How do you wake up a lithium battery pack?

[D308]

Hello all,

Ive got several lithium ion packs made of 18650s. Occasionally they will go offline due to being at or below the minimum voltage per the BMS. At this point they will not take a charge either. If I read the voltage on the output side of the BMS it’s essentially 0 volts. On the Input side it can show around 11 volts on down. Is there a way to reset the BMS to turn it back on to allow it to charge the battery pack? When we receive these packs they are turned off and require us to plug them into the equipment to charge them. Sometimes they sit to long and you cannot turn them back on. The battery that is.

These are commercial made battery packs for medical equipment. Customers think they are dead but the cells are fine. I’ve got several of these packs that are nominal 14.8 volts and will charge up to 16.8 volts at 11 amps.

Thanks.

Don.

 

[dweick]

You can bypass the BMS and directly apply a charging voltage to the battery until they reach the voltage needed to for the BMS to allow charging.

Not that I would recommend doing so for batteries that would be used again in medical equipment

 

[Substrate]

Lithium-based equipment is normally shipped due to hazmat reasons at the 30% capacity mark. Or should be.

The equipment your customers are receiving are getting stuff that has been self-discharging due to improper storage, long term storage without any use, or other abuse like high-heat storage if they are indeed considered to be "new".

The solution is to get this equipment to your customers sooner, find out where the logjam in your supply chain storage is, or if customers are simply ignoring received equipment when they should charge them upon receipt.

The fact that they won't charge with the OEM equipment is that they are designed specifically to prevent problems like new-old-stock scams, or previously worn out banks from functioning in potentially life-saving environments (where trusting in CRAP can be lethal)

You may indeed be able to "restart" them, but you may be considered liable by customers or patients if they fail in a medical environment, and discover that you revived the packs with unapproved oem practices.

If this is just for goofing around, then yes, there are techniques to bring them back to play. But don't even THINK of putting these back into medical equipment with diy revival techniques.

 

[RCinFLA]

LiPo packs often have a permanent disable function if any single cell drops below about 1.0 -1.5v. This is because in this territory the cells can grow dendite shorts. It can be dangerous to try to recharge a very low voltage LiPo cell, setting off a thermal runaway. When any LiPo cells are below 2.5-2.8v and greater then 1.0-1.5v the charge controller will only allow a trickle charge until all cells get above 2.8-3.2v.

Most all laptop batteries work like this. Many folks have discovered just replacing cells got them nowhere. There are videos and info on hacking various model laptop battery packs to reset the disable setting.