I found a small 3 digit LED battery voltage monitor on Ebay for under $1.50 with free shipping. Here is a picture of the unit installed with double sided tape on dash. Only two wire plus and minus to hook up to a power. Here is a picture of unit installed.

 

Nice and unobtrusive. Do you have the link to the ebay site?

 

What's the benefit of a battery monitor?

 

The monitor lets me check the voltage going down the road while running. This checks the health of the charging system. I running about 14.2 volts driving around. By turning on the power without cranking the car I can see the battery voltage and check that it is not going bad. A good cheap Ebay link for one is http://www.ebay.com/itm/Green-DC-0-30V-2-Wire-LED-Display-Digital-Voltage-Voltmeter-Panel-Car-Motorcycle-/381266462068?pt=LH_DefaultDomain_0&hash=item58c5408574
with free shipping.

James