1 or 2 Batts for Starting and House?

[Tin Man]

I currently have one group 24 LA batt that is used as both a starting batt and house batt. Boat came equipped this way new.

I was first thinking about adding a second group 24 LA batt as it will fit in the batt compartment. This is the max configuration that will fit.

However, since I went with 2 12V LiFePO batts at bow for my TM, I was thinking of getting rid if the LA all together and going with ONE Group 31 AGM for starting and house.

Uses....livewell, 2 FF, runn. lights, 12V aux plug for phone/etc.

Will a dual purpose Group 31 AGM handle the house items (ex. 8 hours of use) and still provide for starting my Merc 60hp?

Thanks!

 

[jethro]

What size are your graphs and do you have any imaging? As long as they aren't 15's or above and as long as you don't have imaging processors I'd say that is plenty of power. Even with you'd probably be fine for 8 hours. A 31g AGM is a lot of power.

 

[flatheadsteve]

Gotta figure out your amps at max draw . A 10" garmin draws 3 amps, a rule 800gph livewell is 3.3....if running lights/nav are led its not much under an amp. Charging phone idk .... based on what you provided id say your looking at 10-13 amps tops... if your battery is 100ah youve got 7.6-10hrs. Idk your specifics exactly but gives ya an idea .

 

[airshot]

What about aerators or pumps on livewells ? Ship to shore radio ? Interior lights or other missed electrical draws ? I wouldn't want to cut it close then end up short. I use a small starting battery only for my outboard and charge off the motor. My house is a gp 31 deep cycle and I can go an easy 8-10 hours and no need to worry about starting my motor. Dual purpose won't last as long as a deep cycle.

 

[MrGiggles]

I think you will be just fine with the single group 31, especially since you have an outboard with enough charging capacity to top it up pretty quickly.

House batteries come in handy for multi-day trips, or for those like to fish all night, running lights and such constantly. For most it is a little overkill.

 

[flatheadsteve]

I think you will be just fine with the single group 31, especially since you have an outboard with enough charging capacity to top it up pretty quickly.

House batteries come in handy for multi-day trips, or for those like to fish all night, running lights and such constantly. For most it is a little overkill.

Or anybody that runs a stereo. Even a small Bluetooth reciever with 4 60watt speakers is 20 ish amps.

 

[thill]

I ran a group 31 deep cycle for years for starting and house, and it served me very well. No issues, even with all the stuff I have on the boat, including a 300W stereo system, (2) GPS units, lights, radios, powered livewell, etc.

I had two trolling motor batteries as backup, but never needed them. Have had the starter turn over a little slow, after sitting a long time, but never had it where it wouldn't start. Even so, for overnight trips, I would even bring an extra battery as backup, but never needed to hook it up.

I guess it depends on what boat you have, how long you sit without running the motor and what you are running while sitting.

 

[flatheadsteve]

I ran a group 31 deep cycle for years for starting and house, and it served me very well. No issues, even with all the stuff I have on the boat, including a 300W stereo system, (2) GPS units, lights, radios, powered livewell, etc.

I had two trolling motor batteries as backup, but never needed them. Have had the starter turn over a little slow, after sitting a long time, but never had it where it wouldn't start. Even so, for overnight trips, I would even bring an extra battery as backup, but never needed to hook it up.

I guess it depends on what boat you have, how long you sit without running the motor and what you are running while sitting.all

Depends how long you go without firing up the outboard I guess. We go out swimming with the kids at our favorite cove we could be anchored for 4 or 5 hrs straight with the stereo on.

 

[Tin Man]

UPDATE:

According to Mercury...they want the starting battery to be a starting/cranking battery...NO deep cycle and/or Dual purpose. Reason....60hp motor uses a stator type charging system (not your typical alternator) and the 60hp is not designed to charge deep cycle /dual purpose type batteries. No engineering/testing has been done with these batteries so they can not recommend.

With that, said, I need to find the largest capacity LA starting battery (group 27/29/31) that will be used as starting battery AND house accessories.

Motor batt requirements per manual:
465 MCA; 350 CCA; 70Ah

My amp usage: Approx. 13amp (2 FF/GPS, nav. lights, live well, 12V aux charger (phone, GoPro).
My use: primarily trolling with my Terrova LiFePo batts 4-6 hours per outing, 60hp motor run time (5-15 mins between locations several times per outing), and anchored via Terrova spot lock 1-3 hrs avg time per outing. As you can see, 60hp motor gets little run time per outing, so very little time to charge batt.

Are any of you following these same requirements with like/similar outboard?
What single battery are you running for both starting and accessories?

 

[MrGiggles]

I have always ran Everstart 29DCs and had excellent luck with them both for starting and trolling use.

 

[flatheadsteve]

I think your pushing it on a starting type battery with that amp draw especially since you have short intervals running the outboard. How many amps does the "alternator" put out?

 

[Tin Man]

I think your pushing it on a starting type battery with that amp draw especially since you have short intervals running the outboard. How many amps does the "alternator" put out?

18

 

[flatheadsteve]

18

That's not much higher than what you draw and most likely is at hi rpm. At 18amps you would have to run the outboard for roughly 40min to replace an hr of everything running off the battery. If you could start the outboard off the trolling motor battery incase you killed its battery I would just keep a set of jumper cables onboard and roll if not I'd go 2 batterys

 

[airshot]

"Dual purpose" are still deep cycle batteries !! You will still be going against recomendations. A simple 450-500 starting battery then find or create a place for a deep cycle house battery.......

 

[80monark]

1982 Evinrude 35 hp elcnd electric start.
Stator output 5 amps.
Accessories two helix dephfinders,
Bilge pump, livewell pump, led lights,
Bow and anchor lights, horn, compass heading sensor, ammeter and
Usb charger.
Group 34 dual purpose agm battery.
I have had no issues with the battery so far. The battery is designed for starting the outboard and powering the accessories.

 

[airshot]

1982 Evinrude 35 hp elcnd electric start.
Stator output 5 amps.
Accessories two helix dephfinders,
Bilge pump, livewell pump, led lights,
Bow and anchor lights, horn, compass heading sensor, ammeter and
Usb charger.
Group 34 dual purpose agm battery.
I have had no issues with the battery so far. The battery is designed for starting the outboard and powering the accessories.

If you have a long ride in and out, you should be fine..a 34 is a "big" battery..if your rides are short then you will need extra charging sooner or later.

 

[KevinWI]

Wish I was a bit more technical on this. I have an Interstate lead battery in the back which starts my motor, runs the bilge, navigation lights, helix 9, Humminbird network switch, horn and Mega live.
I have another battery up front for Terrova 55, spot light, led boat lights, helix 7.
Each has an option for charging phones, camera or whatever.
I have never had an issue...though my fishing expiditions last around 6 hours and I plug the charger in between morning and evening fishing plus overnight.
I've never had issue. That said...I'm now adding a helix 10 to the starting battery. We'll see if I have enough power.

 

[80monark]

If you have a long ride in and out, you should be fine..a 34 is a "big" battery..if your rides are short then you will need extra charging sooner or later.

I always start off with fully charged batteries before going out on the water.
Iam fishing most of the time with the trolling motor and dephfinder turned on, so mostly short rides with outboard.
When I get home the batteries are hooked back to the charger.

 

[thill]

First time I've ever heard that a dual-purpose, a battery MADE to start engines primarily with an enhanced reserve capacity, was not allowed by a manufacturer. They make it sound so special, but almost ALL 2-strokes (except Optimax) use a stator to charge, and DP batteries have been used for many years.

That being said, they have a point. If you run a big DC or a DP battery all the way down, you do NOT want to be recharging it with a little 60 HP motor, whether it has an alternator or stator. So don't do that.

 

[airshot]

First time I've ever heard that a dual-purpose, a battery MADE to start engines primarily with an enhanced reserve capacity, was not allowed by a manufacturer. They make it sound so special, but almost ALL 2-strokes (except Optimax) use a stator to charge, and DP batteries have been used for many years.

That being said, they have a point. If you run a big DC or a DP battery all the way down, you do NOT want to be recharging it with a little 60 HP motor, whether it has an alternator or stator. So don't do that.

They are great in motorhomes and trucks with high drain issues, just not a good fit with outboards where the charge rates are low.