Starting Battery

Semi new to boat ownership. Had a starting battery go bad in my 2010 Lund Explorer 1825 last year. Replaced it with a inexpensive off brand group 24 battery mid season on a trip (availability). With the motor (115 Mercury 4 stoke), two graphs (12 inch and 9 inch), and other accessories (live well, 12v charging port, radio…) my graph alarms for low power went off pretty regularly when I would leave graphs on and troll using the Terrova (separate batteries). What battery should I get for a longer term replacement starter battery with the needed (or more) power supply?

NAPA group 31 if you can fit it.

Generally speaking, you should try to use the biggest battery you have space for. That would be a size 31 cranking or dual purpose battery (not a deep cycle or a lithium).

Even with new battery of this size, you could run low on power and the issue then becomes that you may not have enough left to start your outboard. Some people use a separate starting battery for their graphs, pumps, radio, etc. That’s if they have room. A power pack (like a noco) or jumper cables might be a good idea, just in case.

I have a jump pack and also long jumper cables just in case.

acarroline wrote:

I have a jump pack and also long jumper cables just in case.

Good thinkin’

I can almost guarantee if you bought spur of the moment in a trip it was a group 24. Just to small for what you are trying to run.

RigJiggen…Indeed. I checked my initial post and edited it as I thought I put that in there.

Are you keeping the battery charged when not in use?

Also, do you have a battery cutoff switch?

Modern electronic brainboxes are always active, especially GPS-enabled gear. Even when devices are switched off, some of them consume power.

I helped another forum member who thought he had a dead short because his starting battery was always dead. Turns out his pair of Humminbird units had a significant power draw even when turned off. That draw alone would pull enough current that the battery was too dead to turn over the outboard after 10 days.

On every boat, I’m a big fan of:

1. Installing a battery maintainer. The problem is if your battery is 50% discharged, you may still have enough power to start the outboard, but unless you run the motor for an extended period, you may not get enough charge to even stay ahead of your electronics as far as consumption.

2. Installing a master cutoff switch. This cuts off the power draw form all electronics. Really nice to know everything is off and this is an important safety feature IMO.

I have a master power off switch and keep my batteries on a trickle charger (maintain) at all times when not on the water. I’ve never had the problem of the boat not actually starting with this battery change, but just the low power alarm. I think it may just be too small for what I’m asking of it, as alluded to above.

Any Group31 AGM starting battery sales out there???

https://www.samsclub.com/p/duracell-agm-deep-cycle-marine-and-rv-battery-group-size-31dtmagm/prod3590232

This one says deep cycle but isn’t it dual purpose?

That one is a deep cycle. If it says deep cycle on it, it’s a deep cycle.

Not sure if they make a size 31 AGM cranking battery. You might have to try a lead acid version.

I have been using a Cabelas brand dual purpose (Crank & Deep Cycle) group 27 as my starting battery for the past 6 years, never had any issue. I use 2 of the same ones for my trolling motor as well, those are only 4yrs old I think

Bought the duracell grp31 SLA for $125. The “temporary” battery was a Durastart grp24. Now i’m wondering of I should just go ahead and replace my trolling batteries. They are interstate grp27 deep cycle and have been fine but dis run out on the water a couple times on long days in strong winds. Bought the boat with 3.5 yrs ago with these in there. Two deep cycle Duracell’s grp27 would be about $240. Cheap insurance?

3.5 years for lead acid batteries is getting near the end of their life span. Mine lasted 3-4 years when I used them.

240 bucks is pretty reasonable for a pair of batteries. I would probably go that route again if you got 3.5 years out of them.

Menards has a group 31 dual purpose for around $125

Attachments:

1. 

   Screenshot_20240312-064428.png
   

I looked to see if I could fit grp31 batteries in the area where my trolling batteries are located. It’d be a really tight fit so I’m not sure it’s worth it.

29 should be fine. Adjust your screens so they aren’t sucking major juice, pretty drastic pull differences from 100% to 85% brightness.

Those low voltage alarms on finders can be pretty off, I’d measure the actual state of the battery on a trip with a meter and see if your wiring is just messing w each other.

Not much size difference between a 29 and a 31…may as well just do the 31’s then.

acarroline wrote:

Not much size difference between a 29 and a 31…may as well just do the 31’s then.

To each their own, if it saves me 20 to 30 bucks and capacity is similar I’m going cheaper for a 14 jon

If I’m airing on going with a 29 or 31 yes do the 31, but if I’m between a 27 and 29 it’s the latter all day

acarroline wrote:

I looked to see if I could fit grp31 batteries in the area where my trolling batteries are located. It’d be a really tight fit so I’m not sure it’s worth it.

I run two 24 size for my Terrova, I need to redesign my rear compartment to fit a larger one but my run time is not to bad can go multiple days running it quite a bit.

Heck with it, buying all three in 31’s. One Duracell 31 DP for starting and two in the Duracell 31 DC for trolling. Either cut the side lip off the trays or get new ones ($10 each) as there is room in both spaces (Re-measured over lunch… 13.5 so good 1/2 inch at least of space to fit in trolling battery area.

Installed and on the trickle charger. Duracell 31DP for starting battery, two Duracell 31DC’s for the trolling motor. $423 for all.

I did a super deep dive into this recently. I would be that will solve your issue but if it doesnt it might be worth adding a battery to just run graphs.

Update after getting the boat on the water this past weekend.

Two new grp31 DC batteries for trolling motor worked great. I charged it overnight but both days were 8 plus hours with the trolling motor in use often. Never had any issues with losing power.

The new grp31 Dp starting battery worked well but I have a question. Early in day 1 I got the low voltage alarm (under 11, how I have it set) from my graph once, but not again the rest of the weekend. Battery was fully charged to start the day, ran 30 mins up river, usually ran the big motor every 3 hours. Ran two graphs 7 and 12 inch Lowrance TI2’s), two auto recip live wells, and a 12V phone charger plug in to the kid’s phone most of the day. I did adjust the brightness down 1-2 levels on the big graph but any lower is hard to see. While running it shows 13.7v-13.9v.

Just had my battery die on the lake (thankful i bought a noco awhile back)

Yamaha Sho 90hp, 2 helix 9 and livewell pumps.

In a pinch, do i buy the below battery they have in stock or do i travel 1hr one way to get something else? I think this should be just fine and an upgrade from the factory 24 battery that came with it new

SLI31MDP Duracell Ultra BCI Group 31M 12V 700CCA Flooded Dual Purpose Marine & RV Battery

Check the power wiring to the graph, I had similar issues with my HB and the spade connector to the power switch on the dash was at the end of the line of 5 jumpers. I rewired it directly to the fuse block and problem went away. The factory Lund power comes in from a fuse block and then jumped to 6 switches, so the power went through 6 connectors before getting to the graph.

I got to believe my starting battery is getting close to the end too? Has to be 6 or more years old. Still turned my Yamaha F150 over fine many times this year and ran my main graph but I did notice my voltage while running under power was only showing 13.7v. Shouldn’t this be closer to 14.4? Is this my sign to go shopping? Anybody got input…………..TIA

I always run my motor for a few minutes if it dips below 11.5v just because.

John Timm wrote:

Menards has a group 31 dual purpose for around $125

This is the battery I use and no complaints. Good luck

Voltage readings on graph are never accurate only sure way to know is use a multimeter to check voltage. My 3 Helix 12`s none show the same or even close to accurate voltage readings.

thanks Tom. last time out a few weeks ago and my one Helix 10 was showing 14.4 while cruising so I guess I will keep on keepin on and make sure my jump pack is charged