CR2450 and CR2032 are button batteries used to power small portable electrical devices like pocket calculators, garage door opener, wristwatches, implantable cardiac pacemakers, hearing aids, etc. Most electronic devices that use a coin battery require very little power, which gives a longer service life. Both CR2450 and CR2032 batteries hold their charge for a long… Read More »CR2450 vs ...
There is nothing worse than buying a battery for your child’s favorite toy, or your camera only to get home and realize it doesn’t fit. You know it’s a big fat round one but that’s all you recall. Not a truer word can be said for the CR123 and the CR123a battery. Rather than feeling… Read More »CR123 vs CR123a: What is the Difference Between These Batteries?
A penny is 1.52mm and a dime is 1.35mm, according to the specs from the US mint.
The OP is incorrect about the thickness of the CR2032 and CR2025, but correct that the name indicates the thickness... 3.2mm for CR2032 and 2.5mm for CR2025. The difference is therefore 0.7mm.
While many folds of aluminum foil will no doubt work, my preference would be to use a dime for best conductivity and to keep the battery secure from moving under the spring.
Since he has been using two CR2025 batteries (bad plan on several levels - stressing out the spring and the voltage regulation circuit as the two biggest problems), we can be sure that one CR2025 plus a dime will fit in the space. But now that the spring is stretched out (guessing... Likely but maybe not), a penny might be better in his case.
As far as a "life hack" goes, a simple dime would be ideal (you have one available 99% of the time, and no "work" is required for the hack), and a penny will often suffice although it will stress/overextend the spring slightly more.
As far as options for optimum outcome, buying the right battery is always the best way to go.
