i did a while ago a battery pack using 12x 18650 trustfire 2400mah (the flame one) in 3s4p conf.
using for a year in a video light, that pull about 0.5C from each battery. all working fine, and batts seems healthy with great run-times.
but a month ago, i noticed the last 2 series of batteries having a lower voltage, like 4.2v, 4.0v, 4.0v, right of the charger (the pack have a led voltmeter)
until last night the light went off about 30% of the normal run-time. the protection circuit of batteries has tripped off.
trying to find the cause, disassembled the pack and measured each battery. most of them looks like they got a high internal resistance, im getting only 600mah from some of them (discharging at 1A). after fully discharged, the voltage goes up, but more than usual, like 3.8v, wich i believe tell it have developed as imagined a really high internal resistance.
as i did other packs with the same type/model of batteries, and all of them are working fine, i wondered if the charger was to blame.
as at the time i didn't have a proper hobby charger (my partner was using, not me), i used the only one i had in hands, a small e_sky charger/balancer that came with my RC helicopter. it charges at 0.8A. very low, i know, but i didn't have options back then.
at closer inspection, i opened the charger and guess what? 2 IC's and one diode where blown up!
well, better the charger be the problem, as i like the batteries
so, to sum up, my questions:
how the charger could kill them so fast like this, even if all batts had protection circuit?
using for a year in a video light, that pull about 0.5C from each battery. all working fine, and batts seems healthy with great run-times.
but a month ago, i noticed the last 2 series of batteries having a lower voltage, like 4.2v, 4.0v, 4.0v, right of the charger (the pack have a led voltmeter)
until last night the light went off about 30% of the normal run-time. the protection circuit of batteries has tripped off.
trying to find the cause, disassembled the pack and measured each battery. most of them looks like they got a high internal resistance, im getting only 600mah from some of them (discharging at 1A). after fully discharged, the voltage goes up, but more than usual, like 3.8v, wich i believe tell it have developed as imagined a really high internal resistance.
as i did other packs with the same type/model of batteries, and all of them are working fine, i wondered if the charger was to blame.
as at the time i didn't have a proper hobby charger (my partner was using, not me), i used the only one i had in hands, a small e_sky charger/balancer that came with my RC helicopter. it charges at 0.8A. very low, i know, but i didn't have options back then.
at closer inspection, i opened the charger and guess what? 2 IC's and one diode where blown up!
well, better the charger be the problem, as i like the batteries
so, to sum up, my questions:
how the charger could kill them so fast like this, even if all batts had protection circuit?
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