Battery v Alternator

[Grin-a-lot]

Before I spend money on the wrong thing, I'm trying to figure out what needs replacing.  Here's the story:

This morning the battery was dead, jump started it and drove an hour to the run out at Sherston.  Left after 3 hours and it started fine.

Got home after 25mins, had a cup of tea and went out again with no problems.  After 30mins of being out we stopped and car wouldn't start again.

Jump started it and all good. Drove 15 mins home sat down and puzzled over it, went out to start it and it's fine.

So any ideas whether it's (probably) the battery not holding it's charge or the alternator not charging?

I figure that if the alternator was dead it wouldn't have charged the battery between home and the pub and allowed me to start the car when we left the pub.

I'm going to get the battery tested tomorrow but will probably replace it because it's at least 6 years old and spent most of its life stationary.

[paintman]

Try giving the battery a long trickle charge over a couple of days using a pulse charger (can't over-charge the battery).  Will bring most batteries back to full efficiency as long as a cell hasn't gone.

   Tony 

[Bulldog Bri]

Also sounds like there could be a loose wire somewhere, check as much as you can, I've found one of my earth wires from the battery wasn't in fully and it made a difference.

[Hairy Santa]

As Brian has said, sounds like dodgy connection, try undoing any bolts a bit on earth and main poss lead, give them a twist to make a good connection and then retighten, also pull small lead of the starter solinoid and push back on ( normally a thick brown one from memory)- also could be the ignition switch, try the leads on that as well       

[Grin-a-lot]

When I started it the time before last the ignition light remained on (which I'm sure it didn't used to). I started it a second time and it went out, perhaps it suggests a fault somewhere on that circuit?

Will check the wiring as best I can and look at giving the battery a good charge.  It's retained 12.5v over the last few hours, will look again tomorrow morning.

['The Gaffer']

Loose wires, especially earths can cause a problem.

6 years is quite old for a battery that you have no history of. Is it sealed or can you check levels? I would have expected a tad more than 12.5V after a prolonged charge.

The ignition light should always go out and stay out, somtimes this might need a small rev or two dependent on how the alternater is wired. In some cases the circuit through the light itself is used to 'excite' the alternater into charging.

Can you put a DC volmeter across the battery with the engine running? You should see volts rise once started to about 13.5 to 14 volts. This would indicate that the alternater is doing its job. leaving only the battery at fault.

As Tony mentioned, a good conditioning charger can sometimes revive a tired battery but maybe a drop test will show a fault.

Can you borrow a battery out of somthing else for a while and try that?

Hope you get it sorted.

[Grin-a-lot]

Righty-ho.  Turned out that the battery was indeed "boobies vertical"  so now replaced and car started first time and was most excellent.

Managed to get hold of a voltmeter and checked the battery output whilst off, will do the same again tomorrow while it is running to see if the alternator is doing its thang...

Checked as many of the electrical connections as I could find and they all seem to be good, the ignition light does extinguish now so I wonder whether that was a function of the battery being kaput.

Also assumed that the lights were not working because the battery had died but that was wrong too, a blown fuse was the problem and I was quite pleased with myself for finding it, replacing it and restoring the lights today.  All in all small victories but most succesful; fixing snags with these cars is quite good fun isn't it!

['The Gaffer']

Glad all is sorted.

Keep an eye on the lights, fuses dont always blow for the fun of it. It could have just been a worn fuse though after several years of switching.