Many thanks to all for your good advice and council! I do have several digital multimeters but I'd like to install a switched panel voltmeter inside my U-Haul
that will always be connected to my 12 VDC electrical
I found an excellent article with a detailed description of how to convert a 0-15 VDC analog panel voltmeter into an expanded-scale 10-15 VDC analog panel voltmeter at the following website
. The article (part 5.0) includes the circuit diagram and the specs for the zener diode and resistors.
10 V 1 W zener diode
4.8 K ohm resistor
100 ohm resistor
I made a trip to my local RadioShack but they didn't have the parts in stock. I found them online at Partsexpress.com
(10 V zener diode = $0.39; 4.7K ohm resistor $0.69; 100 ohm resistor $0.69 / total parts = $1.77) but the minimum shipping and handling cost was $12.50! This would bring my total cost to purchase and modify the 0-15 VDC RadioShack meter ($12.99) to about $27.30.
So... I went ahead and bought the marine grade BlueSeas expanded-scale analog voltmeter from my local boating supply store for $32.00. The BlueSeas voltmeter covers the range of 8-16 volts and also includes an internal LED backlight as an added bonus. As you can see the expanded-scale voltmeter gives you a much better indication of the status of your battery with line increments of 0.2 volts.
Thanks again for your help!