Electronics

domiflichi · Joined: 11 Oct 2006 Posts: 5

Hi,

I followed the instructions at this site:

http://www.i-hacked.com/content/view/207/44/

to charge a few standard alkaline batteries. I had a 9 volt that I drained down to about 2.5 or 3 volts. Anyway, I tried charging it using a 15 Ohm 1/4Watt resistor as mentioned in the above article, and set my 1 Amp Switching Power Supply w/ Selectable Output to 12volts. I stopped the charging when it got to about 9.3 volts. The only weird things are that it charged in only about 3-5 hours. And it is slowly losing it's voltage: just overnight, it lost about .4 volts. So I tried charging a couple of AAs that were drained naturally (by normal usage) that had about a combined voltage of 1.75volts. I charged them to about 3.3 volts, which is great, but it only took a few hours also - the information in the above link said that it took him overnight. And as with the 9volt, they're slowly draining - I checked this morning, and now they're at about 3volts combined.

Am I doing something wrong? What's happening here?

thanks

neon · Joined: 25 Feb 2006 Posts: 580

THERE IS NOTHING WRONG Batteries do loose charge slowly no matter what. I don't know the reason for the diode except for polarity protection. that guy will constantly supply .083 amp as long as the input is greater the then the dropout voltage. it does not matter what the input is DC wise as long as not greater then max voltage i believe 35v. you can leave them batteries connected but increase the15 ohms to trickle charge the battery then it will be better. Battery hate heat get them hot and they will not last long.

domiflichi · Joined: 11 Oct 2006 Posts: 5

Thanks for the info.
But I do understand how batteries lose charge slowly no matter what, but isn't going from 3.3 combined voltage to 2.5 combined voltage in about 5 days a little too much drain? I tested them last night and that's where they're at now: 2.5 volts together.
Ok, so what about a 68 OHM resistor instead of the 15 OHM resistor? Is that a big enough change? Or too much difference?

Thanks.

neon · Joined: 25 Feb 2006 Posts: 580

batteries all battery loose charge. when is a battery fully charged is just like the mathematical quizz when do i get there mathematicaly never. how go half the distance stop then proceed half a distance stop and so on. mathematicaly speaking you never get the same for capacitors or battery.

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