# only two batteries for 24v troller and starting



## handyandy (Jul 15, 2020)

So I swear I've seen the question on here before but can't seem to find the thread. I've got a 24v terrova I want to upgrade to from my 12v powerdrive. Currently I run one battery it's my starting battery, runs the trolling motor, and my electronics. It's never been an issue for me, it's always had enough juice to run my trolling motor as much as I ever do in any given day, and still had plenty to start the engine, and run the fish finder. I got a 24v terrova this past fall I'm finally wanting to switch to I bought it used I'm too cheap for new lol. Anyways I'm wanting to just run two batteries as my boat is only 15ft I have a place for a second battery upfront, currently the one battery is in the back. I don't really have a good spot for a third battery, and I really don't want the weight either. I'm fully aware I have to wire two batteries in series to get 24v to the the trolling motor, my question is can I still just hook up the engine to and electronics to just the back battery to only get 12v to those? I'm considering the yandina trollbridge as it seems like the best solution for what I want to do. But if it's not truly needed to do what I want then why buy it. I know having one dedicated starting and electronics battery, and then two dedicated trolling motor batteries is best. But it's just not really an option in my boat. I know it would give me better range, but I'm not worried about the range I've been fine running one battery for everything for a long while now, I think I've had the boat 8-9 years now. Has never been a problem for me having just one. There was one time when my battery just crapped out suddenly and left me jump starting the boat for a duck hunt, but I've never had an issue of not having enough battery for my trolling and starting needs with just one. So I feel like with a 24v motor I would be fine with just two.


----------



## Pawatch (Jul 16, 2020)

I'm far from electrical expert but here are a couple thoughts.
How far of a run would you have from your motor to your battery's? You would have to use heavy wire I would think.
It could be cheaper just to pick up a starting battery then buying all the materials to make the run for the motor.


----------



## eeshaw (Jul 17, 2020)

Just a thought here. If you can pull start your engine in a emergency situation then I'd just give it a shot and see what happens. A seperate "house" battery and starting battery I feel is always best but it's not a real concern I wouldn't think if I can pull start the engine.


----------



## LDUBS (Jul 17, 2020)

If you go with the two batteries, would you have to isolate the trolling motor battery when running your outboard? I'm thinking in terms of alternator output to your starter battery.


----------



## handyandy (Jul 20, 2020)

LDUBS said:


> If you go with the two batteries, would you have to isolate the trolling motor battery when running your outboard? I'm thinking in terms of alternator output to your starter battery.



That's what I'm trying to figure out and that's what that trollbridge does. And to the other points I already have heavy gauge wires running from my one single starting/trolling battery in the back. Right now I'm running a 12v powerdrive and I use one group 27 deep cycle for my trolling, starting, and electronics. I've had one time when I had to pull start it was my own fault really, I used the boat one weekend used the troller a fair amount. Parked the boat at home for got to plug the charger in, fished the following weekend and drained the battery enough fishing using the trolling motor that it didn't have enough to start the engine. I break out the ole emergency roap/handle pulled the hood, wrapped the rope, and did the ole pop'eye start. Pull starting a three cylinder 70hp power head is not ideal, but doable if the case arises. I'm really leaning to the troll bridge since I already have heavy wires run from back to front, I'd only have to wire in a front battery and the trollbridge if the trollbridge is even necessary.

If I don't use the troll bridge and my understanding while the outboard is running it would charge the one battery it's hooked to, and the charge would drain off that battery (rear battery) to other (front battery) till there balanced. Obviously at home I'd have the batteries on a charger like I do with my one already so if the batteries weren't balanced after a day of fishing they would be after charging at home. I know two separate trolling batteries and separate start battery would be better, but I don't really have a good place for a third battery.


----------



## LDUBS (Jul 20, 2020)

Thanks, my knowledge is really limited. I recall someone telling me that I would not be able to rely on my outboard to charge both batteries. Sounds like you have that covered.


----------



## handyandy (Jul 22, 2020)

LDUBS said:


> Thanks, my knowledge is really limited. I recall someone telling me that I would not be able to rely on my outboard to charge both batteries. Sounds like you have that covered.



I'm not 100% certain but my understanding is the outboard would charge the battery it's hook to. The second battery would slowly pull from the one charging until both batteries are balanced. Hence if I do a setup like this I would have to do what I do now anyways and hook a charger to the batteries. I do that now anyways since after a good day fishing I the motor usually isn't run enough to have charged the battery up fully since I just run one battery now for everything


----------



## Pawatch (Jul 22, 2020)

I have a 2 bank battery tender for my 24 volt system and each tender gets hooked to the battery like a normal battery.
My motor is pull start so I am not sure about electric start. Do you have a good battery place? They should be able to answer all your questions.


----------



## coosa (Aug 2, 2020)

I might have been the guy who you remembered asking about this before. I asked several months ago and someone told me that he was doing it without an issue. I thought it would work ok, but it concerned me that I never saw anyone setting up a boat this way. I wondered if I was missing something, but apparently not. The biggest concern that some have that could be an issue is that the trolling motor could interfer with a depth finder. I could live with that for the extra power.

I was wanting to replace my Edge with a 24 volt Maxxum. I bought the new motor and carried it home and found that the steering cable was too short to work on my boat. I have a stick steering G3, and it's 7' from the bow to my seat, and the foot control would not even touch the floor. I carried it back and am still deciding how to deal with that.

There is room for only 2 batteries in my boat, so running everything off 2 is the only way I can have a 24 volt motor with this boat. I have a good deal of battery experience with golf carts and a solar powered cabin, and I can tell you that you won't be able to charge both batteries from your outboard alternator unless you have some sort of additional device between them. If the batteries were set up parallel, giving you 12 volts throughout your system, you could indeed get it to charge both batteries. But wiring them in series will result in only the one being charged. 

I don't see that as a critical issue; you will just have to charge the other battery longer when you get home. I already have 2 batteries and charge them separately anyway, so I don't see where that will matter. Good luck with it, and please post back when you get it working.


----------



## jethro (Aug 18, 2020)

I did an entire year of research before I installed my new trolling motor. Mine is a 36v system and the best practice is to use the same age batteries (brand new to start) and make sure you discharge them all exactly the same and in series. Same goes for charging. An unbalanced discharge or charge load will greatly lessen the life and performance of all the batteries in a series system. You absolutely can use one battery to isolate a 12v circuit but it will decrease the life of all the batteries attached in series because they will all struggle to balance themselves, especially with something like a starter circuit that is a short but very high load. I was told to not even hook up my bluetooth heading sensor that way and it uses way less than a single amp on 12v. Unbalanced load = bad is the whole theme of this story apparently. 

For the same reasons I stated above, you do not want to attach the charging circuit to a single 12v battery attached to another in series. You can buy an accessory that will do this, but I am told it doesn't do enough for charging the system, even with my V6, 150hp outboard. Not pushing enough amps.


----------



## coosa (Aug 25, 2020)

Jethro, I believe everything you posted is true, but for someone with a boat like mine, the ideal just can't happen. It would no doubt give me longer battery life to have a cranking battery for the outboard, and 2 deep cycle batteries for the trolling motor that are hooked up in series. There is just no room to put 3 batteries in this boat, unless I want to put one on the main floor with my fishing tackle, and I don't want to do that.

I am just willing to accept that my batteries may not last as long. But even then, I think the issue will be minor. I have 2 electric golf carts, one 36 volts and one 42. I run the accessories off the pack batteries - that's the lights and a winch. The winch uses a lot of power.

The golf cart guys are unanimous in saying not to hook it up this way, but I've been doing it over 20 years without an issue. What I do is to check the winch batteries after each use and give them an additional charge to equalize them with the rest of the pack. I've never gotten less than 7 years out of a battery pack, so any damage I'm doing must be very minor.

Since both of my boat batteries get put on charge immediately after every fishing trip, I don't think it will matter a whole lot that the outboard has already charged one of them to some extent. But I still haven't actually set this up because I haven't found a trolling motor that will work with my boat. Thanks for all the good info here. I will post the good and bad about it if I ever get this done.


----------



## handyandy (Sep 30, 2020)

coosa I have a very similar issue as you in regards to room for a third battery, and I feel pretty much the same in that things will be fine if I do what I'm planning on. I'm like you after each outing batteries would be on a charger so each would get charged up fully after I get home from an outing. with the exception a few camping outings, in which case they might sit a day or two not on a charger. I just put my helix 7 in not too long ago, I'm still just running one battery for everything with my 12v troller and I haven't had an issue with the fish finder when I start or run the troller. I need to find time to go ahead and just wire in the second battery and put on the new to me trolling motor. I think things will be fine.


----------



## Vader809 (Oct 3, 2020)

With a 70 hp outboard on a 15 foot boat, you should have plenty of room for three batteries. Of course I don't know what kind of boat you have, or the layout. I have a 16 foot boat, and run 3 batteries. A Terrova 80#,24 volt. Those two batteries are not shared with anything. The lone battery runs my Helix 9si, and lights. It sometimes runs a 55# transom trolling motor. If I couldn't figure out a way to customize it, that boat would on the market. There are plenty of other boats out there that can fit your needs. Everyone has their preferences. I paid $650. For boat and trailer. Plain old boat, not any more. I didn't put a lot of money into it, but I did my homework and saved thousands. It's got plenty of room and storage. There is always a solution.


----------



## BigTerp (Oct 6, 2020)

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. I have a NOCO Gen 2 for charging that stays plugged in when off the water. 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. But my $30 portable jump starter fired up the motor several times that day to keep me fishing.


----------



## coosa (Nov 22, 2020)

BigTerp said:


> 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. I have a NOCO Gen 2 for charging that stays plugged in when off the water. 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. But my $30 portable jump starter fired up the motor several times that day to keep me fishing.



Thanks for all that info, Big Terp. It confirms my line of thinking on it and what I have been planning to do. There is the absolutely ideal, and then there is what is practical. Using just 2 batteries is the only practical option for my boat, and sounds like it is for yours too.

I finally found a 24 volt Maxxum that is supposed to be shipped to me in the next week. I will have to change the cable out on it before installing, and that certainly isn't ideal, but I do think it will work. I'll post back into this thread and let everyone know how it works, but I expect results like yours.


----------



## MrGiggles (Nov 23, 2020)

You will want individual gauges on both batteries so you do not discharge one, it will not be readily evident if one is weak just from taking a voltage reading from them in series.

Batteries in series will not discharge from one to the other like they do in parallel, but you are only as strong as the weakest battery. If you have a battery at 75% and another at 25% in parallel, the two will equalize to 50%. In series they remain at 75 and 25, however the weaker battery will discharge quickly, if you continue pushing them it will basically reverse charge and totally kill the battery. Plus low voltage is really hard on trolling motors.

Starting batteries are fairly cheap and you don't need a huge one for small outboards. I would not want to run the outboard off of the trolling batteries, you do not want a dead battery when it's time to leave, and sometimes you need to leave in a hurry when bad weather is on the horizon.

Running your electronics and livewell pumps should be fine on the trolling batteries, but I'd want a bilge and the outboard separated for safety reasons. The added 50lbs from a 24MS battery should be inconsequential in a boat big enough to need a 24V troller, and an AGM battery can be placed on end, sideways, wherever it will fit.


----------



## coosa (Nov 30, 2020)

Thanks for the info, Mr. Giggles; I'm sure that everything you said is correct. I have never tried to set up a boat the way that I am considering, but I have a lifetime of experience with FLA batteries, owning 3 different golf carts and a solar powered cabin, so I understand the limitations of wiring in series and parallel.

Let me show anyone interested what I am up against with this boat. It's a 1652, but the hull weighs 800 lbs because G3 used a lot of wood in it. The 45 lb Edge will only move it on the 5 setting, and then not very well. The Maxxum I ordered is supposed to arrive today, so I will plan to be working on it soon.

Here is the view in the back:





You can see there is no room for a battery on the outside of the rear compartment, and I wouldn't want one outside of it anyway. Here is the view with it open:




what is marimo moss ball plant


You can see that the group 29 battery is in lengthwise, and the group 24 is sideways. It will be an extremely tight fit, but I can take up the battery boxes and move them a little and get 2 group 29s in there. I don't see any possibility of a third battery unless I remove the gas tank and replace it with a portable, then remove the top deck and leave it all open in the back. That seems like a radical solution when compared to just using 2 batteries.

The 24 is over 2 yrs old and the 29 is 15 months. Both are still in good shape. I have never found the 24 below 90% soc after a fishing trip, but of course the motor is charging it. I've never ran the 29 below 75%, and that has surprised me. I seldom fish more than 6 hours.

This boat is one step above a jon boat with tiller steering, so there are no gauges except a fuel gauge that I would have to get on my knees to read. I don't need it; I know about how much gas my motor uses and I have never used over a half tank. I know that it isn't ideal, but I am planning to hook the Maxxum to these 2 batteries and try it. I truly don't know what the results will be, but I don't think it will be as dire as some folks have told me. The outboard will be putting power back into the 24, and I have never come close to running the 29 below 50%. I expect the Maxxum to use less power than the Edge because I should be able to run it on 2 or 3 most of the time. I could be wrong about that, but we will see.

I do have a cheap Garmin depth finder that shows the battery voltage, so I will be able to keep an eye on it. If it goes below 12.1 I will know that I am at 50% and need to do something. I could switch the wires to the 29, as it should still have plenty of power to crank the motor. That would be a pain, but it would get me home. I can also crank it by hand.

The most radical solution is to modify the front of the boat. It looks like this from beside the front seat:





The 5' cable is only a few inches too short. If the piece of plywood that is directly in front of the TM foot control were removed, then the cable would not have to bend at all and I believe it would be long enough to work. I would need to pull out the sheet of plywood and the cooler cover and the cooler, and that would not only make the steering cable long enough, but it would also leave me a lot of room in the deck area. I believe it might be possible to fit a battery on each side of where the cable would be and that solves the battery problem completely. Of course, then I will have to have a cooler on the floor somewhere, and that will lose some room.

So you can see there is not a real easy solution. I will report back on whatever I do as I know others are facing similar electrical issues. If something I try doesn't work, I will admit it. But I think any of these solutions could potentially work.


----------



## MrGiggles (Nov 30, 2020)

coosa said:


> Thanks for the info, Mr. Giggles; I'm sure that everything you said is correct. I have never tried to set up a boat the way that I am considering, but I have a lifetime of experience with FLA batteries, owning 3 different golf carts and a solar powered cabin, so I understand the limitations of wiring in series and parallel.
> 
> Let me show anyone interested what I am up against with this boat. It's a 1652, but the hull weighs 800 lbs because G3 used a lot of wood in it. The 45 lb Edge will only move it on the 5 setting, and then not very well. The Maxxum I ordered is supposed to arrive today, so I will plan to be working on it soon.
> 
> ...



Looks like there is a whole lot of space under that front deck. Move the trolling batteries up there. You don't want all that weight in the stern anyway.

I wonder if you don't have an issue with your current trolling motor, I had a 40lb Powerdrive on my 17' Deep V for a while and it would move it around well enough. Your boat should not need a 24v troller.


----------



## coosa (Nov 30, 2020)

No doubt that I can remove the front deck and put 2 batteries there. That's just a pretty radical step and I don't know if I can make it look decent. It would certainly run better with the batteries up front. I can't trim it at all with a passenger in the rear seat or it will start to porpoise.

It could be that the Edge has lost some power over the years, but I think it's just the weight of the boat. I can get by in calm water, but it goes backwards in current and has put me into a couple of dangerous situations fishing tailwater. 

At any rate, the new motor came today and I will hopefully have a little time to work with it tomorrow. Thanks for the ideas.


----------



## coosa (Dec 1, 2020)

I started a new topic in the Boat House forum titled "Deck Modification Question" in the hopes that more people would see my questions. The steering cable on the new motor is just a couple of inches too short the way that it is now. This is what it looks like:





I could easily fit 2 batteries where the front deck is now, but there is no turning back if I start cutting the aluminum. I wanna be sure that is what I want before doing it.


----------



## coosa (Jan 21, 2021)

For anyone interested, I finally decided to split the lid and put 2 batteries in the front deck. I posted details in the other forum, but here is a picture of how it looks:



my best friend poem

So I now have 3 batteries and that is a much better setup. I have no doubt I could have gotten by with the 2 battery setup, but it was the length of the TM cable that led me to this solution.


----------

