Dormant 48v battery will not take a charge

[postech]

I have a 48v battery that will not take charge, the manufacturer suggests using a desktop charger to “boost” the battery back to life but is unable to provide a procedure to do this.
Anyone with experience in this area?

 

[Atavar]

Danger Will Robinson!
If you do this do it outside in your barbecue grill.

https://www.currentconnected.com/le...-starting the dead,a charge from the charger.

 

[postech]

Thank you.
Yes, it’s very scary working with these batteries.

 

[Atavar]

If you have a spare battery you could try charging it up and using it to jump start the sleeping one. Just connect + to + and - to - and run away. Lol

 

[addertooth]

I will try to explain. Today, chargers are "smart". They will try to sense the battery before applying voltage. If the battery is low enough in voltage, it will assume there is no battery there to be charged. It will refuse to provide a charging voltage/current.

What they are suggesting is using a "dumb charger" which continuously provides 48 volts at 1 or 2 amps of charging current, to see if you can get the voltage up on the "dormant battery". Once the voltage is up to near 48 volts, then the "smart charger" which came with the eBike will recognize a battery is connected, and do it's normal charging cycle.

This is not without risk, and as suggested should be performed on a BBQ grill, or some other outside fire-resistant area. If you don't own a voltmeter, and know how to use it, this is not recommended.

If you get the polarity backwards, very bad things will happen.

 

[Anton]

If you have a spare battery you could try charging it up and using it to jump start the sleeping one. Just connect + to + and - to - and run away. Lol

I managed to bring an 18V Makita battery back to life using this method. The smart charger wouldn't accept the battery, and it was reading 0 Volts on the multi meter. The good battery jump started the dead battery enough so that the smart charger accepted the battery.

WARNING: Using the jump start method you risk frying two batteries and burning your house down if you connect it up wrong.