"Andy" wrote in message
oups.com...
Doug Dotson wrote:
"Andy" wrote in message

You don't need plans to build a manual alternator controller. Just buy
a rheostat rated for 12 volts and however much current will be going
into the alternator field wire and hook it up between the battery and
the alternator field wire. Thats what I did when my regulator died
when I was cruising, and it worked like a charm; charged the batteries
much quicker than the old regulator. You have to have a good voltage
meter on your battery bank and know at what voltage to start tapering
down the charge so you don't fry your batteries.

Andy

Your old regulator was junk. No wonder doing it manually worked better as
long as you pay attention. How long did you charge them manually and how
long
did they last?

After my regulator died I used combinations of lightbulbs as my
regulator for a couple of months. (See Nigel Calder, Boatowners
Mechanical and Electrical Manual, 2nd ed. page 71) Then I finally found
a rheostat, and used that from Panama to San Diego, another 4 months,
so I used some form of manual control for 6 months cruising full time.
The batteries still seemed just the same when we sold the boat 6 months
after we got back.

Regulators are not magic; all they do is adjust the current flowing
into the alternator field wire to maintain a certain voltage in the
battery bank when charging. Once you do a little reading and learn
what voltage(s) your batteries should be at when charging you can do
just as good a job as any regulator. The only advantage of a regulator
is that it can't get distracted and forget to turn down the current to
the alternator field wire.

Once you have used a manual contoller for a while you get a feel for
when you need to turn down the current in the charging cycle and it
becomes habit.

But you can never do it as accurately as a good charge controller. I doubt
that manually one can adjust the voltage according to the battery
temperature
when the voltage difference is 0.05 volts per degree C. A couple tenths of a
volt can be the difference between undercharging and boiling off the
electrolyte.
In a pinch doing it manually will get you home. 6 months doesn;t tell the
story.

Andy