This file shows the data the I have gathered with respect to battery depletion on the HP-100/200 series 
palmtops. Bottom line - NiMH batteries seem, to me, to be the way to go. They will give almost the same 
number of hours per charge as regular alkaline batteries. I had used alkaline rechargeables in my Palmtop a 
while back, but found that they gave unreliable performance when used with most flash cards. NiMH give 
comparable performance at a significant cost savings through their rechargeability. I will update this file 
with more data as I use the NiMH batteries over time. This zip file contains the following items:

readme.txt          This file
batttest.c           C source for my primitive battery testing program
batttest.exe       Executable.
batt.wk1            123 file showing results. Load file and hit F10 to see graph of the various discharge curves.

The program is supposed to stop when the battery state reaches the VERY LOW point, but generally the 
program ends by the palmtop turning itself off. While this is a bug in my program, it did not prevent me 
from evaluating the discharge data. All the discharge curves were run on the same Palmtop in the same 
temperature environment (an office at 68F).

Batteries used:

NiMH: Radio Shack 1100mAH batteries. Cost: $10
NiCad: Panasonic 850mAH batteries. 
Alkaline: Kodak brand PhotoCell Batteries.

The NiMH batteries gave the most "classical" discharge curve, with a relatively flat decay followed by a 
steep drop off. I am not sure what the "hitch" in the alkaline curve was, but that is what I measured. Finally, 
the repetitive testing on the NiCad's was to see if the so called "memory effect" could be reversed by a 
series of charges and test discharges. Each column represents another test discharge following a full charge. 
My data indicates that there is enough variation in the performance of the NiCad's that it is difficult to draw 
a conclusive result, but it appears to me that there is limited utility to fully charging and discharging the 
batteries with the idea of improving their performance.

A common beef against NiMH batteries has been "self discharge." To test for this, I fully charged the 
NiMH batteries, used the Palmtop for .5 hours a day for 7 days, then ran a test discharge. I got about 4.5 
hours out of the partially discharged batteries, convincing me, anyway, that the self discharge problem is 
either (a) non-existent or (b) overcome in modern NiMH batteries. 

If any of you have ideas for further testing, I ran these test on my "spare" Palmtop. Let me know if you 
have additional ideas to try. I can be reached at:

bamcilvaine@jumo.com

Happy Palmtopping!

Brian McIlvaine

