Batteries Question

[JEZGUZ]

Hopefully not a dumb question but here goes. I've got a Dewalt Li Ion battery drill and haven't used it for a while, when I did come to use it' it was dead as a doornail, so out with the charger and nothing After a bit of searching I now know you can "jump start" the battery by connecting up to a charged one to give it enough voltage so the "smart charger" will recognize it and start charging. As these batteries can be used in older drills according to Dewalt, am I likely to kill the battery if I fit it to my non-smart Dewalt charger to give it a boost? Or would it be best to charge up a non Li Ion battery and boost it with that?

 

[zx9]

I am not sure but I think I remember seeing a video of the Dewalt ( and other ) Lithium ion battery construction and the Dewalt ones have a huge amount of circuitry in the battery for that reason I would think twice before trying to 'jump start' them.

 

[gaz1]

tried a jump start from one good battery to a bad one nothing it wouldnt charge even in the older type ones

i have other batteries as well and some of those have also failed new li ion battery and that wouldnt start either

 

[eddie49]

Due to the risk of fire or explosion, it can be dangerous to charge, or to use, a Li-ion battery or cell if it is too hot, or the voltage is too low or too high. I think the minimum safe voltage for a cell that should be 3.7v or 4.2v ( depends on exact chemistry used ) is 2.6 volts.To mitigate this risk, there may be protection circuits in the battery pack, the charger, the power tool, or even in every cell.
To revive a battery pack, you would need to find a way of bypassing these circuits, and then gently charging the cell(s) back to the safe voltage.
I would start by opening the case of the battery pack ( if this can be done easily ), identifying what's in there ( circuitry, and numbers printed on the cells ), and measuring and comparing the voltage of each cell.
( See also thread about Universal radio-controlled model battery chargers: http://www.mig-welding.co.uk/forum/threads/universal-charger-for-power-tools.78719/ )

 

[Kram]

If the battery has built in charge circuitry, the only way to save it may be to disconnect the cells and charge with an rc charger, and then reconnect, or continue using only the rc charger.
Modifying lipo/li-ion has some risk and best not attempted unless you have a good knowlege of it.
An alternative you can buy much better RC lipo packs and a charger quite cheap that you can use with any modified powertool.

 

[JEZGUZ]

Thanks for the input folks, I think I'll just buy a new battery as I don't dabble in the black art (electrics).

 

[Onoff]

If they're anything like the Makita BL1830 Li-ion batteries then cut your losses and bin it!

Something about one cell out of the pack runs the circuitry and when that dies it makes the cell unserviceable.

 

[JEZGUZ]

Well as the battery was apparently no good and therefore useless, I thought there's nothing to lose by trying to revive it, so I dug out an old Dewalt charger and a couple of Ni-Cd Dewalt batteries and bunged them on charge, they took a charge even though they hadn't been used for a couple of years( how long they'll last is another question) So I then piggybacked one of them to the Li-Ion battery for about 10 seconds and then stuck it in the Li-Ion charger and lo and behold, it began charging I will keep an eye on its condition and I'll probably buy another battery just in case.