Over-discharged Ampmax 18650 batteries

I managed to trigger the over-discharge protection of 2.5v on four Ampmax 18650 3400mAh batteries by putting my Sky Ray King in my backpack and had it accidentally turned on there. I completely forgot how extremely sensitive the button is.

I have two cheaper chargers that won’t charge the batteries and neither have I gotten them reset by connecting to a fully charged 18650.

Is there any other way to try to reset them, like briefly connecting to a laptop charger?

How much a factor is time? At which point will they be damaged by being in this state?

Any other tips are greatly appreciated.

Ok, to reset the protection you need to hook them up to a good (non-tripped) 18650 in this arrangement. Obviously only do this for about a second.

…and, after resetting protection circuit, put them on charger as quickly as possible - the less time they spend in overdischarged state, the less damage will be done to them.

I tried resetting them with 3-9v batteries and it did not work. However, when I connected a telephone USB charger of 5v 1A to one of them a few seconds it came to life with 2.51v. This does not solve my problem though as it seems my two chargers won’t charge anything below 2.75v, this was something that I had not foreseen.

Is there any safe way I could manually charge them up to 2.75v? I am going to buy a good quality charger as soon one with a voltage display is released.

There is no good safe way of doing that without a charger. If you are in the US Lighthound has a pretty good I4 which will reset ptc and charge them at low voltages.

1A USB charger. Must have for everyone

I'd parallel it with another battery thats at 3.3V max.

I4 doesnt reset PTC, only PCB. :P

It is cheap enough, but what is it, and how would I use it?

These will charge your Li-ion batteries from say your computer.

Just solder wires to the board like the diagram shows. Then on the other end of the wires solder NIB (neodymium) magnets so they will stick to the battery pos. & neg. ends. like these

No reverse polarity protection, so just make sure to get the polarity right, otherwise the board will fry. The wire connected to "BAT+" goes to anode end of the battery, "BAT-" goes to cathode.

Also note it's a mini USB input, so you'll need something like a USB to mini USB. Cut off voltage is 4.2V for the common Li-ion cells, if it doesn't stop at 4.2V then adjust control board where is says "Full"

Good find nekdo12!

Great info here….feeling silly however… :frowning:

I did not know voltage protection could be tripped back “ON”! H)

Recently chucked some over-discharged 18650s that seemed to be “dead” to all testers and chargers.

(Had tried to strike the FF3 on batteries I forgot were dead. The ignition pulse got me a flash and 2 tripped 18650s.)

Many thanks for the pic Scaru! Saved to the hard drive……

How do y’all know which chargers will go to low voltages? HKJ’s reviews seem to only go down to 3 volts?

That is a led, not a trimmer. The voltage is fixed on these board.

The text at the start of my measurements section does usual say how the charger does at lower voltages.

See it now, thank you! :heart_eyes:

By the way, my battery, light, and charger decisions are based pretty much entirely upon your superb information. :bigsmile:

Off to get a cottonpickers’ WCSD… :santa:

And it's not my pic, I stole it from HKJ. ;)