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Still having a bit of hassle with my mums car and starting. Battery is flat again!

Now she has killed the battery 4 times by leaving either the lights or radio on.

Last time, i jumped the car and drove it around for about 15 miles. It was fine for a couple of days, but on the third day not enough juice in the battery to get the car started.

Now the alternator must have been pumping something in for it to have woked for a couple of days, but why it died on the third, i'm not sure.

Anyway i took the battery off this time and left it on a trickle charger for 2 days.


I've put it all back on, given the car a good drive and got my multimeter out.

Battery shows 12.3v, and with engine off and all electrics on (fan, lights, heated window etc) it drops to 10.6v, but as soon as everything is off flips back upto 12.3v.

With the engine running i'm getting 13.6v and that doesn't really change even ifc i have all the electrics on, or rev the engine.

So now i'm in one of these catch 22 situations. is the alternator not charging enough (should it be more like 14v+, or is 13.7v ok on a mkiii 1.3l, does anyone else know what they have on theirs?) or is the battery murdered after being drained 4 times?

Any ideas, as i'd be pissed if i have to change both just to find out which one was at fault!

Sounds like the battery's knackered mate. Whip it out and plug it into the wall for another 24 hours or so, if it's not back up to at least the high 12s (about 12.8?) then sling it and get down to somewhere like Euronics (?)... car doesn't need a massive battery, a simple 36Ah one for £25-30 will do just fine.

Alternator might also be on the blink, but not guaranteed (could just be battery was sick of the abuse) - keep your meter on it and get someone to give the car a rev, it should go up around 14 to 14.4 volts once you're up to 2000 or 3000rpm.