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sapads
Joined: 23 Aug 2011 Posts: 4
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Posted: Fri Sep 02, 2011 4:56 pm Post subject: Battery Dying |
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I've converted my car to negative earth and at the same time converted to an alternator and all appeared to be OK.
However, a couple of weeks afterwards my battery died, which I assumed was due to it's age. A new battery was fitted 6 months ago and now that has died. I've tried using a stand alone charger on it and the reading shows no volts and it won't charge.
Am I just unlucky or should I be looking at something else and if so what? Am a newbie when it comes to car repairs/restoration so any help would be appreciated. |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire
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Posted: Fri Sep 02, 2011 7:29 pm Post subject: |
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Number of variables here!
1) the chance of buying a duff new battery these days is very low.
2) an alternator is much kinder to a battery than a dynamo.
3) what voltage is the battery at after say a 20 min run?
4) to damage a battery in a short time scale, implies that it is being overcharged, what does the SG look like?
5) crude test ; at night how do the headlamps behave as the engine revs are increased ; to bright? To dim? Don't change?
6) what sort of alternator have you fitted? Internal or external regulator
7) how does the battery voltage change from a start to a 20 min run?
With this basic info we can take some of the guess work out.
Cheers
Dave |
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traction39
Joined: 19 May 2009 Posts: 399 Location: South Wales
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Posted: Fri Sep 02, 2011 9:13 pm Post subject: |
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When you added an alternator did you also add an "idiot" light..if so what was it doing when you first converted to alternator...was it on during idle..off with revs? Always on? |
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sapads
Joined: 23 Aug 2011 Posts: 4
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Posted: Sun Sep 04, 2011 5:40 pm Post subject: |
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Sorry for not replying sooner.
Quote: | did you also add an "idiot" light.. | I used the original ignition light on the speedo.
UKDAVE2002, I'm unable to do the checks you suggest as the battery is totaly dead (buying a new battery next week).
Also Quote: | what does the SG look like | Not sure what you mean?
If the alternator is overcharging what do I need to do?
Any further advise would be appreciated. |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Sun Sep 04, 2011 6:03 pm Post subject: |
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If the battery is totally dead and will not pass charging current it has gone "open circuit". The cells are probably fine, but one of the connections between two cells (bussbars) has failed.
That is not as rare as many would think.
With a dynamo it is possible to run an engine at speeds above battery charging speed with a flat or NO battery, but with an alterator - zilch!
I flatly refuse, in spite of the higher alternator charge rate, to change any dynamo car of mine to alternator. Maybe if I installed air conditioning etc I would consider it. But I know that if my battery fails I can always start it with a tow or push AND drive it home. Without modern "extras" and a little common sense dynamos are adequate AND they generally last many times as long.
I have been stranded more than once with an alternator car and dud battery, miles from home. But then I was often topping 50,000 miles a year in my work. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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SV8Predator
Joined: 24 Aug 2008 Posts: 136 Location: Further up the creek
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Posted: Sun Sep 04, 2011 8:03 pm Post subject: |
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I think you will find that you are badly overcharging the batteries and that is what is destroying them.
Did you fit the alternator yourself? Did you test the installation? It has to be carefully regulated. Is the regulator system working? Is the regulator built in to the alternator or external? Is the regulator "regulating"?
What are the running voltages at certain RPM? I'm assuming you've checked all this, but the symptoms are pointing to overcharging.
Once you've fitted a new battery, check the voltage. If (with engine running at, say, 2000 RPM) you find the battery voltage up at 16-18 volts, then you've got overcharging. The alternator is not being regulated.
If the voltage is around 14.5 volts, then the charging system would appear to be OK. _________________ 2000 Jaguar XJ8 4.0 LWB
1974 Jensen Interceptor Mk III
1969 Jensen Interceptor Mk I |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Sun Sep 04, 2011 10:52 pm Post subject: |
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The headlamps or similar load should be on for that test. 14.7 volts being the accepted maximum. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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sapads
Joined: 23 Aug 2011 Posts: 4
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Posted: Tue Sep 06, 2011 10:35 pm Post subject: |
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Thanks for the replies. I will let you know how I get on in due course. |
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