"Gould 0738" wrote in message
...
....

Starting the boat with the battery charger running can disguise a weak
battery.

This is true, especially if your only way of measuring charge state is to look
for 13.2 Volts, which gives you no information. By starting the engine on the
battery you are performing an informal "load test." If you only use your boat
infrequently, this is a good idea.

BTW, if you use a battery combiner it will likely disconnect the starting
battery from the charger when you start. If you use an echocharge, the starting
battery is only seeing 10 amps from the charger.


Turning on the battery charger once the engine is running will not,
ordinarily,
increase the rate at which the battery is being charged. See note below about
proper wiring.

This is generally true, though it depends on the component size. The "standard"
configuration for my boat is two 9.9 hp outboards that only have 10 Amp
alternators - they won't fill the charging capacity of the stock 425 Amp-hours
of the main bank.



There is an upper voltage limit on some of the regulators and controllers used
to regulate charging from alternators, AC converters, or any other sources
like
wind or solar. In some 12-volt system cases, this is 26-28 volts.

Whoa! What's that? My charger could put out 28 volts? Or are you saying they
could be hurt by that much voltage?

An alternator
pumping out 14-15 volts and an AC converter doing the same could blow out some
of these components.

Are you claiming we have to add up all of the voltages of the various charge
sources? If your boat is miswired so this could happen I would think you'd want
to find out about it real quick!

I have direct knowledge of
an alternator that required a rebuild. According to the rebuild shop, the
damage was "consistent with the things we see when people run their battery
charger and their alternator at the same time."

Sounds rather jaxian to me. Are you sure you understood what he said? What
actually got damaged? I run two engines, each with an alternator, one of them
capable of putting out 100 Amps. Why isn't this the same thing? Why aren't
there hundreds of twin engine boats blowing alternators every day?

You still haven't told us what you think will blow.



If a boat is properly wired, there may be only minimal risk of screwing
something up by running the alternator and the AC converter at the same time.
A
good portion of the new boats coming off the assembly lines and a likely
majority of boats that have had any electrical cobbling done after manufacture
are not properly wired.

What kind of miswiring are you talking about? Isn't it more important to find
those problems?


When I worked as a broker, I would never start somebody else's boat with the
shorepower running. Why risk it? If a boat wasn't going to start without the
charger running, the time to address and correct that was *before* a
prospective buyer came aboard.

I suppose its always prudent to test the starting battery on a boat you've never
taken out before. This is different from saying "you should not try to charge
the battery from the charger and run the engine".

Gould,

Very interesting information. I wish I knew where to find out more about the
theory and practice of these things.

I have read conflicting things about the safety of AC chargers and
alternator chargers running simultaneously, but as someone who has blown an
alternator and a voltage regulator over the past two seasons, I say why risk
it.

Now - how to remember always to turn off the AC charger before starting the
engine...

====

Charles T. Low
- remove "UN"
www.boatdocking.com/BDPhoto.html - Photo Contest
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Gould 0738" wrote in message
...
...
There is an upper voltage limit on some of the regulators and controllers
used
to regulate charging from alternators, AC converters, or any other sources
like
wind or solar. In some 12-volt system cases, this is 26-28 volts. An
alternator
pumping out 14-15 volts and an AC converter doing the same could blow out
some
of these components. I have direct knowledge of
an alternator that required a rebuild...

"George Rogers" wrote in message
. ..
Can you use an external battery charger to "quick charge" the boat battery
(after extended storage) without disconnecting the battery leads, or
should
the battery be disconnected first? Didn't know if the charger would have
any adverse impact on the boat's internal charging/electrical system if
the
battery is left connected.


There shouldn't be any issues with regards to the boat's electrical system.
Anything connected to the 12 volt system has to be able to handle the
extremes of voltage that will regularly be encountered, which is as low as
10 volts during starting and as high as 14.2 volts for a fully charged
battery. The situation can be even worse with some outboards with
unregulated charging systems.

There is an issue about safety. The battery on a boat is typically in a
much more confined space than on an automobile which increases the risk of
explosion, either from gas fumes accumulating from the engine space or from
hydrogen escaping from the battery itself.

Be careful and use common sense (like make the connections to the battery
before plugging in the AC to the charger) and you shouldn't have a problem.

Rod