In a grid-down situation, batteries will likely be nearly price their weight in gold. So a lot of our gadgets and bits of high-speed gear depend on batteries to do their work for us.
As everyone knows, there won’t be a supply of disposable batteries post-SHTF, so many people will change to rechargeable batteries. The issue is, how do you cost these batteries with out the grid?
It’s true that we will use our mills or renewable power techniques to run the battery chargers, however we must also be ready to have the ability to cost our batteries independently of those techniques.
The excellent news is that you would be able to construct a small DIY photo voltaic battery charger with available supplies to trickle cost your AA or AAA batteries.
Particular Issues
Earlier than I get into the constructing of this DIY photo voltaic battery charger, a couple of issues have to be thought-about.
- This charger will solely be used for nickel steel hydride (NiMH) batteries, not lithium-ion or LiFePO4. If you wish to construct a circuit for lithium batteries, you’ll want to incorporate a battery safety circuit.
- This isn’t a speedy charger.
- Solely use rechargeable batteries for this charger. By no means put alkaline batteries into it.
Understanding How We Want To Cost The Batteries
On the facet of the rechargeable batteries, there ought to be a capability ranking in milliamp hours (mAh). That is the variety of milliamps that the battery can produce for one hour earlier than turning into depleted.
Realizing this quantity is crucial as a result of, with a circuit like this, we must always not apply greater than 10% of the battery’s rated capability. If you wish to construct a speedy photo voltaic battery charger, many extra parts will likely be required.
The subsequent essential factor to notice is what number of milliamp hours the photo voltaic panel will put out underneath full solar. The utmost capability shouldn’t exceed 10% of the battery’s capability. For batteries of 1300 mAh, you’ll wish to discover a photo voltaic panel with an output of round 130 mAh.
The panel’s voltage must be a couple of volts larger than that of the batteries you are attempting to cost. That is to make sure sufficient voltage is on the market to prime up the batteries totally.
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The design that will likely be proven right here makes use of two AA battery holders that every holds 2 batteries. These holders join the batteries in sequence, which means the capability stays the identical, however the voltage will double.
On this case, every holder has a capability of 1300 mAh and a voltage of round 2.6 volts when totally charged.
I related the 2 battery holders in parallel, which implies that the capability is 2600 mAh and about 5.2 volts between them.
The photo voltaic panel I used was rated 250mAh and 6 volts which ought to work nicely for this charger. Ideally, I would really like the panel’s voltage to be a bit larger, however this was all I had out there on the time.
I may have solely put in a battery holder for 2 AAs, however I felt the charger can be extra helpful if it may cost 4 batteries.
Constructing The DIY Photo voltaic Battery Charger
The development of this charger took lower than half an hour, and all of the parts had been simply discovered on Amazon. The one particular abilities that you will want are primary soldering abilities.
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For tools, you’ll need a soldering iron with solder, wire strippers, a multimeter, and a sizzling glue gun.
As for supplies, you’ll need a 5V photo voltaic panel, a blocking diode, AA battery holders, rechargeable AA batteries and a bit of wooden to mount the charger on. 
Directions
1. Connect the photo voltaic panel to the wooden utilizing the new glue gun. Run the wires across the edges of the board to the alternative facet. Safe in place.
2. Connect the battery holders to the alternative facet of the board that the photo voltaic panel is on. We’re doing this to maintain the batteries out of direct daylight. We don’t need the batteries to get too sizzling.
3. Solder the detrimental wire from the photo voltaic panel to the detrimental wires from the battery holder.
4. Solder a diode to every of the constructive leads from the battery holders. Orient the diode in order that the road on the diode faces the path of the battery holder.
5. Join the diode’s different finish to the photo voltaic panel’s constructive lead. I used a jumper to maintain the diodes separate from one another.
6. Glue the wires in place with sizzling glue.
7. Set up batteries and place the panel within the solar.
Why Is The Diode Necessary?
Photo voltaic charging circuits like this one have a diode on the constructive facet between the photo voltaic panel and the battery.
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This diode serves to offer a one-way avenue for present to circulate. We want this as a result of when there isn’t any solar shining, the panel will attempt to suck the electrical energy from the batteries.
The diode can be used to drop the voltage of the panels if wanted. Every diode will drop the voltage by a specific amount which you need to be capable of discover on the diode’s specification sheet.
Testing The Photo voltaic Battery Charger
I took 4 useless NiMH AA batteries and put in them within the charger. I positioned the charger in direct daylight for your entire day, often checking the batteries.
With the parts I used to be utilizing, it took about ten hours to get the voltage again as much as 1.3V.
This isn’t the quickest charger, however if you happen to had been caught in an SHTF scenario the place you had been scavenging for elements, that is the type of primary photo voltaic charger design you can cobble collectively. Whereas it’s not one of the best, it would do the job.
Though this isn’t a quick technique to cost your useless NiMH AA or AAA batteries, it’s a good factor to bear in mind for after SHTF.
All of the supplies for this may be simply scavenged or repurposed from different gadgets, and it’s easy to construct.
Nonetheless, suppose you wish to construct sooner and extra dependable photo voltaic battery chargers. This may be a wonderful place to begin earlier than you get into the extra difficult circuits.
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