On Thu, 3 Jul 2003 08:03:21 -0700, "Steve" wrote:

I'm preparing to install a 100 amp alternator and AutoMac II charge
controller on my boat. I read over the controller installation instructions
and couldn't find any mention or requirement for fuse in the output lead, to
the battery switch.

I seem to remember that fuse is a recommend (or required) in this type of
installation.

I picked up a 100 amp fuse and holder. However, I got to thinking, if this
fuse blows, then I wipe out my alternator, just the same as if I opened the
battery switch while the engine is running.

While such a fuse is probably desirable, its use is quite rare. If
you do want to install that fuse, you should add a "Zap-Stop" zener
diode across the alternator output. This device will prevent the
alternator output voltage from rising excessively if the fuse blows.


--
Peter Bennett, VE7CEI
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

I too have had the same thoughts about protecting alternator output wiring..
My conclusions a

1) Alternator output wiring should go directly from the alternator to the
battery. This wiring should be protected with a fuse or circuit breaker
within 7" of the battery by a fuse or circuit breaker sized according to the
wiring's current capacity (wire gauge). This provides protection from a
short causing the battery to discharge at a very high current. Also there
should be a switch to completely disconnect the battery from all
connections. This allows the battery to be disconnected in case of fire
caused by current less than the fuse or circuit breaker rating. This switch
is normally left on, allowing the battery to be charged. The handle for
this switch should be readily accessible from the outside of the compartment
containing the battery.

2) Even if a short causes the fuse or circuit breaker at the battery end to
blow or trip, the alternator can continue to provide current to the short.
The alternator output wiring should be sized to safely carry maximum
alternator output. Since the alternator output current is limited to the
maximum amount the alernator can produce, overcurrent protection (fuse or
circuit breaker) at the alternator end of the wiring doesn't work. Instead
the wiring to the battery should be physically protected against damage such
as running it in conduit.

3) The above all protect alternator output wiring from overheating and
causing a fire due to a short or other overcurrent. However disconnecting
an alternator from the battery can cause high voltage at the alternator
output causing failure of the alternator's diodes. A Zap-Stop or similiar
device connected to the alternator's output can shunt the high voltage to
ground, protecting the diodes.

I just went through this alternator rewiring thing this week. I originally
wired the alternator directly to the battery (with a 100 amp fuse), but then
I thought about the fact that the alternator line would always be "hot",
with no way of disconnecting it without removing the battery cable. Could
cause problems while working around the engine. So, I moved the connection
to the other side of the disconnect switch so that its possible to remove
the voltage. I put in a zap-stop in case of careless disconnect. I'm
still debating in my mind what is the correct thing to do....

"Steve" wrote in message
...
I'm preparing to install a 100 amp alternator and AutoMac II charge
controller on my boat. I read over the controller installation
instructions
and couldn't find any mention or requirement for fuse in the output lead,
to
the battery switch.

I seem to remember that fuse is a recommend (or required) in this type of
installation.

I picked up a 100 amp fuse and holder. However, I got to thinking, if this
fuse blows, then I wipe out my alternator, just the same as if I opened
the
battery switch while the engine is running.

The OEM wiring on my Volvo MD2B doesn't have a fuse or fuseable link in
the
alternator output lead. This lead goes directly to the starter cable
terminal.

Thoughts or suggestions??

Steve
s/v Good Intentions

"Steve" wrote in message
...
I'm preparing to install a 100 amp alternator and AutoMac II charge
controller on my boat. I read over the controller installation
instructions
and couldn't find any mention or requirement for fuse in the output lead,
to
the battery switch.

I seem to remember that fuse is a recommend (or required) in this type of
installation.

I picked up a 100 amp fuse and holder. However, I got to thinking, if this
fuse blows, then I wipe out my alternator, just the same as if I opened
the
battery switch while the engine is running.

The OEM wiring on my Volvo MD2B doesn't have a fuse or fuseable link in
the
alternator output lead. This lead goes directly to the starter cable
terminal.

Thoughts or suggestions??

Steve
s/v Good Intentions

You're right. Don't fuse it.

If you're charging batteries via a diode the danger of a short only exists
while the alternator is charging. Make very sure (with your insulation and
installation) that this can't happen to the line from alternator to diode.

Without a diode the danger of a short exists whenever the battery switch is
made. Be even more careful, and switch the battery off when it's not in use!

--
Jim B, Yacht RAPAZ,
Summers in the Med, winters in UK
jim[dot]baerselman[at]ntlworld[dot]com

Several of you have suggested the Zap-Stop to shunt the alternator output
to ground, if the battery is disconnected or the inline fuse were to blow..

Sounded like a workable solution until I read the discription in their ad.
"ZAP-STOP, along with the integral 20 amp slow-blow fuse,...." .

My alternator is capable of 100 amp and the AUTOMAC II is going to be
regulating the output up to that rating. If I have a 100 amp fuse in the
line between the alternator output terminal and the battery disconnect
switch and that fuse blows, then the 20 amp fuse in the Zap-Stop is also
going to blow. This would then render the Zap-Stop useless.

What am I missing here??

Steve
s/v Good Intentions

I believe the zap-stop is to remove spikes on the excitation input to
the alternator by shunting them to ground. The fuse is there in case
the diode shorts in which case you would otherwise have +12 connected
to ground..

On Thu, 10 Jul 2003 10:32:15 -0700, "Steve" wrote:

Several of you have suggested the Zap-Stop to shunt the alternator output
to ground, if the battery is disconnected or the inline fuse were to blow..

Sounded like a workable solution until I read the discription in their ad.
"ZAP-STOP, along with the integral 20 amp slow-blow fuse,...." .

My alternator is capable of 100 amp and the AUTOMAC II is going to be
regulating the output up to that rating. If I have a 100 amp fuse in the
line between the alternator output terminal and the battery disconnect
switch and that fuse blows, then the 20 amp fuse in the Zap-Stop is also
going to blow. This would then render the Zap-Stop useless.

What am I missing here??

Steve
s/v Good Intentions


Bill in Seattle

wrote in message
news
I believe the zap-stop is to remove spikes on the excitation input to
the alternator by shunting them to ground. The fuse is there in case
the diode shorts in which case you would otherwise have +12 connected
to ground..

See, that's the problem with this Zap-stop. A lot of people saying what they
believe it will do for them. Technical data at the Xantrex site is darn
slim, so wishful speculation abounds.

Extraordinary claims demand extraordinary proof. I wanna see a schematic, I
wanna see suppressed transient waveforms, show me why Zap-stop is better
than a zener or MOV or SiC or Transorb or a gas tube!


Ed

"Ed Price" wrote in message news:DPtQa.417$ Extraordinary claims demand extraordinary proof. I wanna see a schematic, I
wanna see suppressed transient waveforms, show me why Zap-stop is better
than a zener or MOV or SiC or Transorb or a gas tube!


Ed

I believe the zap stop is just a zener in series with a slow blow
fuse. You could make one for a lot less than they charge

On 24 Jul 2003 15:35:55 -0700, (Jim Balsley)
wrote:

"Ed Price" wrote in message news:DPtQa.417$ Extraordinary claims demand extraordinary proof. I wanna see a schematic, I
wanna see suppressed transient waveforms, show me why Zap-stop is better
than a zener or MOV or SiC or Transorb or a gas tube!


Ed

I believe the zap stop is just a zener in series with a slow blow
fuse. You could make one for a lot less than they charge

There are several ways to approach this, depending on the alternator.
I don't like integrated regulators because they are hard to safely
control. Particularly those that supply their own field current when
they are running (get starting current through the charge lamp) and
ground the field internally through the regulator. By disconnecting
the trio diodes internally from the regulator, you can convert many of
these alternators to ecternally excited units -supply field current
through the "L" terminal.

External regulator units are obviously simpler.

Now you just need a "crowbar" circuit (like the zap-stopper) on the
regulator feed, with a fuse between the crowbat and the battery/ign
switch. If the voltage excedes 15 volts (or whatever voltage you
design for) the circuit clamps the field and blows the field supply
fuse - guaranteeing you will NOT get overvoltages. Now, if you want to
fuse the output, you need to have an NC relay in the field circuit
controlled by the output of the alternator, and you need to charge the
battery though a diode so when the fuse blows there is no voltage to
the relay coil, and the field drops. Final piece of the puzzle is to
provide startup current to the field, so the alternator can produce
power to close the relay to energize the field. This can be done by
providing power directly to the field(alternator side of field relay)
or to the coil of the relay during cranking.

On Sat, 19 Mar 2005 00:31:02 -0500,
wrote:

On 24 Jul 2003 15:35:55 -0700, (Jim Balsley)
wrote:

"Ed Price" wrote in message news:DPtQa.417$ Extraordinary claims demand extraordinary proof. I wanna see a schematic, I
wanna see suppressed transient waveforms, show me why Zap-stop is better
than a zener or MOV or SiC or Transorb or a gas tube!


Ed

I believe the zap stop is just a zener in series with a slow blow
fuse. You could make one for a lot less than they charge

There are several ways to approach this, depending on the alternator.
I don't like integrated regulators because they are hard to safely
control. Particularly those that supply their own field current when
they are running (get starting current through the charge lamp) and
ground the field internally through the regulator. By disconnecting
the trio diodes internally from the regulator, you can convert many of
these alternators to ecternally excited units -supply field current
through the "L" terminal.

External regulator units are obviously simpler.

Now you just need a "crowbar" circuit (like the zap-stopper) on the
regulator feed, with a fuse between the crowbat and the battery/ign
switch. If the voltage excedes 15 volts (or whatever voltage you
design for) the circuit clamps the field and blows the field supply
fuse - guaranteeing you will NOT get overvoltages. Now, if you want to
fuse the output, you need to have an NC relay in the field circuit
controlled by the output of the alternator, and you need to charge the
battery though a diode so when the fuse blows there is no voltage to
the relay coil, and the field drops. Final piece of the puzzle is to
provide startup current to the field, so the alternator can produce
power to close the relay to energize the field. This can be done by
providing power directly to the field(alternator side of field relay)
or to the coil of the relay during cranking.

And what do you do about the already charged field in the alternator
when the battery gets disconnected? It is already too late.
That's why the zap stop goes across the output of the alternator.

Regards
Gary