Have you considered an automotive voltmeter? A simple 2" guage. It would be inexpensive and easy to mount and make it look nice.DT
I would look at a cheap DVM. Theyare available for 5 to 10 dollars, and I think that a good many of them could be run on 12 volts connected to the 9 volt battery connection in the meter. Done right, the meter would still be available for troubleshooting.Otherwise, maybe Radio Shack, Mouser or Digikey could be some help.Tom CaffreySuncatcherKetchikan, Alaska
He'd be better off with a hydrometer than a voltmeter. Then he can see exactly where the charge state is. They are less than ten bucks and I'd never trust a voltmeter to see what the state of charge is, because it really doesn't tell you....
Not entirely sure what you are after, but I would try this meter,http://www.allelectronics.com/cgi-bin/item/PMD-15V/385/15V_DC_PANEL_METER_.htmlor this one if you have to have digital.http://www.allelectronics.com/cgi-bin/item/PM-21/385/3.5_DIGIT_LCD_PANEL_METER,_20_V_SCALE_.htmlIf you realy want to use the one from Jameco, you will need to add some scaling resistors like it says in the data sheet, page 2 section 5.http://jameco.com/wcsstore/Jameco/Products/ProdDS/108388.pdf
An analog voltmeter is a waste of time to ascertain state of charge through a voltage reading. In addition, the battery should be rested for 24 hours before even a DVM, accurate to 2 decimal places, can be relied upon to give you a viable reading.If he wants to rely on the DVOM, split the pack into A and B banks and alternate use by switching. Check voltage only after the appropriate idle time and charge accordingly.Marc Bourget