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Battery Dying
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sapads



Joined: 23 Aug 2011
Posts: 4

PostPosted: Fri Sep 02, 2011 4:56 pm    Post subject: Battery Dying Reply with quote

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: 4100
Location: South Cheshire

PostPosted: Fri Sep 02, 2011 7:29 pm    Post subject: Reply with quote

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

PostPosted: Fri Sep 02, 2011 9:13 pm    Post subject: Reply with quote

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

PostPosted: Sun Sep 04, 2011 5:40 pm    Post subject: Reply with quote

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

PostPosted: Sun Sep 04, 2011 6:03 pm    Post subject: Reply with quote

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.
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SV8Predator



Joined: 24 Aug 2008
Posts: 136
Location: Further up the creek

PostPosted: Sun Sep 04, 2011 8:03 pm    Post subject: Reply with quote

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.
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1229
Location: Chesterfield

PostPosted: Sun Sep 04, 2011 10:52 pm    Post subject: Reply with quote

The headlamps or similar load should be on for that test. 14.7 volts being the accepted maximum.
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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

PostPosted: Tue Sep 06, 2011 10:35 pm    Post subject: Reply with quote

Thanks for the replies. I will let you know how I get on in due course.
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