Re: 90V ht battery
The 1N4003 across each pack (even a 1N4148 may do) will protect a pack, but not one cell in a pack.
The minimum per pack voltage for NiMH (NiCd are a little different) depends on if a 6, 7 or even 8 cell pack. Most NiCd is 0.9V per cell minimum, NiMH is normally recommend 1V if not a standalone cell, i.e.
6 cell PP3 = 6V min (About 8.1V no load and reasonably fresh, but not on charge, 7.2V @ 50% charge)
7 cell PP3 = 7V min (About 9.45 no load, fully charged, 8.4V approx @ 50% charge)
Note very high capacity NiMH usually self discharge in 2 to 4 weeks unless eneloop type, NiCd has longer life and lower self discharge, but about 1/2 or even 1/3rd capacity.
You can get ready to colour print images online of the 90V packs and make replica boxes.
It could be that 200mAH are 6 cell and 180mAH are 7 cell. Or not.
Actual NiCd are rare now, most are NiMH. There seem to be 3 kinds of NiMH
1) Ordinary: AA cells are 1800mAH to 2200mA
2) High capacity 2500mA to 3000mA (probably really only up to 2700mA). Most of these have rapid self discharge and many models must not be trickle charged any faster than self discharge, i.e. can only be "fast charged", or trickle charged for fixed time. and then maintained at very low trickle.
3) Eneloop type. Medium to high capacity, very low self discharge. No continuous trickle charge allowed.
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