posted to FB group Vintage Transistor Radios today.
I got tired of spending a lot of money on new 9 volt batteries, so I built a dc-to-dc converter, that takes two AA or AAA batteries and converts 3 volts to 9 volts DC. One problem is that I got it to put out about 10 milliamps or 90 milliwatts, so it’s not powerful enough to run a 9 volt radio. But it works great for digital multimeters and other small test equipment. The converter fits where the 9V battery goes, so I had to put the battery holder on the outside of the case.
These have cut down my costs for 9V alkalines. But the converter draws some current when the meter is off, so it needs its own on/off switch. Another solution to low current 9V battery is to use three CR2032 coin cells in series. This gives 9V at a few milliamps, and will fit inside of the battery compartment. It’s not for long term use. I had some CR123 cells, so I connected three in series, and these can power a radio, which might take 20 to 30 milliamps. But CR123 cells are expensive.
One thing I’ve noticed is that I’ve never seen an alkaline button cell leak. 👍
