I have a battery set up consisting of 4 group 24's divided into a
house bank of 3 and a starting bank of 1, controlled by a 3 position,
make before break, switch. The shore power charger is a Xantrex
trucharge smart charger.

The start battery has been running dry, while the house bank is
normal. It turns out that the reefer, while switched at the breaker,
draws from both banks simultaneously, and cannot be isolated to one
bank or the other.

My gut instinct is to sever the common connection. I believe that the
the draw down of the starter battery is a greater percentage of its
capacity than the house bank and thus the charger is frying the start
battery.

My question: Is there any reson for the reefer to be connected in
common to both batteries? What is common practice?

On Sat, 19 Nov 2005 10:48:32 -0500, Marc wrote:

I have a battery set up consisting of 4 group 24's divided into a
house bank of 3 and a starting bank of 1, controlled by a 3 position,
make before break, switch. The shore power charger is a Xantrex
trucharge smart charger.

The start battery has been running dry, while the house bank is
normal.

Do all cells of the start battery require the same amount of water?
If five cells need lots of water, and one very little, it is likely
that the non-thirsty cell is shorted, and the battery should be
replaced - in fact, I'd suggest that the battery should be replaced in
any case. I have a Truecharge on my boat, and the batteries use very
little water.

It turns out that the reefer, while switched at the breaker,
draws from both banks simultaneously, and cannot be isolated to one
bank or the other.

This doesn't make sense - if the reefer draws from both banks, that
would mean that the two banks are connected together, and _everything_
will draw from both banks.

My gut instinct is to sever the common connection. I believe that the
the draw down of the starter battery is a greater percentage of its
capacity than the house bank and thus the charger is frying the start
battery.

My question: Is there any reson for the reefer to be connected in
common to both batteries? What is common practice?

Common practice would be to have the start battery powering only
engine-related loads, with the house battery supplying everything
else, including the reefer.

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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 think you have two problems, maybe not related: the starting battery
boiling dry and a wiring problem. First the wiring problem.

The prevalent wiring scheme for most boats straight from the factory is a
starting battery wired to the "1" terminal of the 1/2/Both/Off switch and a
house bank of one or more batteries wired to the "2" terminal of the switch.
All house loads, starting and charging are wired to the common terminal of
this switch. So, if the switch is in the Both position everthing is all
hooked together in parallel.

You wrote that the reefer, a house load, is independently wired to the
starting and house banks- "draws from both banks simultaneously, and cannot
be isolated to one
bank or the other ". This is very weird, because it negates the switch and
can allow the starting battery to be pulled down by the reefer load at
anchor- not good. Or any other house load, like lights for example can do
the same because the reefer connection always keeps everything in parallel.

So, if it really is wired that way, then the simple solution is to wire the
reefer load only to the common terminal.

I doubt that this will solve your starting battery boiling dry, but it will
at least give you the ability to do something about it. When set up like
above, good batteries and chargers don't behave this way, particularly if
they are all the same type of flooded cells, which they must be for you to
see the electrolyte level. I suspect you have a bad starting battery.

David

David

Marc wrote in
:

Is there any reson for the reefer to be connected in
common to both batteries? What is common practice?

If the reefer is connected to BOTH batteries, and all the grounds are
connected together (negative terminals), then, all the batteries are
perpetually connected together by the wires to the reefer. The reefer
should not be connected to the starting battery....at all! Nothing should
be connected to the starting battery except the engine, which is the heavy
wire from the starting battery to the starter post. The only other
connection from the starting battery is the heavy wire to the master
switch, so the starting battery can be charged from the house circuit or
the engine started from the house batteries..assuming you have one master
switch.

Having just one charger to charge it all, frankly, sucks. Get a dual 10A
charger and connect one output directly thru a 10A inline fuse to the
starting battery. Connect the other 10A output to your house battery
common point, again directly through an inline fuse. Are all 3 of these
house batteries just hooked in parallel as I suspect? I'm not a great fan
of that. I like to keep battery banks separately switched, so if one of
them shorts or something, I can switch it out of the circuit in 15' waves
offshore without a wrench. Screwing around with battery wires is a
dockside exercise, not offshore rolling around. Switches could be as
simple as those direct-to-the-post on-off switches on each one.

Now, you need do nothing. Leave the 3 house batteries in parallel to their
charger and leave the house switched to ONLY the house batteries, the
normal position, say "A". Chance of losing all of them at once is near
zero, but you could run them down. Starting battery is always connected to
ONLY the starter and its separate 10A charger. You never need to switch it
until something fails. If you only have one alternator on the engine, use
a diode battery isolator to keep the batteries separate, charging through
the isolator with the alternator output only hooked to the isolator's
common post. Again, you start the engine and do nothing to charge it all
from one alternator. Simple...always simple. The isolator connects
directly to the battery posts, too, just like the AC charger.

How are the batteries fused? If the starter shorts the starting battery,
does a fusable link blow or do we just let it explode? If you're using #2
cables to hook the battery to the starter and house battery switch, put a
large fuse between battery MINUS terminal and "ground", negative common
engine block. No circuit, including PRIMARY wiring to the batteries,
should go unfused, like all the rest of the boats on your dock....damn
them. Unlike the car, I can't just get out and walk if it catches fire.


Larry

On Sat, 19 Nov 2005 15:06:16 -0500, Larry wrote:


Having just one charger to charge it all, frankly, sucks. Get a dual 10A
charger and connect one output directly thru a 10A inline fuse to the
starting battery.

The Xantrex TrueCharge the OP mentioned has a built-in isolator, and
has three outputs, so he should be able to connect one output to the
house bank, and another output to the starting battery.



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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