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Go Back   SailNet Community > On Board > Gear & Maintenance > Battery Sizing - am I crazy?
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Thread: Battery Sizing - am I crazy? Reply to Thread
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Topic Review (Newest First)
12-20-2012 10:47 AM
hellosailor
Re: Battery Sizing - am I crazy?

The "maintenance free" caps are often welded or otherwise secured down. There may be extra electrolyte, etc. to compensate a bit but the whole idea was "we can make it good enough so you never have to add water". Mainly for the crowd who find tire pressure and oil are also things too messy to do themselves.

Your local stores do carry falt-plate AGM batteries, from all the leading makers. They're almost impossible to spot even if they are on the shelf, but you can always as the clerk, or go right to the local battery distributor. Of course AGM isn't perfect either but that's a whole other debate. They'll be priced about halfway between the Optima and conentional wet lead.

Or of course you can stay with the MF battery and just make sure it needs replacement inside the warranty period. (G)
12-20-2012 12:27 AM
peterchech
Re: Battery Sizing - am I crazy?

Quote:
Originally Posted by hellosailor View Post
Peter-
"Maintenance free" is usually a dirty word. It means a wet lead battery, which will need to have the electrolyte topped up for best life, but with the cells conveniently sealed up so they can't spill and you can never add the electrolyte when needed.
It was a clever idea in the 70's but now, I think everyone would agree that either you want a battery that can be maintained (i.e. plain wet lead) or one that in theory never actually needs topping up (AGM or gel or Lithium, truly "sealed valve regulated").
I assumes the cells could be topped off by opening the caps on top, I didn't open them in the store but every lead acid battery I've bought had something similar to top off the electrolyte. But now that u mention it it does say maintenance free... Im confused...

I would love some agm batteries, but the only brand I find locally in auto shops etc is optima, which are known to be great batteries but just way overpriced, $4 per amp hour more or less... if anyone knows a good brand of agms and where to get them let me know, but shipping costs generally preclude internet ordering or else I'd have two trojan 6 volts and never worry about it again lol
12-19-2012 07:51 PM
hellosailor
Re: Battery Sizing - am I crazy?

Peter-
"Maintenance free" is usually a dirty word. It means a wet lead battery, which will need to have the electrolyte topped up for best life, but with the cells conveniently sealed up so they can't spill and you can never add the electrolyte when needed.
It was a clever idea in the 70's but now, I think everyone would agree that either you want a battery that can be maintained (i.e. plain wet lead) or one that in theory never actually needs topping up (AGM or gel or Lithium, truly "sealed valve regulated").
12-19-2012 07:44 PM
peterchech
Re: Battery Sizing - am I crazy?

Maine I found this battery in Walmart for under $100, is this brand of decent quality in your opinion? It says distributed by Johnson, not really sure what that means...


12-19-2012 02:21 AM
sstuller
Re: Battery Sizing - am I crazy?

This gives me a chance to tell a sea story. I spent a total of eight months in the Bahamas on three separate cruises. I never had more than two twelve volt Group 27 batteries - one for starting and the other for use as a house battery. My main charging source was a 50 watt solar panel. As long as I had a spare battery I knew I could start the diesel. No refrigeration of course. I relied on the local bars for cold refreshment and conversation. I was young (relatively) and foolish and had some of the best experiences of my life. Thanks. Steve S.
12-17-2012 11:48 PM
blt2ski
Re: Battery Sizing - am I crazy?

HERE is an electrical budget pdf sheet I found online at WM a bit ago. "It May" help one decide how big of a batter bank, charging system etc one needs. It does help on figure out how may amps per day/hr etc one uses, then you can figure out how big of a bank, charging system etc you will need.

Something like this will allow one to figure out if you can get away with a single size 24-31 battery as I use for my house bank. OR< if you need a bigger setup as mainsail has, showed in his last post why that client was not able to get away with a size 27, where as I am able to. BUT, if we discussed the power needs of my travel trailer I had.....I used two 6V batteries with the same foot print of a 27 12V, to get me as much or more juice as the 6V MS has, those would last me anywhere from 24 to 48 hrs depending upon how cold it was outside, with the furnace fan running. If my kids turned on the tv, they were drained in 4-6 hrs!

This link or equal links to battery usage charts, will help one decide on how big, many, style of batteries one needs. As one size does not fit all!

marty
12-17-2012 09:39 PM
Maine Sail
Re: Battery Sizing - am I crazy?

Quote:
Originally Posted by asdf38 View Post
I'm sure this is true. However one thing in the back of my mind when discussing/reading bank life discussions is - does it matter?
No it does not matter, until it does matter. Every summer I gain customers who've had batteries fail them at a bad time or leave them stranded. Some times these mishaps get expensive. One of my customers had it happen in a location where the tow cost was multiple times what a properly sized battery bank would have been. He had a single group 27 80Ah battery on a 27 footer. He had no idea his "computer" drew the current it did. Just a laptop right... ? His bank was cheap, dirty and replacing it every two years was reasonable to him, until it became an expensive lesson.

When I finally got called in his "new" battery was resting at 11.2V this after being "charged" two days ago by his alternator.... He was using WAY more power than he ever imagined he could on a 27 footer. His computer alone when charging and running through the small inverter was pulling 4.5 - 8A. His cabin lights he used to read by at night drew another 4A. His anchor light drew another 1A. His plotter, depth and tiller pilot another 3-4A. He also had cell phone chargers and a VHF... Did not seem like a lot but it was for the single G27 battery, and he simply could not keep up..

He spent upwards of $800.00 to be towed to a boat yard who porked him on a new battery, $180.00 for a replacement group 27..... (Sea Tow would have been a wise investment) So this lack of planning, and shooting from the hip, cost him nearly $1000.00 and in the end he still had an undersized bank.....

These types of cases are not just limited to sailors. I have power boat customers whom this happens to as well. I have one who fishes off shore who toasted his batts sixty miles out (massive Furuno system).. Lucky for him a good samaritan came along and got him started with one of their batteries. Bad for him is that neither his wife or kids are willing to do off shore fishing now. Something about 6' seas and everyone getting sea sick while the hand held VHF battery was slowly dying and not knowing if they'd be rescued....

You can still have an inexpensive bank, flooded batts fit this bill, but it does not rid one of the responsibility to size it for safety or to build a system with redundancies in it.. I love inexpensive flooded batts. Our entire bank cost us $210.00 and just ended its sixth season and will easily do a seventh and possibly 8th.. If I had the height to fit 6V's on our boat I'd easily expect I would get 10+ years.. The difference is our cheap bank was sized, installed and designed for longevity and has redundancy/safety built in.... A good design up front can be a cost saver in the long run..
12-17-2012 09:08 PM
hj0516
Re: Battery Sizing - am I crazy?

Thanks to everyone for your info, sounds like I replace with 6v like I have already.
Boat is new to me and survey said the batteries would need replacing within year. At least I know what to look for and thanks again.
sailor0516
12-17-2012 04:33 PM
blt2ski
Re: Battery Sizing - am I crazy?

Quote:
Originally Posted by asdf38 View Post
I'm sure this is true. However one thing in the back of my mind when discussing/reading bank life discussions is - does it matter?

At the end of the day batteries, especially lead acids are actually pretty cheap compared to everything else on a boat. If for space or weight reasons you don't want to add batteries it's not unreasonable in my opinion to decide that you'll just replace them every 2 or 3 years.

Personally I expect to get plenty of life out of my batteries and put a lot of thought into my system. But with $120 of batteries compared to ~4k fixed yearly expenses plus maintenance and discretionary it's not going to matter a lot in the big picture.
This is actually pretty true depending upon what and how you use the boat. I'm 28' on deck, just a skoosh under 30', the OP's boat is from the same era
but a foot or so longer......reality is, for how I use my boat, electronics on it, a single 85ahr batter worked fine! I can get upwards of 24-36 hrs of power out of it. Then again, all I am powering is house lights, running lights and some ST60+ instruments and radio. One does not need a lot of power to do this. Now if you are running GPS, chart plotter, fridge plus a few other things ON TOP of some of the basics if you will on a boat, then yes, one needs more wt in battery pack to function at a reasonable length of time.

Once you get to the a single 12V or two is too small, then as noted by some, 2 6V lead cells frankly is the best bang for the buck/wt ratio to supply your power needs. This is true from land yacht experience, along with water yacht experience.

For either application, it does no one any good to have as in the OP's case 2 150lb batteries, if he only needs a single 12V 65-100 lbs one to serve his needs. At the end of the day, one needs to decide battery sizing based on ones OWN needs, not mine, nor mainsails, nor smackies, CD's etc.

Marty
12-17-2012 04:32 PM
asdf38
Re: Battery Sizing - am I crazy?

Quote:
Originally Posted by hellosailor View Post
$120...What's that buy, 120 AA cells or two el cheapo Group 27's?

I'm starting to look at battery longevity being a better investment than anything the broker can offer. I'm almost afraid to ask where I can find annual battery price information for the past ten years because I *know* what out of pocket has been.
Sams club 24 and 27. Ok maybe it was $135 and I didn't include the disposal fee. But there were no taxes in NH...

If you want to invest in my batteries I'm open to offers.
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