What type of alternator should I use?
I am building a generator with a lawn mower engine. What type of alternator do I use? I've heard to use a 65 amp GM alternator with a built in voltage regulator. Where can I buy one of these or is there something better to use? I want to get as much power as I can from this generator. Enough to power something like a refrigerator or a couple of tvs. The engine is a 18hp Briggs an Stratton if it matters.
I assume you are charging a bank of 12v batteries and using an inverter to power the appliances. If not, then you want a generator head, not an alternator like you would find on a vehicle. They are two different things.
The size of the alternator depends on several factors. You will need to know the maximum rate at which you can charge your batteries without causing damage. You will need to keep the alternator at a size that the engine will have enough power to turn it. You will also need to be able to put out enough power to keep up with your appliances, but hopefully enough that you only have to run the engine/alternator half the time or less.
I don't know the charging capacity of your batteries. That is something you will have to find out from the manufacturer. As far as engine power, an 18hp engine will turn any alternator you can find on a production street vehicle. You will likely need an alternator more in the 140 to 200 amp range to efficiently charge a bank of four or more batteries. For a 200 amp alternator, though, you will only need a 4hp engine, so your engine is overkill, and as such, inefficient.
When you buy an inverter, if you haven't already, spend a little more and get a good one. The inexpensive ones will not hold up to long term daily use.
