I was driving my XH ute around for a while this morning, no dramas. I went to drive it after lunch, no start at all. I turn the key and it has nothing, like the battery is flat.

I check all the fuses, all good. When I turn the key to ON, the fuel pump relay buzzes and the pump runs really slowly, the dash lights come on but are very dull. The battery is reading 5.0v when I do this. Once the fuel pump stops all the dash lights are on at normal brightness. Turn the key to start and everything dies.

Turn the key off, the battery reads 12.5v. Accessories like radio etc seem to work fine with the key in ACC position.

Sometimes I get just enough charge to hear the starter solenoid click, but not enough to start.

I have the battery on the charger now and am looking for dodgy wires. I only just replaced the ignition coil after having the ute out of action for a week so this is really annoying. Any help as to where to start would be greatly appreciated. Thanks.

so I got the battery to indicate fully charged and reads 13.7volts. Turn the key to on, lights on the dash come on like normal, still no start. Each time I turn the key to start, it seems to drain more and more of the battery and the lights on the dash go dim. The battery reads about 10v after I do this.

Turn the key to off, battery voltage climbs back above 12v.

I really have no idea where to start on this one.

ok sounds like battery but you only put it on charge for half an hour,not long enough to put a decent charge into it.So charge up overnight at least.Is it a calcium battery?If so you will need a calcium battery charger.Is there a smell of rotten eggs when you try starting the car from the battery?Get the battery tested if it doesn't fail but is flat check your charge circuit.Kevman.

Its dropped a cell in the battery.
Battery is f**k. Time for a new one.

Jump start the car if possible - if same, starter motor/solenoid might be cactus.
If car starts, check charging voltage and take it from there. OK charging voltage will mean as mentioned, battery may've dropped a cell. A lazy battery is usually a progressive thing.

I couldn't get the ute out to jumpstart it so I checked the battery closely and it looked pretty cooked down one of the filler holes.

New battery, starts like it should. Thanks for the info everyone.

Check your charging voltage - overcharging may fry this battery too, so rule this out.