How many times have you opened a small battery operated device and frowned when you saw it was powered by one of those small rectangular 9 volt alkaline batteries with the button connectors on top?
Yes, they’re expensive most places, and it’s normally not the battery you keep around for a spare.
I have a Sears garage door opener that is 35 years old, it’s given me a few years to study the use of these 9 volt batteries pulling duty in small transmitters where the battery spends a second or two running a tiny transmitter and then going back into a no load state.
It’s some years before they go dead normally, but always good to look at the date on the battery and know how old it is when you put it into service.
About seven years ago, I decided to take some test clips and put one of the 9 volt batteries that was too weak to power the garage transmitter across a 12 volt battery, I may have left it there for about three or four minutes and then back into the transmitter. It worked for more than a year, and I do use it quite a bit in the shop. Next time it went dead, I did the same thing, and another year or two of service.
And several days ago , I looked around and no spare! So I charged it again! working just fine…
So Yesterday, I’m at a place where nothing gets fixed.. there’s a remote key pad between the garage doors than has had a dead battery in it for the last six months or longer. on the floor, I see a standard 12 volt car battery charger.. I gave it a three minute charge and presto!
I know, we hear you shouldn’t do this, but I did, and it does seem viable is this application.. the power draw is very small, the stand by position is open circuit across the battery..
I’ve seen no leaks in this one battery, but that’s always a risk.. keep the charge short, and do experiment..
And who are these people in the picture?
Nothing at all to do with batteries..Marc Chirico and Francis Rogollo. Marc is a local PG Instructor and Rogollo’s simple brilliant design allowed a lot of us to take our very first foot launched flights, two of my Hero’s.