AAA or 4/5 AA option for Spice Series

[Sanjeev Visvanatha]

I came across a HP 38C in very good condition for $10 CAD last week in a local sale. It was missing the battery pack and AC adapter. Since this was my first Spice series calculator, I could not even test it before purchasing it. The contacts were intact, and no signs of corrosion. The only damage is a crack in the screen that does not impede readability.

I wanted a relatively inexpensive battery solution using common AAA's or flat top AA's (both to be charged externally). Reading some more on battery solutions for the Spice series, I also got worried about breaking the battery contacts. This lead me to using AAA size or 4/5 AA size batteries.

Since the battery compartment is too long for either of these types of batteries, I chose to fill the gap on the non-contact side with a dual contact plate to establish the series connection, and some compressible foam. This is a similar arrangement as the 48sx battery compartment.

I plan on using 4/5 AA NiMH 1.2V batteries, which I will order. This will eliminate the need to add foam spacers between the AAA's, and also a foam piece over the AAA's so that the batteries do not get dislodged. I may have to add 1-2mm to the foam area to make up the difference of losing the button top.

   
Fig 1: View showing Contact Plate and Foam

   
Fig 2: View Showing Dual Contact Plate for Series Connection

   
Fig 3: View Showing AAA Batteries in the Compartment

   
Fig 4: View Showing Foam Spacers Between AAA Batteries