Group 34 or 31 battery

THE DR · Post by **THE DR** » Mon Nov 18, 2019 11:47 am

I'm in the market for a new cranking battery. I can't decide if I need a group 31 AGM or group 34 AGM. I just downsized boats from a 21fter to a 19fter, so I was thinking I may be able to get away with the smaller size 34 battery.

This is what I'm running:

95 482VS 19fter
2018 ETEC G2 150hp
two Helix 7 graphs
livewells and acccesories

I'm already running 3 dedicated batteries for the Ultrex, so anywhere I can shave a little weight helps. I don't fish tourneys much and rarely put in 8-12hr days.

I'm open to any and all suggestions

monte300 · Post by **monte300** » Mon Nov 18, 2019 12:53 pm

You sure you aren't thinking group 24 for your cranking battery? That size is same as a car and should be fine. I once used group 31 for my trolling motor and they are massive.

Rod Martin · Post by **Rod Martin** » Mon Nov 18, 2019 3:51 pm

I went group 27 for my starting and accessories battery and have not had a problem .

BUT I added a battery cutoff switch with has 4 positions

0 is all batteries off

1 is starting battery

2 is starting battery and 1 TM Battery

3 is TM battery only

so if I do run into trouble I can jump my starting or add a TM to help it out.

I have a 177Tr and with 4 batteries there wasn't room or weight limit to run 4 group 31's

WRB · Post by **WRB** » Mon Nov 18, 2019 7:26 pm

Your OB charges the cranking battery when it's running, can't see any reason to use a cranking battery larger size then trolling motor batteries. Running your boats electrical accessories including sonar units for 8 hour outing a group 27 deep cycle marine cranking battery should have enough reserve amps to start your engine if charged properly. If you have a concern consider a group 29 or carry jumper cables. If you night fish usse LED lighting very low amp draw.
Tom

scottsweet · Post by **scottsweet** » Tue Nov 19, 2019 8:42 am

Your electronics should also be considered in determining the size of the cranking battery. Unless you have wired a house battery, everything other than your trolling motor runs from the cranking battery. If you have the new larger displays, they use a lot of power over the course of the day.

The Helix 7s don't use much power, but you are talking about running all day. You have a newer motor with an alternator that puts out a lot of juice, but that depends on how much running you typically do during the day.

If I were you, I would put in the largest cranking battery you can afford to ensure over the course of time, you have enough power for the day. The cranking battery cycles the most of any of your batteries and deteriorates the most over the course of time.

monte300 · Post by **monte300** » Tue Nov 19, 2019 12:14 pm

Thanks for mentioning electronics, Scott. The electronics on my 19 year old Triton died a slow death years ago and I never replaced them. Therefore, DO NOT take my previous advice of getting a group 24 for your cranking battery.

DanIsaac · Post by **DanIsaac** » Thu Nov 21, 2019 9:13 pm

no question...31

Bassjunkie17 · Post by **Bassjunkie17** » Fri Nov 22, 2019 8:36 am

Double that.....31.
The weight saved is not worth the piece of mind knowing your motor will start.

mark poulson · Post by **mark poulson** » Fri Nov 22, 2019 8:41 am

Should you use a dual purpose deep cycle battery for your cranking battery, so running your electronics and livewell all day doesn't drain it down too far?

WRB · Post by **WRB** » Fri Nov 22, 2019 11:04 am

The op's goal is weight saving, gr 27 cranking battery is good for any bass boat that isn't tournament fishing, no need to run a livewell. Deep cycle battery is designed to be drained and recharged slowly, cranking battery is design to kept charged as needed by the OB.
The ultimate weight saver is lithium batteries.
Tom

scottsweet · Post by **scottsweet** » Fri Nov 22, 2019 1:27 pm

mark poulson wrote:Should you use a dual purpose deep cycle battery for your cranking battery, so running your electronics and livewell all day doesn't drain it down too far?

Yes. Not all deep cycle batteries are created equal.

Outboards require a burst of power in the form of CCAs to turn the motors over. Most of our outboards require a minimum of 1000 CCA to start. Trolling motors don't require the CCA, but long term power at a particular amp rating (i.e. MinnKota 101 lb- Max draw 46Amp at 36V) .

Depending on brand, most of the deep cycles have the CCA to start your outboard with no issue. You do need to verify the specs though. For example, the Odyssey 31M-2150, a deep cycle battery, has a 1150 CCA and a 2150 Pulse Cranking Amp (5 seconds) rating.

Lithium is another issue. Lithiums have two basic formulas...deep cycle and starter batteries. Deep cycle lithiums have a maximum current rating, over time, (i.e. maximum 160A for 5 seconds, 80A maximum current draw) so they don't get too hot. Lithium starter batteries use a different formula of lithium to give you the burst of CCA to start an outboard. The Lithium batteries you choose need to be sure they support the needs.

Dave Brabec · Post by **Dave Brabec** » Sat Nov 23, 2019 7:13 am

Ive never had a problem running a group 24 starting battery , 3 different boats
Can run live well pumps all day
My boat sits low already with 4 batteries back there

rangerz20 · Post by **rangerz20** » Sat Nov 23, 2019 6:27 pm

Group 27 lead batterywould be fine. If you. Your graphs don't pull much, no power poles, no 16" graphs which are the battery killer. You have nothing to worry about with a group 27.

Pat · Post by **Pat** » Mon Nov 25, 2019 1:16 pm

Dave Brabec wrote:Ive never had a problem running a group 24 starting battery , 3 different boats
Can run live well pumps all day
My boat sits low already with 4 batteries back there

I'm with Dave. Group 24 does everything for me too. I fish similarly to the original poster. Limited tournaments, 2 9" graphs, usually 6-7 hour days, 18 ft boat, 150 ETEC. The Group 24 that's in good shape will do the job. I am using an Everstart from Walmart. I do carry jumpers, but have not had to use them.