Generator help

trebby91September 22, 2012


I live aboard a boat.

All I really wanted to know is would a 3 HP. diesel engine (3000 RPM) run a car alternator, what speed the alternator needs to run and what is the highest amp alternator would the engine run and would I be able to run the pulleys at 1 to 1?

The idea is to run the generator instead of the main engine to top up the batteries and save on main engine hours when not cruising.

Regards, Brian.

Thank you for reporting this comment. Undo

You might want to post this in Electrical wiring. There is more activity there and the practical knowledge might be better there as well.

The short answer is yes. 3 hp translates to about 2240 watts. A generously -sized alternator from a large car can run up to 2500 watts.

The details are more involved. There are lots of different automotive generators. They vary in size and in the rpm required for peak output. Some get higher output at lower RPM and that is what you want. If you dig, you should be able to get output vs. rpm curves for some alternators. That will help you decide if you want 1:1 drive. I expect you will want the alternator at a higher rpm than 3000. Note that in some newer vehicles the alternators are controlled from the main computer rather than an integral or separate voltage regulator.

Here are a couple of examples you can see if page down. Note that the 2004 alternator is controlled by the vehicle computer so you can't easily use that.

An alternator designed for ambulance or other similar use might give you higher output and at low RPM. You might be best off with the engine being the limiting factor. If you overload the genet, the engine will bog down. If the alternator is limiting, the engine might spin happily while the alternator burns up.

Here is an idea. Call some automotive electrical specialist shops and see if they can fix you up. If you can find one that likes to do custom applications rather than just fix things up the way they were, you will be in luck.

    Bookmark   September 24, 2012 at 4:16PM
Sign Up to comment
More Discussions
Geo in old brick home
Background: we put in geo last year and love it. 2100...
PV installation ROI review
My wife and I are researching solar panel systems for...
Best Hot Water Tank to go with Solar
My parents have a big house with a solar hot water...
solar pods?? is it worth it?
first that I remember saw mentioned in "Farm Show"...
Planning for a new green home
I am in the planning stages of building a new home...
Sponsored Products
SteamSpa Saunas & Steam Units Indulgence 9kW Steam Bath Generator Package in
Home Depot
Torre 22 White Two-Light Sconce with Cherry Glass
$247.50 | Bellacor
Laurel Canopy Platform Bed - ND195
$854.76 | Hayneedle
Fitzgerald Chair - Key Largo Graphite Brown
Joybird Furniture
Petit Crystal Gold Four-Light Clear Spectra Crystal Flush Mount Light, 10W x 5.5
$328.00 | Bellacor
Gray Schnauzer with Bandana Ornament
$44.50 | FRONTGATE
Full 200TC Sheet Set - WHITE/CHOCOLATE
$389.00 | Horchow
King Botanical Jacquard Sham - WISTERIA (21X36)
$245.00 | Horchow
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™