Stupid battery switch/inverter question

[Stu Jackson]

Originally Posted by sully75

Hmmm...wondering if I should put a breaker on the alternator from the outboard? It puts out 5 amps, would I be smart to wire in a 5 amp breaker to shut it off on sunny days? I was under the impression that the MPPT charge controller would still work to top off the battery regardless.

Don't interrupt alternator output AO you could fry the diodes. I have read that some outboard alternators are OK with this, but I wouldn't. RFTM for the engine before you do so.

[sully75]

unfortunately my manual got waterlogged, can't seem to get someone to send me a new one, and the one online doesn't mention the alternator at all.

[mitiempo]

Stu is correct. Never interrupt an alternator's output - it can be expensive.

[tinkrman69]

Well my solar puts out almost three times what your outboard puts. But referring to your inverter a breaker is a good idea. When it shorts out and melts the supply wire to it that will also melt other wires run in that harness and possibly short out some other peace of electronics.. Hmmmm compare the cost of that repair to the cost of a circuit greater? ;-)

I might be wrong, but your reply sounds a little snide. Don't ask for help if you don't want suggestions.

[tinkrman69]

Well maybe I'm being a little cynical. I also wouldn't suggest putting a fuse/breaker in the alternator. If it doesn't totally fry the regulator it will sure cause a diode or two to start leaking...lowering the amp output and causing RF noise. when looking in the Manuel you might not find " alternator" but charge coil. they both make alternating electricity but are constructed differently.

[mitiempo]

A fuse (or breaker) in an alternator output close to the battery is a good idea. It should be rated at least 1 1/2 times the alternator output. Alternators are self limiting and will never output more than they are designed to so it will never trip under load. But if a battery shorts for some reason - chafed wire, battery moved in rough seas for example - the fuse or breaker will blow or trip and save the boat.

[sully75]

Originally Posted by tinkrman69

Well my solar puts out almost three times what your outboard puts. But referring to your inverter a breaker is a good idea. When it shorts out and melts the supply wire to it that will also melt other wires run in that harness and possibly short out some other peace of electronics.. Hmmmm compare the cost of that repair to the cost of a circuit greater? ;-)

I might be wrong, but your reply sounds a little snide. Don't ask for help if you don't want suggestions.

Not sure what you are referring to, but definitely not my intention. I appreciate the help. I'm trying to figure all this out as I go which is not easy. So thanks for your suggestions. But I get some conflicting advise so I need to parse through things sometimes.

[sully75]

Another question: I have a xantrex prowatt 600 inverter I'm trying to add in to my system. I don't have an inboard. The manual says to wire the ground "to the vehicle chassis". I assume that would be the inboard if I had one.

Can I wire this safely? I'm confused.

Thanks


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[a64pilot]

Wire it to battery ground, I believe this may leave you with what is called a floating ground on your AC side, unless you hook neutral and ground (AC) also to battery ground?

Maybe someone who knows will chime in, I do want to make a recommendation as I'm not sure what code is.

[Bill Seal]

Originally Posted by unclemack

If I died tomorrow I wouldn't want to leave my heirs a mystery system .

I second that!!
On our home-built hotrod T-bucket, I have lots of clever wiring circuits (relay logic turn signals and such), work great, but if I have a problem, even I have a problem figuring it out. I've been careful to get rid of such crap from previous owners of our ketch as soon as I find it.
Also, WHEN YOU REMOVE A CIRCUIT OR SOME PLUMBING, PULL ALL OF IT OUT.
Rant /OFF

[a64pilot]

Originally Posted by Bill Seal

Also, WHEN YOU REMOVE A CIRCUIT OR SOME PLUMBING, PULL ALL OF IT OUT.
Rant /OFF

That is best, but sometimes just not possible, the bane of older aircraft is a tremendous amount of wire that goes nowhere, want a new radio? Almost always the old wires are just cut off and new ones run, 40 yrs and three different avionics suites, add in all wires are white, and you get the idea.

Every now and again I get to re-purpose wiring, the old 10 Ga wire that powered my old battery charger, will one day power my Watermaker
Why would anyone intentionally place a battery charger 25' away from the battery bank?

[sully75]

Well for better or worth I pulled all the old wiring and I'm starting from scratch. All labeled, fused, wired for a couple of gauges heavier than what appears safe. Not cheap but I'm learning a lot.




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[mitiempo]

Originally Posted by a64pilot

Wire it to battery ground, I believe this may leave you with what is called a floating ground on your AC side, unless you hook neutral and ground (AC) also to battery ground?

Maybe someone who knows will chime in, I do want to make a recommendation as I'm not sure what code is.

Both the DC negative and the chassis ground go to battery negative.

Do not connect neutral to battery ground.

[starcruiser]

Do you mean a breaker between the alternator and the battery? If so, definitely not.

The alternator should be wired directly to a battery and never be disconnected while running--otherwise its diodes will blow.

Would be an easy matter to forget the switch is open, start the engine and-- goodbye alternator.

[Stu Jackson]

Originally Posted by starcruiser

Do you mean a breaker between the alternator and the battery? If so, definitely not.

The alternator should be wired directly to a battery and never be disconnected while running--otherwise its diodes will blow.

Would be an easy matter to forget the switch is open, start the engine and-- goodbye alternator.

Perhaps it would be wise to avoid absolutes.

There should be a fuse at the battery end of the AO wire. Agree the AO shouldn't be interrupted when running. However, to service the always hot alternator, it is also wise to have a means of disconnecting it when servicing the alternator or anything on the engine. For that, we have been recommending an AO disconnect switch, called a SERVICE switch. Or, as I do, remove the fuse while working. Of course, this SERVICE switch should be normally closed. A breaker could provide the same service as the separate fuse and service switch. One simply has to understand the circuit.