Originally Posted by awg

I agree with this, you should have more than 12V with the engine running. Measure it at the battery terminals it should be about 14V with engine running

A few times and alt I have had a flat battery from leaving my headlights on, as my buzzer doesnt work (intending to rectify this issue one day)

So, I jump it with my Lithium jump pack, but it wont idle for a few minutes until the alt has charged the battery, the flat battery sucks the juice out of the jump pack, and I have to keep my foot on the gas pedal.

I have found that disconnecting the battery entirely and just leaving the lithium pack under the hood means it will idle straight up, and I have driven it like that when if I was running late. It is a 1000CCA model and is only about the size of a Bible