Battery killer ?

[eldudereno]

Some advice/ experience required please.

Car alarm went nuts a short while ago with no response at all from the remotes. I've just been out and measured the battery voltage at an unbelievably low 0.46 Volts. I used the car once today, a 10 mile round trip and the alarm went crazy approx 8 hours after returning and locking up the car. I'm almost certain that no electrics were left on but even if they were surely the voltage would have only dropped down to approx 9 Volts? This is the second Halfords replacement battery that I've had in about 9 months so any ideas on whether it's their batteries that are rubbish or is my alternator killing the batteries? I know that the alternator diodes can fail but wouldn't have faulty diodes killed this second replacement battery earlier?

thanks

Edited by eldudereno on Tuesday 24th August 22:29

[Conian]

take it to a proper place that does batteries and have them test it, it'll be free probably
they'll let you know if youre alternator or battery are knackered
it's a start