12/24 wiring question

[jeepinandy58]

Purchased a used boat/motor with a MotorGuide X3 24 volt 65 lb trolling motor. Trolling motor was not going as fast as I thought it should. Checked the setup and found the trolling motor is only getting 12 volts. I drew a basic wiring diagram and attached it. the way the switch {4 position switch - 1, 2, 1&2 and OFF) is set up, the trolling motor and accessories can use battery 1 or battery 2 or both of them in parallel for 12 volts @ 200 Ah. It works but I would really like to be able to switch between 12 and 24 volts for different trolling needs. I'm thinking set up for battery 1,2 in series for 24 volts to the trolling motor and run the accessories off the "bottom" battery. If possible I would like to set up a manual switch to be able to switch back to a 12 volt parallel set up for slower trolling. What I need to know is this a good idea or should I just leave it at 24 volt in series? Trying to not start any fires, etc. I can do all the wiring (a lot of the original wiring has been patched with various colors and I want it all the same) but dont have the experience with boats to know if this is a good idea or not. Hopefully I have explained what I am trying to do clearly, sometimes my head gets a little weird due to military grade ptsd. Please let me know if I need to explain it better.

 

[Kosmofreeze]

I've noodled this scenario as well. If you do a series connection to make a 24V cell, just be careful to isolate that 24V cell from your other 12V accessories and charger. This begins to "smell" like a dedicated 24V trolling motor battery as your #3 battery - separate from your existing 4-way switch. I would let the motor's speed controller handle the trolling speed. Given that you have a 24V motor - it'll be happiest with the 24V dedicated battery.

 

[jeepinandy58]

Thanks for the response Kosmo, that was what I needed. I'll put the #1 and #2 in series for 24 V. Switch the accessories to #3, should be fine. Got one more question on wiring. I'm going to replace the trolling motor wiring due to multiple splices, trying to decide on the correct gauge. If I keep the batteries in the back (probably will), trolling motor is on the front, boat is 16' I think I should probably use 6 AWG. Figuring on approximate 56 amp max draw, with 24 volts, 65 lb thrust. Too heavy or about right?

 

[brodmann]

I don't think any standard marine battery switch will work the way you want it to. Draw out the wiring including the "+" and "-" and how they connect to the switch and you'll see what I mean.

 

[Scott Danforth]

a lot of the original wiring has been patched with various colors

boat wiring colors are specific to the circuit because boats do not have wiring schematics.

you will find the ABYC colors here. https://forums.iboats.com/threads/generic-boat-wiring-information-updated-verified.726970/

but I would really like to be able to switch between 12 and 24 volts for different trolling needs.

you need a custom switch, not a standard battery switch.

 

[jeepinandy58]

I don't think any standard marine battery switch will work the way you want it to. Draw out the wiring including the "+" and "-" and how they connect to the switch and you'll see what I mean.

I see what you mean, I could possibly do it with complicated switching and circuitry.....thats not gonna happen. going to keep it simple. the 2 12 volts in series for 24v to the trolling motor and move the accessories to the #3 battery. Everything will work and I don't have to re-design everything. Thanks!

 

[jeepinandy58]

boat wiring colors are specific to the circuit because boats do not have wiring schematics.

you will find the ABYC colors here. https://forums.iboats.com/threads/generic-boat-wiring-information-updated-verified.726970/


you need a custom switch, not a standard battery switch.

on the wiring, what I should have said is the wiring to the trolling motor has been spliced multiple times - starts out black/red, then green/yellow, then orange/brown, then back to black/red. The soldering and insulating of the splices looks like it was done correctly but I want to have one set of colors. Thanks for the link.
On the switch I am going to put the 1,2 battery in series and go straight to the trolling motor. Move the accessories over to the #3 battery. One day I might go to a complex arrangement (do the 12 and 24 volt thing) but for now simpler is better for me. Appreciate the response.

 

[Kosmofreeze]

Thanks for the response Kosmo, that was what I needed. I'll put the #1 and #2 in series for 24 V. Switch the accessories to #3, should be fine. Got one more question on wiring. I'm going to replace the trolling motor wiring due to multiple splices, trying to decide on the correct gauge. If I keep the batteries in the back (probably will), trolling motor is on the front, boat is 16' I think I should probably use 6 AWG. Figuring on approximate 56 amp max draw, with 24 volts, 65 lb thrust. Too heavy or about right?

Since your max no-fault load is 56A (per your trolling motor's spec) get a 60A fuse/circuit breaker and place it as close as practical to the battery. THEN size your wire. Remember that the fuse/breaker "protects" the wire, not the motor. In addition to max load, there are lots of other factors to consider when sizing the conductor including length of circuit, wire type and construction, cable bundling, ambient temp, etc. 6AWG sounds like a good place to start for your install. You can expect the 6AWG to heat up a little bit while running your trolling motor at max-blast for more than a few minutes. If it never gets "too warm", then you've chosen wisely.

 

[froggy1150]

 

[jeepinandy58]

View attachment 392659

Thanks! Just saved a copy. So you're a squid, huh? Thank you for your service. I was a one and done in the 70's OS2.

 

[jeepinandy58]

Thank you to everyone for the help, I was able to get out today and finish running down the wiring (these multiple splices are killing me). As it turns out the way it was previously set up, only one battery was being used for the trolling motor. When the switch was set to the 1&2 position, batteries 1 & 2 were paralleled but feeding the accessories (fishfinders, pumps, lights). Battery 1 was hardwired into the trolling motor and had a 50 amp circuit breaker on it. Now that I figured out what was done, I have attached a new drawing with what I am thinking of what I should do to make the best use of everything I have. What I didn't put in the drawing is the 60 Amp breaker I will use. If I remember correctly the circuit breaker should connect to the + terminal of battery B close to the battery, is that correct? Next question, I was going to put the accessories all on battery C but havent measured the total current draw yet. Does anyone see any issues there? And last but not least, The boat has a 2 bank charger (Guest Charge Pro 5|5) and I am thinking about swapping that out for a 3 bank charger (Guest 2713A), should I put a switch on battery C so that it is disconnected from C when I am out on the water (2003 Merc 50 2 cycle ELPTO so it charges when running)? In case it matters, about 50% of the time I fish lakes that dont allow outboard use.

 

[Kosmofreeze]

I see that the Guest Charge Pro 5|5 is a 2-channel, 12V or 24V charger - not sure how you select the voltage. How do you have it set up? I wouldn't assume the your charger "sees" a two 12V cells the way your diagram is drawn. Wiring the 12V batteries in series effectively give you a 24V battery that could be charged by a single channel of a 24V charger. If you are hell-bent on charging this set up with a 12V charger you may need to put a "Charge Mode / isolation" switch in the series connection (effectively removing the BAT A+ to BAT B- connection) when charging 2 cells at 12V. If you can get your charger to charge at 24V just connect that channel to BAT A+ and BAT B- and let your charger do it's 24V thing - no charge mode switch req'd.

 

[jeepinandy58]

I see that the Guest Charge Pro 5|5 is a 2-channel, 12V or 24V charger - not sure how you select the voltage. How do you have it set up? I wouldn't assume the your charger "sees" a two 12V cells the way your diagram is drawn. Wiring the 12V batteries in series effectively give you a 24V battery that could be charged by a single channel of a 24V charger. If you are hell-bent on charging this set up with a 12V charger you may need to put a "Charge Mode / isolation" switch in the series connection (effectively removing the BAT A+ to BAT B- connection) when charging 2 cells at 12V. If you can get your charger to charge at 24V just connect that channel to BAT A+ and BAT B- and let your charger do it's 24V thing - no charge mode switch req'd.

 

[jeepinandy58]

Thanks for the response, i've attached two pictures from a manual I was able to find. I'm basically re-doing a lot regarding the wiring on this set up. I think I know what the previous owner was going for but they failed. The first picture is they way I have just set it up, the second picture is what i will have once I replace the Charge Pro (hoping for an after Christmas special). In the meantime, I am replacing incorrect wiring. Current trolling motor wiring is 10 AWG with multiple, multi-color splices. I am replacing that with 6 AWG, home runs (no splices). My thought is to put the accessories on the crank battery but am not sure that is the best way to go; my concern is that firing up the outboard could cause a surge that would damage fish finders, etc. Looking at the Future picture, would it be okay to put the accessories on #2 or #3 and if that is okay, which one is preferable? If I have to add a dedicated battery for the accessories, then thats what I will have to do. I am not locked in on anything other than getting this set up correctly, well actually I am locked in on getting the trolling motor set up with 24V. The main thing for me is to set it up safely and correctly. Appreciate the feedback!

 

[Kosmofreeze]

Looks like the guys at Charge Pro have addressed my concern and designed their unit to handle the 24V trolling motor battery. Follow their wiring diagrams and you should have nice set-up. When you plug it in for the first time just be particularly vigilant for any funny noises, hot wires or smoke. If nothing explodes or catches fire ... you're having a good day.