Dual Batt. 12v system for Trolling Motor

[BoatingCop]

Just wondering if I would hurt anything if I set up my 12v system in parallel with two batteries. I'm thinking you would get more run time out of the batteries. Has anyone done this or will I mess something up? I wouldn't see why it would mess anything up if it was still connected to be 12v. By the way, my TM is a 2003 AT55 Minn Kota 12v 55 lbs. Thanks

Eric

 

[raekmike]

Re: Dual Batt. 12v system for Trolling Motor

No...It won't mess anything up and it will increase your run time. The only drawback that can happen is that if one battery is bad or goes bad it will pull the charge from the good battery down and "equalize" the charge between the 2. That's just the worst that could happen. Alot of people run this setup. Main thing to remember is always charge your batteries after use and never let them sit in a drained stage.

 

[Silvertip]

Re: Dual Batt. 12v system for Trolling Motor

The best way to do this is to install a switch that allows you to run off of each battery individually. Run one down, then switch to the other. You will not have the issue of the weaker battery sucking the life out of the other. Whether you consider that worth the effort is up to you. Other than the equalization issue, there is nothing inherently wrong with a permanent parallel connection and you can use a single output charger to charge the batteries. It will obviously take twice as long to charge both at once.

 

[ProMarJim]

Re: Dual Batt. 12v system for Trolling Motor

Jim from ProMariner here.

If you plan to add another battery make sure your charger can handle it.

Many chargers require a DC output for each battery regardless if they are in parrellel or series.

If you add a battery without a charging lead for it the charger will see it as one large battery. The concern is that it can drive the voltage up on the smaller battery ie starting battery.

Jim

 

[4JawChuck]

Re: Dual Batt. 12v system for Trolling Motor

I have the same the same setup as yourself and run two battery's, I use a BEC selector/charge module to operate the battery's.

http://www.bepmarine.com/Single-Engine%2C-Two-Battery-Banks-180-1460.html

The module allows you to draw on both battery's until the starter battery reaches 12.7 VDC at which point it disconnects the starter battery from the circuit to prevent a "no start", it also reconnects the second battery once the starter battery reaches 13.7 VDC to charge it while under way.

This was by far the best investment I made in my boat as I no longer worry about run down trolling motor battery's while camping etc. It works so well I don't bring my charger with me anymore.

If you want to charge the battery's at home when you get back you connect to the starter battery and let the module do the distribution duties to charge the trolling motor battery, it will reconnect once the starter battery reaches 13.7 VDC.

This year I have not had to charge a battery at all, I keep checking them for charge but they are topped up after every trip...one day I will stop checking I guess...still can't believe it!

Most of my trips consist of at least 20 minute travel times to the fishin hole so this seems to be enough time to top up the trolling motor battery, my Merc has a 16 A stator which seems to get them ready by the time I reach the trailer.

I run all my accessories off the trolling motor battery except for the running lights and dash lights and I have hit 11.2 VDC on the trolling motor on a number of occasions, a 20 minute blast around the lake brings the trolling battery back enough for another couple of hours. Even idling the motor in neutral at 1200 rpm is enough to charge them. I get around 4 hours from my 42pd MinnKota 812 on the two battery's until the trolling battery hits 11.7 VDC...then we go for a drive and do it again!

Most marine dealerships around here carry them and they make ones for 24VDC systems...triple battery's...you name it. You can flip the selector switch to parallel the bats if needed too.

Truly a must have trolling accessory in my books, great product!

 

[fishrdan]

Re: Dual Batt. 12v system for Trolling Motor

I'm with Silvertip on this one, use a switch between the batteries and run them independently,,, then combine them at the end of the day if needed.

I used to run 2 batteries in parallel and then started to run them independently. The 2 batteries last longer when run independently since the weak battery isn't discharging the strong battery. If you have 2 batteries that are the exact same condition it won't make a difference. But, my batteries were purchased at the same time with the same date code, and it make a difference,,, one of them is weaker.

 

[Silvertip]

Re: Dual Batt. 12v system for Trolling Motor

Batteries in parallel do not need two separate outputs from the charger. The charger will detect "system" state of charge and since batteries will equalize, a single output charger will work just fine. There are millions of diesel powered cars and trucks running around the world with parallel batteries being charged from one alternator. It's not an issue. Series wiring is another story.