Three battery dilemma - Sea Nymph 14R

[Midwesterner]

Recently found a deal on a new 20HP four stroke, so I'm resurrecting my old 14' sea nymph that's been in the shed for years.

Here's my dilemma, I was gifted two Humminbird depth finders and a power drive v2 trolling motor. The trolling motor is obviously 24 volts and the depth finders 12 volts.

I've mounted the motor on the bow and I'm considering placing two group 31's behind the front bench. I'm guessing this will be around 100 lbs.

I plan on moving the 12volt battery, size yet determined, behind the seat in front of the driver. Thoughts?

What's a good size for running two depth finders, lights, and a simple bilge pump.

I have a small deck in the blue area of the picture, outside of that, the boat is bare.

https://imgur.com/IpS5tYS

 

[jethro]

Is the outboard electric start? Honestly the fish finders and some small LED lights and a bilge that is used primarily as a safety measure could run off a very small, 12v powersports battery unless they are 12" screens or Garmin Panoptix units. That said, if it were me I would keep a full size, group 27 deep cycle as my house battery and isolate the 2 trolling motor batts. The 20hp will certainly have a charging system that you'll want to hook to the house battery anyway.

 

[BigTerp]

You could run your accessories off of one of the group 31's and save the weight of adding a third battery. On my 1648 I run a 24V, 74# Minn Kota Maxxum using 2 Everstart group 27 batteries. I also pull of each battery independently for 12V for stereo, bilge pump x 2, LED nav lights, LED interior lights, sonar, LED light bar, 12V plug x 2 and starter for my '94 Johnson 50/35 jet. Zero issues with things setup the way I have them in my boat. Although this is not ideal since you're not draining the batteries in series equally which is supposed to be bad for their health. But I have not noticed any ill effects of this. I had zero desire and limited room to add a 3rd battery to my setup. The real disadvantage to this is the potential to run the batteries dead with the trolling motor, which I have done once while fishing for 8+ hours running the trolling motor hard.

 

[jethro]

I have heard that as well but the drain would be pretty minimal for the smaller fish finders. My Helix 5 draws less than 1 amp and my Lowrance Elite 5 is even less. LED lights would be minimal and the bilge is likely only in emergencies.

 

[Midwesterner]

Depth finders are 600 series and draw combined 1.5 amps. Trolling motor has down imaging and rear unit has down and side scan.

I was thinking I could probably get away with a small car battery, thinking I only need roughly 18 amp/hour at the greatest.

No charging system, basic pull start 20 hp.

 

[Midwesterner]

Thought about pulling 12 volts from the first battery in the series, I assume I'd just run the power and ground parallel from the first battery to get the 12 volts?

Thought I'd get feedback on the displays from the motor?

Group 31's near me are $108 out the door, so they aren't crazy expensive.

 

[jethro]

Thought about pulling 12 volts from the first battery in the series, I assume I'd just run the power and ground parallel from the first battery to get the 12 volts?

Thought I'd get feedback on the displays from the motor?

Group 31's near me are $108 out the door, so they aren't crazy expensive.

On my small boat I run the trolling motor off the same battery as my finders and it's not a problem at all.

 

[BigTerp]

On my small boat I run the trolling motor off the same battery as my finders and it's not a problem at all.

Same with me. Zero interference on my sonar (Helix 5 SI) powering it off the same battery as my TM.

 

[gnappi]

Depth finders are 600 series and draw combined 1.5 amps. Trolling motor has down imaging and rear unit has down and side scan.

I was thinking I could probably get away with a small car battery, thinking I only need roughly 18 amp/hour at the greatest.

No charging system, basic pull start 20 hp.

Harbor freight has deep cycle 35Ah AGM"solar" batteries for a bit over $50 and weigh ~25 lbs. I use three of them in my all electric boat. Two for the TM (switched and used one at a time) one as the house battery which runs the DF, LED lights, horn, bilge pump, courtesy lights, GPS, charges our phones, and never gets below 60% after 7+ hours on the water.

https://www.harborfreight.com/12-volt-35-amp-hour-sealed-lead-acid-battery-64102.html

 

[Midwesterner]

Do they make battery boxes for the smaller 35 amp hour batteries?

 

[gnappi]

My batteries are U1 size and there are lots of boxes for them.

 

[Midwesterner]

Ended up running two group 31's up front and a U1 sized 35 amp hour deep cycle battery towards the back for the depth finders.