I have a couple of questions.
When you guys have to weekend in the lorry cab parked up and are sitting powering an in cab fridge, tv ect, do you keep starting the lorry to charge the batterys and do you have a charge level indicator that tells you to start the engine before your power is too low?
The next question is about these rooftop aircon units, are they to be used when parked with the engine stopped or are they the main aircon?
the roof mounts can be used when ur driving or static with engine on or off,
yes you shuld start the truck up& let it run for a decient period, half hour atleast imo as it drains batterys even more by starting it up then switching it straight off, i dont no of any with battery drain warnings.
puntabrava:
I have a couple of questions.
When you guys have to weekend in the lorry cab parked up and are sitting powering an in cab fridge, tv ect, do you keep starting the lorry to charge the batterys and do you have a charge level indicator that tells you to start the engine before your power is too low?
If I’m weekended then I will generally run the engine for an hour a day. It takes the first 15 minutes of running just to put back the charge that the starter motor took out. The starter motor is by far the heaviest consumer of battery power on a truck, about 13 Kilowatts compared to a tenth of a Kilowatt for both headlamps.
puntabrava:
The next question is about these rooftop aircon units, are they to be used when parked with the engine stopped or are they the main aircon?
They work on evaporation and don’t use any current at all. They work on the same principle as your Great-Granny would have used to cool butter. You could drape a blanket on the top of your cab and drip water onto it from a hole in a barrel, the heat of the sun driving it off would cool whatever was beneath it.
puntabrava:
I have a couple of questions.
When you guys have to weekend in the lorry cab parked up and are sitting powering an in cab fridge, tv ect, do you keep starting the lorry to charge the batterys and do you have a charge level indicator that tells you to start the engine before your power is too low?The next question is about these rooftop aircon units, are they to be used when parked with the engine stopped or are they the main aircon?
A decent cab fridge will have a cutout on the fridge, so the engine will still start, but a video or a laptop charger will flatten a set of truck batteries in about 3 hours. I used to run mine whilst listening to the Archers Omnibus 
I use a thermo electric fridge (the fan type) and a laptop running off a 300 watt invertor. I usually run the engine for about 25-30 mins before going to bed and leave the fridge on and that is good for at least 8 hours. Whenever I have a night out in the yard I try and leave starting as late as possible as a kind of test on the batteries.