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Simple charger for ONE 1.2v Ni-MH AAA battery?

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neazoi

neazoi

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Hi I have found this circuit http://iq-technologies.net/projects/power/037/index.html and I want to use it to charge a SINGLE AAA Ni-MH battery.

My first question is, is it suitable for a SINGLE AAA battery i.e. 1.2v or a pair of them in series? This link http://www.learningelectronics.net/circuits/switchless-nicd-nimh-battery-charger_20.html shows an identical circuit, with a pair of AAAs. So which of them is the correct one?

My second question is, will this automatically stop charging when the battery is full?
 

You should never charge batteries in series, unless they are exactly matched and exactly discharged, the voltage across them will be unbalanced and one may overcharge while the other undercharges.

I think they have used a 'double cell' symbol for the batteries when it really means just one, consider that AA and AAA are single cells but 6F22 has six in series! Other wise the two circuits are identical.

No, it has no cut-off, it is just a variation of a standard LM317 constant current generator with the extra parts being to allow more than one output.

Brian.
 

betwixt said:
You should never charge batteries in series, unless they are exactly matched and exactly discharged, the voltage across them will be unbalanced and one may overcharge while the other undercharges.

I think they have used a 'double cell' symbol for the batteries when it really means just one, consider that AA and AAA are single cells but 6F22 has six in series! Other wise the two circuits are identical.

No, it has no cut-off, it is just a variation of a standard LM317 constant current generator with the extra parts being to allow more than one output.

Brian.
Click to expand...

Is there any automatic cut-off simple charger for a single AAA Ni-MH? Simplest possible as the space is limited (active antenna).
 

Your best reference is here:


Unfortunately, there is no simple solution to getting best charge rate and 'full' detection which is why many products simply limit the charge rate to well below optimal and use nothing more than a series resistor. It is least cost but takes longer to charge the cell and may not give best charge or battery life.

Brian.
 
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    neazoi

    neazoi

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betwixt said:
Your best reference is here:


Unfortunately, there is no simple solution to getting best charge rate and 'full' detection which is why many products simply limit the charge rate to well below optimal and use nothing more than a series resistor. It is least cost but takes longer to charge the cell and may not give best charge or battery life.

Brian.
Click to expand...

Indeed, I have two commercial expensive handheld CBs and both use a dirty diode resistor charging circuit!
I ended up in one of the maxim ICs this is indeed the simplest automatic charging solution with many features.
 

"Cheap and simple" means poor performance.
You should use an IC designed to charge Ni-MH cells. The cheap simple circuit is missing most of the features of a proper battery charger.
 

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