How to make a simple solar battery charger

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So i asked in a previous thread if people would be interested in knowing how to make things like this, so here it is. This charger specifically is bare minimum tools and materials and leaves room for improvement, which i will be doing later. I took a few pics and the instructions are written assuming you are smart. Asking questions doesnt make you dumb though.

This will start you off with a charger that will charge 2 AA batteries, the same thing can be done with 3 AAA with only needing to change the battery holder. this will cost you about $40 counting all of the tools needed. if you dont have any interest in doing more electrical work, it would be better for you to just buy a small solar charger. shop around if you dont have the tools already, you could quickly spend way more than you should on a solder iron, pliers and wire cutters.

First you will need to gather your tools and components.
Tools
-Precision pliers and wire cutters (just about any pliers and wire cutters will do but the smaller they are, the easier it will be.)
-solder iron
-scribe (not necessary but it is great for holding hot wires down)
-a hot glue gun will be a great tool here, using air curing glue or epoxy would be fine as long as it is acid free.
Components
1x 1N914 type Diode
1x 0.5W/4.5v solar panel
electrical tape
prototype board (Proto Board will be what you see on the package, it will help but isnt necessary at this point)
enclosure/container of your choice (this can be an electrical enclosure, altoids tin, mason jar, card box... doesnt really matter a whole lot.)
battery holer (x2 AA or x3 AAA holder)
solder
tip tinner will help
solder wick
at this point the battery holder and solar panel have enough wire to get the job done.

heres a pic with the things i used. yes i have a ton of diodes but i use these on other things too.
2013-02-13140324.jpg

to start off on preparing your enclosure, use some hot glue to bind the solar panel to the enclosure. cut a hole in the enclosure and feed the wire leads through the hole. on mine the leads come through the middle of the bottom side of the tin, others may be different depending on what your panel looks like.
2013-02-13140405.jpg

next connect the cathode (the end with the black stripe) of the Diode to the + (red wire) of your battery holder. this step will ensure that in the dark the solar panel will not draw power from the batteries. to get a good hold, grasp the lead with your precision pliers then use your finger to bend the lead in a loop. do not twist the pliers to bend the lead, all you will do is tear the lead out of the diode. feed the tip of the wire through the loop you just made, then solder it together.
2013-02-13140804.jpg

At this point if you plan on using shrink tube to cover you solder points, now is the time to feed them on bother wires, then connect the anode (the end without the black stripe) end of the Diode to the solar panel and connect the black wires.
2013-02-13141847.jpg

Now the simple circuit is done and this will work very well for charging a couple of batteries. all you have to do now is stuff the parts inside of you enclosure and add batteries. my pic shows a lot of extra wires but next week i will be adding a USB port for charging my phone or any other USB charging device. well as soon as i can find a port that doesnt cost $10. keep in mind, it is okay to scavenge parts and material from other electronics. which is likely where i will be getting that USB port.
2013-02-13142235.jpg
 
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Very cool!

Can you please provide us with some specs How long does it take to fully charge your batterys in direct sunlight? How many watts do those small solar panels putt out? EDIT: ok just seen they are .5 watts so really just alike the charger for you cell phone or those batterys! Bada$$ I was worried bout that.

Also most important Where do you get the diodes? I have another project (using a printer track motor to make a small hand crank generator) but need a good place to get quality electrical components at a cheap price.

Thanks for the info! Any thoughts on making a larger one maybe using a powerwheels battery something that will last awhile to power lights for a camp and small radio.

ANOTHER NOTE you mention using either a 2 AA holder or a 3 AAA holder. Keep in mind LARGER batterys last longer smaller batterys discharge much faster. So I would suggest using 2 AA and buying QUALITY Lithium Ion rechargeables so they dont develop a memory and you get the most out of them. WHEN YOU ACTUALLY NEED THIS YOU MAY NOT BE ABLE TO BUY IT AGAIN!!
 
Last edited:
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Also really important pertaining to the output of the panels, how does the output compare to the standard charger? Do you think overtime they will not ever charge fully and develop a "memory" as a result? Do you have a way to tell if they are fully charged? Or plans to implement a way to tell?

Thinking bout making something a tiny bit bigger like a ammo can with hand crank gen set and solar but thinking bout using a larger panel from the auto parts store. But would def like to make one of these to toss in my 72 hr kit!
 
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Very cool!

Can you please provide us with some specs How long does it take to fully charge your batterys in direct sunlight? How many watts do those small solar panels putt out? EDIT: ok just seen they are .5 watts so really just alike the charger for you cell phone or those batterys! Bada$$ I was worried bout that.

Also most important Where do you get the diodes? I have another project (using a printer track motor to make a small hand crank generator) but need a good place to get quality electrical components at a cheap price.

Thanks for the info! Any thoughts on making a larger one maybe using a powerwheels battery something that will last awhile to power lights for a camp and small radio.

ANOTHER NOTE you mention using either a 2 AA holder or a 3 AAA holder. Keep in mind LARGER batterys last longer smaller batterys discharge much faster. So I would suggest using 2 AA and buying QUALITY Lithium Ion rechargeables so they dont develop a memory and you get the most out of them. WHEN YOU ACTUALLY NEED THIS YOU MAY NOT BE ABLE TO BUY IT AGAIN!!
LiON batteries require special charging circuitry, otherwise they explode.

MAX1737 Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller - Overview

NiMH batteries are a lot less dangerous when it comes to charging and recharging as they don't use alkali metals. Usually when you overcharge it, it might leak or go bad. LION batteries explode very spectacularly.

Also NiMH batteries and chargers are compatible with NiCd batteries and have similar charging characteristics.
 
OP
Kevinkris
Messages
1,198
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440
Very cool!

Can you please provide us with some specs How long does it take to fully charge your batterys in direct sunlight? How many watts do those small solar panels putt out? EDIT: ok just seen they are .5 watts so really just alike the charger for you cell phone or those batterys! Bada$$ I was worried bout that.

Also most important Where do you get the diodes? I have another project (using a printer track motor to make a small hand crank generator) but need a good place to get quality electrical components at a cheap price.

Thanks for the info! Any thoughts on making a larger one maybe using a powerwheels battery something that will last awhile to power lights for a camp and small radio.

ANOTHER NOTE you mention using either a 2 AA holder or a 3 AAA holder. Keep in mind LARGER batterys last longer smaller batterys discharge much faster. So I would suggest using 2 AA and buying QUALITY Lithium Ion rechargeables so they dont develop a memory and you get the most out of them. WHEN YOU ACTUALLY NEED THIS YOU MAY NOT BE ABLE TO BUY IT AGAIN!!
unfortunately i cant give you a reliable time on how long it would take to fully charge a set of batteries, we are in the NW and the sun has chosen to only shine half the time. also this charge circuit will not charge larger batteries. to charge a battery, you have to meet a specific point of mA input to the battery. just like any charger, they will cause batteries to develop memory and break the battery down. no, i dont expect this to be any better or worse than any other charger for memory.

also the Diodes come from radioshack, they have shelves of electrical components. the only time it doesnt make sense to buy from them, would be if you needed a lot of components. at that point looking up a supply store would be better.
 
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Thats crazy! Wow good to know Def dont want no exploding batterys. Didnt realize they would explode.

Didnt know they needed a certain MA to properly charge I always thought the battery would just take any power they could get like a trickle charge for car battery. Def a great thread this would be perfect for a set of AAs tho and thats the batterys I use for most my flashlights.

LOL good thing AMP stepped in I seriously always thought LiOn was the best but def not for this!
 
OP
Kevinkris
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i plan on putting in a USB port soon. still looking for a cheap part though. one thing about electronics is the cost. it is incredibly cheap to do, unless you buy the first part you find. far too often you find the parts at 10x what they are worth. as soon as i find a USB port for less than $3 ill be sure to put it in and show how to do it.
 

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