Dewalt 12.0 Volt XR NiCad Battery

©Brooke Clarke, N6GCE

Background

I have started a small business making battery adapters for military surplus electronic equipment so why not see what's going on with my dead Dewalt 12.0 volt battery packs and see if an adapter could be made for them?
Not that many years ago I purchased a new kit containing a Dewalt Variable Speed Reversing (VSR) cordless drill, two 12.0 Volt XR NiCad batteries and a charger all in a metal carrying case.  If this was an A.C. powered electric drill it would still be running, but now the batteries will not take a charge and may be obsolete.  After a long time on the XR Pack charger the LED shows "charging" not defective or "charged" but when used on the drill there is little or no charge available.

I've tried trickle charging, and reconditioning (discharging) but with no luck.
 

Pack Construction

Today, 26 June 2002, I took apart a DW9071 battery pack to see what's going on.  Inside I found that there are 10 NiCad cells, three rows of three on the bottom (that's what gives the battery pack the pointed shape, and one more cell sitting in the "tower" that plugs into the drill.  If a NiCad cell is a nominal 1.2 Volts then this pack is a 12 Volt.

The drill label says DW9072 ... 12.0V DC 0-450/0-1400 RPM...

The cells are about 0.87" in diameter and about 1.6" tall.  This is a little smaller than a "C" cell which is 1.03" dia x 1.97" high.  But an Alkaline "C" cell has a capacity of 8.35 AH and I think this pack is rated about 1.5 AH.  "AA" Alkaline cells are rated at about 2.85 AH almost twice the capacity of the NiCad pack.  Maybe a battery adapter for 10 AA cells would be a good thing.  If NMH AA cells were used the capacity would be about 1.7 AH and there would be no "memory" problem like with the NiCads.

But the main advantage to a battery adapter is that you can fill it with fresh common batteries any time you want to at a very low cost compared to buying a new manufacturers battery.  Also you have the choice of Alkaline that provides a lot more amp hours for little money or NiCad or NMH rechargeable for lower overall life cycle cost.

As I'm writing this I have one battery pack that has been opened on the Maha Charger and the other assembled pack being charged with about 300 mA constant current.  The Maha will tell how many mA Hours were put into the battery and in the
recondition" (discharge) mode will tell how many mA hours the battery can supply.  The idea is that after they have some charge I can check battery capacity and to see if there are any dead cells.
 
 

open pack
closed pack
Voltage
minutes of charge
mA H in
13.8
177
2148
 13.8
148
1788
Voltage
minutes of discharge
mA H out
   


 

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