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batteries in parallel

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treez

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is it ok to put NiMH batteries in parallel?

eg four pieces of annsmann 2400mah in parallel?

http://www.google.co.uk/products/ca...a=X&ei=qamtUIbYOaaa1AXg4YHQAg&ved=0CEwQ8wIwAA

....wont one of them end up supplying all the current and burn out?

if batteries are put in series parallel, then is it best to put them in a matrix, or just separate parallel branches....eg 8 batteries consisting of 4 paralel branchs of 2 in series.
 

T3STY

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First of all: what do you need batteries in parallel for? Maybe what you want is not what you mean...

Anyway, short answer: putting batteries in parallel is ok as long as they are the same type and have the same charge, otherwise, the most powerful battery will overload the others. Forget it if you're thinking at using this trick for charging multiple batteries all-in-one, usually you end up with a kaboom or other kind of disaster - use a proper battery charger instead.
 
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Tahmid

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In your application, is it not possible to use some sort of a DC-DC converter and the batteries in series so that, effectively you get the same energy capacity? Or, why not get batteries with higher capacity? I think that would be better.
 
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tpetar

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Its not so smart to put batteries in parallel connection. NiMh due to aging with time will show problems, caused by cells difference in capabilities and performances.

Better connect cells in serial connection, there will be less problems. And if possible use higher capacity AA have, what I know up to 3500mAh capacity, C can have up to 4000-5000mAh.
 
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tpetar

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You can use LiPo batteries for mobile phones, several in serie. they are not expensive and can have good capacity on small space.

Also check Li-Ion batteries in AA case :

http://www.batteryjunction.com/14500-category.html




Dont forget that Lithium based rechargable batteries have around 3,6V per cell, and NiMh have nominal 1,2V (Full 1,25V).
 
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NiMH cells can be used in parallel if they are selected for same capacity, wear and state of charge. Same for Li-Ion. Best results are with new ones from same brand/batch/manufacture date. That is what laptops have, paralleled cells in series.
 
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Better connect cells in serial connection, there will be less problems.
Connecting in series gives a voltage equal to the sum of voltages - it's not really the same as putting batteries in parallel where the (nominal) voltage remains the same. If he needs to say 3V he may not put more than 2 x 1.5V batteries in series, but may put as many series of 2 batteries in parallel as he wants which will give him more mAh at the same voltage.
Anyway, you're right about the problems, it's something impossible to avoid at long time.
 
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tpetar

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NiMH cells can be used in parallel if they are selected for same capacity, wear and state of charge. Same for Li-Ion. Best results are with new ones from same brand/batch/manufacture date. That is what laptops have, paralleled cells in series.
Laptop have serial connections of battery cells! Maybe some have and parallel connection but I didnt see and hear for that. World is big, everything is possible.

- - - Updated - - -

Connecting in series gives a voltage equal to the sum of voltages - it's not really the same as putting batteries in parallel where the (nominal) voltage remains the same. If he needs to say 3V he may not put more than 2 x 1.5V batteries in series, but may put as many series of 2 batteries in parallel as he wants which will give him more mAh at the same voltage.
Anyway, you're right about the problems, it's something impossible to avoid at long time.
Usually batteries are linked in serie connections, there is smaller number of problems. If you use parallel connection more problems will come up. Voltage and capacity is obviouse in serial and parallel connections, there is no need to comment anything about that. If he need higher capacity, he should choose bigger capacity of cells.
 
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For increasing capacity, it is always better to get a single battery with higher rating. If that is not possible, then, it is better to use batteries in series. You may use quite a few in series and then use a high efficiency DC-DC converter to bring it down to the level you need. eg. If you have 1.5V 1Ah batteries (for example), connecting 4 of these in parallel gives you 1.5V 4Ah battery. However you run across the problems mentioned above. Instead if you connect these 4 in series, you get 6V 1.5Ah battery. You can use a DC-DC converter to bring it down to 1.5V. Capacity of both combinations will be the same ideally. In practice, the series combination will have a slightly lower capacity due to loss in the DC-DC converter. However, this tradeoff might be worth it (keeping the added cost in mind), as you avoid many of the problems of parallel combination.

Hope this helps.
Tahmid.
 
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