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Recharging non-rechargeable batteries

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the_chip_man:
I too read the article 20 years ago, after checking the the circuit worked, I realised that I needed to check the battery voltage periodically with a multimeter otherwise the battery would become overcharged I decided to take it to the next level.

So I built a pic controller to automatically sample each battery in turn using a simple op-amp as a comparator.
I was charging up to 10 batteries, 4off AAA, 4off AA and 2off PP3 so I used 2 op-amps one set to 1.5v the other set to 9v, both were adjustable.

Relay contacts switched each battery in turn from the charging circuit to the comparator circuit, then if the battery as reached the charge level then it would bring on a “green LED” indicating it was charged, It it was below the charge level then it would be switched back to the charging circuit.
I had 3 LED's for each battery

Red - Charging
Amber – Testing
Green – Done

At switch on all the 10 batteries are connected to the charge circuit then every 10 mins each battery is tested one after the other against a 1.5v or 9v op-amp (each is adjustable with a pot)
I've added a small bleeper so I get a bleep when anyone of the batteries is charged.
I also added a pic controlled 4 digit voltmeter so I can see the voltage of each battery as its being tested
This way I can leave all 10 batteries in the battery holders for a full day knowing that once they've reached the right level there safely switch off charge.
Yes I also agree batteries can only be recharged up to 10/20 times then thrown away, I've also found a good supply of still usable batteries from shops using a tub where people can deposes of there used batteries, sometimes the tub gets too full so people leave bags full of fresh batteries which I just pick up most of the batteries are slightly low AA/AAA read 1.3 volt and the PP3 read 7 volt.
Any which  read too low or don't show a increase in charge voltage after an hour I just bin.
If you have any questions just ask.

Dave

DavidA:
... I've also found a good supply of still usable batteries from shops using a tub where people can deposes of there used batteries, sometimes the tub gets too full so people leave bags full of fresh batteries which I just pick up most of the batteries are slightly low AA/AAA read 1.3 volt and the PP3 read 7 volt..


Love it !

At least I know that I'm not the only one here that does this.

(a few week ago I was up at the tip, And in the electronics bin were three cards of CR2016 and CR2025 Lithium cells. I'm set up for life .)

Muzzerboy:
Don't be tempted to recharge CRxxxx button cells. That could be very dangerous - there have been some spectacular explosions.

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