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Thread: WARNING..shore power ON, engine ON is a NO-NO Reply to Thread
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  Topic Review (Newest First)
01-14-2008 06:12 AM
haffiman37 General rule when charging is to DISCONNECT the battery from alternator, normally turn off main. The reason is that all diodes have a certain leakage. Charging from shorepower with main on, this leakage might lead to overheating of the diodes in the regulator and short it. If it 'burns off' (open) nothing will happend except the alternator will not work, but if shorted, unregulated AC goes out, and that might cause fire in cable harness due to overcharging. Another reason for the incident might have been that the batteries have been shorted, and the alternator has been charging at max amp output, more than the harness have been able to handle. Shore power chargers normally goes to 20-30 Amps at max, if an alternator of 75Amps ore more starts it might be a problem. Have see a lot of people changing alternators from std 55-60 Amps to 100+, but they never emodify cable harness accordingly.
01-13-2008 11:49 PM
sailboy21 Agree there should not be any problem running alternator a battery charger at the same time. If something bad happens, probably a result of a fault that already existed and they should be happy it happened at the dock!
About chargers: Anyone using a cheap auto charger should stop immediately. Those things are not ignition protected, and they may contribute significantly to galvanic corrosion, and worst case may cause stray voltage to enter the water via DC ground and hurt possibly kill someone. This is due to the fact that they may not use an isolation type transformer. So there are 3 reasons why using a cheap automotive charger may screw up someone else's boat, and I know there are a bunch of you doing it!!! arrrggg.

So.. trickle charging good or bad?? I have always left my 10amp double bank guest charger on at the dock, never noticed any significant loss of water from the batts. Going 2 years now and I haven't noticed any loss of capacity.
01-13-2008 11:38 PM
Valiente I tend to unplug the "yard shore power" when I'm off the boat, because these days I'm down there every two or three days...or more if work allows.

My other boat is loaned to a woman skipper who lives about 60 miles north of here, so I encouraged her to take that boat's batteries to her house and to keep them trickle-charged on occasion.
01-13-2008 08:00 PM
artbyjody [quote=chuck711;249660]I must be missing something here. Just because you are connected to shore
power it doesn't mean your AC battery charger is on. Isn't the charger on a breaker switch. You only turn it on periodical.

Your right - it doesn't mean that is on - but it probably should be. As you will most likely weaken your battery by not doing so as they have self-discharge rates (plus what happens if you leave a light on or the bilge pumps cycles through a few times and you are gone for a few weeks). Having a trickle charger on them will keep them at optimum charged capacity.
01-13-2008 07:48 PM
I must be missing something here

I must be missing something here. Just because you are connected to shore
power it doesn't mean your AC battery charger is on. Isn't the charger on a breaker switch. You only turn it on periodical.

I find its bad practice to leave your AC charger. It would hide a possible weak battery.
01-08-2008 09:21 AM
chucklesR Correctly wired, it shouldn't matter. Blocking diodes are supposed to prevent any problems - automobile chargers used by people trying to save a buck might blow their systems, but not a properly installed marine grade system. - ArtbyJody writes it up much better than I can - what I can add is hands on.

Summertimes when working on the boat pierside I run the A/C on shore power(after all, why not be comfy) - and the engine at the same time.
I'd hate to have to disconnect my solar panel to run the engine - don't you think that would be a little odd?
I plug a small generator right into my shore power outlet to fire up my 110 only a/c, while underway on the motor, it's two separate systems made separate by folks with electrical engineering creds
01-08-2008 08:20 AM
donradclife There should be no problems with running both shore power and the engine if things are working correctly. The boat in the original post probably had a defective regulator in the engine charging circuit.
01-08-2008 08:13 AM
Idiens What do you guys do when you have solar, wind, shore and alternator power available? - Disconnect all but one source?

The boat should be wired to accept any combination of input without damage, which includes the inverter being automatically switched out when shore power comes on.
01-07-2008 07:51 PM
denby I believe ArtByJody is correct, but I always disconnect shore power or ac charger first. Just a habit.
01-07-2008 07:35 PM
djodenda ArtByJody is correct
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