It’s official, I’m an idiot… help!

[Rockter]

If I understand that you have switched between batteries with the engine running, and the alternator has failed, it will almost certainly be the alternator diodes that have failed.

It is not a lot of work to replace them.

Open the alternator and you will see them clearly. Order a new set, and replace them.

You can buy a "snubber" device... cheap... that will "cushion" the electrical shock next time, or buy a battery switch that will disable the field wire of the alternator if you move the switch.... or buy both.

[capn_dave]

Originally Posted by Omatako

In my experience it's more a case of the voltage regulator seeing the voltage of a fuller battery and then backing off the charge rate so that the flatter battery never gets the chance to charge.

That ain't the way it happens. When the selector switch is in the all position both batteries become one. Then in less than the time it takes to read this the batteries equalize. In other words, the voltage on both batteries becomes the same. It becomes one big battery, which the voltage regulator thinks it is. So there is no undercharged battery or overcharged battery.

Fair Winds

Cap'n Dave

[sailingdog]

I'd third Halekai's suggestion of getting a Battery combiner. The one Jody has pointed out is a good one, and simpler and higher capacity than the one Halekai pointed out, which is an older model and much larger.

The Dual Circuit Plus battery switch Jody has pointed out also has the benefit of isolating the house side from the starting side, so that the electronics are effected by the surge/drop which can occur when starting the engine. Yet, if needed, both banks can be combined to start the engine.

In terms of full disclosure, the DCP series battery switch is what is installed on my boat, along with the ACR Jody pointed out.

[brak]

Originally Posted by artbyjody

I'll second having a newer battery selector switch. I have revamped my entire electrical system on the Barberis, with new panels as well as the new BlueSea Battery Automatic switching system:



I am very pleased with this over the Perko / Guest standard Off/ 1 / 2 / both switch.

I will second that. When I was rewiring my boat, this was my first choice and so far I've been quite happy with the way this system turned out. No switching over, having to remember which position the switch is in etc. It just works.

[brak]

Originally Posted by sailingdog

The Dual Circuit Plus battery switch Jody has pointed out also has the benefit of isolating the house side from the starting side, so that the electronics are effected by the surge/drop which can occur when starting the engine. Yet, if needed, both banks can be combined to start the engine.

The caveat for surge protection is that it is not automatic. You have to connect a pin on the combiner with the starting solenoid positive terminal, so when the starting solenoid is powered up - it also turns on a circuit inside the combiner and protects against the surge that way. It's not rocket science but something else that needs to be done.

[sailingdog]

Actually, IIRC, it is automatic, since generally, without the engine running the banks aren't combined, since there is no charging level voltage on the electrical system. The only time you need to connect the wire is if you have some sort of passive charging system—solar or wind—that might cause the batteries to be combined before the engine starts.

Originally Posted by brak

The caveat for surge protection is that it is not automatic. You have to connect a pin on the combiner with the starting solenoid positive terminal, so when the starting solenoid is powered up - it also turns on a circuit inside the combiner and protects against the surge that way. It's not rocket science but something else that needs to be done.

[Omatako]

Originally Posted by capn_dave

That ain't the way it happens. When the selector switch is in the all position both batteries become one. Then in less than the time it takes to read this the batteries equalize. In other words, the voltage on both batteries becomes the same. It becomes one big battery, which the voltage regulator thinks it is. So there is no undercharged battery or overcharged battery.

So that means that if my starter battery is at 11v and my 600aH house bank is fully charged at 14v, all I need to do is switch to "All" and my starter battery will immediately be charged by the house bank? Then I can switch back and start my engine on the start battery?

That's cool, I never knew that.

Andre

[camaraderie]

Andre...can't tell on line...was that a sarcastic reply or serious?

If serious...I would say that:
1. A full charge is 12.7V...batteries never have 14V charge...that is merely a surface charge.
2. Yes...the depleted battery will be brought up to the same voltage reading as the fully charged batteries but this is NOT instantaneous...but if you walked away overnight, the next morning all the batteries would read the same voltage if tested independently. All would read somewhere above 11V and less than 12.7 volts. (this assumes all batteries in good condition which is no sure thing with one at 11V! )
3. CapnDave is correct that the combined average voltage will be read by a voltmeter instantly, but he'd be surprised if he measured each battery individually.

Sorry if I am being pedantic...but couldn't interpert your "tone". Disregard if I missed it.

[brak]

Originally Posted by sailingdog

Actually, IIRC, it is automatic, since generally, without the engine running the banks aren't combined, since there is no charging level voltage on the electrical system. The only time you need to connect the wire is if you have some sort of passive charging system—solar or wind—that might cause the batteries to be combined before the engine starts.

That may not always be true. ACR takes a while to connect and a while to disconnect. Anytime you shut down the engine and restart it within the ACR disconnect time (which seems to be in a few minutes, at least for my unit), or if the battery was charged by something else (like, say, your shore power charger which you disconnected right before starting the engine) you risk the starting current affecting a house bank.

It's a game of chance, but ACR without the additional connection provides no protection against that.

Here is the link to instructions: http://bluesea.com/files/resources/i.../990170140.pdf

[sailingdog]

Brak-

Considering that the dwell time for the ACR to break the connection is only 30-60 seconds, and that it takes at least that long for me to get the shore power disconnected and rolled up, it really isn't an issue IMHO.