Where to put trolling motor batter?

[sublauxation]

I'm redoing the entire layout of my boat and via some measuring errors it turns out there's no room for putting my fuel tank under the deck. The biggest downside is I now have to find a new place for my batteries.

I have a starting battery and a deep cycle. I had a battery die on the Mississippi River last year and it was a pain switching them out so I wanted to put them side by side so I can use a battery switch just in case this happens again. The problem is, because of the fuel tank fiasco there's no easy place to make that happen. I was hoping you guys could give some thoughts on my options. The boat is an 18 foot aluminum dual console.

1) My main concern is voltage drop. If I put both batteries in back I'll need 18 feet of cable from the deep cycle to my trolling motor. Is that too much?

2) I can put both batteries up by consoles the but I'd need new cables for the starting battery, the current cables are 8ft long, I'd probably need 12 ft total to put them here.

3) I can put the starting battery in back and the deep cycle up front but I'd need at least 12 feet of cable to attach the deep cycle to the selector switch in back.

Is there any problem with moving a battery up to the front? The deep cycle would fit like a glove right at the front of the bow. It's otherwise wasted space but I know it will be bounced around more up there.

 

[MTboatguy]

As long as you use the correct cable and make sure the connections are clean, you should not have much of a problem with voltage drop, but the key is making sure to use the correct type of cabling. Talk to a competition level auto stereo shop and they can get you fixed up on cables, those guys that do the heavy duty competition car stereos actually know quite a bit about wiring. I was surprised when I talked to our local shop.

 

[Silvertip]

There is a very simple solution to your problem(s).
1) Put the troller battery up front. The shorter the cables the better and obviously less expensive regardless of the wire size..
2) Put the starting battery in the rear. Again, shorter cables and less expense.
3) Forget the dual battery switch and just carry a pair of jumper cables. Cheap and effective.
4) Make sure the engine is tuned and you really understand how to start it cold and hot so you don't crank the thing so long thus killing the start battery..
5) The engine can keep the starting battery topped off but unless it has a very high output alternator, even a moderately long run will do little to nothing about charging the troller battery. Install a single (or dual) bank on-board charger and plug into shore power to keep the troller battery charged.
6) Make sure the batteries you have can hold a charge, Just because they accept a charge does not mean they can hold it. Have them load tested.

This avoids unnecessary expense and complexity.

 

[smokeonthewater]

You can put the batts anywhere you want...

I rewired my dad's 18.5' bass boat a couple times moving batts around to get weight distribution how he wanted it...
Factory it had two deep cycles for trolling motor and a start batt all in the back... I put all 3 in front and it worked great... Then he decided he wanted just a little less weight up front so I moved the start batt back to the rear.... I don't have a combiner switch wired in BUT it wouldn't hurt a thing.... Keep in mind tho that the wire to start from a battery in the bow will be pricey..... Quality heavy gauge jumper cables that long will likely be more pricey since you would be buying the same wire plus alligator clamps.

 

[sublauxation]

What do you guys think about putting it right up under the bow on top of the front casting deck?

 

[smokeonthewater]

Anywhere you want it will be fine as long as it's securely mounted and protected from damage.

One thing to consider tho if you run in rough water often is that the further forward it it the harder it will be jolted.... Not necessarily a deal breaker but if you are constantly slamming in the chop at high speed you will need to mount it better and it MAY not last as long.

 

[sublauxation]

I'm going to start a full resto thread pretty soon so I don't know if it's best to just put this there but but at what point is there too much weight up front. I'm adding a 15 gallon livewell to the front but adding a bench seat to the very back, and my kids who will use the bench are only getting bigger. My goal was to move the fuel tanks up and under the floor but that wont work so I'm putting two 6 gallon cans just in front of the splashwell.

 

[airshot]

No solid rule for weight distribution, experiment only! Put your boat in the water and experiment with what you want where and see how it balances out. All hulls are different when sitting in the water so while you have the interior out, just experiment with putting whatever wherever you want it. In regards to the original poster......you have gotten a lot of good info on here.. follow it wisely..

 

[sublauxation]

No solid rule for weight distribution, experiment only! Put your boat in the water and experiment with what you want where and see how it balances out. All hulls are different when sitting in the water so while you have the interior out, just experiment with putting whatever wherever you want it. In regards to the original poster......you have gotten a lot of good info on here.. follow it wisely..

I hear you, the first time I did the boat was before I found this site, hence round 2. Problem is, there's a lot of good advice up there, all smart people, and some conflicting.

 

[smokeonthewater]

no conflicting INFORMATION only conflicting preferences

You are in the process of designing your boat... you will have to make the final call on each step based on what is important to you.... Personally weight distribution, utilization of available space, and functionality would be at the top of my priority list here...

I personally would MUCH prefer to install additional wiring vs having to carry jumper cables BUT if you ever manage to deplete both batts the cables would allow jumping from another boat....

I have never needed to jump start MY boat in 25 years of boat ownership. and honestly I would tow another boat before trying to jump start it for safety reasons.

In the end it doesn't matter what our preferences are nearly as much as yours....

You need to decide how you WANT it done and then we can help you figure out HOW to make it happen.

 

[Grandad]

Remember that the engine requires much more current when starting than your trolling motor normally uses and starting the engine is the most critical function in a boat. With that in mind, to avoid excessive voltage drop, I would be inclined to keep the start battery and any battery selector switch near the engine. Increasing the smaller wire size to the troller will be less expensive than increasing the larger wire size to the engine. Another thought to consider is that if you do want to rely upon your trolling battery to emergency start your engine, the wire size must be much larger for a remotely located troller battery. - Grandad

 

[smokeonthewater]

For the starting batt if it goes in the bow 4 gauge wire is plenty for that length and 2 gauge is overkill if that's your style.

For the trolling battery in the back 10 or 8 gauge.

4 gauge for starting from the front mounted trolling batt.

That would be a 4 gauge ground and a 4 gauge switched positive.

 

[smokeonthewater]

BTW since jumper cables were mentioned earlier understand that they need to be much heavier than the cheapo cables often used for cars..

The reason for this is that when you jump a car, the car supplying power is running and thus charging at 14+ volts so it can charge up the dead batt and then add just a little boost for cranking.

When jumping from a battery you will have no more than 12.5 volts and will not be able to charge the dead battery nearly as well so the cables will need to carry almost all of the cranking amps.

 

[sublauxation]

no conflicting INFORMATION only conflicting preferences


In the end it doesn't matter what our preferences are nearly as much as yours....

You need to decide how you WANT it done and then we can help you figure out HOW to make it happen.

Very true....but you guys are all smarter than me:joyous:

I don't like the jumper cable idea, a guy up here just died that way a couple years ago.

 

[sublauxation]

For the starting batt if it goes in the bow 4 gauge wire is plenty for that length and 2 gauge is overkill if that's your style.

For the trolling battery in the back 10 or 8 gauge.

4 gauge for starting from the front mounted trolling batt.

That would be a 4 gauge ground and a 4 gauge switched positive.

Thanks for this info! If I ran 2 or 4 gauge from the deep cycle up front all the way back to where the starting battery was where would the ground have to go? Would I need a grounding stud and tie in a heavy gauge wire from each battery as well as the ground from the outboard?


It's certainly a frustrating process. On one hand being able to move things around to test it out would be great, on the other hand you can invest a lot of money in electrical parts and pieces in the process.

 

[MTboatguy]

It's certainly a frustrating process. On one hand being able to move things around to test it out would be great, on the other hand you can invest a lot of money in electrical parts and pieces in the process.

Who ever told you owning a boat was going to be cheap?

B=Break
O=Out
A=Another
T=Thousand

:lol:

 

[smokeonthewater]

The negative posts of the batteries would be wired together

IE starting batt has neg cable from motor and negative wire to trolling batt on it's negative post and trolling batt has that cable running to the start batt and the negative wire to the t/m on it's negative post.

Positive cable from the motor runs to the start batt if it's in the rear and and then from that positive post to an on/off switch to the positive of the t/m battery

OR pos from motor to 1/2/both switch and then out to each batt

IF all batts are in front I suggest two switches

Motor to on/off at stern to 1/2/both in front and then out to both batts.

 

[smokeonthewater]

Honestly right now you are getting the cart ahead of the horse...

Work out the space and weight distribution issues first and THEN we'll get you through the wiring portion of the job.... Just know as you lay it out that you need two strands of 4 or more gauge wiring running from the back to the front if you have any batts in front that may be used for starting.... Plan the route and account for the cost of double that many feet of wire along with whatever switches you choose.

 

[sublauxation]

Sounds like a good plan to me, now that I know wiring them in any position wont be an issue. I appreciate the help. I got the whole back deck off and part of the floor out, weather pending next weekend should be a lot more productive.

 

[bruceb58]

When you are ready to make your cables, go here:
https://www.genuinedealz.com/