So if you are like this Lazy Old Geek, you have a lot of rechargeable batteries lying around. I wrote another Instructable with some battery tips.
Amongst these batteries, I have a lot that no longer work or don’t work very well. So I decided to try to revive them.
First step: If the battery isn’t totally dead, stick it in something like a flashlight, turn it on and let it run until it stops working. Try to recharge and see if it works better. I tried this with a couple of cordless drill batteries and was able to ‘restore’ the battery packs.
Second step: However, I have a lot of AA and AAA batteries that still didn’t work. I also have a bunch of battery chargers but none of them will recondition batteries very well, so I decided to make my own.
Well, after years of diligent research (well, actually it was more like days and not very diligent), I decided this method had the most promise:
Okay for the technically challenged, the basics are:
1. Fast discharge the battery from 1.2-1.4 volts, down to 1 volt.
2. Discharge it slower to about 0.4 volts. Then recharge and see if it works.
This may have to be repeated several times.
Step 1: Design Battery Holder
My Design criteria for a battery reconditioner:
Individual circuits for each battery.
Discharge up to 3000mA AA batteries.
Do up to four AA or AAA batteries at a time.
So, since I’m an Arduino Geek, I decided to use an Arduino.
But first, I needed a holder for AA and AAA batteries. Well, I didn’t have any readily available and didn’t want to try to make my own (as seen in many Instructables). But I did have an old Panasonic battery charger that I didn’t really like (See rechargeable battery tips). This one will take AA or AAA batteries.
So I took a screwdriver and opened it up. (see picture). All of the battery contacts are on the PCB. So I took my trusty $4 soldering iron and some solder wick and removed most all of the components.
Now I don’t expect very many readers will have one of these around but you can probably make or buy suitable battery holders. So I’m not going to go into a lot of details about how I modified the PCB. Here is the design criteria for my battery holder:
All the grounds (the – sides of the batteries) are tied together.
My battery slots can take either AA or AAA batteries. The positives for each slot type can be tied together.
So six wires will come off the holder: two black grounds and four red positives. I labeled the positives for each slot.
This Panasonic charger actually charged in pairs so that you had to charge two or four batteries at a time. So I had to do some cuts on the PCB. Then I also had to jumper the AA and AAA positives together for each slot.
Caution: The wire I used is 22AWG. 22AWG is rated for 7 Amps (7000mA) so will handle the currents for 3000mA discharge rate. Since I will have up to four batteries at a time, I have two ground wires. Make sure your wiring can handle the current.
I cut up the housing and labeled the battery slots. (see pictures)