Batteries, Dynamos, Alternators (1 Viewer)

Aug 6, 2013
11,941
16,533
Kendal, Cumbria
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27,352
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Le-Voyageur RX958 Pl
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since 1999
Yesterday I proved once again that an alternator will support a battery until the battery is utterly dead. I found that with a dynamo (and to an extent engines that took a few turns to wake up) there was plenty of warning that a battery was on its last legs. Starting was sluggish or even failed on cold mornings but the battery would stagger on with a little help. Now we have alternators that instantly replace the battery capacity used for starting, and engines that fire within one or two revolutions, the battery will show no signs of failure until the engine won't actually turn at all. Two days ago I took my wife to an appointment in Lancaster (22 miles). The car started from cold with no hint of battery problems. I waited for her in the car with the radio playing for about 20 minutes and when she returned the car failed to start. In fact the starter engaged but didn't turn the engine then the solenoid simply rattled whilst the dash lights came on and went off in time with the rattle. I was in luck in that the next car into the car park was carrying jump leads so no real problem (but a lot of luck!) and we returned home. A subsequent test once home proved the engine would start at least twice but if the headlamps were switched on they dimmed and died within a couple of minutes. So the Smart now has a new battery.
 

Jaws

LIFE MEMBER
Sep 26, 2008
23,821
71,977
Thetford Norfolk
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4,189
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C class, Chieftain
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since 2006 ( I think ! )
Completely agree Tony..and the same thing has happened to me..
As luck would have it I was picking up some parts at the car factors... So I just walked back in and bought a battery :)
 
Apr 27, 2016
6,801
7,839
Manchester
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42,762
MH
A class Hymer
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Since the 80s
At this time of the year the combination of a cold battery (less power) and cold engine oil (engine harder to turn) finishes off a battery that has just about managed through the summer months. But that's not what seems to have happened in this case, the engine was still warm I'd imagine.

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Aug 26, 2008
4,721
24,578
B&NES
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3,823
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Van Conversion
Exp
since 2007
A similar thing happened to the Duxette's previous car when it failed to start just after refuelling at a petrol station.

Called out the AA who arrived quickly and sold her a new starter battery on the spot. (I should point out that there were no suitable new batteries in that petrol station shop)
 

andy63

Free Member
Jan 19, 2014
4,672
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south shields
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29,767
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None
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since 1990
In terms of capacity a start uses very little I suppose ..and as you say if the engine cracks up straight away you can survive on a battery that has minimal capacity..
Bit like these jump starter packs ..they are capable of the very large momentary current required but do not have a large ah capacity..
I thought you would carry one :unsure: :LOL:
Andy
 
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tonyidle
Aug 6, 2013
11,941
16,533
Kendal, Cumbria
Funster No
27,352
MH
Le-Voyageur RX958 Pl
Exp
since 1999
In terms of capacity a start uses very little I suppose ..and as you say if the engine cracks up straight away you can survive on a battery that has minimal capacity..
Bit like these jump starter packs ..they are capable of the very large momentary current required but do not have a large ah capacity..
I thought you would carry one :unsure: :LOL:
Andy
Not for 2 on the road battery failures in 50 years of motoring (although I do carry a spare wheel for a similar failure rate) šŸ˜.

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tonyidle
Aug 6, 2013
11,941
16,533
Kendal, Cumbria
Funster No
27,352
MH
Le-Voyageur RX958 Pl
Exp
since 1999
Completely agree Tony..and the same thing has happened to me..
As luck would have it I was picking up some parts at the car factors... So I just walked back in and bought a battery :)
It's been a battery year so far šŸ˜‰.
 

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