Need Advice: We Lost 12v power this Morning on my 4600 SCB!

[Moretoys]

Hey Guys, I'm needing help diagnosing a critical issue this morning. We're north of Jacksonville, 800 miles into delivering my new 1999 4600 SCB from Hampton to Marathon.
We went to bed last night at a mooring with everything working fine. We fired up the Gennie thIs AM and only saw one leg come up. A bit of on and off with the switches and it eventually came up on both legs, though the voltage was low: 90v rising to 103v as it ran. Somewhere in this process we lost our 12v to the house. It just went dark. The Engines crank, bilge pumps work, but House is dead. We show 12.51v on the two house/engine batteries in the engine compartment , and 14.1v on the Gen battery aft. We have no inverter installed. I've cycled the 12v Main beaker in the breaker panel.
IS THERE ANOTHER 12v house breaker somewhere?
Could this be related to the charger or isolators?
I HAVE to believe that this is somehow related to the Gennie issue: The odds of two completely unrelated electrical failures happening at the same time are high. Any suggestions or advice? GP

[kenyu73]

There's thee main places that I can think of that the failure can occur.

1) At the AFT main dial switch under the hatch
a) critical failure with wire connection

2) The house breaker under the same hatch
a) slide breaker tripped
b) wire failure

3) Main breaker in salon
a) main breaker tripped
b) wire failure

[Moretoys]

Thanks for the help running this down. Turns out we had tripped both house breakers in the aft hatch. My bigger question is what the heck happened to throw those breakers....

[kenyu73]

Did you add any DC devices such as a plug in inverter?

The failure would be on the breaker to house side, not the breaker to battery side. Technically, there's no protection from the breaker to battery, but that wire is super large.

The house lights, and there is ALOT, each draw almost 1 full amp so if you had every single light on in the boat, that could cause strain on the breaker.

There's something like 60 lights on the boat, so your looking at almost 40-50+ amps in just lights. If they are the original wire bulbs, CHANGE THEM ASAP (=

LED bulbs use 1/10th of an amp.

[Moretoys]

Everything was good when we went to sleep. Next morning, the Gennie acts up, starting up without the 2nd leg of 110v coming online. It APPEARS that somehow caused the 12v issue, but I can't figure out the connection.

[kenyu73]

Originally Posted by Moretoys

Everything was good when we went to sleep. Next morning, the Gennie acts up, starting up without the 2nd leg of 110v coming online. It APPEARS that somehow caused the 12v issue, but I can't figure out the connection.

The only connection between the genset and DC system is the DC battery charger. Maybe the DC charger spiked AMPs outbound and popped the breaker. However, DC chargers usually go right to the batteries, not through the DC breaker.

[kenyu73]

Also, I assume you do have the AC turned off until the genset is fully running? Def shouldn't be running AC while starting.

[shrew]

Originally Posted by Moretoys

We fired up the Gennie thIs AM and only saw one leg come up.

I apologize, but I'm having a tough time following your post. Gennie is pushing either 120v or 240AC. The batteries are all 12v or 24v DC.

When you started the Gennie, which 'leg' didn't come up? AC or DC?

I would expect multiple AC leg's, but only 1 DC leg. Start and Gennie Batteries would be isolated from the house bank. If gennie and engine batteries are showing good voltage and cranking, then this sounds like it is the house battery system only.

There should only be a main bank shutoff, then a main breaker on the 12v panel.

It is possible that you drew down the house bank? 14.1 on the generator would tell me that it is being fed a charge either by an alternator or battery charger.

12.5 would tell me that that bank is NOT getting a charge and is around 50+% state of charge.