid red. Battery is not charging. I have heard of a way of "awakening" a dead battery. Hope someone has a answer to help me save it. Thanks.

 

[nutnspecial]

Ooo boy. What is the voltage of the pack right now? Chemistry?

Can you easily test the seperate cell strings also, and even seperate cells?

Your charger and/or bms is not allowing voltage in because the pack is below specified limits. However the cells might not be damaged from the slow drain. Care very slow charging of the pack and/or individual cells and strings could get it back where it will accept a charge and balance, at which point evidence will be available upon cycling as normal to the new overall condition.

 

[keithmac]

The battery poweres the charging circuit (inside the battery) so when completely flat it will never accept charge the "normal" way.

If you can find a way to trickle charge the batteries inside the pack to give them enough voltage to allow the charging circuit to work you can finish the charge on the normal charger.

 

[fechter]

You might try leaving it on the charger for a few days to see if that can wake it up. Otherwise you need to open the battery to get access to the BMS board or the actual cell connections.

 

[dogman dan]

It might be charging in safe mode, till the voltage is high enough for it to start a normal charge. Or just telling you forget it, no charging.

It might be saved, by bringing up some extra low cells one section at a time. But in any case, it's taken some serious wear.

 

[cell_man]

I recommend you open the battery and look for the bms pcb. There will be a multi pin plug (balance plug) that connects to that bms (11 cables, possibly more). Disconnect that plug and it will prevent the battery from being discharged any more.
Now check the dc voltages on the adjacent pins on the balance plug (likely 3v or less). If the voltage on any of the cell groups are 2.5v or higher, they are not damaged, if much lower than this, the cells could be damaged somewhat, or maybe not. This is assuming the cells are not lifepo4, in which case the voltages could be lower. If you tell us the charger voltage, that wil give us a good idea of the cell type the battert is built from. It will be either 42.0v, or it might be a bit higher if it is lifepo4. Maybe take a clear pic of the bms and people will have a better idea of what you have and direct you on how to best proceed.