Solar Battery Charger

Question

I would like to preface this post by saying I have no idea what I'm doing.

So here's what I have going on.

I bought a bunch of solar garden lights at my dollar store. Each light comes with a solar panel and a rechargeable AAA battery.

I've connected all of the batteries up in series, and I've connected up the solar panels in some horrible series/parallel hybrid.

My goal with this is to hook up the batteries to the solar panels, and connect all of that to the interior of a car USB charger to use it to make a solar panel phone charger.

However, I'm not very familiar or comfortable with electricity. So how would I go about connecting the solar panels to the batteries, and eventually to the usb power? Any help is very much appreciated.

tallen121 · Accepted Answer

I suppose I've done it. So for recap: 1. I've wired the solar panels in series into a car charger circuit. 2. I've plugged the car charger into a battery bank. Now it works and the battery bank should disconnect the battery when it's fully charged. The only issues currently are the fact that the solar panels are not providing enough charge to actually power the battery in a reasonable amount of time. I will update my design by doubling the amount of solar panels or at least keep adding them until I can actually charge the battery in less than 3 years.

DAB · Answer

Hi Tallen,

Thanks for the heads up on your skill base.

Hooking the batteries directly to the solar cells is very bad!

Depending upon the battery you use, each is sensitive to the rate at which they charge. Some batteries easily overheat and burst into flames.

You are going to need a charging circuit. I suggest you buy one off the shelf so you match the charger to the batteries you intend to use.

With the charger, you can then select the configuration of solar cells to get the proper input voltage.

You also then have a standard configuration for connecting the batteries, either parallel or serial, depending upon the controller.

The controller will then properly sequence the power to the batteries so that they are carefully brought up to full charge without overstressing any of the components.

While simple in concept, using solar cells and batteries needs to be done carefully.

Be aware, you can end up with a fire hazard, so use the right tools for the job.

DAB

unlimitedpipes · Answer

I think you might have trouble with the voltage you have created. I might be wrong of course. Batteries when connected in series add voltages together. A 1.5 volt battery + 1.5 volt battery = 3 volts +1.5 volt battery = 4.5 volts + 1.5 volts = 6 volts ,enough for an Arduino that has a voltage regulator set at 5 volts for USB output which is good for cell phones I believe. The same applies to the solar cells but they are not voltage regulated. OK now the current supply, if you connect 2 solar panels that you have in series and attach the out put to 2 series batteries they will charge the batteries in ( at regular set period of time maybe 3 hours ) if you connect in series 2 more solar panels and attach them across the 2 series batteries already connected to the 2 solar panels the voltage output will remain the same but there will be 2 times the current available to charge the batteries with which might cut in half the charge time if the batteries will accept the additional charge current. You have mentioned a car USB charger but I did not see it in the photo. So I left out any explanation of that circuit. Hope this helps. Cheers Dale

tallen121 · Answer

All of my garden lights came with this little twiddly thing. Can I do something with this? I just figured it was a NOT gate to make sure the light turns on when the solar panel isn't producing.

unlimitedpipes · Answer

Does the twiddly thing have a part number on it? ou can type the number in to a search engine on the internet to find out what it is. If it is a voltage regulator it will have Plus an Minus input from the solar cells and a plus output to the battery.

Cheers Dale

Solar Battery Charger

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