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Can I replace a 3V watch type battery with two 1.5V AA batteries? Answered

I'm building an edge lit card like the one in the link, but in a frame. http://www.evilmadscientist.com/article.php/edgelitcards I have an LED that came with one of those LED "candles" but it's powered by a 3V watch battery. I want to use the LED and noise circuit, which makes the LED flicker, from the candle and attach it to a solar panel I got from an LED garden light and 2 AA batteries. Can I just hook it up to the LED or do I need a resistor? Shoud I hook it up in series or parallel? How should I hook up the solar panel to charge the batteries? It's similar to a sun jar principal. Thanks.



Best Answer 9 years ago

As others have said, yes you can power the LED from 2 1.5V batteries in series. You don't need a resistor if it is being driven by a noise circuit designed to be run on 3v. As far as the solar panel, you need to make sure the batteries are rechargeable and that the solar array puts out 4-5 volts. Solar calls typically put out so little current that a charge controller is not necessary, but you will want a diode to prevent reverse flow from the battery to the solar panel. This will have an associated voltage drop (commonly about 1v) and so the voltage of the solar array should be more like 4.2v to properly charge the batteries. (batteries are typically charged at a voltage slightly higher than the nominal voltage + the voltage drop from the diode). If the voltage from the solar array is too high, you can drop it with several diodes in series or a zener diode of the correct voltage. If it is too low you will need another cell or two to up the voltage.

Yep, make sure it's in series.

you can use 2 AA battereis but u need really thin wire like from motor coils which are insulated.just wire that to the watch and battery.

Yes, if the two 1.5v batts are hooked in series (plus to minus) and physically fit in the battery case.