The Museum of HP Calculators
HP Forum Archive 13
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|New cells for the 41Cīs battery pack|
Message #1 Posted by Jon on 8 Nov 2003, 10:56 a.m.
I have repaired a dead battery pack 82120A. I have used new 1/3AAA NiMH cells (150mAh). I have charged it for three hour with the adapter 82059D and it works just fine. I have charged just three hours because I know the rechargeable cells are very sensitive to overcharge.
I would like to know how long must I keep it charging for a full charge. I think original cells are 1/2N NiCd (75 mAh aprox.) so the total charge time should be the double. Does anybody know the recommended charging time for the original battery pack?.
Thanks in advance
|82120A charging rates and 1/3AAA cells|
Message #2 Posted by Randy Sloyer on 8 Nov 2003, 6:08 p.m.,
in response to message #1 by Jon
The 82120A manual says 12 to 16 hours for a full charge.
With respect to the 1/3AAA cells, Gold Peak says 16 ma for 16 hours. It just so happens the charge rate of the 82120A is 16 ma. So 16 hours should yield a fully charged pack.
They will typically reach 5.80 volts open circuit when fully charged. I have seen no cell heating (checked with I/R thermometer) after 24 to 36 hours so I would not be overly concerned about overcharging. I charged one for a week once to see what would happen - it seemed to decrease its capacity until it went through two or three discharge charge cycles - it now seems fine and maintains a 16 ma discharge rate for about 10-12 hours.
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