Sanity check, alternator or battery?

lollygagger
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Sanity check, alternator or battery? Nov 1, 2016 11:32:12 GMT via mobile

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Post by lollygagger on Nov 1, 2016 11:32:12 GMT

Not boat, old VW camper.
Same battery and alternator since Christmas.
Battery possibly chosen as best one in a heap of 10, or maybe I bought new, I can't remember.
Alternator was made from 3 scrappers, the slip rings are very worn.
Van start first compression however slowly it turns over. If it turns it starts. It started yesterday with less than 12v, but only just turned so I abandoned trip to supermarket, didn't want to conk out there. Battery SG was 1150, pretty flat!

I charged it up for 8-10 hours by which time the battery was fizzing away bit charger showing only half charged. Disconnected charger overnight, this morning battery was at 13.1v. Put charger on just to see and now it thought the battery was fully charged.

Back on van, engine running reads 14.2v across battery, but turn on the lights and it drops to battery voltage.

What's bust please?

Thanks for reading. I need to get an alt ordered by lunchtime if that's what it is.

Telemachus
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Sanity check, alternator or battery? Nov 1, 2016 11:41:25 GMT lollygagger likes this

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Post by Telemachus on Nov 1, 2016 11:41:25 GMT

Probably both by the sound of it! If the engine was spinning reasonably fast and putting the lights on took it down to 13v or less, the alternator is duff (presuming belts are Ok, wiring is good). I'd fix this first, then see how the battery fares.

tonyqj
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Sanity check, alternator or battery? Nov 1, 2016 11:51:03 GMT via mobile

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Post by tonyqj on Nov 1, 2016 11:51:03 GMT

Nov 1, 2016 11:41:25 GMT Telemachus said:

Probably both by the sound of it! If the engine was spinning reasonably fast and putting the lights on took it down to 13v or less, the alternator is duff (presuming belts are Ok, wiring is good). I'd fix this first, then see how the battery fares.

Yup. Lights dimming with a dynamo on tickover is pretty normal. Doing the same with an alternator spinning reasonably fast suggests it's faulty.

Checked the alternator belt?

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lollygagger
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Sanity check, alternator or battery? Nov 1, 2016 11:55:03 GMT via mobile

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Post by lollygagger on Nov 1, 2016 11:55:03 GMT

Nov 1, 2016 11:41:25 GMT Telemachus said:

Probably both by the sound of it! If the engine was spinning reasonably fast and putting the lights on took it down to 13v or less, the alternator is duff (presuming belts are Ok, wiring is good). I'd fix this first, then see how the battery fares.

Buggerit, that's what I thought. Duff alternator, leaving battery too flat too long has wrecked that too. Quite annoying as I have finally stopped ruining leisure batteries by fitting solar and a built in hook up mains charger. That one loves me at least!

lollygagger
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Posts: 4,533

Sanity check, alternator or battery? Nov 1, 2016 12:16:40 GMT via mobile

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Post by lollygagger on Nov 1, 2016 12:16:40 GMT

Nov 1, 2016 11:51:03 GMT tonyqj said:

Nov 1, 2016 11:41:25 GMT Telemachus said:

Probably both by the sound of it! If the engine was spinning reasonably fast and putting the lights on took it down to 13v or less, the alternator is duff (presuming belts are Ok, wiring is good). I'd fix this first, then see how the battery fares.

Yup. Lights dimming with a dynamo on tickover is pretty normal. Doing the same with an alternator spinning reasonably fast suggests it's faulty.

Checked the alternator belt?

Not the belt sadly. Even with a few revs on with headlights the volts stay at battery level. So it manages 14.2v until it's asked to provide more power. It's probably been the same for the last 10 months. I just haven't been driving in the dark or rain much and given it a mains charge every few months. Now I don't have the convenience of charging without staggering 200 yards with it I have been neglecting it. But it must have got much worse recently, I charged it fully a fortnight ago, then flat yesterday, not the usual few months. Maybe that's because the battery has gone downhill and the alternator has always done no more than power the coil once started.

I drove one around for 6 months with a completely broken dynamo and it only needed charging every week or so, I did quite a few hundred miles between charges and it never let me down so I know daytime running doesn't take much out of it.

Sanity check, alternator or battery?

Post by lollygagger on Nov 1, 2016 11:32:12 GMT

Post by Telemachus on Nov 1, 2016 11:41:25 GMT

Post by tonyqj on Nov 1, 2016 11:51:03 GMT

Post by lollygagger on Nov 1, 2016 11:55:03 GMT

Post by lollygagger on Nov 1, 2016 12:16:40 GMT

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