My first project: Solar battery usb iphone charger, need direction please!

Re: My first project: Solar battery usb iphone charger, need direction please!

Baconite wrote: »

It was dead, so I took it apart, and accidentally broke the board because I didn't know there was a screw in the middle of the board and just snapped the board in half (stupid mistake on my part, I was excited to get something without having to buy extra parts). I measured the voltage using a multimeter, and it was measuring a little over 10V, but I do not know the amperage because I didn't have anything to hook it up to, and I really don't know how to measure amps...

You should purchase a digital multi-meter or two so you can make your own measurements. If you already have a DMM--Then you can use it to measure the output current from your solar panel (shorted circuit current or Isc).

There are lots of tutorials on the web--Such as this one that can teach you how to use your meter:

https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter

Note--Measuring current with a DMM is one of the more "dangerous" operations. If you do not understand/know what you are doing, it can be very easy to ruin your meter or even start a fire if using the Current Measurement function of your meter. Voltage readings are pretty safe (within the range of the meter) because almost no current is pulled from the circuit under test.

However, when measuring current, your meter looks like a "dead short" to whatever it is you are testing. It is easy to forget and have a meter set to test current and touch a power source/battery/etc. and draw enough current to toast your meter, cause sparks, and start melting wiring.

With a solar panel, you know that it has very limited current (probably much less than 1 amp in your case). And it is perfectly OK to put a current meter on the output of the solar panel and measure its short circuit current. Just put the panel in full noon-time sun (point panel at sun), and you will read its (roughly) maximum available current.

I also have a bunch of 18650 batteries (because I am a vaper).

You do have to be careful when recharging many types of Li Ion batteries. If they are improperly recharged, they can shut down or even catch fire (if these are the "unprotected" type cells).

My goal is to create a solar panel that charges the batteries, and at the same time, charge an iPhone 5S (5v @ 1.2A i think), and when the sun isn't hitting it, charge the phone from the batteries.

You may have difficulty just "charging" an Apple phone product--From what little I have read, they may require specific cabling/termination to accept charging current--You will have to do more research on that.

I didn't take apart the solar panel, because it seems to be ready to go since it has a small jack and is already weather-proofed. But do I need to?

Connecting to the jack should be fine. Nothing in the panel assembly you should need to get at.

From all the research I did, I think i need a few diodes (to prevent power going back into the solar panel, not sure if it already has one, and the other to prevent power going back into the battery from the phone?).

The phone should be fine--It should not power anything connected to the charging port.

I think I need a li-ion charge controller, because my 18650 batteries are li-ion... so would I need something like this:

https://www.adafruit.com/products/390

That charge controller has a maximum input of 6 volts--Will not work with your solar panel (most likely). Solar panels are actually a bit difficult to work with from an electronics point of view... Their voltage will run from zero to Voc (voltage open circuit).

And could I use more than one battery?

Would I need a buck converter since the solar panel outputs over 10V and the charge controller only accepts 6V?

This is where a detailed discussion of your requirements would come in... You can charge/use batteries in parallel/series or even series-parallel. Depends on your power needs (voltage, AH ratings, etc.).

the purpose of this project is to have a charging device while i'm biking, and I do get plenty of sun while i'm biking. It would go on my rear panier and I could probably make a container that would allow air to flow right through it for heat dissipation... It is not like plugging into a 3 volt Li Ion battery and getting 2.9-3.3 volts to work with.

The solar panel you have is some sort of "thin film" panel. They are inexpensive and will probably last 2-10 years in sun/weather. However, they are not terribly efficient. A mono or poly crystalline silicon solar panel will usually generate about 2x as much power from the same size panel (2x more efficient).

Also, solar panels are not terribly efficient in how much power they generate for their area... That panel you have may generate something around 2-5 watts. And an Iphone will take 5-8 watts of power when charging (for several hours).

If you are very interested in working with Li Ion batteries (and LED flash lights in general), this forum has lots of information and discussions you can use:

http://www.candlepowerforums.com/vb/forum.php

If this is your first electronics project... I probably would not make an Iphone charger. To do the charging system correctly with an arbitrary solar panel--You really need a switch mode type charge controller circuit--These are not usually a good first project for electronics (although, with the modern chips/kits/pre-built chargers out there--It certainly can be done as a first project). Also, if you mess up, you may toast your $600 Iphone.

I would try something else first--And look at solar charger products that are already out there for USB and such devices.

-Bill