# Charging AA Battery with DC Generator

I am trying to recharge AA Battery (rechargeable, 1.2v, 1000mah) with DC Generator which outputs around 3v to 5v.

The input for DC Generator is from another 1.5v rechargeable battery with a step up voltage booster.

(Though I am not sure how much amps output i am getting from DC Generator,and I don't know how to calculate it.)

After some googling I come to know I need to use voltage regulator to give some constant voltage to battery for recharge from DC Generator.

How much voltage I need to give to battery for recharge and do I need to consider the amps?

Also is that possible to get load and recharge the same battery simultaneously?

I am just learning electronics myself. Some simple words to explain this without much formulas will help me to understand much quickly.

Thanks!

• The Law of Thermodynamics won't allow the same battery to recharge itself... Commented Jan 16, 2016 at 15:42
• A battery is at least two cells, so what you want to do is charge a cell, not a battery. You'll need a voltage higher than 1.2 volts to charge the cell, and you'll need to limit the current into the cell being charged in order to charge it safely. You can find out the charge requirements by going to the manufacturer's website and reviewing their technical literature. You could also go to battery university, an excellent site for learning about batteries and cells. Commented Jan 16, 2016 at 15:58
• A quick note, I'm relatively certain that the easiest way to calculate your output current would be to simply use ohm's law. However, the complication is that it may be difficult to get the instantaneous voltage out of your generator. As for the rest of your question, a constant voltage charger should work at a slightly higher voltage than your battery (cell). In addition, step converters don't work simply by magically making the voltage higher, i.e. you're losing something... in this case probably current. This being the case you're going to drain that other battery extremely quickly. Commented Jul 6, 2016 at 15:27

A battery is at least two cells, so what you want to do is charge a cell, not a battery. You'll need a voltage higher than 1.2 volts to charge the cell, and you'll need to limit the current into the cell being charged in order to charge it safely. You can find out the charge requirements by going to the manufacturer's website and reviewing their technical literature. You could also go to battery university, an excellent site for learning about batteries and cells.

Charging battery:

volts: Need more than 1.2V(as your DC generator is giving 3-5 volts it would be good).

amps: 100 mA would be nice.(can use upto 500 mA it will charge faster but it will heat-up your battery also reduce the life of battery).

Also is that possible to get load and recharge the same battery simultaneously?

Yes, But it will be more energy consuming and costly.

Need to use voltage regulator L7803(it will prevent spike in voltage) and Diode to prevent back flow of current.

As DC generator is giving 3-5V. voltage regulator L7803 need at least 3.5V to give output of around 3V. This won't affect your battery charging but it will consume your volts and current.

To calculate volt/amps multimeter would be nice:

I am assuming that your battery is a Nicd because of the low Amp hour rating. The easiest way to charge it is with a constant current of around 100 mA for 12 hours. That is not the only way to charge it, just the easiest. If it is a NiMH battery, then you might need a more complicated charging system. You would not want to use a constant voltage to recharge this battery. @Aadarsh's answer is not very good.

All power conversion systems waste some power, so if you move charge back and forth between two batteries, eventually both batteries will be discharged. And one battery cannot be used to recharge itself.