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.





How would I identify a replacement part for the thermistor?

 

How would I identify a replacement part for the thermistor?

Why do you need a replacement?

A thermistor with a 10kΩ resistance at 25°C should work.

 

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.

 

I don't understand what the purpose of the thermistor actually is

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.

 

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?

 

It's likely a recharageable battery since there is no purpose for the thermistor with a primary battery.
Where did you get it from?

 

You have to call the place to get a quote.

https://www.realityworks.com/battery-replacement/?v=7516fd43adaa

This is the Youtube video on replacing the device(s).

It is all coming together in my head now...

 

So if I didn't want to assemble this myself I think this replacement version would work.

https://bbmbattery.com/products/varta-2-vh4000-3-replacement-battery

 

Once again the question"Why do you need a replacement thermistor???

 

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.

 

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.

That makes sense.