[C38] Battery box rebuild

Steve Smolinske SSmolinske at rainierrubber.com
Sat Mar 21 03:28:40 EDT 2009


Les, 
 
I did the same last year after having the mast down and had all the wiring inside replaced, it didnt make sense to run new wiring from the mast and ignore the few extra pumps.  I pulled new #10 wiring for all of the pumps and lights including Tom T.s cabin light suggestion with a jumper to the batteries.   I put two 220 amp 6 volt batteries in the box and moved the start battery to the large cockpit locker.  Inside the electrical panel a positive and negative bus bar, with #6 or #8 wire going from the battery switch to dc distribution panels.  I used the plastic wire clamps before the  positive bus bar to take the strain off the connections. The wiring is larger than what was installed in the boat and does not lead to as neat and tidy of an installation behind the panel but the oversized wired greatly reduces the resistance and thus heat in the wiring system.   I also used the heat shrink  connectors from anchor, they made the job much easier than using the old style with heat shrink tubing.  It is sure a nice feeling to know that your connections and wiring are done properly eliminating the worry of having to trouble shoot at an inopportune time.  Also every where possible I eliminated splices and went with dedicated runs to dedicated switches in order to eliminate potential points of failure.  I also added an additional outlet in the battery box for the charger on the AC side so that I could in turn hook it up on my panel seperately from the cabin outlets when using shore power to recharge.  I replaced my panels with Blue Sea, there is a photo on my blog with a link to blue sea.  I like the blue sea battery switch because it has three dedicated circuits that go straight to the battery for 24/7 power.  My furnace needed to be hooked directly to the battery and the bilge pump should have power 24/7 without the possibility of accidentally being switched off.  its only drawback is that it does not register the draw on the ammeter so if in my instance I dont know what the true draw is when I run the furnace and other systems.   I preffered to have all connections fuse protected at one place rather than connecting to the battery and having inline fuses spread throughout different locations on the boat.  You may want to think about adding an additional float switch to your bilge while your in the wiring mode, Mainsheet had a nice article a few issues back on how to wire in a second switch and the placement of it higher than the first.  One thing I would do over is to leave more excess wire one each run coiled in the  bilge or behind the panel than I did.  I didnt notice the same difference in cabin light brightness that Tom got when rewiring my cabin lights, I think my original installation was probably closer to what he suggested as a modification to his wiring,  but I did see a huge difference in my running lights when I upgraded them.  (if you do your running lights make sure you pull a messenger when you pull old wiring out of the stanchions, I didnt and a one hour job took all day).  Also make sure the wiring is marine grade tinned.  
 
I am adding wind instruments next month and when they are at the top of the mast I am having them replace the tricolor and anchor light with LEDS which will reduce the draw from 2.5 amps to about .25 amp for anchor and navigation combined the led for the tricolor will draw only .1 amp when sailing.  Have fun, the wiring was one of the most enjoyable projects I have done.  
 
Steve
Peregrine #312
Seattle

________________________________

From: listserve-bounces at catalina38.org on behalf of Les
Sent: Fri 3/20/2009 1:03 PM
To: Listserve at catalina38.org
Subject: [C38] Battery box rebuild



Hi, everyone,
        I am finally ready to do my rewiring project.  The first thing I want
to do is modify the battery box to accept 4 golf cart batteries.  I seem
to remember that someone said they had already done this, so I am
looking for pictures/process to help me avoid mistakes.

        I think from my measurements that the box needs to stretch about 2.5"
port to starboard, and I can rip out the 2" or so divider, and replace
it with about a 3/4" inch one in that new dimension.  This would move
the inboard battery about 3-3.5" beneath the current seat edge, so that
would probably have to change as well.  I think I could probably just
cut the new desired dimension out of the top, remove the large end of
the box and extend it 1.5".  However this may encounter some issues as
it approaches the truncated end of the settee by the galley cabinet.

        The center divider could be cut out, and fiberglass tape used to repair
the box bottom, with a new divider tabbed in place by the same method.
Probably 1/2" marine ply covered with a layer or two of cloth or tape.
The outboard end would be stretched 1-2" and re-attached with glass tape
as well.  This would give me a box that measured about 22.5"
by 16" and the batteries are 10" by 7", so they would fit with some room
to spare.  Nylon straps across the battery tops would hold them in
place.

I plan to add bus bars as well to make the connections cleaner.  I no
longer have a batterycharger there because I have two 65Watt solar
panels to maintain the batteries.  This gives me a charge current at
just under 9A peak, and here in CA, this gives me about 50AH/day.  This
seems to be enough to let me run the refer with no impact.  At anchor I
would have to run the engine about 4 hours every 5th day to replenish
the house draw (we're relatively frugal on power).  We use about 4
lights during meal times (6A for 2 hours) and 2 lamps for reading (3A
for 3-4 hours).

Under sail, the autopilot draws about 1.2A, so it would deplete the
battery in about 50 hours with the instruments and refer running at the
same time, so about every other day for 4 hours when under sail and auto
pilot full time.

        My total instrumentation is a knotmeter, a depth sounder, GPS, VHF, and
Autopilot.  The knotmeter is very low drain, the depth sounder about
0.25A average, and the GPS is about 0.75A in daylight, a bit higher at
night.  The vhf draws about 0.25 in standby.  Thus my total draw is
about 2.25A continuous underway under sail, and add about 2A for running
lights at night (we are coastal sailors and don't do much night
sailing).

        My engine has a 35A alternator which seems adequate (the batteries
typically drop to bulk at about 12A after 20min run time.)

So how does this measure up to those with more experience?

Regards,
Les H



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