Boat Battery Set-Up

Not open for further replies.


Keeper of San Juan Secrets
When I had the dealership install the sonar on the bow I also had them check my batteries. Have been running two group 27 deep cycles for the trolling motor and a size 24 starting battery. The trollers needed replaced, so I did. But the starting was still reading well.

Have never had a battery issue, we have a 115 mercury four stroke, the one finder at the console and run a few other items variously (small camera battery charging, livewell). I am curious if anyone has had any issues running a few things with only a 24 size battery, with the additional sonar at the bow its peaked my interest and I forgot to ask the dealer if they’d now recommend bumping up to a 27 or 31.

I’m not too concerned as we will rarely be using everything at once, i doubt we will even run both finders at once that much. Just curious to see what smarter people than me’s thoughts might be, whether my not too worried demeanor is correct or I’m just asking for disaster.

The only time that I have had issues was when I forgot and left the bilge pump on while the livewell was recirculating every 5min. I think the pumps drained the battery. Never had an issue with electronics.
I would think if you are not having issues with the 24 starting battery, I would just stick with that. I have the same, and have only had problems when I left the ignition on, and drained the battery, AND had the onboard charger come unplugged over a long period of storage.

While it is true that the 27 would give more oomph, if you have not needed it, it seems like overkill. There was an interesting article in sportfishing magazine about boats and maintenance. One thing they pointed out, is that as you own the boat, you keep adding stuff to it. Over time, your boat will grow much heavier than when you bought it! Something to think about....
I think you will enjoy having the graph on the bow as well. Good luck with it.

Our bass boat, a Tracker Pro Team 190, has a shared group 24 (optima Dual Purpose D34) battery providing both starting (Mercury Opti 135HP) and all onboard electronics. This includes two 7" fishfinders, livewell, marine radio, manual bilge and phone charging. We have run the onboard electronics for a full day of fishing many times without it impacting the starting ability. This is in smaller local lakes where the big outboard was not fired up much during the day, so no charging. Although I have a generator and try and charge all batteries each evening to maximize life, we have powered the on-board electronics for up to three days of general casual fishing activity without impacts to starting ability.

Regarding our newer deep V Crestliner, also a group 24 "house" battery (again Optima Dual Purpose D34) and separate group 24 starting battery, with an isolator between the two (see picture below), so effectively a single group 24 powering all onboard electronic, again including two fishfinders, marine radio, occasional livewell recirculation, automatic bilge pump and phone charging has never compromised our starting...yet! Knock on wood :cautious:...and this includes fishing red canyon most of two days with out firing up the big motor.

Note: the fishfinder at the helm never gets turned off while on the water (except when tied up at shore) and the fishfinder on the bow rarely gets turned off, even if the trolling motor in not deployed, unless we are going a good ways without anticipating deploying it.

That has been our experience, hope that helps. If your battery is a good battery and well maintained, it should be pretty uneventful, other than leaving a larger draw or long term draw on (bilge, ignition, lights, live well, etc.) as others have described.

In any case, this is a great argument for the peace of mind provided by the two battery system with an isolator.
Also carrying of jumper cables if you have trolling motor batteries accessible or carrying one of the small lithium jump packs.


  • IMG_4065.JPG
    466.5 KB · Views: 79
Hi, Preston, have a Crestliner 1950 FishHawk. I agree with the other of always carrying a set of jumper cables. One thing we have found is it is smart to pull the keys totally out of the ignition. It's a safeguard to keep the bilge pump from automatically cycling. In winter storage, always keep your batteries charged. Depending on the age, usage, quality, and maintenance, you will get 3-5 years out of your deep cycle batteries. Hope this helps. PS The only time we have used our cables so far is to help some bass tournament fishermen to get to their weigh in on time! Hope to see you on the lake in March! Say Hi to Nixon!
I ALWAYS carry with me one of those small lithium ion battery jump packs. That way if I every lose the ability to start my motor due to unforeseen circumstances I have a way to start and get off the lake. You can get a cheap one at costco, or there are much better ones on the market. I use a noco genius g40. I always carry one while snowbiking in the winter in case I lose a charge then, move it to the boat in the spring. You can also charge a phone or other electrical device with them. 4162
just bought one of the same NOCO jump starter, cheap insurance for lake powell. We had starting battery go dead way north a few years ago. Was catching allot of fish, livewell running for a couple of days, 2 sonars on all day long, long days and a short run to fishing spot so battery never got charged from motor. My advice is buy a 31 if it fits and don't look back, never heard anybody complain because their battery did not die!
I have a vapor proof disconnect/switch where I can use my trolling motor batteries to start the main engine if needed. Sq

That is how my Blue Seas Systems, add-a-battery system (pictured in my previous past) works as well.
I have been very pleased with it...

It has both a "vapor safe" battery switch and electronic charge controller relay that allows you to:
  • completely isolate batteries from the boat (master battery switch)
  • automatically allow both batteries to be charged from a single source (big engine alternator), while protecting the starting battery from discharge
  • automatically isolates the "house" battery during starting, to protect electronics (no more low voltage affecting fishfinders or radios at big engine startup)
  • manually switch both batteries to "combined" to start the big engine in the event of the starting battery failure
  • see status and charging/starting system indicators when desired
My switch is in the locking battery compartment, so I like that my starting and house batteries can be completed disconnected during storage, travel and in a slip, reducing a chance for discharge, shorts or theft, yet can still be charged via the on-board charger AC plug from any available AC, shore power or generator.

With that said, I certainly agree with the others above...within weight, space and cost considerations, maximum battery capacity is a good thing!
My setup isn’t that fancy, but it’s a 29 year old boat and installed by “SQUIRRELCO” I like the idea of having a dedicated battery for the electronics but a 4th battery is a lot more weight in the stern. Sq
Slightly off topic question....Like Preston, I have 2 trolling motors and a starting motor. With the Minn Kota DC chargers, would I need the MK-2 or MK-3? My AC onboard charger is a 3 bank, but I am thinking the DC charger would only need 2 banks, since the motor is directly charging the starting battery. Is this correct?
Like Dorado I have another question as well. What voltage level does everyone set their sonar alarms too? Probably want to set that up correctly as well.
Slightly off topic question....Like Preston, I have 2 trolling motors and a starting motor. With the Minn Kota DC chargers, would I need the MK-2 or MK-3? My AC onboard charger is a 3 bank, but I am thinking the DC charger would only need 2 banks, since the motor is directly charging the starting battery. Is this correct?
MK DC-2 would be for a 24 volt TM system, the MK DC-3 would be for the 36 volt TM system OR a 24 volt TM system using the 3rd battery wire set to charge a dedicated electronics battery for fishfinders, radios or other electronics. There are 3 sets of 12V charging leads for each battery on the 36V system.
Dorado, you wouldn't need the 110V onboard charger using the MK DC 3 Sq
I have my voltage alarm set at 10.5v, my Humminbird works until about 10 volts. Never had the alarm go off.
But I have things setup a bit different on my boat, than most other boats.
20' WeldCraft 350 mpfi / 8 hp kicker, remote steer and start.
I have a Minn Kota bow mount Terrova 55 lb ipilot 12v with two group 27 deep cycle batteries in parallel. These batteries also run my Humminbird ci si hd, this stops it from shutting down when I start my main motor. These front batteries are isolated with a VSR from my starting battery. (27 Marine) I think the VSR I use was $30. (Boeray 12V 125 Amp Voltage Sensitive Relay (VSR) Automatic Charging Relay Dual Smart Battery Isolator)

When my main motor is running or my kicker is running, (alternator voltage 13.5 volts), the VSR allows charging power to my front batteries but protects my starting battery from being drained when the motors are off. I also have a quick connect on the front batteries so I can connect my folding 100w solar panel to them, when I’m at base camp eating or napping. This keep my trolling motor batteries charged for a week out on Powell fishing. Knock on wood, I've never had a dead starting battery and never ran out of juice for my trolling motor.
I also have a Minn Kota MK106 120v charger mounted and connect to the front batteries for charging at home.

Another trick I've found is running my kicker at 2.5 - 3 mph and having my Terrova down steering the boat on a recorded track or on Autopilot. Hand free trolling so I can run the downriggers and help the kids fish.
Not open for further replies.