For the times when you don't want an electrical circuit to be fused ... and a new tool

[mcmxi]

I'm converting the single battery system on my boat to dual batteries, and many months ago ordered the optional auxiliary charging cable that connects to a plug on the Yamaha engine and is used to charge a second battery. The ECU on the engine figures out which battery needs charging. With two batteries one can be used to start the engine which is all it does, and the other is used to run all the electronics and equipment requiring 12 volts. The idea is that the starting battery will always have enough charge to get home since it's only used for starting.

My confusion began when I noticed that Yamaha shows a fuse between the engine and battery on the auxiliary output for the second battery, but none on the connection to the starting battery. In fact, there's no fuse at all in the starting circuit so I had to do some research. It turns out that the American Boat & Yacht Council (ABYC) doesn't require boat manufacturers to put a fuse or breaker in the starting circuit. Their rationale here is that the current can spike significantly during starting which could blow a fuse or trip a breaker, rendering the engine inoperable. This could result in the boat and occupants being in serious danger, so that's why there are no fuses in boat engine starting circuits.

I also bought a Blue Sea Systems battery switch which closes the circuits for both batteries in the first position and combines both circuits in the second position in the event that the starting battery alone won't start the engine. Since the fuse for the auxiliary battery is between the engine and the battery, and the positive cable from the auxiliary battery goes to the switch, the fuse only has current flowing through it during charging but not when both batteries are combined for starting.

I've been doing a fair amount of wiring with 2AWG and 6AWG cables and a few months ago bought a neat tool that does a great job of crimping ring terminals onto cables. It does a professional job for sure and came with lots of different mandrels for various gauges.

 

[North Idaho Wolfman]

Put some good silicone around the joint of the jacket and fitting before you shrink wrap it.

 

[GreensvilleJay]

yeesh, last thing I want is a fuse between battery and starter motor ! Don't know of ANY machine that has that(car, truck, Kubota ) for the simple reason is that when it blows, you're 'dead in the water', literally,
i have to wonder how many boaters have spare 100,200,400 amp fuses AND the tools to change them ?
Can you imagine the 'fun' of changing it it even slightly choppy seas ?
The two battery install is easy ,$50 for 2 high powered diodes in an aluminum case.
Did that in the forklift, one battery to start, one for the single glowplug. Worked flawlessly.

 

[Sidekick]

I just bought the same thing for a solar project I am working on. Amazing how nice they work. Get the glue lined shrink tube to seal them up good.

I can't believe the price of welding cable these days.

 

[mcmxi]

Put some good silicone around the joint of the jacket and fitting before you shrink wrap it.

Good idea, but I bought 6ft of marine grade heat shrink tubing which is glue lined. That stuff is pricey. You can see the squeeze out in a close-up of the ring terminal. I used black on this 14" cable since it connects both negative terminals of the two batteries. I could have bought some black 2AWG rather than 25ft of red, but since I have excess red it made sense to color code with shrink tubing. Robalo uses yellow cable for the ground wires which is weird, but it looks nice.

 

[mcmxi]

yeesh, last thing I want is a fuse between battery and starter motor ! Don't know of ANY machine that has that(car, truck, Kubota ) for the simple reason is that when it blows, you're 'dead in the water', literally,
i have to wonder how many boaters have spare 100,200,400 amp fuses AND the tools to change them ?
Can you imagine the 'fun' of changing it it even slightly choppy seas ?
The two battery install is easy ,$50 for 2 high powered diodes in an aluminum case.
Did that in the forklift, one battery to start, one for the single glowplug. Worked flawlessly.

I hadn't realized that the starter circuit on all machines was unfused. Maybe I came across, and if I did I sure didn't remember it.

So in your diode/aluminum case set up, if both batteries are seeing the same load I guess it's simple enough. But if they see different loads what controls charging priority or are they both receiving the same current from the alternator when charging i.e. possibly overcharging one of them?

Two or more batteries in a boat typically see different loads and so discharge at different rates. Blue Sea Systems makes an ACR which routes energy to the battery that needs it. Yamaha can handle that even more elegantly via the ECU and the auxiliary output from the 70A alternator.

 

[mcmxi]

I just bought the same thing for a solar project I am working on. Amazing how nice they work. Get the glue lined shrink tube to seal them up good.

I can't believe the price of welding cable these days.

See my post above. I bought marine grade heat shrink tubing which is glue lined, and appears to be thicker walled than standard heat shrink tubing. Yes, those hydraulic crimpers are really nice.

Everything is expensive these days ... or so it seems.

 

[hedgerow]

mcmxi I have had a crimping tool with many sets of dies for years. Have built a lot of battery cables and cables for high output alts. I always use the heat shrink with the liner. If you want to see a wiring starting cable mess Google up series parallel starting. Back in the day {50's 60's} a lot of the semi truck company's set there trucks up to start on 24 volt and run and charge on 12 V. It was a cabling night mare when the trucks got older. The series parallel switch was always giving trouble. I changed many over to 12V starting in later years. Motor homes are fun to work on with all there battery isolators and charging systems. Years ago my one uncle had a factory bus motorhome conversion. That thing was a wiring night mare. It started and run including running lights on 24 volt and the house system was on 12 volt. We finally put another alt on the engine and just used it to charge the house batteries and kept the 24 volt system by it self.