When on shore power

Kyle282

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#1
Just purchased first boat, 2008 Sailfish. I’m wondering if you can turn on batteries while plugged into shore power? Thank you!
 
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seasick

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#2
Yes you can. Being on shore power does not automatically give you 12V dc, only the batteries do. If you have a battery charger, and are on shore power ( and the charger is turned on) then the batteries will stay charged.( note that The batteries do not have to be turned on for a shore powered charger to keep the batteries charged)
If you turn on the batteries and run things like the stereo, lights etc, the batteries will remain charged as long as you draw less than the output of the charger. If you draw more the batteries will discharge of course as they would if you were out at sea with accessories on but the motors not running ( and not recharging the batteries).

If you have equipment on the boat that only runs on line power ( 120 volts) they will only work when shore power is connected unless you have an inverter that converts 12v dc to 120v AC. For example some fridges run on 12 volts only or either 12 volts dc or shore power.
Hope this wasn't too confusing.
 

Kyle282

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#3
Yes you can. Being on shore power does not automatically give you 12V dc, only the batteries do. If you have a battery charger, and are on shore power ( and the charger is turned on) then the batteries will stay charged.( note that The batteries do not have to be turned on for a shore powered charger to keep the batteries charged)
If you turn on the batteries and run things like the stereo, lights etc, the batteries will remain charged as long as you draw less than the output of the charger. If you draw more the batteries will discharge of course as they would if you were out at sea with accessories on but the motors not running ( and not recharging the batteries).

If you have equipment on the boat that only runs on line power ( 120 volts) they will only work when shore power is connected unless you have an inverter that converts 12v dc to 120v AC. For example some fridges run on 12 volts only or either 12 volts dc or shore power.
Hope this wasn't too confusing.
Thank you! This was very helpful.
Cheers
 

everwhom

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#4
Great explanation. Just an addition: My understanding is that one should not run the motors with the battery charger on. i.e. you can turn your motors on while on shore power (not sure why you'd want to!), but if you ever do, you should make sure the battery charger circuit is off on your circuit panel.
 
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Kyle282

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#5
Great explanation. Just an addition: My understanding is that one should not run the motors with the battery charger on. i.e. you can turn your motors on while on shore power (not sure why you'd want to!), but if you ever do, you should make sure the battery charger circuit is off on your circuit panel.
Thank you very much!
 

DennisG01

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#6
Great explanation. Just an addition: My understanding is that one should not run the motors with the battery charger on. i.e. you can turn your motors on while on shore power (not sure why you'd want to!), but if you ever do, you should make sure the battery charger circuit is off on your circuit panel.
Just out of curiosity... I'm thinking this over and it's, honestly, the first time I've heard of it. Most likely because "why would someone do that"? Meaning, there's no real reason to run both at the same time. BUT... why is it bad? Wouldn't the charger just shut off it's supply to the battery if it senses a full charge (which the engine would likely be supplying)?

Thinking more... When I had my Sundancer in my driveway (Pro Mariner ProNautic charger), I can't recall ever turning the charger off when I would run the engine.
 
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seasick

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#7
I leave the charger on also when connected and motors running. My understanding is that a quality model of smart charger will protect itself. In any case, I haven't had any issues.
At the same time, I will dig up the docs for my charger to see if there is any mention of switching it off.
 
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#8
Interesting point Dennis, I read that fact somewhere ..... not sure where
Consequently I always disconnect shore power if m going to crank the engines...
 

seasick

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#9
There is nothing mentioned in my Guest manual about turning off the charger when starting/running the motors. I couldn't find anything on the Marinco web site either