Question About Shorepower

The Dog House · Post by **The Dog House** » Thu May 10, 2012 6:59 pm

This is my first boat with shorepower. Today I turned the VHF radio on while the shorepower was on and the VHF fried. Needless to say I won't be turning any electronics on anymore unless the shorepower is turned off first. I thought the AC system would be isolated from the DC system. Is it normal to have to turn off the shorepower first before using the DC electronics, or is the boat not wired correctly? Thanks for any insight you can provide.

Allen Sr · Post by **Allen Sr** » Thu May 10, 2012 7:04 pm

NO! Its not normal at all! I would say you have a very serious problem! It also could of been a freak accident. Take a multi meter and check the voltage at the plug for the radio. Should be reading in the 12 - 13 volt dc range depending on what state of charge your batteries are in.

k9th · Post by **k9th** » Thu May 10, 2012 7:16 pm

I cant imagine anyone cross-connecting AC & DC. I'm voting for freak accident or strange coincidence.

gettaway · Post by **gettaway** » Thu May 10, 2012 7:19 pm

I'm voting coincidence as well, you would have burned the boat to the water line by now if the two were connected, at the least, you would have certainly blown the shore power panel breaker

Big D · Post by **Big D** » Thu May 10, 2012 7:35 pm

Agree with above. Also, was your charger turned on? If so, turn all DC power off and check what the output voltage of the charger is. You should be able to do this at one of the batteries.

prowlersfish · Post by **prowlersfish** » Thu May 10, 2012 8:02 pm

Big D wrote:Agree with above. Also, was your charger turned on? If so, turn all DC power off and check what the output voltage of the charger is. You should be able to do this at one of the batteries.

X2 and check the voltage at the VHF too with the shore power on and off . Then check it on the AC scale on the meter to see if your getting any ac cross over

The Dog House · Post by **The Dog House** » Thu May 10, 2012 8:12 pm

Big D wrote:Agree with above. Also, was your charger turned on? If so, turn all DC power off and check what the output voltage of the charger is. You should be able to do this at one of the batteries.

I'll check the voltage at the VHF connection and see what it is. The battery charger turns on automatically when shorepower is connected, so maybe the battery charger is putting out voltage that is too high. I'll let you know what I find.

For my own knowledge, the AC system and DC system are totally separate? The only connection between the two would be the battery charger? The boat has been modified many times by many owners over the years, and I'm still trying to figure out what all of the wires behind the panel connect to.

Thanks for your help.

Big D · Post by **Big D** » Thu May 10, 2012 8:33 pm

The Dog House wrote:... The battery charger turns on automatically when shorepower is connected.... the AC system and DC system are totally separate? The only connection between the two would be the battery charger?.....

Charger turning on automatically is not a good idea. Are you saying there is no breaker or ON/OFF switch for the charger so you have the option to shut it off if you want?

Electrically, except for grounding, AC and DC is separate, however in a typical older installation, the electrical panel containing the two system wiring has little room and no isolating panels for separation and shorts can occur.

And yes, no telling what a previous owner has done. Check your voltages.

mitch · Post by **mitch** » Fri May 11, 2012 12:43 am

ready123 · Post by **ready123** » Fri May 11, 2012 1:02 am

mitch wrote:Hey, ya are missing the point. 110 volts AC connected to a 12 volts DC battery? DC power supply is battery, NO AC on battery, Radio blew up by self? YES

It may not be as simple as that... suppose boat ground for AC and DC are connected and the shore power has a leak to ground leg...still think DC is only 12V

mitch · Post by **mitch** » Fri May 11, 2012 1:10 am