How can I build a solar panel based battery charger?

Batteries and Chargers Chargers
1

I was thinking about building a standalone solar panel based Li-ion battery charger station, but I don’t know enough about electronics to do it. I would like to build it outside so that people can just bring their rechargeable flashlight batteries there to charge them.

So, I was wondering if I could take a couple of solar panels to charge, let’s say a motorcycle battery, or even a car battery for storing electricity.

Then from the car/motorcycle battery, I want to connect it to a Nitecore i4 v2 charger, or a Fenix ARE-C2 charger.

Sounds simple, right? But I don’t know what components to get and how to design the circuitry, if there are any.

First, I don’t know what volts or amps rated solar panel to get.

What I don’t understand is why the solar panel doesn’t burn up if you connect an auto / motorcycle battery to it. I’m thinking there must be a diode or some kind of circuit that allows the electricity to charge the battery, but prevents the battery from burning up the solar panels. Also, how does one prevent the solar panels from overcharging the battery?

Second, when I look at the Li-ion chargers, they have a 12VDC input so you can connect, for example a cigarette lighter adapter to it and charge your Li-ion batteries in your car. However, when I look at the electrical requirements, for example the Nitecore i4 v2 charger, it says it requires 12vdc @ 2amps. This is all fine and dandy, but what prevents the charger from getting more than 2 amps? Is there a circuit that controls the voltage and current?

Here is what I figured out so far.

The solar panels has to put out more than 12 vdc to charge the battery. A fully charged battery puts out about 12.7vdc. So to charge a car battery you can use up to 16 or 17 vdc. But how many amps does the solar panel have to put out? Rather than trying to figure this all out, I think I would rather buy a charge controller. What kind of charge controller would I need?

So then after that, how does one regulate the power to the electrical devices?

2

They sell solar chargers pre-assembled. How much are you looking to spend?

3

About $200 max for everything including battery

4

Just get a USB charger and a solar panel with a USB output - they’re all over amazon and you can choose which size panel you want.

Or can get something like this, crack it open and use it like a battery box.
http://www.amazon.com/iClover-5000mAh-External-Battery-MP4-Black/dp/B00CPU9CBG/

5

Done…open source…inexpensive

In fact you can even use those small variable voltage buck/boost, adjust out for 6vdc, any voltage can then be tuned to 6vdc and that charger will charge a Li Ion battery

load sharing, charge a battery in, get 5vdc output from the addon mintyboost module

Solar charger handbag and/or backpack

6

i just bought a 15watt Crystalline 12 volt solar panel onsale for 35 bucks that powers my I4 charger perfectly charging 2 18650’s in clear sunlight. ( and 2 of these panels should provide enough amps to charge 4 cells in the i4.

7

2A output?

8

in direct sunlight im getting 1.23 amps output. i conected it to the 12 volt input on the i4 and the charger powers up, and begins charging but only up to 2 cells at a time.
when i place a 3rd cell, the blue power light blinks dim and it appears to not charge. im picking up a second solar panel on the weekend to see if it can run it for full charging ability.

9

Thanks for all the info!

10

Or, get a cheapish solar charge controller, and a smallish 12vdc battery (think motorcycle battery), charge that battery, then use it to push 2A+ into the i4…and then maybe even a smallish 400watt DC->AC inverter

11

I already have one of these GelCell Power box units with a built in Inverter, 12volt outputs, ( and i already added USB charging ports, a multi-voltage charging converter, LED lights, DC outpout connectors, etc. ( maybe i can mount an I4 onto it permanently for charging cells when camping) and plan to use the Solar panels to charge it on camping trips.>> http://ecx.images-amazon.com/images/I/31CGCUCi34L.jpg

12

Cottonpickers has a thread on the other forum for solar panels et.al.

13

I just got this solar USB charger. It can charge AA/AAA with a USB charger or charge one of my USB battery packs, and that pack can charge anything else.

The thing I like about this model is that it’s super lightweight, which is why it cost a little more. It’s about half the size of the other 14-15W units.

14

Now that is neat! Pricey…but neat as hell!

15

Thanks. It’s perfect for the emergency bag. Next up I think will be a lightweight 4 x Panny 3400 USB battery pack. It should come it pretty close to that beast posted above except a fraction of the weight. Or maybe a 2x pack. Seems like a li-ion based solution is going to be lighter and more compact (and expensive) than a lead acid battery or something.

I’m currently doing a review on this panel. It looks pretty good from the quick test I did today, considering it was late afternoon, I’m in the northern latitudes and I didn’t try to hard to point it at the sun. It’s super light. So far I’m impressed.

Here it is charging the wife’s HTC One with the USB meter connected:

It fits nice on the back pack. I used a pair of Nite-tize twist-ties to hold it to the pack.

It has a nice zippered cubby for your device to live in while it’s being charged, though be careful not to overheat your device.

Results were pretty decent:

16

How flexible are the panels themselve, hard glass or a bit bendy as to not snap them

Technology advancing…nice!
http://www.solarstik.com/stikopedia/solar-stiktm-system-overview/choosing-power-generators/amorphous-vs-cigs

17

In one of the Amazon photos it shows someone trying to fold one of the panels to break it. Supposedly it’s very rugged. I won’t be trying to destroy mine as part of the review, so I’ll take their word for it. So far it looks and feels rugged. It even has rugged looking zippers in the charging pouch. I feel really confident adding this to my disaster bag. Right now I’m trying to decide if it replaces my WakaWaka charger or that now becomes a backup.

This is also a neat little device, though it’s a little underpowered. But still, a 2200 mAh solar USB charger/power pack that can fit in your pocket. And it does have a built in lantern which promises 2 hours of light for every hour of charge.