Re: [Amel] Stock Alternator on a Perkins Prima M50

GrahamJohnston42 <>

Hi Joe,

We have a Valeo 70A service alternator to which I fitted a smart controller and it seems to cope with 315Ah battery capacity pretty well. I was considering a larger alternator but the drive belt on our M50 is a puny car sized one and I am sure it would not cope with the load. Indeed the belt fires black debris all around as it is with the smart controller. I have now fitted an OFF switch to the controller so if the batteries are really down the standard regulator can bring the batteries up to a level where I can switch in the smart controller without tearing the belt to pieces. Quite where that point is I have no firm idea yet as I have only had it fitted for one season. 

 If your engine is the same as ours then perhaps a double belt or another crankshaft pulley would be in order to fit a 120A alternator. I now have a spare groove in the crankshaft pulley as we no longer have an engine driven fridge and at one time I was thinking of making up a double pulley to use double belts should I go down the larger alternator route.  

My preferred option now is what I consider to be a simpler option to fitting a larger alternator, it is to use the two existing 70A ones in tandem controlled as is shown on the Adverc website. With our system it is not possible as the Valeo alternator is Positive field and the Lucas Negative but if you chsnges one or the other the system would be easy to fit without any engineering as it is all in the wiring and accessories. A bonus is that the two alternators would then be interchangeable for spares.I

If you have not already seen it may be worth having a look here


From: joemac4sail <>
Sent: Friday, 1 February 2013, 13:58
Subject: Re: [Amel] Stock Alternator on a Perkins Prima M50

Thanks Graham
Just the info I need, I hope to fit a larger alternator (Bosch 120amp with an external smart charger) to cope with the 300amp battery bank while doing the spring fit out. But if that does not work out this year at least we will have the current alternator serviced.
Regards Joe

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