Boat Battery Questions - Cranking

[GMTK]

2004 Hurricane with a 4.3L Volvo inboard. No trolling motor.

When I got the boat it had two Interstate 27m-HXD cranking batteries in it with a selector switch (one, two or both).

Last year one of the batteries died and I went to the local battery dealer (the only one) and all they was a 24m-XHD in stock so I took it. Now, my second battery, a 27m-HXD, has died and needs to be replaced.

I've gone down the rabbit hole on this site and others and there seems to be a lot of consensus to have one deep cycle to run the radio, and one cranking devoted to starting the engine.

My issue - I'm on a VERY secluded lake where 99% of it has no cell service. I want to stay with two batteries devoted to cranking (I also carry a small jumper pack but it's only good for one start). Wanted to hear from yall on if I am over-thinking this or if I should just get a deep cycle 27m and be done with it. My battery boxes will not hold a size 29 and size 27 is the largest I can put in.

 

[Texasmark]

The deep cycle/starting, size 27 battery does exist. Here is an ad for such. Knowing something exists helps you to have confidence that you can find what you want for sale where you can obtain one.

https://www.batteriesplus.com/battery/marine-and-boat/dual-purpose-(starting_cycling)/bci-group-27m

I purchased a John Deere 4010 older tractor once that used a combination battery for starting for years. Your 4.7 Liter, compared to a cubic inch engine is 61 cu. in. per liter. Your engine in cubic inches is 286 and it's gasoline with less compression....like 8.7:1. My "diesel" tractor's cubic inches were 400, and the compression was 16+:1. Cranking amperage requirement is much lower on your engine so even a regular Marine Deep Cycle (not combo) would probably work just fine if you keep it charged up before using. Considering the cost differential when you look at a regular 27 deep cycle vs 27 combo....starter/deep cycle rated..... like in the advertisement I posted to me would be a no brainer. I'd go with the deep cycle and spend some of the money you saved in purchasing a trickle charger ($20) to keep the battery topped off when not in use.

 

[GMTK]

I know the 27 cranking is out there. Just contemplating if I should run one cranking and on deep cycle.

 

[airshot]

Get two new gp 27 combo batteries. They are a cross between deep cycle and starting type battery, commonly used in motor homes and larger boats without trolling motors. WallyWorld has them as well as most battery dealers. Always replace batteries in pairs when running them together.
Deep cycle only type batteries are not fond of the heavy charge rate from your alternator, the dual type batteries will handle that type charge much better and you can still use your switch.

 

[crazy charlie]

Stick with 2 group 27 dual function batteries with over 700 cranking amps and NEVER EVER buy an Interstate battery .NEVER.They dont last and they deplete your 2nd battery.Interstate are the absolute worst. .I have run with this setup in my Regal Commodore which has twin V8s and a fridge and never had an issue. Whichever battery you decide to buy do a quick google search first asking "Who Makes _____ batteries" Look for batteries made by Johnson Controls.I have had my best luck with these batteries.Also Walmart batteries have treated me very well and have a great warranty.Charlie

 

[GMTK]

Thanks Airshot and Crazy Charlie. I can't find any 27 dual purpose at walmart but going to look at sams. t4 on the interstate.

 

[dingbat]

Deep cycle only type batteries are not fond of the heavy charge rate from your alternator,

Have a link to support?
Be interested in the technical aspect of this claim

Kind of a moot point given nobody makes a “true” acid deep cycle anymore.

 

[MikeSchinlaub]

I don't know much about batteries or electronics, but I asked my supervisor about the batteries for boats not too long ago out of curiosity.

His explanation, the point of a deep cycle marine battery is that they have a higher capacity. They are mostly to run all of the electronic accessories. Typically what I see is a single battery for the engine, and three for the accessories, such as trolling motor, audio stuff, and fish finding equipment. They work independently from the cranking battery, so they won't deplete it.

So, my opinion, one cranking battery for your engine, and deep cycles to run your accesories.

 

[crazy charlie]

Thanks Airshot and Crazy Charlie. I can't find any 27 dual purpose at walmart but going to look at sams. t4 on the interstate.

Walmart.com. and a good price!!

EverStart Lead Acid Marine & RV Deep Cycle Battery, Group Size 27DC 12 Volt, 750 MCA​

$93.76You save $0.00

Price when purchased online

 

[Chris1956]

Gee, without a trolling motor, do you have any other big users for juice? If not two starting batteries is just fine. Two 24 series will work. Two 27 series is probably overkill.

If you have any doubt about the condition of the batteries, do what the sailboat skippers do. Start the motor on both batts, then switch to one battery after a few minutes of charge to both. Then use bat #1 on odd days, and batt #2 on even days.

 

[cyclops222]

How do we know the size of his motor ?
Does it always start hot or cold in 1 second ? How long do you have to crank ? Hot or cold ?
Then we can pick a battery

 

[bajaman123]

I suggest Odyssey dual purpose...I have them and they are incredible.

ODP-AGM27M - ODYSSEY Battery

Like an athlete that is both a sprinter and a long distance runner, the ODYSSEY Marine Dual Purpose battery has both massive starting power and amazing deep cycling capability – up to 400 cycles at 80% depth of discharge. With twice the overall power and three times the life of conventional...

www.odysseybattery.com

 

[airshot]

Have a link to support?
Be interested in the technical aspect of this claim

Kind of a moot point given nobody makes a “true” acid deep cycle anymore.

Ask any battery mfgr, we have two different mfgrs in our area. Their engineers as well as the instructions that come with every deep cycle battery I have ever bought claims that high amp charge rates can lessen the life of a true deep cycle battery....thus the reason for the dual purpose batteries (RV ) batteries.

 

[cyclops222]

How high, for how long, on each size of battery ?
We are allowed by law, to cause fear and confusion in any customer............Sales group.

 

[mike_i]

I installed two group 27 Interstate batteries in my boat several years ago bought from Costco because of their return policy. After a few trips out with my bait tank running whichever battery I had switched to run the accessories would be running down near the end on the trip. Long story short I realized the capacity was lower than batteries that I have used in the past. I will not use Interstate batteries again.

 

[Pmt133]

My vote on batteries has always been get whatever is widely available near you. They're consumables and are all more or less the same level of quality... Even the "deep cycle" ones are more of a dual purpose. Which is what I would (and do) run vs a straight starting battery A compromise on both ends but will get you the most of life from them.

FYI my 4.3 has a group 24 on it. The twin diesels in my 33 use a single group 27 for each engine and those give tons of cranking on that application as well.

I do think you're over thinking it. It worked fine for how long before?

 

[Texasmark]

I don't know much about batteries or electronics, but I asked my supervisor about the batteries for boats not too long ago out of curiosity.

His explanation, the point of a deep cycle marine battery is that they have a higher capacity. They are mostly to run all of the electronic accessories. Typically what I see is a single battery for the engine, and three for the accessories, such as trolling motor, audio stuff, and fish finding equipment. They work independently from the cranking battery, so they won't deplete it.

So, my opinion, one cranking battery for your engine, and deep cycles to run your accesories.

My take on deep cycle is that they have thicker and fewer plates. Apparently a thick plate tolerates the ups and downs of deep cycling and the fewer is just because of the space limitation.
Also, the fewer plates means the less surface area in contact with the H2SO4/H2O mixture so the max current available is reduced which impedes starting applications. I have no idea as to how a combo battery is built.

 

[airshot]

What folks need to understand here is.....a deep cycle will work to start an engine, same as a starting battery will run a trolling motor...no one is saying it won't work !! But ...is it healthy for the battery ? Ask any battery engineer, a deep cycle is designed to give a long steady draw over time where a starting battery is designed for a high amp draw over a short period of time. Using them for other things will shorten the life cycle of the given battery. It does not mean it will kill it overnight ! Your money....spend it how you like..
You can follow the mfgrs recomendations, or you can choose your own. If your not getting 5-6 years of service from your batteries then consider the quality and maintainence on your chosen type of batteries.

 

[JimS123]

What folks need to understand here is.....a deep cycle will work to start an engine, same as a starting battery will run a trolling motor...no one is saying it won't work !! But ...is it healthy for the battery ? Ask any battery engineer, a deep cycle is designed to give a long steady draw over time where a starting battery is designed for a high amp draw over a short period of time. Using them for other things will shorten the life cycle of the given battery. It does not mean it will kill it overnight ! Your money....spend it how you like..
You can follow the mfgrs recomendations, or you can choose your own. If your not getting 5-6 years of service from your batteries then consider the quality and maintainence on your chosen type of batteries.

Personally, I only use Dual Purpose. It's worked for me for 50 years.

If I ONLY got 5-6 years out of a battery, I would seriously look at what I was doing.

 

[cyclops222]

No battery lasts long if you have to crank the main motor 20 times to get the engine to just idle.
But I am saving so much more money cranking soo much.