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Old 07-12-2018, 07:57 AM   #8
Maerin
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City: East Coast
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Vessel Name: M/V Maerin
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Join Date: Jun 2013
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Quote:
Originally Posted by Gordon B View Post
Hi to all,
Hopefully soon we will be building a new battery bank using 6 volt golf cart batteries. The question arouse as to the advantages and disadvantages there are using 4 lower AH batteries or two higher AH batteries.
I could not answer it. Any insights ?
Thanks
I'd offer that when building a bank, bigger IS better. Refer to information on the peukert effect. Simplified, for a constant amp draw, a larger bank will yield a disproportionately higher capacity than a smaller bank. Then there's the DOD (depth of discharge) to factor in. Battery life is not measured in time, but in cycles, each discharge/recharge being a cycle. If you look at the manufacturers' ratings, you'll see that the same battery is rated for more cycles at a lower DOD. For example, a battery may be rated for 1500 cycles at 50% DOD, and 2000 cycles at 35% DOD. Each manufacturers' spec will vary, but all will follow that basic profile. So for a given load, a larger bank will result in lower DOD, with the end net that it will deliver more cycles, ergo, a longer lifespan.

So it's good to know with some degree of accuracy your daily energy use in order to build the bank that will provide that with the lowest manageable DOD. Remember, with lead acid you're only utilizing half of the rated capacity.
You'll rarely hear the complaint that "my battery bank is just too big...." The bank is part of the system, assess the SYSTEM of which the battery is just one piece.
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