Recycled Solar USB Charger Build 2





Introduction: Recycled Solar USB Charger Build 2

Howdy y'all I wrote a quick little instructable a while back about how I took some salvage stuff and made a Solar phone charger. I would like to introduce you all to "Recycled Solar Charged USB Charger 2 The Second Build".

The only thing that was reused was the panel from the first build.

The Sealed Lead Acid battery from the first instructable just didn't have enough capacity to charge my Galaxy Note 3. and the constant deep discharging of the SLA killed it beyond revival after a relatively short time. So Sacrificial blackberries are fine using the old design the new phone needs something with a bit more umph.

So lets get started in documenting how I came up with this one.

List of Materials:
1x Solar Panel 12v, greater than or equal to 1.5W (picked up used / recycled from other builds)
1-4x 18650 cells (Recycled from laptop batteries)
1x 12v Micro USB car charge cable
1x Small box ( I used a washed and dried baby food tub)

1x USB 18650 Holder I used this one but there are plenty to choose from I picked this one as it was cheap and already had the charge circut and 5v USB transformers in it with some form of protection as I am using unprotected cells.

Soldering Iron / solder
Desoldering Braid
Third Hands
Screwdrivers: Flat and phillips
Wire Cutter/stripper
electrical tape.

Step 1: Step Acquire Something to Store the Life Giving Energy of the SUN!

I cant believe that I spent almost 20 years in IT and never took apart a laptop battery before.

Well after poking around on instructables I saw that people were getting lots of Li-Ion Cells from laptop batteries. HOW COULD I HAVE OVERLOOKED THIS SOURCE OF POWA!!! I have used LiPo batteries for R/C Aircraft so piece of cake I already had chargers to tinker with Li Ion cells I just needed to get some. Time to root though the parts bins.

I found 2 batteries in laptops that were being stripped for parts and tested them in known good laptops. They came up as failed so time to get cracking... The HP battery yielded 4 Sony 2400mAh 18650 cells and the Lenovo pack provided 8 Panasonic 2900mAh batteries. Needless to say I am going to button this all up with the panasonics however the Sony cells are shown in some pictures as I was testing to ensure that the charger charged.

I am not going to go through the particulars of stripping a laptop battery as there are plenty of good instructables on that all over here. I just started at a corner and kept prying with a screwdriver and case separation tool.

After I had my batteries apart I checked each one over for damage and a minimum charge under 3.0v. I picked 3.0 volt as that is the lowest a LiPo battery should ever be discharged if the charge protection circuitry worked in the pack properly they should have never hit below that. The "Good" cells all were over 3.5V with 2 from the HP pack that were below 2V, and one Panasonic that i sort of ruptured the case on separating it. It went into a bucket of Sand I keep around incase of fire/disposing of something hot and was carried outside.

And now on to assembling the USB pack holder thingy.

Step 2: We Dont Need No Documentation...

Seriously there is none. I assume that is why my holder was so cheap. One holder and a small Micro USB cable.

Well lets open it up and put in the batteries. The positive end I assuming is side toward the circuitry as that is the end with the red wire. The black wire goes to the bottom side. This battery pack uses a 18650 batteries in parallel and one can install any number between 1 through 4. You will need to add batteries of the same capacity and type as if you don't the cells could fail prematurely (best case) or explode and burn your house down (worst case)

Hey but I am using batteries from the same laptop pack so they are already matched up. To get the specifics on each battery I googled the numbers on the sides of the cells. With 4 of the Panasonic cells in a 1 Serial 4 Parallel, The USB bank will hold a combined 11,600mAh of current at between 3.7-4.2V That is twice what the old SLA setup provided at a substantial weight savings.

I put the 4 smaller capacity batteries into the holder and plugged it into a stand alone phone charger with a 1A output just to see if the charge block worked.

If you use the same battery holder I did, here is the documentation that is not included. There is a button surrounded by a half moon of blue LED's they will illuminate in sequence while it is charging. If not charging they will be blank. To turn on the USB outputs press the button momentarily one time and release you will see the LED's illuminate indicating the state of charge then they will go out to a single LED that indicates that the USB outputs are on. I thought mine was broke until i plugged in the sacrificial blackberry and started pressing the button and flipping the switch. Pressing and holding the button until this light turns off turns off the unit.

Pressing the button twice (double click) turns on a white LED flashlight. I am not sure the switch actually does anything. But it is listed that the output protection is adjustable from 1/1.5/2amp So I assume that to be the case but I have no way to test it. I set it in the middle as 1.5 would be a 1/2 C discharge rate. With Li-Ion batteries you don't want to pull more then a 1C rate. To find the charge rate it is pretty easy you dont want to pull or put in more then the batteries capacity in one hour. For example the 2400mAh batteries would have a 1C rate of 2.4 Amps The 2900 mAh the 1C rate is 2.9A

Step 3: Now the Fun Part, Charge It Up.

I popped apart a 12v car micro USB Charge Cable to get a idea of the stepdown converter involved and had an Idea. My theory was that the conditioner was set to provide a fixed 5V DC output from a Noisy fluctuating 12 vehicle electrical system.

The cars electrical system can fluctuate anywhere between 10-15Vdc. My guess was that the input needed to be any voltage over 5V. Hello Mr 9v Battery we are going to use you for a minute to test a theory. Using some clip leads from my bag of tricks I hooked the 9V to the proper poles of the car cable while it was plugged into the USB battery. Hey the LED's are indicating that it is charging and my 9v is only showing 7v This might actually work.

Step 4: Its the Final Countdown....

Ok we know that the 12v car cable will charge the USB battery with a relatively low powered 9v battery so my relatively weak solar panel is a go.

I cut the 12v automotive socket off the solar panel cord (saving for later of course) and stripped about 1/4 inch of insulation from the solar panels wire. Check your polarity of the lead coming from the solar panel one last time for good measure. Cover the panel or disconnect your wire to stop it from producing electricity.

Then I de-soldered the 2 pieces of wire from the 12v Car USB cable's voltage regulator board. Using a bit of desoldering braid to clean up the holes so that I can solder the solar panel wire in their place.

Positive and negative are indicated on the component side of the board. VCC= positive on the right GND= Negative on the left. Insert the ends in the corresponding hole fold them over insert the board in your third hands and secure the wire with bit of solder. Trimming the excess after the solder cools and you test the joint with a slight tug.

The case to protect the voltage regulator is pretty crude I just used a washed and dried baby food tub until i can find something better. But as you can see from the picture in the first step it works I just don't have a clip on ammeter so I have absolutely no clue how much charge current is running through this setup on the 5v USB side. But it seems to charge however it will probably take 30 hours of direct sunlight to charge the battery from a completely depleted state If current is not boosted when the voltage is reduced to 5v. So lets just say that it puts out a minimum of 100mAh charge current. Yes this is a slow method to charge a battery but it gives me another opportunity to charge my phone or USB devices while camping or in an emergency.

Until next time,



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Thank you, The solar panel is currently on the dashboard of my car and will charge my battery pack whilst I work. The little baby food tub and the battery fit perfectly in the unused cubby under my radio.

Unfortunately the quality of the solar panel is not weatherproof but who knows perhaps in build 3 it will be all weather capable.