Marine batteries

My fishin buddy has a 1 year old 18' boat with a V-6 inboard/outboard on it. This is the third battery he's put in it because they're going bad. Other than the issue that something is causing them to go bad my question is, why would he need to replace it with a Marine battery. It's a v-6 with an alternator so it is virtually the same as a car. It's not like my canoe where i'm out all day, run the battery down and come home and charge it. Anyone have any input on why a marine battery is required in this boat?

mostly because the marine battery has a tougher case to with-stand the pounding it gets in a boat.

You ever go off roading in a 4 wheeler with a 'car' battery?......they don't have Marine batteries.........
from my understanding it's the 'deep cycle' charge or should I say 're-charge' ....
So you're saying a sealed marine battery is better than a sealed car battery cause it can take a beating????

Yep that and I believe that I read or heard that they also have a little heavier plates to handle the re-charging situation .

Dogsled, your buddy needs to have his charging system checked out. I would suspect it is overcharging. He is some good reading about batteries. Marine Batteries

IBN,
Thanks for that link. It explained everything. I told him to get the charging system checked but in the conversation we came up with the marine battery question. Thanks for the answer.

The only real difference that distinguishes "marine" batteries is the screw terminals versus the automotive style terminals. Boats have ring terminals on the cables, so you need the marine type battery.

If there is a difference in how rugged they are, it's in the spacers that hold the plates in position, not the case itself.

Nobody is going to make a battery case tougher than it has to be because that will just make the explosion more violent when the battery blows up.

Thicker plates are a feature of deep cycle batteries in general, not marine batteries. Cranking batteries, both marine and automotive have many thin plates to produce high currents for short periods. Deep cycles, both marine and RV, have fewer, thicker plates that can produce moderate current and stand up to frequent deep discharge.

The deep discharge thing with the abilty to constantly bring it from, aka 'my canoe that I use all day and run down and want to constantly recharge' is actually the only viable reason. a boat that has a V-6 chevy engine, who sits still that long to run a battery down that much that they can't fire it up, move to a new location and put a little sumtin sumptin back in the battery alon the ride.............
As for the beating the battery takes and that is the reason, 'durability', I can throw some foam padding under a boat battery and it'll suck up the enough 'extraordinary' pounding a boat gives.
At some point in boat size the marine battery ceases to be of no difference than car battery.
Drive for 2 or 3 weeks in the spring in a car before the potholes are patched and you got major beating on the suspension.....how many batteries are shot because of this???
This whole topic is excellent and has a fine line drawn between the two types of batteries and the term I'm questioning is 'deep cycle'. I've run a car battery for 2 years (sealed) in my canoe. I bring it home and recahrge it (slow) and it comes right back up to a full day of use.
I think somebody is pulling somebodys johnson when the the only difference we are seeing is plate spacing and shock absorbancy.

you also have to look at the reserve capacity of the battery. Big difference between the auto and marine.

Also it takes a very long run to recharge a battery, don't rely on the alternator to put a full charge on the battery. Could be the battery's were left over long periods with low amps.