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Battery advice?

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GregOnC25
Deckhand

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USA
22 Posts

Initially Posted - 09/17/2003 : 20:10:52

As a distraction from thinking about Isabel, I thought I would post a newbie question. I plan to replace batteries on newly acquired C25. My power requirements are minimal...daysailing w/ radio, typical electronics and possibly autotiller. I just bought a 10W Siemens solar panel and charge controller. I was thinking about "scrapping" the two bank system and installing single bank of two golf cart batteries in series with output of ~200 amp*hr. Does this sound reasonable or is the typical two bank setup with 100 amp*hr deep cycle batteries preferred? Thanks in advance!
Greg

GregOnC25
87/#5615/WK/TR

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ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 09/17/2003 : 20:41:31

IMHO follows:

From the description of your usage, I'd think 2 generously sized deep-cycle RV/Marine batteries on an A-B-Both-Off switch would do fine.

Extended cruising with wife/kids... demands of TV, blender, stereo, fans, lights.. then I'd go for the golf cart batteries.

Currently maintaining two holes in the water...'77 Venture 23 and new to the family,
'78 Catalina 25

Edited by - on

Sea Trac
Master Marine Consultant

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Vanuatu
1357 Posts

Response Posted - 09/17/2003 : 20:47:29

FYI - I bought two 60 amp hour deep cycle marine batteries from the Evil Empire for $60 each, and then discovered that Wally World has 75 amp hour deep cycle marine batteries for $55 each. <img src=icon_smile_blackeye.gif border=0 align=middle><img src=icon_smile_blush.gif border=0 align=middle>

J.B. Manley
<img src="http://im1.shutterfly.com/procserv/47b3d609b3127cce8d2e212441c60000002010" border=0>
Antares '85 FK/SR #4849
36°29'58" -94°59'59"

Edited by - on

Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 09/18/2003 : 12:23:57

CostCo also has them

Doug&Ruth
Triska (Alberg 29)
Tacoma Wa.

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 09/18/2003 : 13:21:49

way overkill. I can go daysailing every day for 2 weeks, running VHF, autopilot, and stereo without bothering to charge my 2 75 amp hour gel batteries. Shore power, solar panels, and engine alternator are not needed.

Cruising is another story. It's the cabin lights that eat your amps. If you're doing lots of overnights and don't have sunny weather for your panels then those big batteries make sense.

<img src="http://www.indiscipline.org/cat25/pictures/icon.jpg" border=0>Indiscipline 1978 FK #398

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 09/18/2003 : 13:38:43

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
FYI - I bought two 60 amp hour deep cycle marine batteries from the Evil Empire for $60 each, and then discovered that Wally World has 75 amp hour deep cycle marine batteries for $55 each. <img src=icon_smile_blackeye.gif border=0 align=middle><img src=icon_smile_blush.gif border=0 align=middle>
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

JB - Are there new synonyms for Boat US and West Marine that I didn't know about? Or does your neck of the woods have different stores?

D. Wolff - "The Flying Wasp" #401 sr/sk
Chief Measurer C-25/250 National Assn.
<img src="http://www.flags.com/images/layout/category_images/t_3964.jpg" border=0>

Edited by - on

Stu Jackson C34
Admiral

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844 Posts

Response Posted - 09/18/2003 : 14:22:39

Rather than Guessing

Greg

What you should consider doing is an energy budget. Figure out the loads and the amount of time you have them on, and calculate your useage per day or between charges. You battery bank capacity should be enough so that you only use 35% to 50% of the total capacity between charges. This is because you shouldn't deplete your batteries more by than half, and the last 15% takes a long time to charge.

West Marine Advisors and BoatUS catalogs have handy load information for regular 12v DC thingies.

Your small solar panel goes a long way to keep your batteries up without being tied to the shorepower cord all the time you're away from your boat. That small panel could also run your raio/cassette/CD player all day and save your batteries for other uses. Good idea.

Since we don't have engines to start, there's really no need to have a separate dedicated starting battery. Even if you have an electric start motor, there's always the hand option.

In answer to your basic question of one or two banks: Also the best way to increase the life of your batteries is to MAXIMIZE the house bank size, because then for the very same daily draw, you are using up less of the total capacity. If your existing batteries are in good condition, just wire 'em together rather than having 1 and 2 (assuming they ar BOTH in good condition). If you need new batteries, the 6V golf carts give you the most bang for the buck in the smallest space for the same 200 or 220 amp hours.

Nigel Calder's Boatowner's Manual is very good on electrical systems, and far superior to Casey's little electric primer, but more expensive.

As others have said, shop around, you can find good deals on batteries, not necessary to use a marine store.

Stu

Edited by - Stu Jackson C34 No. 224 1986 on 09/18/2003 14:26:08

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Sea Trac
Master Marine Consultant

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Vanuatu
1357 Posts

Response Posted - 09/18/2003 : 14:49:09

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
JB - Are there new synonyms for Boat US and West Marine that I didn't know about? Or does your neck of the woods have different stores?
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I thought West Marine was the Evil Empire, perhaps my mistake. Wally World is, of course, WalMart. (Or, I suppose it could be Boater's World, but I was referring to WalMart.)

Regarding, loading and depletion I worked up the following in attempt to determine if I could go out for three days. Note that the stereo draw has not been confirmed. Additionally, you can deplete your batteries below 50% IF you don't mind replacing your batteries earlier than you would otherwise. So, I'm surprised by Jim's power usage experience, although mine is just theoretical and the applications sound quite different.

(Sorry, I can't figure out how to make this format any better.)

90% Amp Hours 120.0 0.9 108.0 108.0

Hrs/Day Amps/Hr Amps/Day Days Total Amps

Solar Charger 9.0 0.21 1.88 3.0 5.6
Instruments 24.0 (0.07) (1.68) 3.0 (5.0)
Cabin Lights 2.0 (0.50) (1.00) 3.0 (3.0)
Anchor Light 9.0 (0.75) (6.75) 3.0 (20.3)
Stereo 1.0 (10.00) (10.00) 3.0 (30.0)
Thermoelectric 6.0 (5.00) (30.00) 2.0 (60.0)

Total Amp Hours (112.7)

Amp Hour Balance (4.7)

J.B. Manley
<img src="http://im1.shutterfly.com/procserv/47b3d609b3127cce8d2e212441c60000002010" border=0>
Antares '85 FK/SR #4849
36°29'58" -94°59'59"

Edited by - Antares on 09/18/2003 14:50:13

Edited by - Antares on 09/18/2003 15:15:29

Edited by - on

GregOnC25
Deckhand

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USA
22 Posts

Response Posted - 09/18/2003 : 19:50:03

Thanks to all for the sound advice! I read Casey's book which is a good primer. Granted, I havent done the energy accounting exercise but I will when I have a chance. From all of your comments and my crude estimation of needs, I will go with two banks of ~75amp*hr and hook up my little solar jobby for peace of mind (golf cart batteries are overkill, I agree). Off to Wally World....
As Stu recommended to me previously, I am reading, reading, reading! Most of it right here on this forum and its archives. Thanks again!
Greg

GregOnC25
87/#5615/WK/TR

Edited by - on

deastburn
Captain

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USA
334 Posts

Response Posted - 09/20/2003 : 11:10:53

Just to confuse things even further...

I found that using my small solar panel resulted in a net discharge! I fared better with the batteries switched off when not on the boat. Hard to believe, but... there may be a bad ground somewhere that is draining the batteries faster than the solar cell can recharge them.

Also, if your motor has an alternator, running it for ten minutes after the boat has not been used for a while helps enormously to keep the batteries topped off. I just (like many others) buy two 75-amp RV/Marine batteries for $50 or $60 from BJ's. If I top them off every two months or so, they last five seasons.

Reminder: if you have an alternator-equipped engine and a battery switch, and you decide to charge the other battery, always switch through "Both" to get from 1 to 2, never through "Off" with the motor running.

Dave on "Wood Duck" (#2616)

Edited by - on

GregOnC25
Deckhand

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USA
22 Posts

Response Posted - 09/20/2003 : 23:10:06

Gee, Dave, that is strange! Most reading I've done says solar power gets you longer battery life by keeping them topped off. You may be right about the "ground" in your case. Interestingly, I went to buy the $50-60 batteries and walked out with 115amp batteries at that price! The 75amp batteries were $40 at Wally World here in NJ. On re-reading these posts the 75's would have been good enough. Oh well, I hope they fit in my battery compartment. Thanks for the reminder on the battery bank switching....I have a Honda 9.9 with alternator and I dont want to fry it!
Greg

GregOnC25
87/#5615/WK/TR

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RichardG
Admiral

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USA
990 Posts

Response Posted - 09/25/2003 : 13:45:47

I've done the math and compared the numbers of different batteries. But there seems to be other variables which makes reality diverge from theory.

But I am sure that my new battery setup (two 6 volt golf cart batteries hooked in series) provides more days and nights of VHF radio, lights, stereo, auto-pilot, TV/VCR and other electricity-sucking toys for me and my family than my previous setup (two 12 volt Group 27s from Costco) without recharging. And I think the golf cart batteries are designed to take more discharging abuse.

Costco now carries the golf cart batteries -- cost for two is about $12 less than two of their Group 27s. While the golf cart batteries are a bit taller, they just fit in the battery locker after I replaced the terminal wingnuts with regular nuts.

<img src="http://im1.shutterfly.com/procserv/47b2cf39b3127cce92448c0b84670000001010" border=0>

RichardG 81 C25 SR/FK "Sanity"

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jsummerfield
1st Mate

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USA
96 Posts

Response Posted - 09/27/2003 : 00:02:39

I have an electric starter on my outboard. This should be among the largest loads but for a short duration. I have two of the lead-acid combination marine start/deep cycle batteries. One from West Marine and the other from Acadamy are both made by the same company. For a lot more money you can get the spill-proof marine batteries with tubular cells.

John
C25 3973 FK/SR
"Texas Tango"

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wupdike
Deckhand

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USA
10 Posts

Response Posted - 09/29/2003 : 22:12:15

No expert here, but if the solar panel is not equiped with a regulator, I understand that on sunless days you can get a reverse current flow. The larger panels all, I think, come with regulators. The smaller ones may not. Check that out.

I had lots of problems keeping batterys on charge 24/7. It is a 3-stage 10A device and the mfgr says it can be left connected and will maintain a float charge. I now have it on a timer and charge 1 hr.per day. Batteries always ready and never run out over a 3-day weekend.

GrayCruiser

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