Choosing boat batteries

[baconbiscut]

I've got a 25ft cabin cruiser with a Mercury 383 MPI engine. At the moment it has two group 31 Werker cranking batteries that I purchased from battery plus and was under the impression that they would be superb in quality, but I'm beginning to think that I was wrong. We've had them since 2007 when we repowered. They worked well up until recently, I can't get them to hold a charge for very long and they crank slow.
So, unless anybody has any ideas on what I can do with my current batteries, I've come to the conclusion that they need to be replaced. But my question is what will be the best option for my application, The engine is obviously big enough where it needs a lot of cranking power, I also like to take the boat camping and run the lights and the radio. So if you guys have any suggestions that would be awesome.

-Dan

 

[NYBo]

Re: Choosing boat batteries

If the batteries spent a lot of time less than fully charged, that could account for the problem.

 

[BaileysBoat]

Re: Choosing boat batteries

I like Delco Voyagers. Had good luck with NAPA marine as well. Must say you have done well with what you have. I replace my batterys every 3 years regardless.

 

[bdblazer1978]

Re: Choosing boat batteries

Don't have a lot of experience, but I thought cranking batteries were for starting the engine, and that was about it. I didn't think they were designed to be drained significantly, for things like lights/radios. My recommendation would be to set up with at least one deep cycle to run the lights, since they are better suited for the constant drain/recharge cycle.

 

[baconbiscut]

Re: Choosing boat batteries

Well, They probably arn't maintained as well as they should be, However I thought it was bad to run two different batteries on the same system. So could I go with a deep cycle and a cranking battery and use both of them at once to crank the engine when its cold?

-Dan

 

[642mx]

Re: Choosing boat batteries

Look at the Interstate SRM-29's. You get the best of both worlds, 675 cca and deep cycle capabilities. http://www.interstatebatteries.com/cs_eStore/content/product_info/marine_f.asp

 

[LippCJ7]

Re: Choosing boat batteries

4 years out of batteries isn't really bad but its not great either, how you use them has alot to do with battery life problem is here is where the opinions come in. Group 31 batteries are beasts. Are these the batteries that you purchased?

http://www.atbatt.com/product/22075/sla/werker/wkhr12-100c-fr/battery

If these are the batteries you have then there's your problem, these batteries are not designed to start a motor, easily the biggest draw a battery will ever see, these batteries are designed for low draw long capacity, they are amp hour rated not cold cranking amps rated, they would probably be great if you never needed to start your motor but ran everything else on the boat and then used another battery to start the motor. Look at the applications this battery was designed for: "Amstron SLA batteries are utilized in a wide variety of applications including electric vehicles, wheelchairs, scooters, UPS backups, computer systems, industrial and medical equipment and more." These all have a very common issue to them, they don't draw the huge amount of power required to start a motor but they do require a decent amount of energy and may need that energy for a very long time. Starting batteries are different, they are designed for starting first thats why starting/automotive and marine batteries have a Cold Cranking Amps(CCA) number rather then an Amp Hour rating thats a dead giveaway.


I would use the same type of batteries, two group 27's or 29's, whatever, in my system but thats my opinion....

 

[RGrew176]

Re: Choosing boat batteries

I spend several weekends per season on the hook. When I ordered my boat I had the dealer install 2 more batteries giving me a total of 4. They set me up with 2 cranking and 2 deep cycle. When it came time to replace them the first time I kept the same configuration. In July 2006 I had to replace them again. This time I went with 4 deep cycle batteries. This past October gave me 4 1/2 seasons of use. I will have to wait until spring to see if I can squeeze another season out of them. They are Sears Die Hard's. They have served me well to date.

 

[kilowatts]

Re: Choosing boat batteries

Hi Guys:

I think the answer to your problem lies in reading the following link:

http://www.yachtsurvey.com/boat_battery_basics.htm

In my opinion the author pretty well lays it all out right there. I hope this helps.

kilowatts

 

[kilowatts]

Re: Choosing boat batteries

Hi Guys:

Further info from a Mercruiser bulletin I used to buy my batteries:

B. Battery requirements for Mercruiser Engines - All Models.
To obtain adequate cranking power for the 4 cycle Mercruiser engine, select a battery with a "Cold Cranking Amperage" of no less than:

* 2 Amperes per cu. in. displacement for 4 Cylinder Engines.
* 1 1/2 Amperes per cu. in. displacement for 6 Cylinder Engines.
* 1 Ampere per cu. in. displacement for 8 Cylinder Engines.

The above is the "meat and potatoes" of the bulletin although it does go on at more length. If anyone wants a copy, feel free to send me a PM and I'll send you back a pdf. I hope this helps.

kilowatts.

 

[captain zac]

Re: Choosing boat batteries

More needs to be known about the whole system,

Type of on board charger if any
do you have a bat selector switch (1 or 2 or Both OFF)
Do you turn the switch to OFF when away from the boat
Do you select 2 ( should be a Deep Cycle Bat) when on the hook
when running does your bats get charged through an isolator (how is it wired)
What engine do you have
does your cranking bat have the cold cranking amps required by Merc for that engine ( I have a 6.2 MPI it requires 550 CCA/150Ah for example)


Bat life is more dependent on how it is maintained over anything else
over charging is the worst thing you can do to the life of a bat.

Harry

 

[baconbiscut]

Re: Choosing boat batteries

Each battery has 990 CCA, both are cranking batteries they are sealed. The boat does have a battery switch there are times where I've forgotten to turn it off and that's when they're dead but I've never had that problem before. I have no Idea how the boat is wired, I do know that the batteries are supposed to charge when its connect to shore power. My question is should I get a deep cycle and a cranking battery?

-Dan

 

[642mx]

Re: Choosing boat batteries

My question is should I get a deep cycle and a cranking battery?

-Dan

Dan...

Get the Interstate SRM 29 and have the best of both worlds (like I said earlier). Having a dedicated cranking battery and a dedicated deep cycle is just silly when you can have 2 identical batteries that will do it all.

 

[captain zac]

Re: Choosing boat batteries

Dan

you said that you have left the bat switch on sometimes ( we all have)
that can result in overcharging depending on the charger
it would be nice to know what type of charger you have?
but to correct the problem I would suggest that you
buy 1 starter and one deep cycle
Bat switch off at the dock
Bat switch #1 starter to start and run to the hook
bat switch #2 when you are on the hook
bat switch #1 to start and run back to the dock
bat switch to off at the dock and away from the boat
charger will recharge and top off the bats
If you have a smart charger these bats should last 4-7 years

 

[captain zac]

Re: Choosing boat batteries

bacon

another thought

have the bats tested.
could be the starter going bad ( when they go bad they draw more amps)
if it is the starter I would still go to a deep cycle for the house bat when you do have to purchase new bats

Harry