Author Topic: Charging circuit for rechargeable batteries  (Read 580 times)

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Offline vipulan12Topic starter

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Charging circuit for rechargeable batteries
« on: February 28, 2013, 07:50:45 PM »
hey guys, I want to create a circuit where i can recharge my batteries from other DC batteries
what would i need to consider when creating it?
 i am going to need a diode,  but what else would i need?

Offline waltr

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Re: Charging circuit for rechargeable batteries
« Reply #1 on: February 28, 2013, 10:04:17 PM »
What type of battery chemistry??
This is the most important aspect since each type of chemistry requires a different 'charge profile'.

Next question is How many cells?
The from what battery do you want to charge from?

Offline jwatte

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Re: Charging circuit for rechargeable batteries
« Reply #2 on: March 01, 2013, 03:15:35 PM »
When charging batteries, from any source, it's important to be able to measure the voltage of the target battery, and control the current going into the battery (by lowering the voltage.)
You can then set up the right way (profile) to charge the battery based on how many cells, what cell type, etc.
The easiest way to do that these days is to build a switching DC/DC converter to get the voltage to where you want, use a current sensor on the output of the converter, and make the converter controllable from a microcontroller (typically by using a digital potentiometer or similar tied into the feedback voltage divider of the DC/DC converter circuit.)
You then program the microcontroller to provide the right voltage and current variations for the battery you are charging.

Offline vipulan12Topic starter

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Re: Charging circuit for rechargeable batteries
« Reply #3 on: March 01, 2013, 03:19:36 PM »
its a nickel metal hydride (NiMH)double AA battery from energizer(1.2v and 200mAh)
i want to be able to recharge two of them

Offline waltr

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Re: Charging circuit for rechargeable batteries
« Reply #4 on: March 01, 2013, 07:06:08 PM »
Two is series? s 2.4V.
Search for "NiMH battery charging circuit".
Also, look up the data sheet for these batteries (or look at Panasonic's NiMH battery data sheet, they also have some good App Notes on battery charging) for the proper changing methods. Pay attention to the Charging rates in the data sheets and do not exceed the maximum rates (if it says 0.3C max charging rate, where C = capacity in A-Hr , the rate is 0.2 * 0.2A-Hr = 0.04 Amps max). So the circuit must limit the max current to this value.

 


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