I thought about a way to solve the expensive oddball battery problem that is so often found in old electronics like portable radios. The B battery voltages of old portable tube radios are 45 V, 67.5 V and 90 V. The number of 1.5 VDC cells in each of these is 2/3 of the number of volts. 45 V is 30 cells, 67.5 V is 45 cells and 90 V is 60 cells.
Different sized cells have different current capacity ratings. A typical alkaline AAA cell is rated for 800 mAh. The button cells have lower ratings. The LR44 AKA AG13 button cell is rated for approximately 100 mAh.
The LR44 cell is 5.4 mm or 0.213 inch high (according IEC 60086-3). The cells can be stacked to get any voltage in increments of 1.5 VDC.
I can buy 100 LR44 cells on eBay for less than $10.00, name brand cells are more expensive. I can stack them easily – I’ve used this method with AA and AAA cells and it works okay.
I stacked the cells, end-to-end with them all pointing positive to the same direction. I cut a piece of paper to the same width as the length of the cells. Then I put the cells on the edge of the paper and rolled them up in a roll. I put a few rubber bands around the paper to hold it tight and to not unroll. I later put clear adhesive tape once I was satisfied.
I would break up the cells into two equal stacks and put them side-by-side so the plus and minus were next to each other on the same end. The problem with making a 22.5 V stack is that it’s an odd number of cells – a 7 cell and an 8 cell stack. So it makes sense to add one cell and make both 8 for a total of 24 V.