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zul 09-22-2008 08:42 PM

Advice needed on some basic charging issues...
I've upgraded my house bank to about 250Ah to cater for a small fridge. I have a 51A Prestolite alternator running on a Perkins 4108 and a solar panel for top-ups between weekends. I'd like some advice from anyone who can help...

1) Does it make sense to add a 3-step smart regulator (or is this only appropriate for larger alternators)?

2) Does anyone know if the ubiquitous Prestolite 8EM2017KA is a P-type or N-type alternator (no response from Prestolite)?

3) If it does make sense to upgrade, and the Prestolite is N-type (as I suspect), can I remove the internal regulator completely and run a field wire to the positive brush from the 3-step reg?

4) My pulley ratio is about 1:1.4, giving an alternator RPM of 2,100 at an engine RPM of 1,500. Anyone have a sense of whether this is enough RPM for the alternator to deliver efficiently?

Many thanks

tommays 09-22-2008 09:02 PM


My fancy at home battery charger 2/10/25 will put out 6.5 amps at 14.5 volts and while i can tell it to charge much higher i don't like to get the battery all that warm from a higher charge rate

sailingdog 09-22-2008 09:17 PM

You'll probably want a three-stage smart regulator for the alternator. It is going to be better for your batteries if you use a smart regulator and an intelligent battery charger.

camaraderie 09-22-2008 10:33 PM

It makes no sense whatsoever to go to a lot of additional expense for your type of use. If you are plugged into a dock somewhere and inexpensive 3 stage charger would be a good addition but otherwise...just take care of your cheap flooded batteries by keepint them topped up with distilled water and using your existing alternator and built in regulator.

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