what wattage solar cell do i need?

i want to be able to charge one aa enelope in 5 hours or less.

An Eneloop AA is generally estimated to have a little under 1 watt hour of storage. So, a fold-up 28-watt solar panel w/charge controller like the one I have from Bioenno Power would be about the minimum on a sunny day. If you can't guarantee it will be sunny, you'll need a bigger panel!

Oops --​ a AA is about 2.5 watt hours! So, make that a 60 or 70 watt panel, minimum!

cool ty i may even have one

raggie33 said:

cool ty i may even have one

Click to expand...

Wait! I was wrong! A AAA is about one watt hour. A AA is about two and a half! Sorry for the screw-up!

cool that makes more sence

Just be aware that in most situations, even on a sunny day you're probably lucky to get about half the rated output from a solar panel. And by the time you run the output through a controller to get a usable voltage, it's even less than that.

it really doesn`t scale down too well, I have 100W pannel on my workshop roof along with controler and all that, I can charge 4x eneloops in a couple of hours even on a cloudy day, but a 25W may not do One on the same cloudy day unless it had been wired specifically for that with a suitable controller.
Try and aim for 5v @2A that`s sustainable in a variety of light conditions and just use a regular charger then.

Or...

if you want a fixed setup you can use a smaller size and charge a USB powerbank, doesn`t matter if it takes days to do, and then use the powerbank to supply your eneloop charger. that`s probably the easiest way using off-the-shelf parts.

Although I don't have any solar charger I think the USB powerbank setup with solar panel is the ideal solution as you can charge batteries from it at the max a charger can manage off the powerbank and recharge it as the sun allows off the panel.

Katherine Alicia said:

if you want a fixed setup you can use a smaller size and charge a USB powerbank, doesn`t matter if it takes days to do, and then use the powerbank to supply your eneloop charger. that`s probably the easiest way using off-the-shelf parts.

Click to expand...

Yup. Or, use the solar panel to charge a SLA deep-cycle battery. Then, use a charger that accepts 12v input to charge your small cells like Eneloops. The SLA battery will store up 1000 Wh, enough to charge a couple of hundred Eneloops if there's no sun. Or your laptop, phone, etc.

WalkIntoTheLight said:

Yup. Or, use the solar panel to charge a SLA deep-cycle battery. Then, use a charger that accepts 12v input to charge your small cells like Eneloops. The SLA battery will store up 1000 Wh, enough to charge a couple of hundred Eneloops if there's no sun. Or your laptop, phone, etc.

Click to expand...

Yup, Mine`s got a 100A car batt hooked up, so I get all my lighting and radio and charging for free whenever I`m in there

I hook a small, light, Bioenno 9ah 12V LiFePO4 to my panel. Works very well and is pretty portable.

I have no affiliation other than as a customer.
I have not used this product personally.
https://www.clouddefensive.com/prod...-power-battery-pack-and-nitecore-ui2-charger/