Quote Originally Posted by Sillymangoes View Post
Hi Threedogs or anyone else,

So I have a Piranha Battery "Monitor" which is just a light bar with about 10 bars if full. I installed the new battery and with ignition on it is reading only half. When the car is running it is reading almost full. Why is it different between ignition and running? My old main battery was reading the same level and was tested at marginal. ????
Ign on means there is a draw on the battery and it should be 5 or 6 bars (12.5 volts or so) depending on Diesel/Petty/Glow Plugs/Ignition/Accessories fitted etc

Engine running means the Alternator is putting 13.8 volts or more at the battery so should be 9 bars (13.2 or more).

Voltage when the engine is running (or recently run) means very little in regard to battery condition.