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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #11  
Old 06-06-2007
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You generally have a separate starting battery bank, which is not normally connected to the house bank. That gives you the backup. You'd still need a battery switch.

If you've seen what 12VDC batteries look like... you'd understand. A 210 Amp-hour 12VDC battery usually is an 8D battery. It weighs 130 lbs or so. It is 21" x 11" x 10". A T105 6VDC golf cart battery weighs 62 lbs. and is 10.5" x 7" x 11", and is much more manageable.

You can generally fit two or sometimes three T105 batteries in the space of an 8D. This means you can pack in more power in the same amount of space, without blowing out your back.
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  #12  
Old 06-06-2007
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More Space Required

According to your measurements, two 6V batteries would take up the space of 21x14x22 @ 124 lbs. vs. an 8D that is 21x11x10 @ 130 lbs.
Altough cheaper, the two 6's would require a bit more space. Something to consider.
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Dog,
you know I luv ya like a brother (ok, so I tolerate those twits, but you know what I mean) but mary, joesph and baby jesus, not everyone needs a bank big enough to power las vegas. remember what the guy said.

"OK. My boat is an S2 8.0B with an alternator and full charging capabilities. I only plan to use limited electrical, such as nav lights and radio when needed."


also he has a saildrive... so that gives him what, a 20 amp alternator?

so put your solar stik down for a minute willya? (tongue firmly in cheek)

go to pepboys, sams, wallyworld, napa, tractor supply house and grab a group 31 wet cell for less than 75.00,
(110 Ah/535 CCA) hook the darn thing up to the big red switch and go sailing!

Or, if he has a wild hair, got nutz with a 4D! (160 Ah, 800 CCA) for a hair over 120.00

yea, yea, acid spills, venting.... pfffft, if he heels that
S2 -8.0 over far enough to spill battery acid, that'll be the least of his problems.
cost justification? youbetcha, agm/chromeplatedtittleatorvalves and 400.00 bucks for a battery that will last 5-6 yrs just doesn't pass the smell test in this case. The wet cells even with heavy cycles will last 3-4 years, at least.
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Last edited by cardiacpaul; 06-06-2007 at 11:38 AM.
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Old 06-06-2007
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For a boat this size and use, a Group 27 or 31 deep-cycle is fine for the house battery. A simple On-1-2-Both switch is all thats needed to control the two batteries. Just remember not to leave the switch in "Both" when at anchor or you may not be able to start the engine in the morning!
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Old 06-06-2007
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some months ago there was a discussion on an other net or maybe this one about leaving the battery switch on "both". One guy did that & measured the actual currents between batteries for several days before charging them. His conclusion was that if all the cells of both batteries are good then the higher charged battery will NOT be drawn down by the lower charged battery. Any load will be 'shared' in proportion to their charged state. Also, that the charging currents are proportional to the state of charge of each battery.
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Quote:
Originally Posted by USCGRET1990
According to your measurements, two 6V batteries would take up the space of 21x14x22 @ 124 lbs. vs. an 8D that is 21x11x10 @ 130 lbs.
Altough cheaper, the two 6's would require a bit more space. Something to consider.
Ummmm... You might want to check your math. Two 6V T105 batteries take up 10.5x14x11. You're measuring for eight T-105s, not two—as you've doubled all the measurements... getting the size of two batteries, side by side, doubles only one of the measurements....


CP-

I wasn't saying the OP needed to have this much electrical battery capacity... but also was mentioning that a 75 Amp-Hour house battery is pretty small. If you're sailing for an overnight trip with the instruments and VHF on for sixteen hours or so (eight hours sailing per day) and then an anchor light for the night... you may be pushing the limits of the single 75 Amp-hour battery.
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a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Last edited by sailingdog; 06-07-2007 at 07:37 AM.
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Old 06-07-2007
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Geeze, all I wanted was another battery! HE HE Just kidding. What I've done is, I ran to TRS and bought two batteries of the same size and price and compatable with the one O got from West Marine, they are identicle twins. My house system is set up for two 12V batteries, that's what the forms in the engine well are ment to be. I feal better running things on one battery for as long as needed then if I switch to another it's because I need to. Double redundancy is most favorable with as few complications as possable, K,I,S,S. Sailingdog, you've been a great help, I'm glad I talked to you. You've layed out some basics I had to know. Keep up the good work, You are appretiated!!!! Buy the way,, If I ever spill the acid of those batteries, I'm sailin' em like I got em!
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