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### Topic: Another battery charger question (Read 779 times)previous topic - next topic

#### dannable

##### Aug 18, 2012, 02:28 pm
Greetings!

I am contemplating building a charger for my NiMH batteries.

They require a constant current supply, and this in itself isn't a problem as I can use an LM317.

The problem I do have is this - if I want to charge more than one battery how do I go about it? For two would I need to double the current or the time? Do I connect them in serial or parallel?

David.
Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

#### jackrae

#1
##### Aug 18, 2012, 07:27 pmLast Edit: Aug 18, 2012, 07:29 pm by jackrae Reason: 1
You build or buy another charger.

You could put the batteries in series but you have no simple way of controlling the voltage developed across each bank.
You could put them in parallel but you have no simple way of controlling the current distribution between the banks.

You can simply double up on the constant current circuits using the same transformer/rectifier system.  You then have two independent charge circuits.

#### dannable

#2
##### Sep 22, 2012, 12:51 pm
Ok, not the answer I really wanted but I can cope with that!

So what sort of voltage would I charge the typical 1.2v AA battery at/with?
Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

#### mauried

#3
##### Sep 22, 2012, 01:08 pm
Nimh batteries usually get charged at C/10 till the voltage hits 1.4 V per cell.
C/10 means the batteries AH rating divided by 10 , a typical AA of 2000 maH
you would charge at 200 ma till it reaches 1.4 V .
A 5 V source would be fine .

#### dannable

#4
##### Sep 23, 2012, 05:41 pm
Thanks, I'll start playing around with these ideas.
Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

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