Well if you try to use a connector thats not soldiered or at least crimped to pass a continuous 40 plus amps of current, you pretty much just went hunting and shot your dog. Second, diodes in alts do not keep electricity from backfeeding to another alt... it's part of what and how ac volts are converted to dc volts, by eliminating half of the sine wave ac voltage produces (60hz will run your blender). And Im not to sure I would admit using a jive ass connector in a wire that 99.9% of your voltage is created from to begin with. Alternators make AMPERAGE, NOT VOLTAGE, and if you have no other choice than to create a break ANYWHERE in the main charging wire to your batteries, and don't make a properly soldiered, weatherproof connection... then don't badmouth something that was never intended to be installed incorrectly or used for the highest current passing wire any vehicle, boat or whatever has... it's probably the closest to a fuseable link you could find, and WORTHLESS.

Scott, How did you know your alternator was bad? what were the symptoms? I have one engine that reads close to 14V on the gauge and the other is just over 12V. (when running) could the 12V one be bad?

My old Liberator {twinns} I ran the Batt switch in "ALL" for 10 plus
years...no problems.......My Cig says right on the panel..Do NOT
run in all unless you have to for short periods......
Got Me ???.....I have an Isolater...I thought that would be OK..
I just run 1&2 now..

Ray,
The Gauges on that side are all a little low compared to the other. I have been chasing a crazy oil pressure gauge problem for two years and have been told from Gaffrig "You must have at least 12vdc to the gauge for it to work like it should" I also show around 10 vdc on that side and the gauge does not budge when you rev it up. I finally decided to pull the Alternator when I did I fired it back up and there was no change at all on any of the gauges, I assumed the Alt was bad after seeing this! It is not bad and I am back to square one. I will find the problem and let you know. The first thing I will do after I re- install the alt is to check the charging system with my batt and charge system load tester if I have nothing I will start looking for a fuse or breaker on the output and it seems to me that I saw one when I was looking at the diagram.

Diodes and mixed charging!
I spent some time last night looking at alt schematics and hookups none were exactly what I have. I did notice on all the schematics the cathode side of the diodes were toward the battery that should stop the back feed. But I also realize ratings and current come in to the setup at this point.
One more thought why don't the battery chargers fry the alt if you think about it they are doing the same thing as having the switch in All you are sending a different 12vdc source to the alt.

Just a thought;)

I know I have beat this to death and everyone will and should do what they are comfortable with. I did learn one thing you should never change switch settings while the engines are running. This will or could fry the Alt (surge related) they like to see a load.

Hey FindMe, excuse me for trying to point out to other boaters that Napa was marketing a connector that sucks, and its right on the board with all the good ones with no clear difference. Geez. Have a beer.

Oh, by the way, soldering connectors on a boat is the worst thing you can do.

I use ultrasoft low temp solder on all my boat stuff. Love it. It's not brittle, and doesn't corrode (I put liquid tape on them anyhow).

Solid state voltage regulators won't fight each other - mechanical ones will.

My Formula has all the trimpumps (drives and planes) hardwired to the respective battery (port to port - stbd to stbd). If I don't run in ALL, then one battery goes tits up from the pump loads.

I only use "1" or "2" setting when rafted to avoid killing both batts. Back to ALL when ready to run again.

No isolator on this boat. In fact, it had no battery switch from the factory - it had to be added to be legal for dry rack storage.

12 years. No issues.

As far as what it might be that "kills" alternators on the "ALL" position, you got me. I don't see what the problem is. I have a hard time believing that "fighting regulators" would cause the trouble. All a regulator does is change the field voltage in order to vary alternator output current. It does this by reading line voltage. Voltage drops, it asks for more current output from the alternator. Voltage gets high, it tells the alt to stop throwing out current.

Diodes shouldn't argue about anything unless they have nowhere to pass the current being thrown into them. If the alt is throwing out a lot of current, and the batt switch gets flipped to OFF, there is a possibility that the ignition system will not be able to use as much current as is being thrown out. In that case, the diode or triac can possibly saturate and pop before the regulator gets the alternator shut down (it's a magnetic field, which does not respond "instantly" cause it has to "collapse" as opposed to just being turned "off").

I don't want anybody to have electrical troubles at all. I just don't see why running on ALL is an issue. Please continue to post explanations and I'm sure we can zero in on it.

M

You can run your switch in the "both" position all day long. This will not hurt your alternator. It is the same as running a double size battery. The only time not to is at anchor. If you leave something on, both batteries will be dead.

You should not use solder on most connections. Just be sure you are using a quality crimp tool and connector such as 3m brand. Having said that I still do solder some connections, such as the alternator output wire.

Two alternators running together will work fine, even if they are set at slightly different voltage. One will just stop charging before the other. This is used on many off road and heavy duty marine apps. Even some of the stereo guys are doing this.

It is not a good idea to flip your battery switch with the engine running. However most regulators these days are lightning fast and will probably live.

I agree, most connectors from most auto parts stores are useless.

oh yeah, I do own an alternator shop. Worked there since I was 12yrs old.

Steve H