Deep cycle or dual purpose battery?

[Kidder522]

Hey guys

I have 2 interstate batteries in my boat, but one is very weak, other one is good. They are both deep cycle.

Question is; do I buy a deep cycle to replace or dual purpose?

All information is appreciated.

Richard.


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[larry_arizona]

Last boat dealer installed dual purpose interstate marine batteries.

New boat they installed interstate 27MXHD

They are marine cranking batteries but have far more reserve than my previous dual purpose batteries.


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[MLA]

Boat has dual banks and switch, correct? You need at least one cranking or dual purpose for doing the engine cranking on a regular basis. A deep-cycle can crank an engine in a pinch, but its not designed to do it on a regular basis. On the flip side, a cranking battery can allow for some short engine off play time, a deep-cycle is much better for this.

If you like to drop anchor and chill for a while playing the tunes, id go with a cranking on one bank and a deep-cycle on the other bank. Other wise, dual purpose on both banks is great for occasional anchor times.

[larry_arizona]

Here is the specs on the 27M-XHD

It’s a cranking battery but has 22 more reserve minutes than my last dual purpose battery.




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[KnoxMojo]

I have ran 2 group 29 deep cycle batteries for years, never an issue starting or running low on power while out on the water. Was actually looking at a single dual purpose for my truck, but going to just buy an Interstate battery from the actual Interstate store instead.

[Holdmybeer]

I have ran 2 group 29 deep cycle batteries for years, never an issue starting or running low on power while out on the water. Was actually looking at a single dual purpose for my truck, but going to just buy an Interstate battery from the actual Interstate store instead.

If you can find what you need at Costco they are cheaper than the interstate store for the same part number. I bought 2 for my truck last year and saved $60 compared to my corp discount at Interstate

[KnoxMojo]

If you can find what you need at Costco they are cheaper than the interstate store for the same part number. I bought 2 for my truck last year and saved $60 compared to my corp discount at Interstate

Good call! I forgot they sell them there. Thanks

[2in2out]

An item to consider is how often you intend those batteries to drop below 50%. Lead acid batteries if they drop below 50% will lose charge to 50% or below on first dip below 50%.

AGM batteries won’t suffer as much loss when falling below 50%, but at best will recover only 65% of original state.

The problem lies in that Lithium batteries usually don’t have cranking amps that LA or AGM batteries have, but have more Amp hours as a result of being able to be dissipated to 5% without charge loss.

LiFePo batteries are more stable across temp extremes than LA or AGM batts.

Problem is that automotive ( thus boat) regulators are not adjusted to charge LiFePo batts, and don’t appropriately adjust float or bulk charge.

So, to answer the question we must know what you have on the good bank (LA or AGM, deep cycle or cranking batt) and what you intend is use it for (starting or radio play). Neither will last beyond 50% dissipation, but the likelihood of a cranking Batt going below 50% is infrequent, but possible. I would consider putting the good bank on the starting leg, and get a deep cycle AGM battery for the “Party” leg. Both will start the boat, the cranking Batt has shorter use, but faster dissipation.

A deep cycle “Party” battery will last longer, and typically offer enough reserve for starting and retain charging cycles for longer.


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[Kidder522]

Hey guys.

Yes, I have a deep cycle battery for the party/accessories and I am going to purchase a cranking battery for the house/start up. We don’t do much sitting around on the lake, maybe for lunch or a swim but not hours sitting listening to tunes.

I am looking at a cranking battery that has 675 MCA and 90 minutes of reserve. Not sure I need one with 1000MCA but if someone thinks it would be a good idea let me know.

Interstate cranking battery is $250 up here in red deer so I am going to drop by Costco and see what they have in stock.


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[Kidder522]

Actually just purchased a dual. Same amount of cranking with some more reserve.
20 bucks price difference.


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