Easily Recharge Alkaline Batteries!

Did you know that you can recharge alkaline batteries? Well, they're not perfect (don't have very good recharge capacity, few recharge cycles, etc) but you can recharge them to an extent. Many people have developed fancy charging circuits, but I was able to get charge into some Alkaline batteries with just an old cellphone plug.

The adapter says 3.7V, 300mA. With that sort of current, you shouldn't leave the batteries connected very long at a time. The voltage on the batteries will go up quickly, but the actual amount of charge will not. Because of this, you have to disconnect the batteries frequently to let them "cool down" (though they usually don't even get warm, the voltage will quickly drop down to around 1.5 V after disconnecting). After they have leveled off (usually around 1.5V) put it back on the adapter for another minute or so. Repeat this a bunch of times to get the charge up. I've just started experimenting, but I was able to get enough charge in two completely dead batteries to start up my power-hungry Canon digital camera and take a few pictures (with screen and flash) and turn it off without it dying on me (died the next time I turned it on). With a better circuit, you could automate the on/off cycles to charge them up.

Step 1: Get Your Power Source!

You'll want to find an adapter plug from something you don't care much about. Backwards powering batteries can lead to current backflow (battery power going through adapter) which can ruin some adapters, though usually at 1.5v you're safe (burned out a cheap 5v plug trying to recharge a 9v though). I found a Nokia phone charger works good.

You also don't want really high amperage. Since high current charging leads to leaking batteries, try to find as low current plug as possible (look at the mA rating). A good charger has only 65 mA or so going through the battery, but mine has 300 so that's why I have to keep cycling the power to the battery.

Step 2: Take a Stand!

You'll need something to put your charging battery on. If, by chance, it should leak, you don't want to get battery acid on anything nice. I used a LEGO baseplate to protect the floor and then used an old LEGO motor power pack (took 6 AA's) to hold the charging battery. To connect the battery to the adapter, use alligator clip wires.

Step 3: Connect!

Remember, when charging, always go + to + and - to -. Normally, a series circuit would go + to - because current flow will stay the same (+ to - to + to -, same direction through both batteries). However, since charging is the opposite of draining a battery, you obviously hook it up backwards (+ on transformer to + on battery, - on transformer to - on battery).

Most transformers are "Plus-tip" meaning the inner circle (the hole in the center of the plug) is positive and the outer ring is negative...but test it first, some are Minus-tip (opposite).

I use a small length of wire with a bent end to stick into the center hole, that way I can clip wires to both connections on the transformer plug.

Step 4: Charge!

Just wait. Yeah, that's right, stare at it. It's a battery, it's hooked up to some wires, and it's charging. Charging. Yes, just what the label says NOT to do. Well you don't care, you're staring at it...boring, isn't it? If you want, you can test the voltage going across it with an electrical tester, mine came out around 2V. Yeah, just keep staring. Touch it every once in a while, make sure it doesn't get hot. After a while (not more than a few minutes, to be safe) take it out of the charger and test the voltage it puts out using the multimeter. If the voltage is high (about 1.65 or greater) let it "cool down" (let the voltage drop back to 1.50 - 1.60V) and then put it back in for a while more...Repeat this step...and then keep repeating it.

Step 5: Try It Out!

Once you've repeated step 4 a bunch of times, take your batteries and stuff them in something useful. I used my digital camera (Canon PowerShot A520). Turn it on, and watch as it amazingly WORKS on batteries you thought were DEAD. Take a few pictures, try the zoom out. Eventually it will probably stop working, probably before the low battery light comes on. Why? Well, the batteries have high voltage but low charge. The camera usually measures voltage to determine when the battery is dead...so it probably will die without warning. This can be fixed by repeating step 4 a ridiculous huge amount of times.

Step 6: Enjoy!

Charge up some Alkalines and reuse them. Think of all the landfills you're helping to keep battery-acid-free and all the money you save from the big companies. Think about the price difference between those fancy NiMH 15 minute rechargeables and your $4 Alkalines that can be recharged maybe 25 times. If nothing else, think of your accomplishment as an experiment and a proof of concept.

Comments

[Matthew Yang]

Awesome! Now I can charge a bunch of my old alkalines! Nice job. Great work. Well written.

[ergas]

Do not used adapter directly connected to a battery. If adapter is rated 3.7V 300mA, it does not mean it will limit current to 300 mA. It means at >300mA it will overload, overheat, and output voltage will drop. So possibly it will charge your battery with 1A and that is bad.
Use a serial resistor to limit current. To charge one battery from 3.7V, calculate voltage difference as V = 3.7V-1.5V = 2.2V. Limit your current to 40mA, so calculate serial resistor as R = 2.2V/40mA = 55 Ohm. Use a standard resistor 56 Ohm. Charge 2 days with some pauses. That is most simple charger.
You can add serial diode to protect reverse current. In that case, we have additional voltage drop on a diode of 0,7 V. So calculate voltage difference as V=3.7V-1.5V-0.7V = 1.5V. Calculate a resistor to limit current to 40mA as, R=1.5V/40mA = 37Ohm. So if you use a serial diode, apply resistor closest to 37 Ohm. Charging will last few days, but you will lower a risk to damage a battery.
I have found recently this possibility to charge alkaline batteries. I use my lab current source adjusted to 40 mA. On the output, I have added a PWM circuit with 80% duty cycle.

[amirbaseball]

Interestingly your method works! I have a power supply 25mA-3A but it has a floating voltage which is 0-32V DC, is it ok to use this supply or we need CCCV?
and by the PWM you mean u use it before the battery? or what?
can I use a PWM to desulfate a lead-acid battery? is it pulsing?

thank you so much for the good information.

[locofocos]

I've actually built a power supply to feed it the proper current and voltage (but more the proper current). I followed the instructions on http://www.afrotechmods.com/reallycheap/batteries/batts.htm to build it. For some reason (either I got the wrong kind of transistor or my resistor is bad) it's giving WAAAAAYYYY too much current. I fully charged 2 AA batteries in less that half an hour :P . I guess I'll keep it because I might need to charge some batteries really quickly, but I'm gonna go to radio shack to get some real parts to build it from and maybe even a generic PCB. My advice- be very careful recharging button cell batteries. I tried to recharge some little ones that went in my laser pointer cause radio shack wanted 5 bucks each (3 batteries times 5= 16.50 with tax) and left them on for a little too long.... the one on bottom exploded. And I mean exploded. The other two batteries got shot into the air. I looked at them, and the 2 flat sides were bulging out, about to pop.

[bsagreg]

Radio Shack where do you live 1994? Lol just messing with you.

[locofocos]

Oh man, what a nice little piece of my adolescent history. I love the random Instructables replies after a decade. Yeah, RadioShack was a thing back then! I hope you also had the joy of rummaging through their parts bins with the rolly metal drawers.

[NitroCopter]

Most button cell (cr2015, cr2030 i think those are their designations) are lithium, and 3v per cell. If you buy a hobby grade charger, (the ones for rc cars, and helicopters) you can make tons of different connectors and charge all kinds of batteries (pb, NiMH, NiCd, Lipo, Life, Li-ion) not alkaline because it's generally not safe and if you charge them with a charger for alkaline (one that pulses the battery hundreds of times a second at about an 80% duty cycle) they only charge a handful of times. I built a nice charge case that I use all the time. Its a pelican style case, with a 1000w charger that can charge the chemistries i listed above. I took a couple of 18650 sleds and glued them together, wired them in series and wired a balance lead to it as well and use the charger to charge them as a 2 cell lipo, it makes sure they are balanced (same charge in each cell) and charged at a safe rate. Those chargers will even tell you how many mAh it put back in to the pack. What im getting at in this long winded reply is if you use batteries for anything it is worth your while to get a hobby charger and some rechargeable batteries for your electronics and make the connectors that fit all the different size batteries you have.

[Yard Sale Dale]

I get button cell batteries from the dollar stores, usually Dollar Tree. They are not the highest capacity, but at 1/5 the price or even less, suits me fine. I use them in turkey scopes, lazer toys, bicycle computers, no problems. Look on Fleabay, too, or battery hobby websites. You can buy in bulk.

[extrordinary1]

We used to put those old dead button batteries on the electric stove until the popped. As for your high priced Radio Shack gouging your pocket, go to walmart back in electronics. The 357 button cells are a cross reference battery replacement. Don't go to the jewlry counter, they'll charge just as much to sell you batteries. One jewlry gal told me the 357's in electronics are the same thing. She was right, I've been using them since.

[KaylaC44]

I was wondering if it was possible to splice some wires (from a charging cord) to a wall device(an old camera charge), that doesn't take the batteries I'm charging(AAA Alkaline) and connect them to the proper + & - sides, on a safe surface of course, would it charge the batteries without having them mounted in an actual charging port and no motor, bc I don't have a motor.

[KaylaC44]

A couple questions if someone could please answer for me: should I separate the 11, AAA alkaline batteries when charging them, like in two different batches? Or I suppose that depends on the wattage and voltage of my wall adapter right? Also, what should my wattage and bolts be if I did them all together or separated. I have a Li-ion Olympus LI-41C camera battery charger, input says 4.4W, output 4.2V. And a wall adapter that I could splice the existing wire and know it would hold it. Input 24v, output 5.0V. Please help I really want to try this! I have a hurricane headed my way!

[trispark]

I'm in Europe and bought an advanced battery charger (Medion 15 Euro). It can charge 4 batteries individually. It can also charge alkaline batteries. The power ratings show about 500mA for NiMh and 180mA for alkaline. I didn't have much success as I expected. Most batteries didn't charge too well or show as 'bad'. They appear full very quickly but run out in seconds in toys. Some cheaper batteries grow in size, ready to explode! My most successful charge were the batteries in my new Canon camera. Panasonic professional alkaline. They took longer to charge but still drained pretty quick.

[CalcProgrammer1]

I've read if you charge them at currents <100mA and you let them charge for a long time (like a day) you can get enough power to almost completely recharge.

[SteveM433]

You are on the right track. I am in a position to know. The factory uses a 80% PWM current limited to 20 to 40mA; then charge to 110%, but no higher than 113% of the listed battery voltage, which can be measured connected. DC will never give you the saturation desired.

[PKM]

Firsly, I believe the "alkaline" bit means they don't contain any battery acid :) "battery acid" is commonly used to mean the sulphuric acid in car batteries, which there definitely isn't in alkaline batteries, but the KOH electrolyte is still nasty stuff that you don't want on your skin, eyes or furniture.

Secondly- your adapter should have a symbol like + ------ o) ----- -, meaning it is plus-tip (positive centre) , or - ------ o) ----- +, meaning it is the other way around (negative centre, positive ring). Excuse my terrible ASCII art :)

A decent wall-wart adapter will often have a switch letting you change the polarity of the plug, but I would expect all sensible power sources to at least have this diagram.

[ac-dc]

Most wall wart adapters do not have a polarity switch, the only type I've seen with one is those crude ones with multiple transformer taps and a sliding switch to change voltage in steps. The vast majority of them don't need a diagram because the outside of the barrel plug is negative and inside positive, but do go ahead and check that with a multimeter since it only takes 10 seconds to do.

[CalcProgrammer1]

You'd be wrong on that one lol...neither one of the two phone chargers I tried had said diagram. Most do, but a lot of new "specific use" plugs that are designed to work only with one thing don't put the diagram on the plug. If you get one from RadioShack, for instance, you can flip the plug around to change polarity, or just stick wires in the adaptaplug socket (the special two pin socket that they use to change tips with).

[Hajra Naeem]

how much voltage is required to charge 10v battery?

[DonS74]

There's a formula you can use for charging batteries- Bat voltage x7 divided by 6. So if you have a 10 volt battery you would 10 x 7= 70 /6= 11.66666 volts.

[KochiyaYamato]

you use a adjustible power supply, hoook that up to the battery, turn on your amp meter and adjust current so that it slowly reduces and reduces, if the current reduces that means its charing up, if its increacing that means your dumping too much power into it and your discharging that bad boy instead, but also it will blow up if it cotniunes on