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?
…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.
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"