Battery switch

[Broadwater]

I have been looking at previous posts regarding the Blue Seas battery switches. If I have a main and a kicker do I need two battery switches? The Blue Seas info seems to say that. Currently I have one Perko switch which has been working well but the more I read the more I think I should upgrade.

 

[profisher]

I have my main and kicker on one switch. I have all my rear of the boat positive terminal ends (devices to switch) on a terminal post mounted on the underside of the aft gunnel. My downrigger positive and both engine positive terminals are mounted here as well as a short heavy positive lead to the battery switch. Then a heavy positive lead to each battery back to the battery switch. So power from the batteries go to the switch, when turned to on..power goes to the terminal post and then out to the devices attached there. All this does is keep the number of wires connected to the switch to a minimum as there isn't a lot of clearance between the switch and what ever you mount it to.

 

[YachtMech]

Yes you should have two switches, because if the wiring goes bad on your kicker you need to be able to isolate it. same with the main engine, they need to be independent of each other. They can pull from the same battery but need to be switched to the battery individually. You always need to be able to independently isolate systems

for example (and I've seen this happen) the main engine starter got stuck on, and caused a fire requiring the battery switch to the engine to be shut off, if your kicker is tied into the same switch then you cant start it now and you are left unpowered until you can remove the power leads to the main engine.

also seen wiring sheath worn off causing a short and again a fire, so the main battery switch needed to be opened. and same thing stuck without power.

I could probably dig though my files to find the ABYC code that outlines this, but at the moment I cant be bothered

its the same reason you cant put high demand loads on the same breaker/switch, ie fridge and stove, there are a lot of reason why some if it has to do with inductive load vs resistive load vs capacitive load.

And remember in the marine industry every regulation is written with blood, someone had to die for that rule to be made.

 

[YachtMech]

Also yes Blue Sea System's website and documentation is an excellent resource for these things. They go by the book and provide great simple diagrams and instructions.

 

[ericl]

Use this Blue Sea tool to design your system; select number of engines & number of batteries:

Battery Management Wiring Schematics for Typical Applications - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

 

[Broadwater]

Use this Blue Sea tool to design your system; select number of engines & number of batteries:

Battery Management Wiring Schematics for Typical Applications - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

Thanks everyone. I'll have a better look at the Blue Seas and maybe do a complete rewire. I stated off thinking about changing the Perko switch.

 

[profisher]

Yachtech...with my setup what is wrong with just taking the main engines positive wire off the positive terminal post under your starter failure scenario?

 

[YachtMech]

Yachtech...with my setup what is wrong with just taking the main engines positive wire off the positive terminal post under your starter failure scenario

Don’t take this as berating you I’m just getting straight to the point, it simply does not comply with ABYC, RYA, Transport Canada, or any electrical codes related to ship construction or standards, that’s just a fact and I’m not going to debate that. there are plenty of reasons why, one would be that the battery switch is a weak link in the chain, and if you have a short like that it could very well weld or melt parts of the switch making the switch useless. Do you really want to be undoing a hot, and potentially burning wire with welded posts while getting pushed towards shore, sucked though portlier pass, dent Island devils hole, sookumchuck or any other of the tens of thousands of bad scenarios. Its potentially putting your lives and vessel at risk and a 50$ switch will prevent that. Heck if you don’t want to spend that money I will give you a switch!! (I actually do have some used ones lying around if you want one, no joke).

In reality you should have one battery per engine including the kicker, and there is plenty of reasoning behind that as well, because if you are running a single main engine and a kicker, and the regulator in your alternator fails you could discharge or fry the battery quite easily, then neither engine will work.

there are other regulations that are often overlooked that shouldn’t be, Like you cant have more than 3 connections on a battery terminal, missing adequate fuse protection, not properly mounting batteries to prevent acid from spilling out, undersized wiring, too many devices on a breaker.... the list goes on and on, and I see it nearly daily. And I’ve lost count of how many times I’ve seen bilge pumps wired with marettes, heck one very well known 68' Grenfell at RVYC was wired almost exclusively using marettes.

Again there is a good valid reason for every regulation, and I am not joking when I said for every regulation is written in blood. The marine industy is one of the oldest in the world, there is a reson behind every regualtion and for one to be written it means something went wrong that caused loss of life.

 

[Broadwater]

Don’t take this as berating you I’m just getting straight to the point, it simply does not comply with ABYC, RYA, Transport Canada, or any electrical codes related to ship construction or standards, that’s just a fact and I’m not going to debate that. there are plenty of reasons why, one would be that the battery switch is a weak link in the chain, and if you have a short like that it could very well weld or melt parts of the switch making the switch useless. Do you really want to be undoing a hot, and potentially burning wire with welded posts while getting pushed towards shore, sucked though portlier pass, dent Island devils hole, sookumchuck or any other of the tens of thousands of bad scenarios. Its potentially putting your lives and vessel at risk and a 50$ switch will prevent that. Heck if you don’t want to spend that money I will give you a switch!! (I actually do have some used ones lying around if you want one, no joke).

In reality you should have one battery per engine including the kicker, and there is plenty of reasoning behind that as well, because if you are running a single main engine and a kicker, and the regulator in your alternator fails you could discharge or fry the battery quite easily, then neither engine will work.

there are other regulations that are often overlooked that shouldn’t be, Like you cant have more than 3 connections on a battery terminal, missing adequate fuse protection, not properly mounting batteries to prevent acid from spilling out, undersized wiring, too many devices on a breaker.... the list goes on and on, and I see it nearly daily. And I’ve lost count of how many times I’ve seen bilge pumps wired with marettes, heck one very well known 68' Grenfell at RVYC was wired almost exclusively using marettes.

Again there is a good valid reason for every regulation, and I am not joking when I said for every regulation is written in blood. The marine industy is one of the oldest in the world, there is a reson behind every regualtion and for one to be written it means something went wrong that caused loss of life.

I've been looking at Blue Seas website. They have great info but I can't figure out what size wire and fuse from the battery to the ACR even though they try to explain it. Is there an easy way?

 

[YachtMech]

I've been looking at Blue Seas website. They have great info but I can't figure out what size wire and fuse from the battery to the ACR even though they try to explain it. Is there an easy way?

wire size is a function of amperage and distance, and the fuse size is determined by the maximum safe current for the conductor and the maximum supplied current/amperage draw by the device. So you find a happy middle ground by making sure the conductor can carry more current than what will be demanded of it and the maximum fuse size should be less than that. Then you look at the amperage supplied (by alternator) or demanded by device, and times that amperage by 1.25 (this gives you 125% current capacity on the fuse compared to the nominal circuit draw before blowing). in the case of alternator to ACR you need to determine the maximum charging output of your alternator, and times it by 1.25. and I would suggest determine the minimum wire gauge for that distance/amperage and go one gauge up, this will keep the wire well within safety limits. Now these are rough calculations with a healthy safety margin.


so for example:

main engine alternator max output 125amps
distance from alternator to ACR 2 meters
distance from ACR to battery 1 meter

the calculations put the wire gauge 4AWG so if you really want to be super safe you can go up to 2AWG.
next you need to rate the fuse, which should be 125 x 1.25 max = 150amp breaker (rounded down)

However if you download the Blue seas system app onto your phone it will give you much more precise calculations, ie the fuse calculated out to 135A using 4awg at 3% loss over 3m on a 12 volt system and an 800 cold cranking amp battery.

here is the ABYC compliant literature from Blue sea systems.

Part 2: Select a Fuse and Fuse Holder For Your DC Product Installation - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

 

[YachtMech]

also make sure the ACR can handle the alternator output. because there is the M-ACR which only handles 65amps, fine for a small outboard but no good for a wakeboat with high output alternator.

 

[YachtMech]

I was bored so I dove into the documents because I remembered something about not needing a switch if you're kicker had its own battery and this was the line, and there was only one exception to having a battery switch dedicated to the engine.


EXCEPTIONS: 1. Trolling motor conductors connected to dedicated trolling motor batteries provided with overcurrent protection at the battery and a manual means of electrical disconnect separate from the trolling motor controls.

meaning if you have a dedicated trolling motor battery you can technically use a manually trip-able breaker instead of a battery switch, not a big difference since they cost the same lol.

As far as circuitry is concerned there is nothing wrong with two devices being connected to one switch, but "high tenstion" wiring such as engine starters having two connected to one battery is not a good idea. however in in terms of standard circuitry theory this would be passible as you could run one switch as long as you have a way of disconnecting the main lead to the trolling motor like a breaker, this would comply with how the circuitry regulations are written. But again, this would prevent you from easily isolating an engine and run the other, it would only let you isolate the kicker power leaving you with your main and not vise versa. but again its a bit pointless because it doesn’t provide redundancy.

But the main problems is having two charging systems going to one battery, there have been documented problems with this such as one alternator failing and causing over voltage issues that can fry the computers in modern engines. It can cause problems with tachs, control systems, all sorts of things. Heck the last generation of Evinrude etec motors had massive issue with voltage induction causing issues, to the point the if you used the VHF radio to broadcast that was enough induced voltage in the system to cause the engine to increase its revs by 1500rpm, regardless of if it was in or out of gear.

and FIY Blue sea systems does make a dual pole battery switch so you can legally put two engines though one switch but its designed for two main engines, so this is technically two switches inside one switch, bit of a work around the regulations, because it is still one switch per engine, but also prevents you from isolating engines individually, which is unfortunate, but would be fine if you had a independent kicker.

also these particular standards have been under review for a while now, as it used to be very common practice (although not recommended) to run two engines off one battery when everyone used to be running twin two strokes, as the engines were less susceptible to voltage spikes causing issues with electronics. I cant remember the last time I saw a single battery for two engines, as most people have proactively made the choice to have independent systems for the sake of reliability.

For the last 20 years I’ve been doing this its been 1 battery per 1 engine.