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Battery Pack Dead

Anyone know why a 24 Drill battery pack would read 0mV overall and for every NiCd cell? No open cells since the total resistance is about 2.5 Ohms.

I didn't know cells could discharge completely to 0V since whatever load they are connected to will limit the current as the voltage reduces. So, if the load is 10 Ohms and the voltage is 1V we have 100mA but once the battery goes down to 1mV we have 100uA. I suppose over a long enough time frame the voltage might be below 1mV but seems like it would take a very long time to discharge the battery so it would read 0V? Specially since the pack was just working a few days ago.

In any case anyone have any idea why the battery pack is dead? (was it simply discharged completely?) and how to fix it? NiCd is supposedly fine with deep discharge but the charger will not charge it. I figure I can charge it with two 12V car batteries in series enough to get some charge in it so the battery charger would work but not sure if this is a good way since the cells might actually be fubar.

The packs costs about 100$ and have 20 NiCd cells. I was thinking if nothing else fells I could replace them. Was thinking about using Li-ion or NiMH but these supposedly are not great for "power tools".

Any ideas?

Reply to
Jon Slaughter
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Harbor Freight sells a NiCd 18V cordless drill with battery for about $25. If the battery pack dies, you're out only a few bucks for a replacement battery pack, or a replacement drill.

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Reply to
Michael

"Jon Slaughter"

** This PITA puke is too damn lazy to even read wiki.

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.... Phil

Reply to
Phil Allison

It is very common that NiCad and gell type batteries fail in the way you are describing. Sometimes when they fail, they can damage the charger circuits. You can test the charger with a volt meter to know if it is working.

The fix is to replace all the battery cells together. In the case of a drill and most portable equipment, I believe the batteries come as a battery pack. The battery cells have to closely match in order to charge properly. Even if you find an old cell that tests okay and use it with newer cells, after some charge cycles it cannot be accurately the same as the newer ones. The one bad cell can damage the rest since the charging is all in a series type circuit.

Jerry G.

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Reply to
Jerry G.

The fix is to replace all the battery cells together. In the case of a drill and most portable equipment, I believe the batteries come as a battery pack. The battery cells have to closely match in order to charge properly. Even if you find an old cell that tests okay and use it with newer cells, after some charge cycles it cannot be accurately the same as the newer ones. The one bad cell can damage the rest since the charging is all in a series type circuit.

Jerry G.

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Yes, thats what I figured. But I\'ve just never seen a cell fail so that it 
read 0mV yet not be open(as as switch). Usually they read something like 
.1V.

I was going to replace the cells if I can find some the right size.
Reply to
Jon Slaughter

Didn't think to use the ohmmeter part of your instrument, now, did you?

The failure mode and a "cure" has been common lore for--what?--30 years?

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...and if you're going to use that POS software, you should do ALL the updates on it:

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Reply to
JeffM

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