[C38] Battery box rebuild

[Tom T.]

Hi Les,

I just enlarged my battery box to hold two group 31 batteries instead of
the smaller original group 24s.  I fabricated a common hold down clamp
instead of using nylon straps but that is a minor issue.  You will get more
amp hours from the golf cart batteries than using group 31s but I'm sure
the project will be more complicated.  If you still have an amp meter on
your engine panel, you will gain a lot of engine charging if you replace
the amp meter with a voltmeter and run the alternator output to the
batteries instead of to the engine panel.  This is a highly recommended
Catalina upgrade for both safety and charging performance.  I think I may
still have the information that I wrote for Mainsheet some time back
detailing the conversion.

It seems you have put a lot of thought in your electric needs but I do have
one other suggestion that regards the auto pilot.

If you use a bungee cord on the wheel to neutralize the helm, it will
almost eliminate the current needs of the auto pilot.  When I first tried
this, my servo motor was hot to the touch.  After using a bungee cord, the
motor cooled to near ambient temperature and almost no load on my battery,
even in rough seas.  The bungee will increase your battery life as well as
take wear and tear off of the expensive steering servo motor which will
fail if allowed to overheat.  The nylon gears tend to melt without the
bungee if you run the auto helm with a lot of weather helm like reaching in
heavy seas.

Good luck,
Tom Troncalli
Renata #95


> [Original Message]
> From: Les <hlhowell at pacbell.net>
> To: <Listserve at catalina38.org>
> Date: 3/20/2009 4:03:12 PM
> 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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