I got a cordless drill from DeWalt on a big sale two years ago I remember it
was on some clearance for $129.95 or something and it came with two
Now the batteries will charge up in 30 minutes but will drain in much
shorter time. I checked for new 12v ones and they are $70 a piece! I could
not believe it.
So, first, is there anyway to "fix" the batteries. I assume they are
draining must faster because I did not wait till they are totally drained
before recharging or I left them on the charger for too much longer after it
was charged? Is there a way to fix the problem other than getting new ones?
Batteries have a finite life. The cells are going bad and not holding
charge. There are rebuilders that will do them cheaper than new and can
also upgrade to more powerful.
I've used these guys http://www.primecell.com/pctools.htm with good results
but there are others.
As Edwin says, take the packs to a rebuilder. Yellow Pages is bound to
have quite a number in a place the size of Miami metro area...
As for causes, your surmises may (or may not) be correct. Better
chargers have self-limiting circuitry that senses the batter is fully
charged and shuts off so as to not overcharge them--cheaper ones may not
or not effective. So, depending on the charger, leaving them on it for
long periods of time could be a contributing factor.
Some chargers simply do a better job of charging than others--they sense
charging rate, etc., and are designed such the the charging cycle
matches the particular type of battery. Again, others don't.
Lastly, of course, there's simply the type and quality of the batteries
If you're lucky, you have nothing worse than some cells that have
reversed in polarity, and they can be corrected by charging each one
individually by applying a current of approximately 50-200 mA for a
few minutes and then immediately charging the battery normally.
Shorted cells can usually be fixed, at least temporarily, by applying
some brief pulses of high current at about 30-100 volts from a
capacitor, but it's likely the shorts will grow back in a day or a
week. I've taken the good cells from a pair of identical faulty
battery packs to make one good pack. The cells are best attached with
a spot welder, but with a high power iron and some rosin flux, the
cells can be safely soldered together, if you work fast enough to
prevent overheating them. When repairing a battery, use only
identical cells so each cell carries the same load. Cells vary in
type (nicad, NiMH), capacity (a sub-C cell can range from 1,000-4,000
mA-H), and impedance (usually because some cells have plates made of
foamed metal, others of sintered metal).
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