Hi

A request for help.

I have been searching the internet trying to find a reliable source of voltage readings.

Recently, I purchased a XJ 351 R Sport 3.0 Diesel (2017) in the UK and I am trying to assess the quality of the battery and alternator using an electric meter plugged into the cigarette lighter socket. Currently, my car is fluctuating around 12.2 volts to 12.4 volts with the engine off but the background computer /infotainment systems running and between 12.5 volts to 13.4 volts with the engine running.

I appreciate that it would be more reliable to take the readings directly from the battery terminal but perhaps a Forum Member may have experience of using a similar type of electric meter and or a source of comparable voltage readings for this model of Jag.

I am also considering trickle charging the battery while it is connected and wonder if anyone knows a preferred " ground point " in the boot for the negative lead of the charger ?

Thanks