I will be pumping over 200 amps for as long as an hour every day while
cruising. I had to go back and look at some of your previous posts to
figure out why you are thinking the way you are. Then I found the post
about having a 0-75 MPH speedo and realized that you are a hot rod ski
boater with no idea of how a cruising boat works.
A typical 35' to 50' cruising boat with a well balanced electrical
system will have anywhere from 350 to 1200 amp hours of battery bank and
will regularly draw it from 75% to 50% to keep the charging cycle in the
bulk current range. They will have an alternator capable of outputting
20 to 25% of the bank's capacity per hour and run it once or twice a day
for up to an hour at as close to full capacity as possible. That is
what those fancy three stage regulators with temperature sensors and
recombinant caps are for.
As an example, my boat will have a pretty heavy duty system but it is
not as large as some in that size range and not all that much larger
than most. It is 800 amp hours in four L16HC batteries charged by a 250
amp brushless Niehoff fire truck alternator with an external three stage
regulator and external rectifier. The energy budget calls for charging
and making water for 45 minutes to an hour every day while cruising.
Should a guest unknowingly turn the master battery switch during that
time I could be out about $1,000. In this situation, which is not
unusual for a cruiser, a $25 investment in a Zap Stop is a no brainer.
The single most common reason for failures in cruising boat alternators
is load dump spikes with bearing failures a distant second. OTOH, a ski
boat with only a cranking battery, no master battery switch and a stock
60 amp alternator would never have to worry.
Ed Price wrote:
snip
There are a vast number of auto owners, with alternator systems, who will
NEVER experience 60-amp load dumps. And there are many, many small boat
owners whose electrical systems are close copies of automotive systems, and
they also operate under nearly the same conditions as a car. So that's
another whole cohort that will NEVER see those 60-amp load dumps.
So who does experience these load dump conditions? How often will Glenn, in
his cruiser, be pumping 60 amps back into his battery bank? And for how
long? And with what probability that he will do a trick with the battery
changeover switch during that short period of exposure?
So help me out here, Phil; what class of vessel often sees 60-amp charging
currents? Does that class of vessel usually have switch-twiddling idiots
running the below-decks division?
It seems to me that the Zap-stop is being hyped as needed for everyone with
an alternator, while the conditions of 60-amp load dumps are experienced by
only a small slice of small boat owners.
Or maybe I'm just a troll.
Ed
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at:
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