My recent slew of projects have given birth to yet another project. I guess they say that no good dead goes unpunished. After rebuilding my hydraulic steering helm pump, replacing my trim tab, and troubleshooting my TM gremlins, I have decided it’s time to clean up my entire wiring and house battery system.
This will include:
Moving my house battery from the rear starboard hatch to the front battery hatch, since my new lithium TM battery won’t fit in there. That’s about a 10-15’ distance from original location (will have to measure exactly soon).
Un-installing my old lead acid onboard battery charger
Installing a PVC trim panel on the left side of my console to allow me to install a new charger and . . . .
Develop and install a hinged panel (mounted to the above PVC panel) that will hold my fuse box, bus bar, and wiring loops. If I can pull this off, I will be able to lock this down to the side of the console, but swing it to the console door opening to make wiring work much less painful. After the boat re-wire, I have a lot of extra wire length in the console that I think will make this console work without putting any stress or bend in the wire - more on this later.
The first project will be figuring out the wiring I’ll need from the front hatch to the rear hatch where the main switch is (positive wire), and where I’ll connect the negative to the engine negative wire. This will require heavy gauge wiring and a heavy duty negative bus. Hoping @iMacattack and New Wire Marine can help advise on this. The good folks over on the Maverick Boat Group forum provided this handy chart, so I’m probably looking at something in the 4 gauge to 1/0 gauge wire, with cost being the only reason not to go bigger than necessary.
Hey @iMacattack It definitely cannot. The battery is currently only about 3’ total wire length to the engine. There is more wire than that, but not much. I need to move the battery about 10-15 feet forward . . . so it’s gonna take some heavy duty wire and a bus on the negative side (positive will just go through the switch).
I was actually going to take you up on your offer for a call to talk through this and see if NWM had what I needed for the job. Let me know if you are amenable to sharing your expertise!
Whatever you do when measuring how much wire you need, always add 15% to the length. You can always loop some extensions or shorten, but lengthening is not good… good luck
I moved the battery from my rear hatch to the bow on my Whipray. I had my shop do the work since I had them also taking care of some glass work.
The main reasons I did it was to free up the rear hatch, but also move more weight fore to help reduce porpoising.
It really helped with opening up storage. It did not help much with porpoising (that’s another thread).
Here is what I learned after redoing some of the work myself.
With a long run, go with the biggest cable that makes sense. Do not go with the minimal, or step down. It is better to step up one size. The reason is the voltage drop that happens.
Size 4 is too small IMO. Based on what I found, that length would need 1/0 based on a 15’ run. The actual run would be 30’ since the negative wire needs to return power to the battery.
The same size wire should be used for positive and negative. If a smaller size is used, it is the denominator for the voltage.
You could get by with a size 2 and see approximately a 0.7 to 0.9 volt drop. That’s well within range. But cold starts will increase draw.
Add a 50A breaker next to the battery. That’s a long cable run and it’s better to have a fuse next to the battery.
The terminal blocks will be sized based on your cable and get the largest ones you can find. Each connection causes a small voltage drop, but not much. I have 3 terminal connections between my battery and engine (breaker, switch, engine wires). Each connection is approximately a 0.04 volt drop based on the started on my Tohatsu 50 starter that draws 150 to 200 amps.
Get a marine-grade cable. The rating on these should be UL 1426.
Yes, pay attention to bullet 2. Its very important! Many get this wrong. The run length you use to look up in the tables is there AND back. Some tables on line fail to explain that. Dont just measure one direction, you can melt something down. Adding 15% cant hurt, or go one size up in cable.
Some charts may not call it out directly and are doing the math for you based on the round trip since it only works that way. The length in the chart is for one cable with the round trip assumed.
I used ChatGPT for mine and then double checked against an outside source. What was good about ChatGPT was having it pull up the load from my engine’s starter and also calculate voltage drops based on length, mismatched cables done by the shop, and terminal connections. It was accurate - I checked voltage myself with a meter and also using NMEA.
On NMEA, if your engine supports it, you can view alternator power and battery power on the unit. Very helpful - I have a low voltage alarm set when the battery dips under 11 volts. Anything under 10 volts and my starter will not turn over the engine. This happened to me one time - I was out of cell phone range and in area with no other boats around. But I bring a battery jump pack every time, so it wasn’t an issue.
What caused it was I used my Simrad on my center console that has a transducer. When I put the SImrad back on my skiff, I had the sonar enabled, although it was not connected since I don’t run sonar on it. The unit was trying to power sonar, so it used more power. There isn’t a one touch “turn off sonar” on Simrad - it’s convoluted, but I figured it out. And I figured out how to add an alarm to the unit to warn me when voltage drops.
good luck
- the “there and back” thing was definitely not in my calculus! Thanks