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Thread: Alternator - Charging Issue

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    Bodger

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    Alternator - Charging Issue

    Hi,

    My Mk2 has always needed pretty high revs before it will charge the battery. Think it has got progressively worse as I run the battery down recently but did have the lights on.

    The alternator fitted is a Bowers BA03058, 55A.
    The battery is in the boot, looks like it is an adequate cable fitted.
    The crank pulley is 4.5" / alternator pulley is 2" - I read that the ratio should be 3:1 for sufficient charging at idle. This correct?

    Any advice on what to do to solve this? Change pulleys? Not sure what condition the alternator is in now. Is this Bowers make good enough?

    Cheers, Allan

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    Re: Alternator - Charging Issue

    do you need it to charge at idle? unless your talking modern cars, most alternators cant maintain a full charge rate at idle with lights etc on. if you have a high revving engine you wont want to speed the alternator up, if your engine revs to say 7000 a 3 to 1 ratio will give a stator speed of 21,000rpm, which is way too high i had a mate that used to go through a new alternator every few weeks until he put a bigger pulley on it to slow it down

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    Bodger

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    Re: Alternator - Charging Issue

    Hi Graham,

    I didn't mean idle, around 3000 rpm would be good. When I last checked it it was way up at about 5000 before charging the battery. I think I need a bigger pulley same as your mate then.

    Hopefully alternator might be okay still.

    Thanks

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    Re: Alternator - Charging Issue

    it shouldnt need 5000 to start charging, there are a couple of possibilities, it could be the alternator itself, is the charge light functioning? if so its most likely got worn brushes

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    Bodger

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    Re: Alternator - Charging Issue

    Yes the charge light is working fine, always needed high revs to knock off light. I checked battery voltage a while ago and it was about 5K before it would charge. Can you get replacement brushes for this aftermarket alternator? Yeah maybe worth investigating this first before changing the pulley.

    I found Bowers UK online, I'll give them a bell with the part number and see if they can help.
    Last edited by Allanscort; 18-02-2019 at 14:25.

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    Racer Decade Plus User rallyrob's Avatar

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    Re: Alternator - Charging Issue

    Not sure if this is right or wrong. But an old friend once told me an alternator effectively has 2 charging circuits in it. One to give a charge at below approximately 2000rpm then a 2nd circuit that comes in above that.

    Is this right...?

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    Re: Alternator - Charging Issue

    Quote Originally Posted by rallyrob View Post
    Not sure if this is right or wrong. But an old friend once told me an alternator effectively has 2 charging circuits in it. One to give a charge at below approximately 2000rpm then a 2nd circuit that comes in above that.

    Is this right...?
    thats a new one on me, more likely to do with the charge light circuitry, my race car has an alternator with a big pulley so when you start it it will put the light out because it generates enough juice to do just that, but it doesnt actually charge until higher revs

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    Racer Decade Plus User rallyrob's Avatar

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    Re: Alternator - Charging Issue

    Quote Originally Posted by Graham View Post
    thats a new one on me, more likely to do with the charge light circuitry
    Ok thanks Graham. Thats probably what he was getting at then tbh, I must've misunderstood it though.
    Either that or it's just my age/memory showing up, it was a long time ago, probably about 30yrs ago..

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    Bodger

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    Re: Alternator - Charging Issue

    Cheers for the comments. The charge light doesn't go off until higher revs in sync with the battery not registering charging voltage until higher revs.

    I think I'll remove the alternator and send it off to the manufacturer Bowers in Midlands to get checked out and at least it eliminates that. The guy I spoke to in the workshop seemed decent, said they will test it free of charge.

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