Which alternator?

Durcott

Durcott

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Hi Folks,

I've had a daft idea, that I think will never be cost effective, but perhaps EBay might come to the rescue...

I've got a small yacht, with an 80 Ah starter battery, and a 110 Ah 'leisure' battery.

Charging at the moment, is via a pick up coil on a 10 HP outboard, or via a couple of ancient solar panels.

I already have a cheap 240 V gennie, and a couple of reasonable mains battery chargers.

BUT - the gennie is one of those really cheap ones, and it's already falling to bits, (Didn't cost me anything ;-) ) and the chargers belong in a garage, not on a boat.

So - why not get a small Honda engine, and hook it up to a decent alternator thinks I. Then I could get one of those smart alternator regulators, and keep the batteries in good nick. With a suitable engine, I could even mount the thing in my cavernous under cockpit locker.

I've got old copies of things like the 12 Volt bible etc, but nothing up to date.

I was wondering if there is an obvious choice of alternator, that is easy to mount, easy to drive, easy to hook up to a regulator, and generally work well in a marine environment. If it happened to be cheap, so much the better I guess.

Does anyone have any suggestions?

Thanks folks

Jeff
 
Unless they are dead flat, those two batteries will not take a huge current to charge, so you don't need a particularly big alternator.
A modern car alternator takes a lot of torque at low rpm, a small Honda engine might struggle to drive it under start conditions when the battery initially takes a big current.
I think the mechanics of driving the alternator will be the easy bit compared to making it safe and quiet.
A car alternator could be made to work, if the smart regulator can be made to ramp up slow enough on start up.
But unless you are going to build your own regulator, it might be more cost effective to buy a decent used generator, or even a cheap horrid one like my £70 (ages ago !) job, which has a 12V output which gives about 7A into a hungry battery bank.
There was a long thread on this subject a couple of years ago...

In my view, it pays to understand how much electricity you are going to need and when, then try to meet that demand via the best mix of engine(s), solar, shore and maybe wind.
A good solution for our boat might not suit the way you use yours.

You could get a 125cc or smaller bike engine with built in alternator perhaps?
 
Great idea, I thought of doing something similar a few years ago to make an inverter generator, the plan was to use a 5HP lawnmower that I had with an alternator and a battery plus an inverter.. By the time I had worked it all out it really wasn't that cost effective and I would be better off just buying an inverter generator.. Not only would it work better and quieter but would be more convenient too..

For what it would take to design and build I would think it's probably be more cost effective to add more solar or some wind generation to your setup.. Would be quieter too.. :)

Really it depends on your power requirements and for what period.. If you need to top up the batteries during the week that will then be run down at weekends the the wind/solar plan should work well.. If you need more capacity then it might be better just to add another battery..

If you need constant power that will be used every day then that's a different scenario..
 
Hmmmm - food for thought. I'd had the idea of firing up a PC to do a bit of navigation etc.

I think I'll put this one in the 'nice ideas' box, and concentrate on keeping the boat afloat instead ;-)

Thanks for your thoughts though.

Jeff
 
I did this when I cruised a Jaguar 22.

Do the maths say 70 amps at 15 volts = 1050 watts or 1.4hp which is easily attainable by any 50 cc or even a 30cc weedwacker 2 st which is what I had driving a Lucas 18 ACR.

Again work out the pulley size to match engine rpm to alternator rpm. You might find you need to add a switch to cut the field current to allow the rpm to build up. I did.

Mind you having gone to the trouble of building this thing I would do ANYTHING to avoid using it. The noise was unacceptable.
 
TQA said:
I did this when I cruised a Jaguar 22.

Do the maths say 70 amps at 15 volts = 1050 watts or 1.4hp which is easily attainable by any 50 cc or even a 30cc weedwacker 2 st which is what I had driving a Lucas 18 ACR.

Again work out the pulley size to match engine rpm to alternator rpm. You might find you need to add a switch to cut the field current to allow the rpm to build up. I did.

Mind you having gone to the trouble of building this thing I would do ANYTHING to avoid using it. The noise was unacceptable.
Click to expand...

But better than the sound of your engine not starting?
 
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