17670 NI-MH Batteries

[Nikos A.]

Hi everyone,

I unpacked a 17670 NI-MH battery pack from an electronic device. As you can see from the picture attached there is a series component (with red leads and something like a black bulb) on the negative side.

What is this component and what its purpose? Furthermore why there are two paraller negative cables?

Thanks in advance

[capt bullshot]

That component most probably is some kind of a thermistor, so the charger can stop charging if the temperature of the battery is too high or too low.
Paralleled wires increase the current capability (by lowering the resistance), this is the most common reason for having paralleled wires.

[Nikos A.]

Thank you for your promt reply,

Is there any reason that places in paraller negative side instead of positive?

[capt bullshot]

Normally, one would use parallel wires on both sides if one wanted to increase the current capability.
Here, it just might be done to compensate for the longer run of the black wire in comparison to the red one. But you'll never know without knowing the complete design or asking the original designer.

[Psi]

Sometimes you also see a thermal fuse.

[mikerj]

The additionally ground wire is likely to prevent battery charge/discharge current causing errors with the thermistor measurement, effectively a Kelvin connection.

[Nikos A.]

Thank you guys!!

The additionally ground wire is likely to prevent battery charge/discharge current causing errors with the thermistor measurement, effectively a Kelvin connection.

You are right, after searching I found that this is actually a 3 wire RTD (Resistance Temperature Detector) configuration. Actually it doesn't matter which one is the double wire (negative or positive). The key point is to maintain equal lenght in order to achieve equal resistance among the wires.

This site was helpfull

https://www.omega.com/en-us/resources/rtd-2-3-4-wire-connections