Instructions: Reviving the battery - My tip for batteries that have been declared dead

After pre-charging with the Olight UC, the BC700 also accepts the battery again.

Today a short, but (hopefully!) Helpful everyday tip that I found out by chance: If your battery charger reports that it cannot recognize a battery or thinks that it is defective, then that doesn't mean that he's really dead. I had this experience at least yesterday when I took three batteries out of an LED night light with a motion detector in order to charge them. Since the night light has not been on for a long time, the batteries had probably been discharged beyond their pain threshold for a long time - which should actually be avoided. But it happened anyway because every time I walked past the LED night light, I was too lazy to change the batteries.

Defect: The battery is no longer recognized

So I have the batteries in mine TECHNOline BC700 Charger (which I can highly recommend!) clamped and looked what happens. With two of the three AAA rechargeable batteries (type NiMH) he started charging immediately and with the third it was only permanently "ZERO". Which means, "I have no idea what you stuck in there, but that doesn't appear to be a battery. I'm not loading that!“. Don't be surprised: In the photo below, instead of the three AAA batteries, I only have two AA and the affected AAA battery in the device, because I've tried something else in the meantime.

The TECHNOline BC700 acknowledges defective batteries that it does not recognize with the message "ZERO". So also my AAA battery after deep discharge (photos: Sir Apfelot).
The TECHNOline BC700 acknowledges defective batteries that it does not recognize with the message "ZERO". This also applies to my AAA battery after deep discharge (photos: Sir Apfelot).

My first thought was: Oh crap, the battery was still relatively new (3-4 charge cycles) and I broke it. After a few desperate attempts to get the device to charge, I gave up briefly. After a few minutes, however, I fell into mine cool USB battery charger (the Olight UC) that I still had in a box. I thought I would give it another chance and attached the defective battery to this device as well. Unfortunately, the status message that the battery cannot be charged also came up here - indicated by the red LED flashing briefly. Nevertheless I had it hanging on the Olight UC for 3 to 4 minutes because I had been looking for something in the meantime.

My attempt to charge the battery on the Olight UC actually failed, but apparently it was precharged a bit despite the error message.
My attempt to charge the battery on the Olight UC actually failed as well, but apparently it was precharged a bit despite the error message.

But not so dead: a quick summons helps!

When I came back, the status message was still unchanged, so I unplugged the battery and - actually just out of spite - clamped it into the BC700 charger again. Lo and behold: it suddenly recognized the battery and started charging it! Eureka!

After pre-charging with the Olight UC, the BC700 also accepts the battery again.
After pre-charging with the Olight UC, the BC700 also accepts the battery again.

Since I had another AA battery that was not recognized by the BC700 either, I tried the same game again. The BC700 reported "ZERO" again. In the Olight UC, the defective battery was also acknowledged with the status message "Error". After five minutes I put the battery back into the BC700 and lo and behold: it was charged. There seems to be a system behind it! :D

My attempt to explain

The only way I can explain it is that the batteries that are not recognized have too little residual voltage. The Olight UC will - even if it reports an error - send a certain current into the battery, which ensures that it is charged a little. This charging raises the voltage of the battery to such an extent that it is sufficient for the "right" charger to recognize the battery again.

If you want to take a look at my two devices, you will find it Olight UC and I baked the TECHNOline BC700 here at Amazon:

Olight UC USB battery charger
197 Reviews
Olight UC USB battery charger
Is simply plugged into an existing USB charger and detects and charges many different types of batteries. My most common of these are: AA, AAA, 18650 - but it supports many others as well.
TECHNOline BC700
The charger can only handle AA and AAA NiMH batteries, but it is easy to use and offers single-cell charging. In addition, various programs for conditioning batteries, for discharging, etc. A pretty good device that has been doing its job for me for years.
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The page contains affiliate links / images: Amazon.de

10 comments on "Instructions: Revive the battery - My tip for batteries that have been declared dead"

  1. Simply leave the "dead" batteries in the BC 700. The device has a very low trickle current on the channel even when the display shows ZERO. At some point, that little bit is enough for the battery to be pre-charged and recognized.

    1. Hello Mactec! Thanks for the tip. I'll try that with the next zombie battery. It would make things a lot easier, of course. : D

  2. This is also much easier: Take a second charged battery and bridge for 5 to 10 seconds (e.g. with two bare paper clips) plus to plus and minus to minus (similar to starting a car). Then into the charger. Has worked for me every time so far…. ;-)

  3. Hello Sir Apfelot, do you know how to use the charger to find out whether the batteries are still good? The test mode seems a bit meaningless to me. Maybe I just don't understand something.

    1. I currently have the Voltcraft CM 2024. It shows you how many mAh have flowed into the battery and how many it was able to get out when discharging. So you can see quite well how high the capacity is currently. Your charger may also show you the mAh that flowed during discharging. So you have a clue.

  4. Simply place the battery in a charger for ten seconds and it will be recognized. I wish I had figured this out years ago because I've lost count of the number of "dead" batteries that have been thrown away over time.

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