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post #86 of Old 12-17-2012
Maine Sail
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Re: Battery Sizing - am I crazy?

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..

-Maine Sail / CS-36T

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