Battery selection

lc43727

Recruit
Joined
Sep 10, 2019
Messages
4
Boat battery question from a rookie. I have a 17 ft boat with a 40 hp Evinrude 2 stroke. I am about as new to boating as one can be, but am trying to learn. I saw that the battery near the stern is a deep cycle. Shouldn't this be a cranking battery? It's use is for the outboard and nothing else that I'm aware of. When I got the boat, the battery for the auxiliary equipment froze and cracked. The previous owner left both batteries in the boat over the winter. I bought a new deep cycle and mounted it in its place near the bow and all the auxiliary equipment then worked correctly. Now.....I've seen that some have recommended that a dual purpose cranking/ deep cycle battery be used to start the outboard. Is there a reason for this? When I saw that the battery hooked up to the outboard was a deep cycle, I was happy because I could move it to the bow and wire it into the system and use it to power my 12/24v trolling motor. I was just going to replace it with a cranking battery. Were those suggestions for a one battery boat that would use the single battery to power the outboard and accessories or should a dual purpose battery be used, even if it is only going to be used to start the outboard? Or.....should I leave well enough alone and leave the deep cycle in the stern starting the engine????? Thanks in advance and sorry for the long story, but I wanted to give as much I do as I could.
 

Mohawkmtrs

Chief Petty Officer
Joined
Jan 13, 2010
Messages
560
You're right...Deep Cycle battery for the accessories and a Marine Cranking battery for the engine.

IMO those dual-purpose batteries do not perform either function very well.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,413
Really doesn’t matter one way or the other.

I got away from starting batteries long ago. Get much better life and performance from deep cycle batteries.

Starting batteries are only good at one thing, starting the motor. They are not designed for use as an auxiliary power source. A couple of deep discharges and you have a dead battery on your hands.

Having said that, if you have minimal power requirements outside the motor, a starting battery has some short term cost benefits. If your power hungry, a deep cycle is the only way to go.

As a halfway measure you could go with a marine dual purpose battery. The extra heavily plate construction gives you that extra burst of power for starting yet retains a lot of the power reserve attributes of a deep cycle.
 

lc43727

Recruit
Joined
Sep 10, 2019
Messages
4
Really doesn’t matter one way or the other.

I got away from starting batteries long ago. Get much better life and performance from deep cycle batteries.

Starting batteries are only good at one thing, starting the motor. They are not designed for use as an auxiliary power source. A couple of deep discharges and you have a dead battery on your hands.

Having said that, if you have minimal power requirements outside the motor, a starting battery has some short term cost benefits. If your power hungry, a deep cycle is the only way to go.

As a halfway measure you could go with a marine dual purpose battery. The extra heavily plate construction gives you that extra burst of power for starting yet retains a lot of the power reserve attributes of a deep cycle.

I was thinking that, but with my limited confirmed knowledge, I wanted to be sure. I'll get a regular cranking battery to hook to the outboard and double up the deepcycles up front. I'll grab a couple solar tenders to maintain them between uses and I think I'll be good. I appreciate the response. It makes me feel better about what I'm going to do!
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,413
I was thinking that, but with my limited confirmed knowledge, I wanted to be sure. I'll get a regular cranking battery to hook to the outboard and double up the deepcycles up front. I'll grab a couple solar tenders to maintain them between uses and I think I'll be good. I appreciate the response. It makes me feel better about what I'm going to do!
Solar tenders are pretty useless, especially on deep cycles. Not enough output. The batteries need amp hours. The panels supply milli-amp hours.
 

lc43727

Recruit
Joined
Sep 10, 2019
Messages
4
Thank you, Dingbat! I'm learning more every time I come in here. I appreciate the advice. I'll just go with the original plan of burying a conduit with an electric line in it and mount an outdoor outlet beside where I park the boat and use a bigger tender on the batteries after a recharge after a day out. I'll pull them out and bring them inside when I winterize and keep them on the tender in the basement. So far, you two have help me bring the plan together much better than when I started....a big thanks to both!!
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,413
I'll pull them out and bring them inside when I winterize and keep them on the tender in the basement.
Unless you live in the tundra, bringing the batteries inside for the winter isn't doing them any good.

The self discharge rates for a lead acid battery are much lower in the cold. Not to mention the out gassing of hydrogen gas and hydrogen sulfide into the living space
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I leave my batteries in the boat years around. Top them off after the last use of the season (December). Then top them off again when the boat goes back in the water the middle of March.
 
Joined
Oct 11, 2018
Messages
28
Hello-

If i can continue on this battery selection subject:

I have a 2000 Crownline 266br, 7.4 MPI with dual batteries. The batteries will be 3 years old this Fall. I dock my boat and run a trickle charge after every use. I do not have any extensive electronics and never anchor longer than 2-3 hours.

What type of batteries should I be looking to buy? I see they range from $100 to $200 each which I am not looking forward to.
 
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