NiMh Temperature sensor error NTC

[Beeping-Sleauty]

Hi,
can anyone please tell me how i go about tracking down a Temperature sensor NTC error, this is a NiMh battery, it happens immediately i plug the charger, a 3PX0-N70XX smart charger, into the battery, so i am inclined to think it is not actually rejecting the battery temp, but maybe a faulty thermistor....?, How can i check ?

my thanks in advance

beeps

 

[Ian]

You need to identify the pins on the battery connector pins that connect to the internal thermistor. In the case of a 3 pin connector one of those will be common, another will go to the other battery terminal and the third will go to the other thermistor terminal. The 2 pins that have no measurable voltage across them should be the thermistor connections, alternatively you could open the battery case and look! Once the thermistor connections are identified the resistance across them can be measured with a multi-meter, at room temperature the resistance should measure somewhere between 6-18 kohms, the exact figure depending on the thermistor type, and should decrease as the temperature rises (ntc = negative temperature coefficient).

The battery thermistor does need to be matched to the charger in order to feed back the correct battery temperature reading, If you find the thermistor is ok the problem is likely to be a mismatch.

 

[flecc]

Check as Ian has said. These chargers are made by Shenzhen and use 10 kOhm thermistors with a Beta value of 3960.

Measured resistance will normally be around 8 to 11 kOhms at room temperature.

The most likely faults are a dead short or open circuit, and the latter is most likely since Shenzhen usually design their models to refuse to operate without a valid in circuit thermistor.

If you need a new one, RS Components Bead Thermistor Stock Number 151-237 will do the job at £2.07 each.
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