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Dead Rechargeable Batteries Don't Have To Be Dead

Capt. 2110

Experienced Member
Joined
May 23, 2015
Messages
362
Location
Texas
This is my first blog post. Impressive. Anyways, welcome! I found two REALLY old Ni-MH batteries lying around yesterday, and I thought I would try to save them. A few years ago, they had been considered dead, and I only narrowly saved them by saying I had a use for them. I didn't, but I do now. I started by placing them both in a new Duracell smart charger. It said almost instantly that it couldn't charge them(blinking red led). I then shorted the charger by being stupid, and it reset. A few minutes later, it said they were done charging(green led). I put them in my battery munching flashlight and timed them. I tested the newest one only once, due to it being very worn out. It was from around 2005, and was WAY over used by comparision to the year 2000 one. I may try again later. I have brought the 2000 battery back from the dead though. Here are the times.

~Year 2000 Rayovac Ni-MH AA 1600 mAh
1st try: 5M 30S
2nd try: 6M 17S
3rd try: 10M 34S
4th try: ~27M 03S(lost track of time)
5th try: 40M 00S
6th try: N/A
7th try: 40M 00S
I'm not sure what I just did, so if you know, please say so in the comments. The flashlight is supposed to last 51M minutes with a normal Alkaline battery, so I feel good knowing I saved a crippled battery and got it to about 80% of it's capacity. I did something similar with an old 1993 Sega Game Gear Ni-CD battery pack, too, but it's still kind of dead. It went from running for a few minutes to running for around 1 hour. Not that good, but better than nothing. Also, keep in mind, if the light is still on, it counts. Even if it's a completely useless light that won't come back if you cut the power, it's still running. It runs out of usefulness around 30M. The final death voltage is about .8 volts.
 
A typical Ni-MH won't last as long as an Alkaline anyway, your 80% mark may be pretty good.

I have done this as well, more with NiCad than NiMH. But, I usually use bench supplies to get them started. The key is to keep them cool. When they get hot, they get damaged. I recently had a NiCad pack that was an open circuit. I applied about 50VDC to it just long enough to get it to start flowing current. When it got to 1mA, I shut it off and put it on its normal charger. It had been an open circuit for maybe a decade. It sort of works for a little while now.

It's hit-or-miss. Some batteries come back pretty good, others just won't.
 
KC9UDX;bt808 said:
A typical Ni-MH won't last as long as an Alkaline anyway, your 80% mark may be pretty good.

I have done this as well, more with NiCad than NiMH. But, I usually use bench supplies to get them started. The key is to keep them cool. When they get hot, they get damaged. I recently had a NiCad pack that was an open circuit. I applied about 50VDC to it just long enough to get it to start flowing current. When it got to 1mA, I shut it off and put it on its normal charger. It had been an open circuit for maybe a decade. It sort of works for a little while now.

Ok, cool. I HAVE SAVED A 15-YEAR-OLD BATTERY! * plays https://www.youtube.com/watch?v=ldYCM6F3Xhw *
What was your battery for? Was it just a normal AA/AAA battery, or was it a specific battery?
 
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