What is this bead thermistor for and what purpose could it serve? How do I identify a replacement thermistor?

Thread Starter

Riskinit

Joined Jan 28, 2022
65
I have a 2.4v 3800 mAh battery pack (2 1.2v batteries in series. They are connected to a 3-wire connector (red is positive, black is negative, and white is also negative but appears to have a bead thermistor on the white line.

What is the purpose of the thermistor (this battery pack powers a mechanical baby one might use in a high school class where you are required to take the baby home)?

I unhooked the thermistor and measured 9,300 ohms across it. The thermistor changed its base value when i applied heat up to about 9,600 ohms.

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How would I identify a replacement part for the thermistor?
 

Thread Starter

Riskinit

Joined Jan 28, 2022
65
Why do you need a replacement?

A thermistor with a 10kΩ resistance at 25°C should work.
The company selling this charges $140 for replacements versus $10 for the parts but I don't understand what the purpose of the thermistor actually is or could be and then how do I know what model of thermistor to pick? If I understood the design better I could at least be sure I am not wasting my time.
 

Thread Starter

Riskinit

Joined Jan 28, 2022
65
It's used to measure the battery temperature while charging, and the charger then reduces the charge current to avoid overheating if the temperature gets too high.
Ohhhh. That makes sense because it was folded up against the battery when i took the outer plastic wrap off.

However, I don't think this is a re-chargeable battery. So the device this is for must use it to sense if the batteries are overheating and then stop pulling current. If the current thermistor is 9,300 ohms at room temp and I put in a 10,000 ohm thermistor won't the device think the room is cold then?
 

Thread Starter

Riskinit

Joined Jan 28, 2022
65
Once again the question"Why do you need a replacement thermistor???
I was going to build one for $15 instead of paying the company $140. Sorry if that wasn't clear in my initial post.

But now that I understand it's purpose and it isn't anything special I am comfortable just ordering the one I found for $30.
 
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