Single battery question.

lrdchaos

Petty Officer 1st Class
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Feb 11, 2008
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265
I have a tahoe q7i with the mercruiser 5.0 mpi. I need a new battery. My boat has one battery for starting and accessories. Would you go with a deep cycle battery or a starting battery? Interstate makes a dual purpose battery, they are expensive. I have had a deep cycle in there since new, but I have to replace it every couple of years. Just wondering if there is a better option.


If this is in the wrong section, MODS please move.


Thanks
Doug
 

Don S

Honorary Moderator Emeritus
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62,321
Re: Single battery question.

You don't want a straight deep cycle battery for a starting battery. The deep cycle will show too much voltage drop to the ecm of the mpi engine and not allow ignition or fuel system to operate. The dual purpose batteries seem to avoid that problem.
 

UncleWillie

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Oct 18, 2011
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3,995
Re: Single battery question.

Unless there is a need for a Deep Cycle Battery there is no advantage.
The deep cycle is not able to deliver as high a current for starting as a Start Rated Battery.
The Start Rated Battery will not last long is you use it in continuous service. (Trolling Motor, HP Stereo).
If you want only one battery and a deep cycle is warranted, Get a larger Deep cycle to compensate for the Start currents. Or a Dual purpose.

Proper maintenance should make the battery last many years.
Stored in a Garage/Basement and charged once a month during the winter helps immensely.
Checking the water level is a must.
 

lrdchaos

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Feb 11, 2008
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265
Re: Single battery question.

So basically what you are saying is just get a starting battery. The interstate battery that is dual purpose that will fit in my boat is only 550cca, 690 Mca. They make a starting battery that is 800 cca, 1000 mca with a 135 minute reserve capacity. I usually start my boat every hour and let the battery recharge while on the lake.

I don't have a hp stereo, just a basic radio with 4 speakers.
 

UncleWillie

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Oct 18, 2011
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Re: Single battery question.

If you are essentially just using it for starting and running a sonar, and a stereo low enough to "Not scare the fish" for an hour;
The starting battery will be the fine.
 

lrdchaos

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Feb 11, 2008
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Re: Single battery question.

Thanks for the heads up. I looked in my book and it stated minimum requirement at 750cca/950mca. So starting battery it is. Thank you all for the help.
 

sweet addiction

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Re: Single battery question.

Then I personally would go with Interstate 27M-XHD.
 

NYBo

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Oct 23, 2008
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7,107
Re: Single battery question.

No room for a second battery? You could add a Group 24 deep-cycle for your house loads and use a cranking battery for, well, cranking. Add a battery switch and you're golden.
 

stonyloam

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Mar 13, 2009
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5,827
Re: Single battery question.

IMHO Get the largest Marine starting battery you can fit in there, a group 27 or even a group 29 even if you need to put in a new battery box. Then get yourself a good battery maintainer (a microprocessor controller one), if you have AC available, or a solar powered one if no power is available. Keep the maintainer on 24/7 all year and you will have a fully charged battery ready to go anytime.
 

lrdchaos

Petty Officer 1st Class
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Feb 11, 2008
Messages
265
Re: Single battery question.

I ended up purchasing a dual purpose blue top optima. The battery I pulled out was a deep cycle with 550 cca. Sounds like I'm lucky everything worked like it did. Thank you for the help.
 

UncleWillie

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3,995
Re: Single battery question.

... The battery I pulled out was a deep cycle with 550 CCA. Sounds like I'm lucky everything worked like it did.

The CCA Rating is at 00 Degrees F
The MCA Rating is at 32 Degrees F

You likely never used the boat as an Icebreaker!
At 70F, they perform a lot better.
It would deliver the 750+ without issue!
 
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