Hello,

I have build a (parallel) system were 9 LEDs (3.2V 20mA) are powerd by 2 x 3.6V 2600 mAh lithium AA battery. I would like to use a solar cell to charge one of the batteries, while the other is powering the LEDs. Once one is depleted, the solar cell should change to charge the empty one. The system would be for indoors office/living room setting, so never in actual sunlight. Does anyone know what kind of solar cell i should use or need? And what the system would look like. Or is it simply not possible?
Im sorry if it is all a bit unclear, as i am a layman when it comes to electronics.

I hope someone can help me with this.

Thanks

 

There's no need to charge one cell and then the other , the way it's usually done is to just have one cell which is charged , and you can use it for the light , even when it's being charged ....

But your main issue is that indoor light just hasn't got the power ... it might seem bright in your office , but for generating electricity you only get a few % you would if the panel were outside ... if you had it very close to a window , perhaps 5% ...

Your leds would consume 9 x 3.2 x 0.020 = 0.7 W ... not much .. so a 30 W panel should do it (about 50 cm x 40 cm )

If you reduce the total power to the leds to 0.1W they will still look fairly bright , the panel can be much smaller

 

There's no need to charge one cell and then the other , the way it's usually done is to just have one cell which is charged , and you can use it for the light , even when it's being charged ....

But your main issue is that indoor light just hasn't got the power ... it might seem bright in your office , but for generating electricity you only get a few % you would if the panel were outside ... if you had it very close to a window , perhaps 5% ...

Your leds would consume 9 x 3.2 x 0.020 = 0.7 W ... not much .. so a 30 W panel should do it (about 50 cm x 40 cm )

If you reduce the total power to the leds to 0.1W they will still look fairly bright , the panel can be much smaller

Thank you for the fast reply!