How to adapt Li-ion batteries to replace AA batteries

Li-ion batteries are so much better than AA batteries, with few of them we can get the energy of several AA
my question is, would all the mAh damage the circuitry of ordinary toys and stuff?
How can I use 2 3,7 v 1000mAh batteries to replace 8 AA batteries?
what circuitry is needed for diminishing the amperage and rise the voltage?

julianzolo said:

Li-ion batteries are so much better than AA batteries, with few of them we can get the energy of several AA
my question is, would all the mAh damage the circuitry of ordinary toys and stuff?
How can I use 2 3,7 v 1000mAh batteries to replace 8 AA batteries?
what circuitry is needed for diminishing the amperage and rise the voltage?

Click to expand...

To replace 8 AA's with Li-ion's you will need to make it three, not two.
I suppose it depends on how sensitive the equipment it, but I myself use 3X 14500 batteries in my radio control remotes instead of 8X NIMH or alkaline AA's. I use dummy batteries to fill in the spaces. Capacity will be down, but in my case I don't mind as the batteries in the remote will outlast any of the batteries in the actual vehicle you are controlling with the remote.

Edit. Oh and I see it is your first post. Welcome here.

julianzolo said:

Li-ion batteries are so much better than AA batteries, with few of them we can get the energy of several AA
my question is, would all the mAh damage the circuitry of ordinary toys and stuff?
How can I use 2 3,7 v 1000mAh batteries to replace 8 AA batteries?
what circuitry is needed for diminishing the amperage and rise the voltage?

Click to expand...

Li-ions come off the charger at 4.2v, 3.6v and some come off at 4.35v. NiMH are ~1.45v off the charger, alkalines are ~1.60v and lithium primaries are ~1.80v.

Capacity (mAh) isn't your concern, it's shoe-horning fewer cells into a device that requires more cells physically.

the 14500 li-co/li-mn is about the exact same size as a AA, but nominally, it's got 3 times the voltage, so if you had a 3xAA device, like my TecSun PL-390 SW radio, I might be able to add one of my 14500s and two spacers and get it to work, but how many 3xAA devices do you have?

Making the connections might be hard, at least removable connections.

Chris

Hello, noobie here with questions:

Have a 12 LED lantern which uses 3 x AA batteries, and also has a 1 Ohm resistor. However two 18650 li-ions fit nicely into base in series. ( panasonic CGR18650E). What load resistor should i need to use or should i just leave it alone!

Lantern is just a simple 12 LED Lantern from Milestone Camping, and have not been able to find out specifics of LED array voltages or current drops.

Thanks in advance.

lkomnino said:

Hello, noobie here with questions:

Have a 12 LED lantern which uses 3 x AA batteries, and also has a 1 Ohm resistor. However two 18650 li-ions fit nicely into base in series. ( panasonic CGR18650E). What load resistor should i need to use or should i just leave it alone!

Lantern is just a simple 12 LED Lantern from Milestone Camping, and have not been able to find out specifics of LED array voltages or current drops.

Thanks in advance.

Click to expand...

If you could get those two 18650 cells in parallel instead of series, you would be right on the money. Three AA cells would be a nominal 4.5v, slightly more than a single 18650. After a little use, the voltages would be closer to 3.6v and 3.7v, respectively. Adding a second 18650 in series would double the voltage and probably 'poof' all the LEDs, if not at once after only a short time. But adding that 18650 in parallel would leave the voltage the same and double the run time available.

1 li-ion=3 alkalines/nimh.
or close enough.
your lantern is probably pushing those leds hard so check current with your li-ion.depending on type most small 3-5mm leds want no more than 30ma for long life.smd can take more as they get rid of heat better.
if 2 18650 fit in parallel add a tp4056 usb charger board while you are in there.then you can charge it like a phone.just need to find a way to mount it and create the opening for the jack.i like to glue the board to a flat surface with a slot for the jack to come through.reinforces it a bit

Why even run parallel. If it is indeed just 3mA, a single 3000mAH cell would lasts 1000 hours. Such low draw on LiIon, the battery protection circuit better be cutting out at 2.8v-3v. All the PCB's I've ran into cuts out at 2.4V to 2.6V. Drawing at 3mA will have basically no voltage sag, and that will take it down to 2.4-2.6V. Not nice.

On another note:

I think the drawback with LiIon for such low current is mainly is the cycles. With the Eneloops, you can do over 1500 cycles. That would be 2-3x the service life of LiIon.

I bought a night vision monocular that calls for 5x AA batteries. Would two 18650s in series work/ be safe?

You can use these AA batteries which is li-ion rechargeable and regulated to 1.5 volt. No modification needed.

Dasbimmerman said:

I bought a night vision monocular that calls for 5x AA batteries. Would two 18650s in series work/ be safe?

Click to expand...

Yes/No.

Yes the voltage should be within the same range.
No, I cannot say it would be safe by default and lithium ion cells in series has a potential to be dangerous if not handled
properly. Lithium cells (both rechargeable and primary) possesses enough power that if shorted or discharged beyond safe current limits can result in fires and even explosions. When you put several in series you further add the risk of reverse charging into the mix and you cannot just put about 8.5 or so volts on a pair in series and not have problems, you need to charge EACH cell individually and have circuitry doing so that keeps them from being overheating while charging and not overcharging. Most series cell packs also contain temperature probes that the charger and the device the battery is used in monitor the battery temperature and shut the power off when it exceeds a certain level to prevent runaway heating (very dangerous).

If you are unwilling to put in the time to learn about all of this stuff...... don't do it is my advice not worth the risk.
If you can find a battery pack that has a built in protection and balance circuit and a charger to properly charge the battery that fits that would be easier.

A place to start to learn about making series cell lithium rechargeable packs I can think of would be the R/C community these people build packs for cars and drones etc and know about 100 times as much as I do...... likely a few also frequent here maybe they would chime in perhaps.

lightseeker2009 said:

To replace 8 AA's with Li-ion's you will need to make it three, not two.
I suppose it depends on how sensitive the equipment it, but I myself use 3X 14500 batteries in my radio control remotes instead of 8X NIMH or alkaline AA's. I use dummy batteries to fill in the spaces.

Click to expand...

Where do you get AA spacers? I have an Energizer COB lantern which has two bays of 4AA, it runs with 4 in either bay or all 8. Dunno how the voltage is handled.

fivemega said:

You can use these AA batteries which is li-ion rechargeable and regulated to 1.5 volt. No modification needed.

Click to expand...

Yes, but why would you? In most applications, they offer no advantage over NiMH AAs (like eneloops), but cost considerably more.

lumen aeternum said:

Where do you get AA spacers? I have an Energizer COB lantern which has two bays of 4AA, it runs with 4 in either bay or all 8. Dunno how the voltage is handled.

Click to expand...

I never bought any, instead short-circuited dead (totally depleted!) AAs by soldering a short wire between "case" (minus) and button (plus), after removing a short section of the plastic sleeve.

If your lantern also runs with only 4 of the possible 8 AAs, the 2 bays are very likely connected in parallel, meaning a voltage in the 4 to 6 Volt range. That's a bit difficult to replace with LiIon.