HP 35S battery drain

[Steve Simpkin]

Yes, it looks like you probably have a defective one. Most people seem to average about 18 months from a new set of batteries.

Regarding your reverse-engineered schematic. Most people who investigated the battery connections show the two cells as wired in parallel, not in series as you have drawn. Make sure yours are wired correctly as shown in this photo:
http://www.finetune.co.jp/~lyuka/interes...-35s-2.jpg

Here is some additional information about current drain.
https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=164075

http://www.finetune.co.jp/~lyuka/interests/calc/hp35s/