In a grid-down scenario, batteries will be almost worth their weight in gold. So many of our devices and bits of high-speed gear rely on batteries to do their work for us.
As we all know, there will not be a source of disposable batteries post-SHTF, so many of us will switch to rechargeable batteries. The problem is, how do you charge these batteries without the grid?
It is true that we can use our generators or renewable energy systems to run the battery chargers, but we should also be prepared to be able to charge our batteries independently of these systems.
The good news is that you can build a small DIY solar battery charger with readily available materials to trickle charge your AA or AAA batteries.
Special Considerations
Before I get into the building of this DIY solar battery charger, a few things need to be considered.
- This charger will only be used for nickel metal hydride (NiMH) batteries, not lithium-ion or LiFePO4. If you want to build a circuit for lithium batteries, you’ll need to include a battery protection circuit.
- This is not a rapid charger.
- Only use rechargeable batteries for this charger. Never put alkaline batteries into it.
Understanding How We Need To Charge The Batteries
On the side of the rechargeable batteries, there should be a capacity rating in milliamp hours (mAh). This is the number of milliamps that the battery can produce for one hour before becoming depleted.
Knowing this number is essential because, with a circuit like this, we should not apply more than 10% of the battery’s rated capacity. If you want to build a rapid solar battery charger, many more components will be required.
The next important thing to note is how many milliamp hours the solar panel will put out under full sun. The maximum capacity should not exceed 10% of the battery’s capacity. For batteries of 1300 mAh, you’ll want to find a solar panel with an output of around 130 mAh.
The panel’s voltage needs to be a few volts higher than that of the batteries you are trying to charge. This is to ensure enough voltage is available to top up the batteries fully.
Related: Turn a Car Battery Into an Emergency Power Source For the Home
The design that will be shown here uses two AA battery holders that each holds 2 batteries. These holders connect the batteries in series, meaning the capacity stays the same, but the voltage will double.
In this case, each holder has a capacity of 1300 mAh and a voltage of around 2.6 volts when fully charged.
I connected the two battery holders in parallel, which means that the capacity is 2600 mAh and about 5.2 volts between them.
The solar panel I used was rated 250mAh and 6 volts which should work well for this charger. Ideally, I would like the panel’s voltage to be a bit higher, but this was all I had available at the time.
I could have only installed a battery holder for two AAs, but I felt the charger would be more useful if it could charge four batteries.
Building The DIY Solar Battery Charger
The construction of this charger took less than half an hour, and all the components were easily found on Amazon. The only special skills that you will need are basic soldering skills.
Related: 18th Century Skills That Will Become Life-Saving When SHTF
For equipment, you will need a soldering iron with solder, wire strippers, a multimeter, and a hot glue gun.
As for materials, you will need a 5V solar panel, a blocking diode, AA battery holders, rechargeable AA batteries and a piece of wood to mount the charger on. 
Instructions
1. Attach the solar panel to the wood using the hot glue gun. Run the wires around the edges of the board to the opposite side. Secure in place.
2. Attach the battery holders to the opposite side of the board that the solar panel is on. We are doing this to keep the batteries out of direct sunlight. We don’t want the batteries to get too hot.
3. Solder the negative wire from the solar panel to the negative wires from the battery holder.
4. Solder a diode to each of the positive leads from the battery holders. Orient the diode so that the line on the diode faces the direction of the battery holder.
5. Connect the diode’s other end to the solar panel’s positive lead. I used a jumper to keep the diodes separate from each other.
6. Glue the wires in place with hot glue.
7. Install batteries and place the panel in the sun.
Why Is The Diode Important?
Solar charging circuits like this one have a diode on the positive side between the solar panel and the battery.
⇒ World’s Smallest Battery Powers House For 2 Days
This diode serves to provide a one-way street for current to flow. We need this because when there is no sun shining, the panel will try to suck the electricity from the batteries.
The diode can also be used to drop the voltage of the panels if needed. Each diode will drop the voltage by a certain amount which you should be able to find on the diode’s specification sheet.
Testing The Solar Battery Charger
I took four dead NiMH AA batteries and installed them in the charger. I placed the charger in direct sunlight for the entire day, occasionally checking the batteries.
With the components I was using, it took about ten hours to get the voltage back up to 1.3V.
This is not the fastest charger, but if you were stuck in an SHTF situation where you were scavenging for parts, this is the kind of basic solar charger design you could cobble together. While it is not the best, it will do the job.
Although this is not a fast way to charge your dead NiMH AA or AAA batteries, it is a good thing to keep in mind for after SHTF.
All the materials for this can be easily scavenged or repurposed from other devices, and it is simple to build.
However, suppose you want to build faster and more reliable solar battery chargers. This can be an excellent place to start before you get into the more complicated circuits.
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this was a good article. i’m not handy doing projects but this was written with easy to follow directions. thankyou
Good info on DIY mini solar charging. Kinda funny how America is dependent mainly on China again. Sure there are smaller rechargeable manufactures in other countries.
The USA doesn’t really have rechargeable battery plants here anymore they are offshore. except possibly for govt security programs, not for the public yet.
American battery manufactures that are left do the alkaline type batteries. The one use type batteries.
America better get on the stick to produce civilian rechargeable batteries for us here.
Wishful dreaming that “Fry’s Electronic Stores” would come back. These stores sold new, older electronics and individual parts, items for DIYers.
The store footprint next time could be smaller in size, packed with goodies we need for projects.
Hey “Fry’s” come on back. “F” Amazon under cut many businesses with online marketing. People like the hands on physical shopping. We can see the item in-person to make sure it will work. Amazon, we are looking at pictures which sometimes is different from what is sent to us. As stated in customer’s comments.
To bad Fry’s & Radio Shack type store are gone an whatever is left is mainly online these days. There are some Mom & Pop stores left but miles away in locations.
Anyway keep these backyard home projects coming, thanks!
A friend went to Radio Shack right before they closed their chain.
They asked to see a RADIO.
The employee looked horrible confused and said they don’t sell radios. LOLOL
They were into the lame cell phone garbage…
You can use the little lights that you put around your house that you get at stores for a dollar or 2 wire them to gather hot to neg to get higher voltage,They make great little chargers.
@Robert. Thomas: Could you be a bit more specific? What “little lights” do yo mean?
I believe he is talking about the solar pathway lights like you put up to help you stay on the sidewalk getting from the house to the car. Those have small solar panels that output about 1.5v so hooking 8 of those in series would give you 12v. The amps output would be small but it would be enough to recharge the batteries that come in those lights. It would take a lot of them to charge something like a car battery but it could be done.
I used a “bouquet” of $1 path lights as night lights for my late husband who died of Alzheimers. It was cheap and dependable. They sat in a vase next to a window.
I bought 2 small solar battery chargers. Nothing to build and each charged 4 batteries at a time. One did 4 AAA batteries while the other did 4 AA batteries. I also have a battery charger made for AAA, AA, C, D, and tiny disk batteries. It’s 110v and I can use it on my camp solar generator or in my solar powered home.
For camping I have a small solar panel with multi connectors that charged my phone, 2 flashlights, and a camp lantern with a fan. Paid under $20. Last summer my son and grown grandson were camping with me. I bought a $34 solar panel that charged everything small plus the grandsons I Phone. I had my son put together a 100w solar panel, charge controller, a 100 amp hr 12v battery and an inverter. Pretty simple set up. At camp we had 2 long corded 12v lights over the table and at the little bathroom tent. In the big camp tent we had a string of 110v lights, an array of chargers with phones and 2 laptop computers plugged in charging.
My home is fully off grid. 12 older150w secondhand solar panels, a good charge controller, 8, 100 amp hr 12v batteries, reconditioned, wired to make a 48v system. Lights, 2ceiling fans, full-sized fridge, electronic ignition gas stove, small TV, LED lights, a washing machine, a microwave used occasionally, 2, 8″ fans, and my digital keyboard. Heat is a gravity fed pellet rocket stove with a heat activated fan on top. Half the year I heat water and cook there.
It’s all out there and not too expensive and not all Chinese either. Look at EBAY and Amazon. I have a lovely stack of 270w used Canadian made solar panels. Now I’m collecting simple bedframes to make frames to use the panels. My cheap wire fed welder will help put it together. It has short work times before it’s too hot. That works to weld a bit then let the batteries charge up. Then work a bit more. Just right for this 76 year old woman.
All the electrical supplies were on EBAY. The welder is Harbor Freight. I appreciate your inventiveness but I bought mine cheap. I’m on just a small fixed Social Security income.
I now have a small 12v blender, 2 12v herb and salad chopping machines, and more. Loose 110 power in the area and I still have everything in either 110v or 12v versions. I haven’t fired up any of my gas generators in several years.
Yes America could be doing better to make what we need. I’d buy all American made if I could. I still support local Mom and Pop shops ahead of conglomerates and Chinese made every chance I get.
I am switching (over time) to Re-chargeable flashlights, hand warmers, fire starters, lanterns etc. etc. I have a 12″ x 24″ solar panel with enough output for all (but not all at once). The point is to have redundancy and stay on top of the charging issues. I have camped for three days without having to change (tote) batteries or recharge anything. But I believe as the batteries age they will provide shorter duration and power out. Stay tuned.
Hmm, parts everyone has lying around their house to make a DIY battery charger? Unless you are a tinkerer like me then it is doubtful you would have any of these parts lying around let alone a soldering iron, solder, and a multimeter. Not a bad article on how to make your own simple battery charger. For most people purchasing a pocket size portable solar battery bank to charge their rechargeable batteries is a better choice. In a SHTF scenario Russia will have nuked our electrical grid which also takes out our small electronics. No phone, no lights, no motorcar, we will all be living on Gilligan’s Island. Skills are what is going to keep you alive. Hunting, fishing, orienteering, clothing production, fire starting, self defense, building or finding shelter, and food prep and storage are all necessary skills. If you are in a group, small or large, everyone learning all of those skills is imperative. There can be no compartmentalization. Bob may be good at hunting and fishing but what if Bob dies? Who will be able to fill his shoes? So it is imperative for each member of a group to learn everything. You can survive alone for a while but you can survive a lot longer in a group who knows what to do in every situation.
As posters have said, China more likely won’t nuke us, since they own a lot our American farmland here. Russia might try it. Believe China would pit Russia against the USA, then eliminate the victor in a weaken depleted state of armament.
The smaller one-nuke states would try rattling sabers. India and Pakistan probably nuke each other before taking on China. The CCP maybe the big winner in strategy.
There is more to a lone wolf, as history shows groups come and go they are not always stable. Groups breakdown too.
Anyways back to the gist of the original article, we need more of these practical DIY!
Thanks for sharing!
Excellant article
really appreciate
more on this type for those who dont know a lot about electronics and electrical
Do the research
dont expect everything hand fed or given with out effort
When nothing given , then nothing appreciated
you all tend to apprecite more when you are having to work for it
Some of the basics you will need :
small plyers , small screwdrivers , soldering irons , solder
Led , relays , silicone, electrical tape, or spray insulator
colored wire , small
Most of this can be salvaged from most household items and old cars
if in time of need , resource anything out there
appliances, diswashers , vehicles
Need to know : basic knowledge of soldering , electonics , electrical theory
Capacitors, Choke coils, Diodes ( ac or dc) , How they work , Filter s
easily found on the internet ( Now ) , later No Internet , copy priint , make binder s and file s
Time is NOW
I believe they DO make an alkaline battery recharger.
There are a couple of alkaline batt chargers, but alkaline batteries are normally one time use. That technology is not fool-proof, those batteries can explode while charging. Best get advice from someone into electronics. I do ask a local electronics tech for advice.
Have anyone seen or heard of existing electronic surplus parts dealers that cater to DIY, like “Fry’s” did? Please let the rest of us know too, those stores are a dying bred.
Keep in mind that NiCad batteries build up as “charge memory” after a while and will no longer accept a charge. It does take a lot of charges though for this to happen. Best practice is to run them the as dead as you can before placing them back on charge. If you seriously want keep these batteries in stock then get a bunch of them.
Have tried NiCad, Nim, some didn’t last more than 10X, others lasted for 100 charges.
It depends on the manufacturer, Japan, Malaysia, China, Viet Nam, Canada, Korea and so on.
Sometimes those smoke alarm extra alkaline batteries last a good long time. Depending on how our preps are done. The Alkaline batteries are a little cheaper to buy. The rechargeable type are expensive and we need to a have a charger for them.
Which this posted article helps spark interest in the recharge batteries and chargers.
Sometimes those gel-cell batteries may be substituted for more power in applications.
It’s good to have a mix or variety of batteries on hand.
When it comes down to it, eventually if the supply chains breakdown completely. It won’t matter. Manufacturing may become restricted to certain groups in charge.
A ‘small’ correction to the article re: the voltage/amperage for serial/parallel connections:
Putting two cells in SERIES doubles the VOLTAGE, the amperage [mAh] stays the same. As per the first example two 1.3V NiMh 1300mAh batteries in series would be 2.6V and 1300mAh.
Putting two cells in PARALLEL doubles the AMPERAGE while the voltage stays the same. So two 1.3V NiMh 1300mAh batteries in parallel would be 1.3V, 2600mAh.
So for this particular, two 1.3V, 1300mAh batteries in series = 2.6V, 1300mAH.
Two of those battery holders in series = 2.6V, 2600mAh [NOT 5.2V]
The setup will work, possibly better, since there’s a great difference between the charging voltage and the max battery voltage [2.6] . The closer to full charge it will continue to ‘push’ in the charging current. A 3-4V panel would still work but a little slower since the voltage difference is less than if using the 6V panel.
Nice idea, just a typo[?] on the parallel calculation. I do agree that most people would have little if any of these items just sitting around, let alone the tools, especially the VOM or a soldering iron and know how to use them. I’ve fixed a whole bunch of things in a few minutes or less with a soldering iron; it often takes longer for it to heat up than to make a couple solder connections. I’m forever grateful to my dad who never met too many things he couldn’t fix, and imparted that knowledge. Also glad I was no more than 20 minutes away for most of my life. Sadly, these days there is precious knowledge and skills being passed on. I see it all the time when people complain about how they ‘had to’ buy this or that item because of a bad power cord, blown fuse, lack of tools, etc.
Skills and tools will be essential in the days ahead of us. Keep learning and preparing. Blessings.
That should have read,Two of those battery holders in parallel = 2.6V, 2600mAh [NOT 5.2V]
I have lots of wire and electrical supplies thanks to a late husband who was an electrical contractor. My father taught me homework to solder when I was very young. I still have both ood style soldering irons and electric soldering irons. Also a pretty good supply of ectrical tape, then I learned to work with solar panels so I have the special tools and fittings. It’s been interesting learning and doing.
Great editorial!! Very informative; appreciate!!!
I have my ups/downs with off grid projects (. Cheap low profile ones) different sizes of cheap Chinese solar panels: the smaller ones gave 5 volts; have two larger ones, those gave 19.5 volts, average ( in cloudy weather too) but very low Amperage.
I put all the 3 5 volts panels parallel into a solar controller ( MPPT), charging a 12 Volts acid car battery; the 19.5-20 Volts ones, same in parallel, into an other MPPT controller, charging a larger truck ( acid) battery; there connected a AC/DC 750 watt Inverter with two 100 Volt sockets ( live in Japan) .
With the 5 volt set up I charge the mobile battery banks from the solar controller USB outlets.
With the 20 volt setup with Inverter is a preparation for power shortages.
But it’s a basic issue: the battery type:
Acid batteries no good for solar bank, only LIFEPO4 type very expensive batteries.
So in a sense I’m stuck with mediocre results.
After a time the acid type battery doesn’t charge more than 12.6-7 volt.
If detached from solar system and connected into a car; it won’t crank the engine…
Only if charged with a battery charger…
Driving the car with the charged battery it would resurrect, but returning to solar system it would become weak again.
The large truck battery cannot release too much energy at once; can’t even run the vacuum…
It may run a smaller fridge; water tank pumps, lights; small appliances only.
More than nothing but not enough.
Sorry for incorrect English
I’m using deep cycle batteries made for handicap scooters. I run my entire home on 8 100amp hr batteries. They are reconditioned used batteries. The first set lasted 4 years till vandalism ruined them. The current set up has been operating almost 5 years and is still going strong.
I watch EBay for specific batteries I like. They are good reconditioned batteries. 100 amp hr 12v deep cycle. Lately they have been around $169 each with free shipping. 4 years ago I was paying $149 for about the same batteries. I use 8 of them to run my home and 1 more for a portable solar generator I figured out and my son assembled it with some improvements for portability.
My next project is planned to power the well on my property. The 2nd well is set up to use with a manual winch setup. I could power a 12v 1500 lb winch with just a single battery. For daily living for two families, animals, and gardens I plan to power the submersible well pump. Running tap water is very nice. That will take a larger set of batteries and a good sized inverter. I have most of what I’ll need.
For a friend needing to vent a storage area on hot days I’ve purchased a single flexible 80w solar panel and an 8″ 12v fan that plugs into a USB port. The panel has dual USB ports built into it. No battery back up needed. I have screened vents. So he’ll use what he needs for intake and exiting air. If needed we have 2 12v fans from an older vehicle. Those could be wired directly to the panels 12v output. They will only run in daylight unless a battery is added.
Most used solar panels will produce 20 years or longer. So I’m not afraid to use panels that were only used 2 or 3 years. They are cheap and still work just fine. If an attack on our power happens I won’t be out a fortune and I’ve saved money while they are in operation. I also learned to be saving in power usage when I had less power available. I don’t use toaster ovens and such. Rarely use a microwave. Limit vacuums to daylight hours. Dry my wash on clothes lines. My choices.