[Public-List] Alternators

[Jonathan Bresler]

Michael,

Take the cheapo clamp on meter from Harbor Freight and place it around one
(and only one) of the two wires connected to a 12v incandescent lamp.
The ammeter reading should equal the wattage of the lamp divided by the
voltage of the battery.  Measure the battery voltage as well.
Would expect the meter to give a reasonable reading as long as the current
draw is reasonable, say a couple amps or more.
Dont have the model number of the one that I bought at hand, but expect
that it is this one:
https://www.craftsman.com/products/craftsman-digital-clamp-on-ammeter-03482372000p


Accuracy is about 3%.

Jonathan

On Fri, Jul 20, 2018 at 5:14 PM, Michael Grosh via Public-List <
public-list at lists.alberg30.org> wrote:

> I've looked at the electronic voltage regulators optimized for sailboats a
> few times. They change the on/off charging rate of the alternator so 1 or 2
> hr. running time fully charges a deep cycle battery. Looks like a simple
> wiring modification from the wires on the alternator.
> I never pulled the trigger on that one because I don't have much electrical
> draw, and when I motor it seems like I motor for hours.
> I bought a cheapo clamp on meter from Harbor Freight and never felt I got
> an accurate reading-12 volt or 110. Makes me feel like a real electronic
> technician though and impresses the heck out of the family. It's got a
> zippered case and everything.
> Michael Grosh
> #220
>
> On Jul 19, 2018 12:24 AM, "Stephen Gwyn via Public-List" <
> public-list at lists.alberg30.org> wrote:
>
> A few points:
>
> 1) Don't get a clamp on ammeter to measure power. They aren't very accurate
> a low level DC currents. And they are expensive. Do get a instrument panel
> mounted ammeter. I just got one for 35$.
>
> 2) If you can't find the RPM-> Amps curve for your alternator, take to an
> alternator shop. They can put it on a machine and tell you. They can also
> change your pulley for a smaller one which will give you more amps per
> engine RPM. If you do that however, you will almost certainly need a
> different alternator belt.
>
> 3) The excitor doesn't need high RPMs to work. It gets it's power from the
> batteries. But alternators do usually have a steep power curve at low RPMs.
>
> 4) Your sailing style heavily affects what kind of alternator you need.
> Normally, I motor maybe an hour a day (half an hour to get in and out of
> harbour) once a week. That also carries over into normal cruising, where I
> spend a lot more time sailing (or at anchor) than motoring. This summer,
> I'm up windless inlets and fjords a lot more, so if anything my batteries
> are over charged.
>
> SG
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-- 
Jonathan M Bresler
S/V Constance Alberg 30 #262
Annapolis/Eastport MD