allenone973 said:
my battery has died and no longer accepts a chrage. any ideas? i have
read about and tried the deep freeze, thaw , charge thing and it did
not work for me. can anyone tell me which terminals are postive and
negative? i have also heard of "jump starting " the
batteries by applying a short current across the terminals. it worked
just fine until a few days ago
If you need your drill to be reliable, eg for your business, forget about
trying to revive the battery pack. Even if you manage to get it to take a
charge, it is likely worn out and will give poor running times and poor
charge retention. Once one or more cells become weak, when a load is placed
across the battery, ie your drill, the weakest cells take a reverse charge
from the stronger cells which causes permanent damage to them. A DeWalt
drill is likely to draw several Amps, and this high current reverse charge
will kill cells very quickly indeed.
My advice is to buy a new pack, or if you are handy you could probably
repack the old one with new and possibly higher capacity cells, which may or
may not work out cheaper. Bear in mind all cells must be changed together,
it's no good just replacing the obviously weak ones.
A common way of trying to get individual cells to take a charge after they
have developed an internal short is to pass a substantial current through
them to 'blow' the short. It can work but IME it is a short term measure at
best. Just attaching a large current source across its terminals to zap
shorts won't work, the shorted cell(s) have to be identified and zapped
individually. I have used large capacitors charged from a bench power supply
in the past to zap shorts, usually upwards of 2200uF, the bigger the cap the
bigger the current pulse. However, too large a capacitor could cause the
cell to fail completely or even explode.
You certainly shouldn't zap the entire battery by shorting it out- this will
likely make things very much worse or even cause cells to explode.
Dave
