My automatic charger didn’t want to charge a battery, it has “NULL” displayed on the screen, it was dead for him.
Reference : NeBatte Ni-MH Battery AAA 1.2V
Reviving the Battery
/!\ WARNING Do not try with a Lithium battery !
Using a similar battery (same mAh) :
- connect the (+) from the good and the bad battery together
- connect the (-) the same way
- wait 20 seconds
- test the bad battery in the charger, if it fail goto step 1
Source : instructables.com from Paul1212
The explanation in the instructables article is interesting :
“Some batteries die when a short developes between the positive and negative terminals of the battery This happens a lot with NiCd batteries and can happen with other chemistries. The short is caused by a metalic dendrite crystal. The electric charge between the two terminals of the battery encurages dendrite formation. by connecting a fully charged battery to the dead shorted battery you willl get very high current flow through the dendrite. That will casue it to get hot and melt. Hopfully that breaks the short. Modern lithium ion batteries rarely short out in this way. Also lithium ion batteries are very sensitive to overcharging. If they overcharge they can catch fire . So I would not recommend this with lithium ion batteies.” Thank you steven4872 for the explanation.
Storing a battery
If not used :
- Ni-CD battery must be stored Discharged
- Ni-MH battery must be stored Charged
And battery must have a disharged/charge cycle every 6 months
Source : ni-cd.net (In french)