Thank you very much for all the reporting. At least two others (roombacommunity) have gone this re-build route, but neither provided adequate information so others could envision the entire process. One source of NiMH cells had been given (www.amondotech.com
), but their pricing can't compete with your source. Would you be kind enough to post the URL for your pack-supplier? Or mail to me at gsplewsATverizon.net.
On the "PTC":
1) I too noticed, in your pix, the almost shorted condition and wondered about that as a problem!
2) I would say the thermistor has the NTC chemistry. Here are some data which I acquired on two of my batts:
The next day (040531), with ambient (and batt-) temps of about
69-degF, or 21 degC:
SERNO 082503's sensor resistance was 11.74 k-ohm. While...
SERNO 022003's sensor resistance was 11.72 k-ohm.
A few days later, attempts were made to measure thermistor resistance
as soon as the Rapid-Charger's LED went OFF; the data are:
3.58 k ohms following charging of #082503, and
3.30 k ohms following charging of #022003 both on 040604.
Data from #022003 was captured without much delay after charge
completion, whereas the #082503 batt had cooled more before
3.23 k ohms following charging of #022003, on 040611.
So you see resistance decreases with increasing temperature.
Once again, thanks for your pathfinding efforts; I know *someday* I will be breaking the case open to re-pack it! One thing I intend to do is drill 2-mm dia. holes, both through the Cover and the Case's bottom, on 2X6 grids roughly in alignment with the cell's axes. When a battery shows degradation, I can begin to load-probe each cell to learn whether one cell is causing the problem.