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Forum Battery charging calculations. help.
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Battery charging calculations. help.

supper_slash
supper_slash over 9 years ago
My thinking.

I am making a battery supply for a device so that it will be portable.  While plugged in I am going trickle charge the batteries.

 

Here are the thinking problems.

 

 

let us say I have 1 battery, and it has 1.5v, and 1000mah (just for easy calculations).

To charge it, I will charge it at 1/10th the power rating.  So, a discharged bat will be at 0.5v.

the difference is 1 volt, so the math will go like this.

 

1v/100=10ohm resistor.

 

For safe current limiting, I would have a 10-ohm resistor in the place.

I have done this before and it works (This is very simplified as there are diodes etc. in the circuit in order to make the system work).

 

 

Now comes the problem. if I have 4 batteries in series to increase the voltage, will the "mah" be the same 1000mah, or will it now be 4000mah?

 

And the same thing if the same 4 batteries are in parallel. what will the calculations be then?

image

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  • michaelwylie
    0 michaelwylie over 9 years ago

    I don't want to sound rude or blunt here, but my main concern is your safety. It worries me that you are building battery chargers, but that you can't answer this question on your own. Please be really careful, batteries hold a lot of energy. If you are sure that your method is safe, series batteries will all see the 1000 mAh to charge. Parallel batteries in the configuration you have drawn above will not be limited by the resistor. That resistor does nothing wrt charging.

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  • michaelwylie
    0 michaelwylie over 9 years ago

    I don't want to sound rude or blunt here, but my main concern is your safety. It worries me that you are building battery chargers, but that you can't answer this question on your own. Please be really careful, batteries hold a lot of energy. If you are sure that your method is safe, series batteries will all see the 1000 mAh to charge. Parallel batteries in the configuration you have drawn above will not be limited by the resistor. That resistor does nothing wrt charging.

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