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V berth batteries

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jking
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110 Posts

Initially Posted - 04/30/2006 : 14:33:58

Am considering removing the aft battery and replacing with 1 or maybe 2 12 volt batteries in the v berth. Many posts, and Don Casey's book, provide a wealth of information, but a few questions remain:

1. Can I hook 2 batteries together in series without using a switch (switch seems like more hassle than needed- both will be house batteies, probably gel cells, could charge both simultaneously with solar panel or 12 amp alternator--is there really a need to isolate the batteries?)

2. Is there a danger in adding wire to the factory alternator wiring in order to reach the v berth? Should I try to up-size the outboard wiring, or just splice with the same size wiring?

#. I like Al Maniccia's(sp) battery mounting setup, but how safe is it to screw into the v berth floor (hitting the ballast tank seems like a really bad idea!)

John

John
250 WB #887
'Flying Wasp' , formerly 'MAD MOM'

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Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 04/30/2006 : 15:23:04

John,

If the outboard has electric start, I'd consider leaving the group 24 aft and wiring the motor to it and then adding additional battery capacity forward or if the group 24 craters, even going with a smaller lawn tractor battery for starting the outboard.

No electric start, I'd move all batteries forward and convert the aft compartment into storage.

You said, "series" in reference to two twelve volt batteries and likely meant parallel. Series would add the votages giving an unwanted 24 volt system. If two six volt golf cart batteries were placed forward, they would be wired in series to obtain 12 volts.

I don't see huge issues with wiring similar batteries of like age in parallel without all the combiner stuff, but DC power takes a significant voltage drop (likely several tenths) for longer runs and for this reason I'd not mount one battery forward and one aft and parallel them without a switch as charging them would be a problem. The distant battery would never reach optimum charge before the near battery told the charger... "I've had enough, cut back".

Mounting forward should not be done by putting scews into the ballast tank. IMHO the best option is to add a plywood floor to the locker cut to fit between the hull sides to lock it in place. It should be buffered from the ballast tank by carpet pad to allow for irregularities so that no pressure points stress the ballast tank. The plywood will distribute the weight of the batteries over the whole of the locker area. Two golf cart batteries weigh 140 lbs and with the bow hammering into a sea trough... that might translate into some significant forces.

Battery boxes can be built into the plywood floor or bolted to it.

I've outlined what I did at this [url="http://www.stewartfam.net/arlyn/batterybox.html"]location[/url]

Edited by - on

Tom Potter
Master Marine Consultant

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1913 Posts

Response Posted - 04/30/2006 : 15:32:33

Hi John,
Did you mean Parallel instead of Series?

I have 2 #27 deep cycle batteries located aft and they are hooked in [url="http://ourworld.compuserve.com/homepages/g_knott/battr2.gif"]Parallel[/url]
I don't have a switch, so they are not isolated. Many say you should put a switch to isolated them from each other so you won't run the starting battery down and not be able to start you motor. My thought is if they run down I can always use the rope start to fire off the outboard. I've stayed aboard 5 days running all kinds of stuff and not had any problems. If you have a inboard then the isolated battery hook up would be better. But for me the parallel hook up without a switch to fool with is the easy way to go. Both batterys charge off of my solar panel and the outboard when running.

A couple important things to remember when hooking parallel is you should use the same size battery's and its best that they be of same age. The con's of the system is, if one battery goes bad then it will draw down the good one. That's why you should use the same size and age battery.

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jking
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110 Posts

Response Posted - 04/30/2006 : 16:32:28

Yes, I did mean parallel (sorry.)

Thank you both for the input; Arlyn, how did you secure the plywood bottom so that there is no bounce in rough sea ( or on the road)--with 4200, 5200, or is the weight of the batteries sufficient to keep the entire arraingement from bouncing?

John

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Al
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269 Posts

Response Posted - 04/30/2006 : 20:29:02

John,

After considering wiring runs, voltage drops, switches, lengthening outboard wiring, bow hammering, etc., the advantages start becoming apparent of two new aft mounted AGMs in parallel with some dead weight up forward.

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jking
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110 Posts

Response Posted - 04/30/2006 : 21:43:21

How much does the dead weight forward shift or otherwise move when sailing/trailering? How have you best secured this weight?

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Al
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269 Posts

Response Posted - 04/30/2006 : 22:05:03

I use four 60 lb. bags of mortar mix (heavier per bag than sand or gravel) from Home Depot. The bags aren't secured other than wrapping them in plastic wrap, which makes them "stick" to one another. When I drop them in, they conform somewhat to the shape of the hull or the bags beneath them. They haven't budged.

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Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 05/01/2006 : 07:51:38

John, I didn't secure the plywood down. It sets on 1/2 inch foam carpet pad that gives some cushion and allows for slight irregularities in the water ballast tank top.

The wood boxes are glued and screwed to the plywood base.

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jking
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110 Posts

Response Posted - 05/08/2006 : 13:30:34

Arlyn:

What gauge wire did you use to connect the v berth batteries to the aft battery? Even with a very large gauge wire, do you still think that there would be sufficient voltage drop such that the v berth battery would not properly charge?

Edited by - on

Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 05/08/2006 : 14:26:54

I used #6 wire to the V berth batteries with no problems.

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johnsonp
Admiral

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USA
606 Posts

Response Posted - 05/08/2006 : 20:09:08

Starboard battery even with front water tank.

Portside battery also even with front water tank.

Wiring running from aft to forward. Shown with out covering.

Main electrical panel.

paulj C250wk #719

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WindDancer
1st Mate

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USA
34 Posts

Response Posted - 05/10/2006 : 00:42:15

Paul,

Nice set up. How did you mount your plywood battery holder and secure it in the compartment?

Bruce

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johnsonp
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606 Posts

Response Posted - 05/10/2006 : 22:04:14

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.