I have a Canon compact digital camera Model IXUS70 which I want to use for time-lapse photography. The battery doesn't power it for long enough so I propose to gut an old battery and turn it into a power connector so I can externally power the camera indefinitely.

The battery has three connections:

Canon NB-4L battery

labelled +, - and the third is unmarked, though I understand that this is a thermistor connection.

How should I connect this third pin, assuming that I am feeding 3.7 VDC into the + and - connections?

  • \$\begingroup\$ It could be a one-wire protocol connection. If thats the case, then adding a dummy thermistor/resistor wont help, you might have to salvage the circuitry inside. Be careful with that thought, as cutting this battery up is a real fire hazard. \$\endgroup\$ – Wesley Lee Feb 26 '17 at 2:44
  • \$\begingroup\$ The center terminal may not be required. thingiverse.com/thing:17437 \$\endgroup\$ – Bruce Abbott Feb 26 '17 at 6:12

The thermistor is often using during charging, to ensure the battery does not overhead. The camera should not care, so try to leave the terminal disconnected and see if it works.

If this fails, you can always retain original thermistor (you will be gutting the battery anyway), or measure the resistance of thermistor and place a regular resistor with the same value instead.


A battery eliminator for Canon power shot and similar models simply need V+ and Gnd. No special circuitry required.

But as long as you have a real battery in, you could power it from the external power input, which should be about 7V or so.


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