Anyone have ideas for batteries for these type of calculators? Edmund Scientific?

[Gene Wright]

Edmund Scientific small calculators

These used a small battery pack that plugged directly into the wall to recharge. Anyone have an idea of refurbishing these? I plan to take it apart since the link above suggests it ran off coin cells. Perhaps I can simply use some alkalines...?

Ideas?

FYI. The one I have is the Edmund Scientific actual Scientific version that is missing keys in the picture. The one I now have is in great shape, but won't turn on. Batteries? perhaps...

[Bill (Smithville, NJ)]

Hi Gene,

I would think that standard button rechagable cells could be used to recreate the battery pack. Some of the Fujitsu Stylist tablet computers used a strip of 4 button rechargable batteries to maintain the clock and other settings while switching the main batteries. Not sure if Fujitsu directly sells replacement, but I would think they could be obtained from a battery distributer.

The harder part would be re-assembling the battery pack so that it could still be plugged into an outlet without risk of shocking yourself.

Bill

Edited: 6 Dec 2011, 1:18 p.m.

[Bob Patton]

You might look at American Science & Surplus (sciplus.com) item 36404.In the past I have bought several different kinds of such packs from them and disassembled them to get the tiny batteries inside. They won't be the button shape but they might fit in the space.

[Gene Wright]

Thanks guys.

I will gently disassemble the battery pack tonight and see what size "button" cells are in this thing. Be really nice to get this very well preserved tiny scientific calculator up and running.

[Gene Wright]

Ok, who thinks they can repair this battery pack? :-)

The calculator is in such beautiful condition, it would be nice if it worked. Tomorrow, I plan to apply voltage to the calculator contacts to see if it works at all. If so, then battery pack repair is the next step.

Thoughts? Ideas?

Edited: 6 Dec 2011, 11:05 p.m.

[robert rozee]

to be honest, i'd seriously consider using three AAA or AAAA sized cells (whichever will fit), along with an external charger - or just make a holder that will take non-rechargables.

i'm afraid the current system employed, just series resistors and a diode, is inherently unsafe and sub-optimal in terms of battery health.

[Thomas Chrapkiewicz]

Gene:

Given the vintage of the machine and the I.C. inside (I believe I saw a TI part in one of the pics), it likely operates on about 5v. It appears that the silver contact is the positive (+), and the gold contact is the negative (-).

The pictures of the batteries (3 button cells in series) and circuitry appears to be some sort of half-wave rectified charging system. I would certainly NOT connect this to the 110VAC under any circumstances!!!!!!!!!!

Assuming that it will ultimately operate, it would be interesting to measure the current consumption, then figure out if more modern button cells (LR44 - NOT rechargeable) would be a viable replacement.

TomC

[Gene Wright]

5V DC did not turn the calculator on here at the lab bench.

Might be dead. :-(

[Thomas Chrapkiewicz]

Darn!

Can you verify that the on/off switch has good continuity?

TomC

[Katie Wasserman]

How about these cells? Do the dimensions match?

Or maybe switch to NiMH and get the V40H cells from The Nicad Lady. Ask her to weld some tabs on for you.