recovering low voltage batteries

[kingfieldbill]

So I put a bunch of batteries into storage mode via a reasonably smart charger and now I have several batteries that the charger wont recognize. When I plug them in to a meter they register nothing but a volt meter shows them at 10.4 volts. Is there a way to get a charger, perhaps a dumb charger, to raise the voltage to a level that a smart charger will recognize them or are they bricks destined for the recycling bin?

 

[quorneng]

I presume they are 3 s LiPo so nominal 11.1 V and up to 12.6V at full charge
What voltage were each of the cells at when the storage mode was complete?
It is obviously vital that all the cells have an equal (to within 0.01V) storage voltage of say 3.80V?
Unless the individual cell storage voltages are truly equal it is very likely that the LiPo has a weak cell.

How long were the batteries left a storage mode?
A LiPo in good condition has a very low self discharge rate so provided a suitable storage cell voltage is set should not drop to a critical low voltage for as long as a year although a check every 3 months is advised.

Depending on your charger it may be possible to use a short period of a 12V PB (Lead acid) charge to raise all the cell voltages to above the minimum required for LiPo charging but it does not solve the issue as to why the voltage on one or more cells dropped low in the first place.

LiPo batteries have a high energy but 'delicate' chemistry. Any difference between cell voltages in a pack is a sign of permanent and irreversible chemical damage.

 

[Merv]

I agree with quorneng, the lead acid setting is worth a try. Just a word of caution, watch everything very closely, don’t leave this unattended. If it’s going to work, it should not take more than 15 minutes to bring the voltage up enough to stop and switch to a lipo setting.

 

[Foamforce]

I used my cheap balance charger to bring my over discharged battery back up high enough for my good charger to recognize. The one I have looks like this one but is a different color and brand.

https://store.flitetest.com/b3-20w-compact-charger/

 

[Ryan O.]

So I put a bunch of batteries into storage mode via a reasonably smart charger and now I have several batteries that the charger wont recognize. When I plug them in to a meter they register nothing but a volt meter shows them at 10.4 volts. Is there a way to get a charger, perhaps a dumb charger, to raise the voltage to a level that a smart charger will recognize them or are they bricks destined for the recycling bin?

If you do ever try to revive batteries, ALWAYS charge them in a lipo bag from then on, which you should be doing for other batteries anyways. Also, leave it somewhere where you could hear it if it starts on fire.

 

[Bricks]

Do you have a balance board, if so take a good battery use main plug ( not balance lead ) plug into the balance board, plug battery at low voltage into the board let sit for a good 10-15 minutes. Be sure batteries are the same cell count MAH does not matter.

 

[L Edge]

Additional point:
If you do get revive the battery, suggest you discharge/charge the battery pack a number of times. Keep track of stetting's.

If unsure or doubt it's reliability, do you really want to put it in the aircraft and risk destruction?

 

[Liam B]

I echo all of the above, but add that measuring internal resistance before and after reviving is a good idea!