I use one of the yellow HF meters at the farm for monitoring the bank. What I did was put a momentary push button on the face of the meter and wired it into the lead of the battery. When I need to check the voltage, just push the button and the meter turns on. This way I can leave the selector switch on the 20v level. The battery has been in for 2 years now. The newer red HF meters have an on/off switch right where I put mine on the yellow one. I would post a pic but the meter is at the farm. Sorry I have some extra switches if you need one.
Fishbonz