I guess I'd better move mine too. (:

Doug Dotson wrote:

I guess I had better move my entire breaker panel into the
battery compartment then. All my equipment is protected with breakers.
I only have inline fuses where the manufacturer pre-installed
them in a power cable. If you chooses to mount fuses near the
battery then you better get moisture-proof ones. The atmosphere
near a battery can get pretty corrosive, especially when using the
old liquid lead-acid type batteries. If a fuse is intended to be placed
near the batteries, the why do the pre-made cables for things like
VHF and GPS come with the fuse just a few inched from the
radio? In any case, connecting anything directly to the battery is
gennerally only accepted for a bilge pump.


Doug
s/v Callista

"Chris Newport" wrote in message
news:1742835.ilLHM71fsm@callisto...

On Sunday 02 May 2004 4:21 am in rec.boats.electronics Doug Dotson wrote:


Put it where it is easy to get at and the elements won't attack it.
There is no electrical reason to put it close to the battery.

BLOODY DANGEROUS ADVICE.
The fuse protects the wiring, all circuits should be fused as close as
possible to the battery to prevent the wiring burning in the event of
a short.


--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

"Mika" wrote in message ...
On Sun, 2 May 2004 10:55:17 -0400, "Doug Dotson"
wrote:

I guess I had better move my entire breaker panel into the
battery compartment then. All my equipment is protected with breakers.

No, just put a large "main" fuse near your battery and that will
protect in case there is short circut.

Of course. I have an 800A T1 fuse close to the battery.

Have your panel and circut
brakers the way they are now.

That would be "breakers".

Needless to say, make sure you have
your fuses in the positive lead.

It is better to have the large fuse in the negative line. It is just as
effective and is safer. Check out www.amplepower.com for
a good justification of this.

I have a large 20 A fuse near the battery: it would blow if there was
a major short circut such as my positive cable coming to contact with
ground potential. No need to replace that often, as individual
equipment have 2-5 A fuses in the panel.

Having the 20A in the negative line will do just as well. Hopefully you
will never have to replace it if the rest of the system is properly
designed.

Two fuses and several switches will add some resistance, but voltage
drop will not be a problem unless you are running something in
100..150 Watt range.

The resistance of fuses and breakers is minor and of no significance
in most cases.

Other people have already posted warnings, and I would also like to
emphasize that lead-accid batteries have very low internal resistance,
leading to high short circut currents. It is possible to melt a wrench
or other tools if they come to contact with plus and minus terminals.

Nothing special about lead-acid. My AGMs and gels will melt a wrench in
pretty short order as well.

Almost twenty years ago I was in the Army (Signal Corps), and in field
exercises we run high power HF radios with car battery power before
AC generators were up and running. Could get on the air a few minutes
faster.. Anyway, this one guy managed to short circut a heavy cable
used to jump start cars. Poof, it vanished in a cloud of smoke. That
time we were glad we had gas masks on , that probably saved his
eyesight.

No kidding. Big batteries are to be respected.

Mike
OH1NZQ

"Cired" wrote in
lkaboutelectronicequipm
ent.com:

Is there any advantages/disadvantages of placing the inline fuse
closer to the battery or closer to the radio in a direct wire to the
battery installation?. Thanks

EVERY wire in the boat needs to be protected at the SOURCE, not the load!

Unfortunately, the primary power system, in most boats, has no protection
at all from loading and shorts beyond the wire's and battery's capacity to
provide. So, a primary short causes the wires to catch fire or the battery
bank(s) to explode as the electrolyte boils into steam.

You'll find "Lionheart's" primary fuses located between the 6V golf cart
batteries in each bank of 700AH. Her original primary power wiring and her
battery capacity to produce power without boiling electrolyte is fused at a
safe 150A, about the peak current it takes to crank the Perkins 4-108 on a
cold day. She'll be dark, but safe and afloat. Her starting battery, a
high-current regular starting battery is also fused at the battery terminal
at 150A. Large fuses are all "slow blow" taking some time to melt such
large elements. Works great.

As to your directly connected radio, the radio is fused at the radio,
probably in some cheap inline fuse out of a CB radio. Icom is. This fuse
should be increased to one that won't blow (no sense blowing two fuses) and
the proper fuse for the capacity of the wire and about 150% over normal
radio drain at full power should be located on a fuse block mounted right
on the battery box or on the bulkhead next to it....so the wire won't burn.

Larry

Let's short your starter hot terminal to ground and see if the boat
survives. Let's short your ALTERNATOR battery terminal to ground to see
what happens if it survives test 1.

Larry,

You have actually shorted out your mains to blow the 150A
fuse? How long did it actually take to melt the fuse? Must
have been fun I haven't had the guts to try and blow my
T1s on purpose, especially since they cost something like $50.

Doug
s/v Callista

. Large fuses are all "slow blow" taking some time to melt such
large elements. Works great.

"Doug Dotson" wrote in
:

I guess I had better move my entire breaker panel into the
battery compartment then. All my equipment is protected with breakers.
I only have inline fuses where the manufacturer pre-installed
them in a power cable. If you chooses to mount fuses near the
battery then you better get moisture-proof ones. The atmosphere
near a battery can get pretty corrosive, especially when using the
old liquid lead-acid type batteries. If a fuse is intended to be
placed near the batteries, the why do the pre-made cables for things
like VHF and GPS come with the fuse just a few inched from the
radio? In any case, connecting anything directly to the battery is
gennerally only accepted for a bilge pump.


Doug
s/v Callista


No, actually you need to fuse the batteries to the lowest value of amperage
either the batteries can tolerate without boiling the electrolyte
(exploding) or the ****ty, half-assed wiring the boat manufacturer has
buried in the bulkheads from the batteries TO the breaker panel....

Boats with #10 house wiring from the batteries to the panel need a 30A fuse
AT THE BATTERY. You know the ones I'm talking about. Boats with starter
cable to the house breaker panel should be fused AT THE BATTERY for 150% of
the maximum planned load, not 350A just because the wires will "take it for
a few minutes". 350A will boil boat batteries in no time through heavy
wiring which won't catch fire before the batteries explode.

God it's awful stupid what you see in boats people are SLEEPING at SEA in.
I've seen a 2KW inverter hooked to the house panel main DC input. Math and
common sense have nothing to do with it. The inverter, loaded, over 150A
through that #6 wire that goes between the bent wood panel and explosive
fiberglass hull. That's ok, right?

Here....try this destructive test....

Short the battery supply cables together in the house breaker panel and
let's see how safe it is. Short the starter battery cable to the starter
case right next to it. Short the alternator battery terminal to the case
of the alternator. Think it can't happen to you?.....

Larry
It ain't rocket science, folks....

"Doug Dotson" wrote in
:


Of course. I have an 800A T1 fuse close to the battery.

Please change it....if not for the kids, for me. Fuse the battery at 150%
of the maximum normal load on them. Just add up the breakers in the panel,
you'll never draw that much. Make the fuse smaller if the breaker panel is
lightly wired. NO BREAKER PANELS ARE PRIMARY WIRED FOR 800A, unless you're
driving a freighter!

Draw 800A for 60 seconds and I'd bet the batteries will EXPLODE in a
sulfuric acid steam. Wanna try it?


Nothing special about lead-acid. My AGMs and gels will melt a wrench
in pretty short order as well.


Wet cells are "water cooled". AGMs and gels WILL explode in a much SHORTER
time because they are so compact with no chance of any electrolye
circulation. If you short any of them, of course, the acid steam explosion
is nearly instantaneous.

Wanna bet it melts the cheap plastic case?....

Larry

Comments below.

Doug
s/v Callista

"Larry W4CSC" wrote in message
...
"Doug Dotson" wrote in
:


Of course. I have an 800A T1 fuse close to the battery.

Please change it....if not for the kids, for me. Fuse the battery at 150%
of the maximum normal load on them. Just add up the breakers in the
panel,
you'll never draw that much. Make the fuse smaller if the breaker panel
is
lightly wired. NO BREAKER PANELS ARE PRIMARY WIRED FOR 800A, unless
you're
driving a freighter!

Draw 800A for 60 seconds and I'd bet the batteries will EXPLODE in a
sulfuric acid steam. Wanna try it?

I'm tired. It's a 200A, oops! Sorry.


Nothing special about lead-acid. My AGMs and gels will melt a wrench
in pretty short order as well.


Wet cells are "water cooled". AGMs and gels WILL explode in a much
SHORTER
time because they are so compact with no chance of any electrolye
circulation. If you short any of them, of course, the acid steam
explosion
is nearly instantaneous.

I think that is why we have the fuse. So that point is moot. I doubt if the
electrolyte circulation in an enclosed space will buy much additional time,
maybe a few seconds. I wonder why most military vehicles including all
aircraft switched to AGM years ago if their failure mode is so
catastrophic?

Wanna bet it melts the cheap plastic case?....

I can't tell any difference between the quality of the case in my Trojan
T-105s I had in my old boat vs the case of my 8D AGMs I have now.
I do think the maroon T-105s were much more attractive than the
battleship grey AGMs though

Larry

On Sun, 2 May 2004 21:36:53 -0400, "Doug Dotson"
wrote:

Have your panel and circut
brakers the way they are now.

That would be "breakers".


No wonder I used to get just B´s with all these typos

Mike

That would be "B" for "Breakers".

"Mika" wrote in message ...
On Sun, 2 May 2004 21:36:53 -0400, "Doug Dotson"
wrote:

Have your panel and circut
brakers the way they are now.

That would be "breakers".


No wonder I used to get just B´s with all these typos

Mike

"Doug Dotson" wrote in
:

Larry,

You have actually shorted out your mains to blow the 150A
fuse? How long did it actually take to melt the fuse? Must
have been fun I haven't had the guts to try and blow my
T1s on purpose, especially since they cost something like $50.

Doug
s/v Callista


You won't blow those monsters, which was my point of asking you to reduce
them to something more reasonable. The batteries will boil first.

Yes, I have blown the 150A main fuses, inadvertently. A wrench slipped and
got across the alternator post. There was a big flash, then dead. Never
heard the fuse melt, just saw a spark inside the fuse. The wrench welded
to the post but you could knock it loose. We had to rethread the post
before taking the nut off. No harm done. No explosions. It could happen
to anyone changing belts in a crowded engine room.

Larry