If I play the radio or my laptop etc throught the trucks battery without truck switched on, how long about can I do that without having to run the lorry?
Also how long should I keep the lorry running for before I can switch it off and continue using radio etc
If your truck has decent batteries you should be able to run that stuff all weekend long without the need to start the engine no bother. However, winter is coming and now is the time to find out if your batteries are crap, so use your stuff and if it fails to start in the morning you need to replace them thus saving yourself future heartache.
Sorry if that sounds flippant but it really is that simple and there really is no magic formula to work it out. They either will take it or they won’t.
One thing to keep in mind is starting and running the truck at idle for short periods will also drain your batteries, best practice is to run the lorry for between 4 and 10 miles to allow the batteries to recharge.
You ought to be OK running your radio and the like for long periods, however things like inverters, kettles, microwaves etc will drain batteries quite quickly.
Age, condition, temperature, load, usage cycles etc all contribute to the length of time a battery will hold charge.