Hi, I have a 2019 Lund that came with a 27m-xhd cranking battery only. It had an empty spot next to it, so I got a 27 deep cycle with the intent of running accessories and the trolling motor off of it. It has a single switch with 4 posts on each side, accessories are wired along with the cranking, and there are pre-wired cables to go to a trolling plug up front. There's also a 5amp clean power cable connected directly to the cranking battery... not sure where that goes.

So, I have some technical skills, just not sure of my options here. Should I hook the new DeepCycle battery up to two posts on the switch and move the accessory cable there? Should I get another switch for the other battery? Should I link the batteries? ...should I call somebody?

Any advice is appreciated. Thanks!

If it were me, I'd run accessories off the start battery and run trolling motor directly off deep cycle battery. Would not go through switch.

I appreciate that, and it definitely seems like that's how it's intended. I only started looking into running accessories on the deep cycle for nav and radio while trolling. No biggie? Thanks again.

If you try to run anything except the trolling motor off the trolling motor battery, you are likely to get electrical interference, especially if you are running any kind of fish finder. Run everything off the cranking battery except the trolling motor.

Wayne

Alright, deal. I appreciate the advice - it makes sense. Thanks guys.

That "switch" looks to be one of many available battery cut-off switch models that typically allow the option of having a second starting battery as a back-up.

Those "4 posts on each side" appear to be bus bars where each of the posts in the group are electrically connected as they're all connected to a metal bar. I can't tell for sure, and you didn't say. You would never hook a battery up to those if that's a bus bar as you would be putting battery voltage on whatever is already there. One of the bus bars may be a common Ground for everything as many battery switches only turn the + lead on or off.

If you do decide to connect something to those posts, be sure you understand what you've got electrically before you connect a battery - the wrong move could blow up a battery, and that's a bad week. I agree with the others. Run the boat just like it is, unchanged - except that the new battery will be dedicated to the trolling motor only. As such, that battery should have the cables for the TM connected, and nothing else. You do need an appropriate circuit breaker for the TM. Does the harness have one already? What gauge is the wire for the TM? (Gauge will be something like "6 AWG" or "8 AWG" printed on the wire.) The wire size plays into what size breaker is appropriate. What outboard do you have? What TM do you plan to get? Let us know for more comment.

It's a 24' Lund LX220 (Fish and cruise tri model). It has a 200hp Mercury, and I haven't purchased a trolling motor yet. I agree with you, and definitely had no intention of just hooking things up that I don't understand. If I got some advice and it made sense to me, I may have researched and acted if I was 100%, but I definitely don't want to fry my stuff or hurt anybody.

I'll have to get back on the cables for the TM, they're loose still and will be the only thing connected to the deep cycle - per the consensus here, and the sense it makes. The cables run under the deck and go up to the front section and terminate into a 3-pronged outlet. The battery is 12v, so I'm definitely going to have to keep that in mind when reviewing the line and of course getting a motor. As far as trolling motor, I want to get something with a decent length corded pedal, 12v, enough depth to clamp down to the deck and hit the water (just under 2'), 60+ thrust so I can hang out under the bridges.

I've driven boats forever, but this is the first one that's mine. I've learned a lot over the past 2 months. (like how to park in my slip in 20mph winds lol)

Again, I appreciate the feedback and advice.
Joe

Joe, Your 200hp Merc has substantial alternator output, so unless you are putting a heavy accessory load on the boat, you shouldn't have any problem. Remember, anything on while the outboard is running above idle will be powered by the alternator (therefore not drain the battery during that time) and the alternator will also be charging the battery to help you make it through the day without issue.

I feel VERY concerned about your TM plans. A 12V TM is not going to be enough for your 24' boat. It's almost 3000# without motor, batteries, fuel, people, and other gear. It also has a big wind profile. You're not limited by just what battery trays the boat has - if you can fit 3 batteries (total), you can have a 24V TM, and that will be much better for that boat. Many of us have moved/added/rearranged battery trays to accommodate the right TM setup. A 24V TM will give more useful motor-on time since it's drawing energy from 2 batteries. The amperage draw will be less as well (with a 24V motor). No matter what you do, do NOT connect a TM without confirming you have a circuit breaker, which will be near the battery compartment you showed us photos of, if you have one. I won't be surprised if there isn't as the TM was optional, and the breaker size gets matched to the wire & TM. I can help you get the right breaker once you tell me the wire size and which TM you are getting. Again, I highly recommend you get 24V (which usually has around 80# thrust and longer run time). Lund can probably advise what shaft length TM you should buy (so it reaches the water from your deck).

Ok, I was able to get back to the boat and took some more pictures. Looks like there is a 24v breaker on a 50amp Trolling Motor cable pre-wired, but I can't tell the gauge of the wires (600v printed on there). I think I have room to turn the battery sideways and get another 12v in there to make for 24, but I'll need to look at the battery seat and see the options there.

Thanks again.

That info is helping. Definitely 50A breaker. (I don't like that kind, btw. Mostly because you can't turn them off. TM manufacturers say to unplug the TM or turn off the circuit breaker to charge them - for those who actually read the manual.) A better breaker (that can be turned off) can typically be had for no more (and often less) money than a plug & receptacle cost. You may already have a receptacle on the boat, but that's something I had not thought about as far as amps go - it may be a cheapie one that's too little for the job.

I'd like to know the rest of the numbers & letters on the wire (besides the 600V and 105C). The gauge number is often buried in there in a manner you would not recognize. That wire is likely 8 gauge (based on the boat builder installing a 50A breaker), but I could be wrong. To me, both of those are a joke to be on a 24' boat over 3000#. The right thing would be 60A breaker on 6 gauge wire. DO NOT EVER install a 60A breaker with that wire unless it's confirmed to be 6 gauge. Eight gauge wire can be melted without tripping a breaker if you over-size the breaker. A lot of people think a breaker is sized for the electrical load, but the wire gauge must also be considered.

Regardless of wire size, I'll again point out that an 80# 24V TM will draw lower amps than the largest 12V TM models (that won't even be 80# thrust). It's the nature of how thrust is generated with an electric motor via physics, not something specific to trolling motors.

Measure your battery tray. Make a couple of slightly over-size cardboard rectangles to represent two battery trays, then experiment with placement of them in the space you have to see if two batteries will fit.

I agree with Flippin-Out on the breaker. a Resettable 60 AMP with 6 guage or larger wire for the 24V trolling motor will work well. In my case, I have a battery disconnect on my + battery post in addition to the breaker. Not necessary, but it just saves the switch on the breaker from being turned off and on and wearing the switch out. It was already on the boat when I bought it or I would not have added it.

Wayne

For anyone curious about "wearing out a circuit breaker" turning it off. I had looked into that years ago when that application became a trend. The life-cycle on the switch mechanics inside the circuit breaker for brand name products (such as Blue Sea, Bussmann, or Hi-Amp) is typically rated for 10s of thousands of operations. It is unlikely any of us will wear one out using it as a power interrupt switch.

Here is the longest string of text I could get from a video I took.

SUN RES VM-1 -- 156205 CSR TEW 105C 600V FT1 OR AWM 1 A/3 105C

I appreciate the idea about the cardboard cutouts and I'll definitely look into an external breaker w/ switch.

When you do the cutouts, remember to take into account any exterior tabs on the trays for screwing them down.
If you use 8 gauge wire, your current limit is 50 amps for the circuit breaker.
If you use 6 gauge wire, your current limit is 60 amps for the circuit breaker.

The device of which I speak is a circuit breaker, but it has a push button to manually trip the breaker, giving it a built-in switch function. This button is designed for this use, so it won't hurt the breaker to use this frequently to turn off power to the TM. Given a breaker is a serious safety item, I steer clear of chinese knock-off products. Here's a 50A breaker in a trusted U.S. based brand name on Amazon:

Bussmann 50A breaker

If you use such a breaker, you'll need a short jumper cable with ring connectors on each end to link from the breaker to the battery. Standard hand-held wire crimpers can't properly crimp 8 or 6 gauge wire & connectors, so you'll need a special tool (about $20) or some assistance. There are places that can build such a jumper, shipping it to you ready to use. I'd estimate under $20 for that finished cable. You'll also need a similar cable to connect two batteries in series if you decide to use a 24V trolling motor. One place I know of that offers such custom cables does at least offer free shipping, and they're pretty fast.