"rmcinnis" wrote in message
...

"Nigel" wrote in message
...

I think the system has a positive earth,

That would confuse things! What kind of boat is this on?

What confuses me the most is why both the Positive and the Negative sides
of
the battery are switched. In a typical battery installation the negative
side of all battery banks gets tied gets tied to "ground". If it was a
postive ground system then I would expect the same except it would be the
positive side that is connected to ground.


Ignore for the moment the fact that the batteries have a switched negative
side. The fact that the output of the switches have their negative side
tied together suggests that the system is negative ground. That wire
that
connects the two negatives together is NOT what you want to replace!

The voltage sensitve relay needs to connect between the positive terminals
of the two batteries, preferably between the switch and the battery. In
order for the two banks to charge together regardless of the switch
settings
the negative sides of thebatteries would need to be tied directly
together.

So, the easiest way to install this relay is to add a BIG wire between the
two negatives, then wire the relay directly to the two positives

Rod


Whoops...firstly, the picture has changed I miss labelled the terminals, but
I don't think it affects things so far.
The boat is a steel hulled Roberts 53, (www.jassira.com) and was built by
the previous owner, my understanding is that a lot of the internal fitting
was carried by friends and acquaintances, but the wiring gives the
appearance of being done by someone who was at least competent. She was
built in the early 80's and I think this systems is original and has worked
well so far. I do know that if I remove the black cable joining the 2
switched negatives the domestic system still works ok but the batteries
don't charge. I assume from this that the positive cables must be connected
elsewhere
I'll investigate further today,

On 2004-10-16 17:54:29 +1000, "Nigel"
said:


"rmcinnis" wrote in message
...

"Nigel" wrote in message
...

I think the system has a positive earth,

That would confuse things! What kind of boat is this on?

What confuses me the most is why both the Positive and the Negative sides
of
the battery are switched. In a typical battery installation the negative
side of all battery banks gets tied gets tied to "ground". If it was a
postive ground system then I would expect the same except it would be the
positive side that is connected to ground.


Ignore for the moment the fact that the batteries have a switched negative
side. The fact that the output of the switches have their negative side
tied together suggests that the system is negative ground. That wire
that
connects the two negatives together is NOT what you want to replace!

The voltage sensitve relay needs to connect between the positive terminals
of the two batteries, preferably between the switch and the battery. In
order for the two banks to charge together regardless of the switch
settings
the negative sides of thebatteries would need to be tied directly
together.

So, the easiest way to install this relay is to add a BIG wire between the
two negatives, then wire the relay directly to the two positives

Rod


Whoops...firstly, the picture has changed I miss labelled the terminals, but
I don't think it affects things so far.
The boat is a steel hulled Roberts 53, (www.jassira.com) and was built by
the previous owner, my understanding is that a lot of the internal fitting
was carried by friends and acquaintances, but the wiring gives the
appearance of being done by someone who was at least competent. She was
built in the early 80's and I think this systems is original and has worked
well so far. I do know that if I remove the black cable joining the 2
switched negatives the domestic system still works ok but the batteries
don't charge. I assume from this that the positive cables must be connected
elsewhere
I'll investigate further today,

A survey requirement in Australia for some states is to have both
positive and negitive terminals switched. This is because it completely
disconnects the battery from the system when switched off. This avoids
any possibility of a leakage path except for a switch failure.

--
Regards,
John Proctor VK3JP, VKV6789
S/V Chagall

On Sat, 16 Oct 2004 10:03:32 +0000, John Proctor wrote:

[snip]


A survey requirement in Australia for some states is to have both
positive and negitive terminals switched. This is because it completely
disconnects the battery from the system when switched off. This avoids
any possibility of a leakage path except for a switch failure.

Interrupting just one pole also avoids any possibility of a leakage path
except for a switch failure.

--Mac

On 2004-10-17 14:18:15 +1000, Mac said:

On Sat, 16 Oct 2004 10:03:32 +0000, John Proctor wrote:

[snip]


A survey requirement in Australia for some states is to have both
positive and negitive terminals switched. This is because it completely
disconnects the battery from the system when switched off. This avoids
any possibility of a leakage path except for a switch failure.

Interrupting just one pole also avoids any possibility of a leakage path
except for a switch failure.

--Mac

Thes same survey requirements also demand 3 separate battery systems,
engine, house, radio as well. I have never been able to understand why
the two pole (negative and positive) requirement was there other than
to ensure that the batteries were completely disconnected from the
system. No one I've ever talked to could explain why to me in a
satisfactory way.

--
Regards,
John Proctor VK3JP, VKV6789
S/V Chagall

Nigel wrote:

I do know that if I remove the black cable joining the
2 switched negatives the domestic system still works ok but the batteries
don't charge. I assume from this that the positive cables must be
connected elsewhere
I'll investigate further today,

Leaving aside the issue of whether the engine and alternator are
positive or negative ground, the alternator will have two output
connections, one through ground and one through an insulated
terminal; one of these will be positive, the other negative; for
the rest of this it doesn't really matter which is which, so long
as you can identify them.

Chances are you'll find that the minus output of the alternator
goes via a single cable to the switched minus of the engine battery
(and then via your mysterious short link to the switched minus of
the domestic, and that the plus output of the alternator goes via
two separate cables to the two switched plus terminals. I have a
feeling it might be those black cables with the red tapes around
their ends.

Leave the short link in place.
Remove the plus alternator feed cable from the switched domestic,
either disconnect both ends of the cable and throw it away, or
double it up so both cables go to the engine switched plus.
Then connect your VSR between the two switched + terminals.