24v li-ion battery jump

[topfli8979]

I have a drill battery that is beyond dead, from sitting about a year. It in its sleep mode, charger will not accept the battery cause voltage is low. I have in the past jumped some lithium r/c packs and it worked great. I know lithium batteries are volatile and can explode if overcharged, but I am fully experienced with electronics and feel I can do this. How would I go about getting around 40volts to do this?

[budm]

Re: 24v li-ion battery jump

Are you trying to zap this 24V power pack with 40V? Or you are trying to zap individual cell? The pack will more likely to have PCB with circuit to monitoring the temperature, state of charge, etc. so zapping it with 40V can damage the circuit.

[topfli8979]

Re: 24v li-ion battery jump

Well now that you mention it, I will probably "zap" each individual cell, not necessarily 40 volts, but high enough to "wake them up".

[budm]

Re: 24v li-ion battery jump

There is some info here:
http://batteryuniversity.com/learn/a...oltage_cut_off

[domas]

Re: 24v li-ion battery jump

i have actually had a small 90mah li-ion 1cell battery that was discharged to 0,00V, so the controller would not charge it for obvious reasons. I did apply to it some 3,8V charge from another li-ion battery, and it did charge after that. Of course the capacity was close to zero. After a day it had 2,4V on it, so it was not completely cooked, but not really usable either, ended up getting a replacement (160mAh) one from local r/c store for a dollar or so. It was a tight fit, but it did the job. Oh and that was inside bluetooth hands-free headset

tl;dr: if the voltage drops a little below controllers locking threshold it is safe to jump start it (you are actually fooling the controller not repairing the battery), but if it is less than two volts just deal with that and get a fresh cell pack.. Or at least a used one that is still okay ;-)

Other thoughts:
please do not overvolt the cell to more than 4,2V per cell. Again, in real life, if you momentarily overvolt discharged battery it with lets say 5V it is not very bad, as you don't overcharge it (because even though the supply is 5V and the battery is 2,5V the charging voltage will not be 5V - it will float between 3-4V inside discharged cell i guess) but again, that is a ghetto work and you should never leave it unattended. constantly check temp even with your finger, don't do it for longer than 1-2 minutes