|Re: HP-41CL & Battery|
Message #3 Posted by Dieter on 5 June 2011, 2:11 p.m.,
in response to message #1 by Geir Isene
We had a discussion on HP-41 battery options just a few weeks ago (cf this thread). While current LiIon and LiPo batteries for cell phones are not an option due to their voltage (3,6 V is too low and 7,2 V too high), the solution you suggest is a NiMH battery with 6 V nominal voltage, i.e. it probably is made of five cells instead of four in the original HP NiCd battery pack. Since freshly charged NiCd and NiMH cells may have voltages like 1,4 V and higher, the 5-cell pack may provide 7 Volts and more. That's why I would prefer a solution with the usual four cells.
Anyway, the essential point here is the higher power consumption of the 41CL. Let's take a look at what we can expect from different power sources:
- 70 - 80 mAh: former 1/2-N-size NiCd cells in 82120A battery pack
- 140 - 170 mAh: current 1/3-AAA-size NiMH cells for refurbished battery packs
- 500 mAh: current N-size NiMH cells
- 700 - 800 mAh: single-use N-size Alkaline cells
- 2000 - 3000 mAh: current AA-size Alkaline cells (external battery packs)
- 2000 - 3000 mAh: current AA-size NiMH cells (external battery packs)
So, what do we need for the 41CL? Without the card reader or wand, single-use N-Alkalines were a good option for the 41-series. In case of rechargeable batteries, even the original 82120A pack with less than 100 mAh capacity was fine. If you look at the figures again, there is an elegant solution with more than sufficient capacity: use simple rechargeable N-cells in the regular battery holder and charge them externally. Some more thoughts and ideas can be found in the thread I mentioned, including an external battery pack with four AA batteries (NiMH or alkaline).