Following a longer than usual spell of sitting on the driveway not being used, I charged the battery and began using the car, but within a day, the battery was flat again, and would not turn over. It's fitted with a sat nav, so has no volt meter, but I don't know if it's a battery fault, a power drainage issue, or a charging issue. I have charge light on. Any pointers welcome.

 

Basic idea is to start with a known good battery and charge it. Then use a meter to find any drain. Can require a lot of time and logical thinking.

Also, to check whether alternator is charging.

There are threads about this all over the site (& net) you may as well read.

 

That sounds like the battery might be bad. Also sometimes it's hard to charge a very dead battery.

I tracked down a parasitic drain on my car. Not too bad but there are a lot of fuses!

 

There are 3 things you want to look at first. 1. Check the battery with a load tester; 2. Check the output of the alternator; and 3. Check the operation of the voltage regulator. If it's not one of those 3 then look for parasitic drain sources. I once had a brand new car die on the way home from the dealership due to a bad voltage regulator. The VR is the gateway between the alternator and battery. It can prevent a good alternator from charging a good battery.

 

There's a 4th thing to check; make sure the battery connections are tight. If one or both connections are the tiniest bit loose, the battery will not charge properly (speaking from experience...).

 

Good point! I'd actually rate that as #1!