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post #36 of Old 11-21-2012
Maine Sail
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Re: Battery Sizing - am I crazy?

Originally Posted by asdf38 View Post
Ok well the answer is in. According to Trojan, as Mainsail said, Golf Carts will have almost 50% longer life. The tradeoff, as I suspected, is in cranking amps - apparently even the deepest "Marine Deep Cycle" battery is still designed with cranking performance in mind.

This comes directly from Trojan tech support when I asked them specifically about the differences between their SCS200 G27 and T-105 Golf Cart batteries. Credit to Trojan for the quick response.

I'll say that I find it disappointing, and counter-productive that manufactuers don't make these tradeoffs clear. There are a ton of marine buyers who want nothing but the very best deep cycle performance and published literature makes no note of these lifetime tradeoffs.

Anyway, as far as I'm concerned the verdict is in. I have little doubt that a normally sized golf cart house bank can start any engine in it's sailboat. So...

Never buy a marine battery for your boat unless you absolutely can't fit a GC.
And even two T105's or similar will still start a large Cummins even on the coldest winter days. We had a 300HP Cummins in our old power boat. Started easily with two T105's...

This is one of my power boat customers who is also a sailboat customer. He takes his batteries and charging as seriously on his twin screw power boat as he does on his blue water cruiser that has been across the Atlantic and beyond about 6 times..

These 4 6V batts start the twin screw/engine 6 cylinder turbo Volvo's @ 260HP each, with zero effort. The engines start in 0.75 seconds as measured with my Midtronics analyzer.... He starts both motors off the house bank down to 50% SOC easily....

So yes, as I have been saying, unless you can't fit the height of 6V batteries they are the best bang for the buck..

-Maine Sail / CS-36T

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