DeWalt tool 12 V battery pack - what is the code for the ID pin?

Thread Starter

Berninia

Joined Nov 21, 2015
15
A 12 V DeWalt power drill has three contacts. B+, B- and a third pin which is either a thermistor (TH) or an identifier (ID). I have connected 12 V to the B pins, and the tool LED lamp flashes momentarily when tool is turned on, but tool refuses to work. I suspect this is related to the 3rd pin.

What must I supply on the 3rd pin to get it to work? This may be a static voltage or an analog signal.

Appreciate all information.
 

Externet

Joined Nov 29, 2005
1,667
Extra pins in the battery / tool / charger connectors can be a thermistor enable/disable signal; an overcurrent/undervoltage, a fixed resistance that tells what voltage/current pack it is, for communication between
battery and tool,
OR / AND
battery and charger
in unknown or both directions !
and every manufacturer will do it their way per model telling nothing. Can be a low thermistor signal for too hot; can be low for good temperature range and a hi for whatever they want. :confused:
Playing with them the guessy way can cause a circuit failure somewhere in one direction, the other or both.
 
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bassbindevil

Joined Jan 23, 2014
176
I disassembled a scrap 18V Dewalt drill and there was no connection to the 3rd battery contact. Same goes for some older Makita and Porter-Cable drills I've taken apart. I'm pretty sure those additional contacts are only needed for chargers.

Are you sure your 12V power source has enough current capacity to run the drill? If in doubt, test it with a load like a car headlight.
 
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Thread Starter

Berninia

Joined Nov 21, 2015
15
Mystery solved. The 3rd pin in the tool is for the battery pack thermistor, and is not an identifier. As long as the thermistor is cool (i.e. resistance high), the tool is happy and works. Insert a 47 kohm resistor between B+ and the 3rd (thermistor) pin on the tool. Tool will not work without this resistor. Drill is the 12V DCD701 drill.
 

Thread Starter

Berninia

Joined Nov 21, 2015
15
I disassembled a scrap 18V Dewalt drill and there was no connection to the 3rd battery contact. Same goes for some older Makita and Porter-Cable drills I've taken apart. I'm pretty sure those additional contacts are only needed for chargers.
Thanks for the information.

With the DCD701 12V drill, it does actively check for pack temperature. Charging may happen at 2 to 5 A. But discharging is sometimes at 20 A or more. The 47 kohm resistor (see previous post) is mandatory.

Are you sure your 12V power source has enough current capacity to run the drill? If in doubt, test it with a load like a car headlight.
Good point. This was another issue which I had missed. I was powering with a 3 amp supply. So then I realized I have to turn the drill on at very low RPM and then gradually I can increase the RPM, or the drill would trip for low voltage.

Now I have an external 180 Wh 3s3p 21700 pack, which I can put on my belt, and still have a very light tool.
 

Thread Starter

Berninia

Joined Nov 21, 2015
15
Extra pins in the battery / tool / charger connectors can be a thermistor enable/disable signal;
Thanks. The issue was solved, please see two posts above. The 3rd pin was not an identifier but a thermistor pin to keep the pack cool during discharge and probably recharge.
 
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