Bosch 4.0 amp battery dead?

[Pete]

My Bosch 4 amp battery is showing a full charge when I put it on the charger but yet when I attach a tool it will not work, and yes I have tried different tools. When I actually click it into place on the charger the charger clicks as though everything is ok and then flashes permanent green which indicates fully charged. Is it goodbye to this battery or I have heard of things like put them in the freezer for 24 hours and then leave to come back to room temperature and then try charging again. TIA

[Temp]

Careful... Many tricks only apply to NiMH cells. Many tricks only apply to over discharged Li-ion cells.

 

Can you put a voltmeter on the pack?

 

I'm wondering if the internal fuse has blown.... In that case the charger might be raising it's output voltage to try and push current into the battery and that higher voltage is fooling it into thinking it's fully charged. 

 

 

 

[Jeremy Harris]

I wonder if the Bosch packs have something similar to the Makita packs?  If a Makita LiIon pack gets out of balance, after being stored for a time whilst discharged, then when plugged into the charger it will give a battery error warning (flashing red charge light).  If you try and charge it three times like this, the battery will be permanently disabled by the charger and turned into junk.  This happened to me, and I managed to save the pack by taking it apart, charging the individual cells one by one and then fitting a replacement battery management system circuit board (there's no way to repair a board that's been "bricked" by the Makita charger).

 

Bosch may possibly have a similar system, but there's no way to know without taking the pack apart.  I found out about the Makita "feature" because there were a lot of online complaints about battery packs being bricked when they were still under warranty.  A friend who works in a tool store let me have a big box of Makita "scrap" batteries, which were all repairable by replacing the battery management system board. 

[Temp]

Some lithium cells can catch fire if fast charged after an excessively deep discharge. Usually the tool cuts off before the voltage gets too low to safely recharge the pack but if they are put away flat they can slowly self discharge below the safe recharge voltage. Some chargers will detect the low voltage state and only allow trickle charging until the voltage come up enough to allow fast charging.  Some just assume the battery is toast.