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I have an awesome led headlamp and would like to boost its effective run time. At max output it only lasts 30min - 45min, it's really stinking bright. 

This is the battery the light came with.

PL 922845. 3.7v 
1100mAh. 4.07Wh 
160414. BPI 
This is the battery I would like to add.

6x run time. :brows:
Sound good?
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You've got three wires on your current battery and only two on the replacement.  What is the third wire for?  I'm guessing there's a thermister in there to monitor temperature during charge.  You likely will not get the battery to charge without it, although you can probably use a resistor to simulate it.

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I was wondering if someone was going to notice that.


I looked on the circuit board and there are only two copper traces coming from the connector.


However, after taking the board out I found on the back side that all 3 pins are in fact soldered in place and labeled as such.


B+             Red wire

NTC+       White wire

B-             Black wire

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Yeah, NTC means "Negative Temperature Coefficient" in reference to a thermistor.  You should be able to see what resistance it is from that pin on the battery connector to the B- to get the room temperature resistance.  Then just go buy a little resistor that is near that resistance or higher and wire it in on your new battery.  You also can probably cut that old battery open and fish the thermistor out of it, if you want to be more proper.  You're going to need the connector off it anyways.



Edit, assuming the board you have is a multilayer or such and there is actually something hooked to the NTC+.  Otherwise just nip the connector off your old battery and put it on the new one.

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Well I went ahead and ordered the battery. Ran into an issue though, adafruit would not ship the battery solo, some kind of new federal regs. They said I had to order an item that used that battery or buy any other random item that they could claim was "device" that used that battery.


Long story short, I went on eBay and ordered it through them. Apparently they don't have those problems. 

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  • 2 years later...


I need to order the same battery and I didn't find exact the same for sale. But I found your post and wondering how were you able to order it through ebay? Could you please explain a little more how to order through ebay? 

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