Ed Price wrote:

"Glenn Ashmore" wrote in message
...
Thanks. I gave up.

There are none so blind as those who will not see.

w_tom wrote:
Glenn Ashmore has accurately described the problem - load
dump. Depending on standard, load dump on 12 volts can be 60
volts or as high as 270 volts. Two standards are SAE J1455
and ISO 7637-1. As Glenn has accurately described, load dump
can be created by disconnecting a major load from alternator -
such as battery.

Well, pardon me for asking you to address my question. In case you didn't
remember, since it always seems to slip your attention during your posts, I
wanted to know why the suppression is applied to the LOAD side of the
alternator diodes. snip

'Cause the average user won't be able to install a system inside
the alternator case? Further, it don't matter much, 'cause the
1/2 cycle of foreward output overvoltage current sinked via
zapstopper is sufficient to load out all the overvoltage current
generated by the no longer energised field as it collapses?

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"phil" wrote in message
et...
So Ed....

Again, I will ask you just like I did during our EMC discussion, what
percentage of boaters have an engineering degree and would understand
joules, ohms, volts, ohms law, etc. to even have an inkling of what the
information meant if it were indeed included on the web page? Even if it
were included, how would it relavent unless the matching information were
provided by the alternator manufacturer under load dump conditions?

I find it interesting that most people don't have a clue how electricity
works and couldn't troubleshoot a light switch, much less understand
alternator load dump waveforms versus load and rpm, joules dumped, whether
their alternator diodes were damaged, and on and on. How many people come
on here and ask "I have no spark and I replaced everything such as the
coil,
plug wires, plugs, coil driver components (mechanical or electronic), and
there still is no spark".

I would suggest most people would just get a protector and just feel good
that there was some additional protection from battery disconnects.

To me, load dump is not mysterious, I deal with it all the time in my job
(don't ask cause I won't tell you).

Phil


Phil:

You are truly a wonderful and mysterious duck.

I will not ask your occupation, partially because I do not care, and
because, I assume, should you tell me, then I suppose you'll have to kill
me.

I do find it troubling that, as in the EMC discussion, you are again arguing
for the cause of ignorance. You say that Zap-stop shouldn't need to provide
technical info since the alternator manufacturers don't provide load-dump
info. And then you say that most in this group wouldn't know what the
information meant anyway.

OK, if that's your opinion, I can't change your mind.

Ed

"Glenn Ashmore" wrote in message
...
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:

Very illuminating, Glenn. Now I understand why your posts have trouble
answering a question and often ramble off into an insulting lecture. You are
obviously distracted by the rigors of searching previous postings looking
for clues about the poster's lifestyle and recreational habits.

I find it truly hilarious that you have concluded that I am a "hot rod ski
boater." Based on that profound logic, I suppose that having a DVM with a
1200 VAC range makes you an electrician? You are becoming a pretentious
twit.

One of the first things I did when you started lecturing me was to visit
your little sailboat construction site. Actually, for an unpleasant person,
you do nice work. If I lived near you, I would be happy to see you complete
the project and sail over the horizon.

But I am learning some interesting things about you and your cutter. I
always thought that sailors chose sail because they liked the "off the grid"
lifestyle. They wanted to get out there with the lee scuppers sloshing green
water, close to nature and in touch with the long heritage of men against
the sea. At least that's what they always said when I offered them a tow off
a sand bar. They liked to look down on "stink-potters" just the way you
casually insult small powerboat owners.

You seem to have some really hearty electrical needs. Yeah, I guess I'm
really out of touch with the average cruising sailor. I mean, on a 31-foot
twin engine cruiser I had, once I shut down the engines, my electrical load
was only an anchor light, a couple of 12 VDC cabin lights, sometimes a
half-amp radio, a minute or so of rare bilge pump operation, a 30-second
burst of the toilet macerator pump, and a rare burst of the freshwater
pressure pump. Then, I had a 50-foot down-east style diesel trawler. It was
more primitive, without an electric head (see how long ago that was?), but I
did have a big battery bank, because starting the diesel (GM 6-71) was a
tough load. And, it was pretty leaky, with two Rule 1200 GPH pumps
disturbingly active. I guess your way of sailing must include microwave
ovens and color TV's and full-time radar and autohelm.

I'm not criticizing your choices, just trying to account for your electrical
budget. Now, you said you had 800 amp-hours batteries, and you plan to use
about 65% of that capacity in one day. That's 520 amp-hours, and with 12
VDC, that's 6240 watt-hours. Averaged out evenly, that's equivalent to a
continuous 23 amp drain. And then, to put that charge back in one hour, that
implies a charging current of 520 amps. But since your alternator has a
capacity of 250 amps, you will need to run the charge for two hours. If not,
then you will hit full discharge on maybe the third or fourth day. But aside
from the schedule, what is your projected load budget?

Meanwhile, curb your imagination. I'm presently doing a restoration on a
14-foot steel displacement hull vessel with a rated 36 HP gasoline engine.
As you can imagine, hull speed is quite a bit less than 75 MPH. Maybe if I
had your battery pack, I could get it to plane for a couple of minutes!


Ed

The reason for the 800 amp hour bank is that I will have two large
computers, a 3000 watt inverter, SSB radio and a rather powerful
autopilot. All of which will eat a fair number of amps. I have
estimated my daily energy budget underway to be between 180 and about
225 amp hours.

Two other factors determined the bank size. The first is that deep
cycle batteries should never ne discharged below 50% to preserve their
useful life. That limits my usable power to 400 amps. The second is
that I would like to keep engine time to a minimum. All the systems
that use engine power, charging, watermaking and refrigeration are
designed to restore themselves in one hour of engine time per day.

Up to about 75-80% charge, deep cycle batteries can accept a charge
current of up to 25% of their capacity. As they approach full charge
the rate has to be reduced substantially. That sets an upper limit for
daily charging at about 80%. The result is a net usable capacity of 30%
or about 240 amp hours.

As I said, You set the tone of the conversation.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Ok here's my take on it.

If you need a zap stopper then you should rewire your system.

I see 1 or 2 boats every year that has problems because someone turned
off the switch while the alt was running. When I get finished it
doesn't matter what they do with the switch as i try to murphy-proof
the system.

The output of the big alternator should go direct to the big bank of
batteries. The sense for this alternator must go back to same bank of
batteries.

Now you can use the switch to combine the banks have more then one
switch to do other things with, have a battery combiner in curcuit or
even an isolater to auto slow charge the engine banks (at main bank
voltage minus isolater drop).

Why are we having this didcussion if your boat is wired up right you
need no zap stop.

The engine manufacture can not do it right as he has no idea how your
banks are hooked up he can only put alternator output to starter. You
must wire it up right.

yup...I guess I am a mysterious duck. And, that's fine with me. Keeps
everyone off balance.

My position is that no one is going to learn about load dump and emc
characteristics / countermeasures by reading this newsgroup. If they truly
were interested, they would research the topic on google or visit their
local library.


"Ed Price" wrote in message
news:1GrTa.3104$Ye.475@fed1read02...

"phil" wrote in message
et...
So Ed....

Again, I will ask you just like I did during our EMC discussion, what
percentage of boaters have an engineering degree and would understand
joules, ohms, volts, ohms law, etc. to even have an inkling of what the
information meant if it were indeed included on the web page? Even if
it
were included, how would it relavent unless the matching information
were
provided by the alternator manufacturer under load dump conditions?

I find it interesting that most people don't have a clue how electricity
works and couldn't troubleshoot a light switch, much less understand
alternator load dump waveforms versus load and rpm, joules dumped,
whether
their alternator diodes were damaged, and on and on. How many people
come
on here and ask "I have no spark and I replaced everything such as the
coil,
plug wires, plugs, coil driver components (mechanical or electronic),
and
there still is no spark".

I would suggest most people would just get a protector and just feel
good
that there was some additional protection from battery disconnects.

To me, load dump is not mysterious, I deal with it all the time in my
job
(don't ask cause I won't tell you).

Phil


Phil:

You are truly a wonderful and mysterious duck.

I will not ask your occupation, partially because I do not care, and
because, I assume, should you tell me, then I suppose you'll have to kill
me.

I do find it troubling that, as in the EMC discussion, you are again
arguing
for the cause of ignorance. You say that Zap-stop shouldn't need to
provide
technical info since the alternator manufacturers don't provide load-dump
info. And then you say that most in this group wouldn't know what the
information meant anyway.

OK, if that's your opinion, I can't change your mind.

Ed

On Wed, 16 Jul 2003 03:03:48 -0700, "Ed Price"
wrote:


"Glenn Ashmore" wrote in message
...
First of all, teh Zap Stop is not intended to protect anything from
external spikes. There are very few situations on a boat that will
cause a damaging spike back into the alternator other than a lightning
strike and in that case all bets are off.

The Zap Stop is only intended to protect the alternator from self
destructing from a load dump. It does nothing else. It does this by
clamping the voltage lower than the damaging point for the rectifier.
In a load dump the voltage spike is what fries the rectifier diodes not
the amperage.

And how do you "clamp" a voltage when a voltage source is trying to drive it
higher? As the Zap-stop does, by presenting a conductive path that has a
very low resistance. The current is limited only by the source's internal
resistance. I have no idea what the internal resistance of a large
alternator is, but I would guess maybe 0.01 ohms. The important point is
that you have to be able to sink a lot of current during the alternator's
field winding voltage excursion. Putting the protective device on the load
side of the alternator diodes is a solution that requires a heavy current
draw through the alternator diodes during a protective event.

For illustration, lets say we have a big honkin' 250 amp Balmar cranking
out full power 15 volts into the house bank (3,750 watts) when somebody
turns the master switch and the output voltage starts to rise. The
regulator is still supplying the same current to the field and the RPM
has not changed. As no additional energy is being supplied to the
alternator the total power output remains the same.

Absolutely bogus assumption about power output remaining constant.

I am assuming that your alternator has an electronic, not a mechanical,
regulation scheme. Are you claiming that the regulation can track load
variations during normal operation, but, if the load is suddenly shed, it
takes hundreds of milliseconds to react?!

Power is volts *
amps so as the voltage rises the amperage has to drop. For that 200-300
milliseconds that it takes for the regulator to adjust the field current
the zenier has to absorb that 3,750 watts of excess power. Diodes that
can handle this amount of power for that length of time are not hard to
find. Digikey sells them for about a buck apiece.

I checked my Digikey catalog, but can't find any "zenier" diodes. Perhaps
you could fix your spull chucker; your consistent use of the wrong spelling
is beginning to bug me, as real experts know the names of their tools. You
know, you pound nails with a hammer, and discussing nail technology is
disconcerting when the other guy keeps talking about his hummer.

But regardless of how much diodes cost, where you buy them, and whether they
will fail trying to carry x kiloamps for y milliseconds, the initial point I
asked was why it was good practice to put the protection on the load side of
the alternator diodes. Telling me that you can get away with it is not a
good answer.

Ed


Ed - there is a simple answer.
VOLTAGE is the killer, not current. What determines the maximum
output of an alternator? Unlike generators that had a current
regulator, alternators are regulated by the internal resistance of the
stator circuit. The diodes in an average 100 amp alternator are good
for close to 200 amps (continuous) of total output, but only for about
150 volts.
Now 150 volts is MORE than adequate for normal circumstances, but when
you experience a "load dump" the voltage can very quickly exceed even
300 or 600 volts for a short time (minimum of number of stator poles
of cycles) as the collapsing magnetic field in the stator collapses,
inducing voltage in the field, which can also contribute to the
voltage spike). Without a load of some sort to keep that voltage tamed
down, the voltage rating of the diodes can be grossly exceded. The
current flow, being extremely short, does not get the diodes hot
enough to fail from overcurrent, as the current is more or less self
limitting.
The Zap stopper shunts this current to ground, keeping the voltage
well controlled for that very short time - and again, the current is
not high long enough to heat the slow-blow protection fuse enough to
pop it.

The trans/zorb or zap stopper can also protect against the same kind
of spikes should the field circuit open under load - and the
collapsing field current induces a (negative?) spike in the stator
which passes through the diodes and is clamped by the zap stopper.

Now, if you attempted to install the zap-stopper on the stator side of
the rectifying diodes, you could have a serious problem - as there is
AC on the stator, not DC. You would need 2 zap stoppers per phase - or
one per diode - to clamp the voltage internally. That is SIX on an
average 3 phase alternator. And ONE on the rectified side does the
job, just as well.