Run engine while on shore power?

O

Oregon Trail

Well-known member
Joined
Sep 28, 2012
Messages
62
Fluid Motion Model
C-24 C
Non-Fluid Motion Model
Cutwater 28
Vessel Name
Northwest Passage
As I write this I am thinking it is a stupid question that I probably used to know the answer to but here goes:
Is there any reason why I should not start and run the engine while connected to shore power?

Thanks,

Mike
CW28
 
Hi

I do this all the time.

Dennis
R27 Tug of my Heart 11
 
As a former journalist and now college journalism educator, I can tell you the only dumb question is the one you do NOT ask. I've asked plenty of seemingly "dumb" questions here and am much the better for it.

John
 
I agree 100% with John, always ask..
 
Should the battery charger switch on the A/C panel be off? If the engine's running, the alternator souls be charging the batteries. Not sure what that means (maybe nothing) if the battery charger on the a/c circuit is also on.
 
The alternator will only charge the batteries if the batteries are low. If you are plugged in and your batteries are fully charged, the alternator will not push power into the batteries. You can't hurt anything.
 
I agree with those that say there's no such thing as I stupid question, but I disagree with all those that say there's no harm in have the engine running and the battery charger working. Whereas I acknowledge my own ignorance on this matter, a boat dealer (who I trust) told me that I should not run the engine at the same time that the battery charger is on, because it could harm the alternator. It's not an issue of being on shore power, just having the charger on. I say that even if that's not accurate, why take the chance. There's really no need to have both the alternator and battery charger working simultaneously.
 
Dante, I suspect you need a new dealer :mrgreen:
To the OP, run the engine to your hearts content.
The regulator on the alternator will see the that voltage on the batteries is already above the cutoff point and simply loaf.
 
" .. .. .. see the that voltage .. .. .."

Wow, my lesdyxia is really kicking up this morning.
 
I agree with Dante. Don't see why it would hurt to have the charger on while the engine is running, but I always turn mine off. On the other hand, if you turn the battery SWITCH off while the engine is running, it will ruin the alternator. I don't know why this is so, except it says so on the battery switch on every boat I have ever owned.
 
If you switch off the battery switch while the alternator is delivering current a voltage spike can result. The spike voltage can be great enough to "blow" the alternator diodes. There is a device which you can install which will dump the voltage spike to ground thereby preventing alternator damage.
The only concern I have with respect to battery charger and engine running is the staring interval. It is possible that the sudden starter current demand will cause a short term overload for the charger. I once blew a so called "smart" charger in an RV by operating the high current electric jacks while the charger was operating. It could be that modern chargers have built in, fast acting, current limits which would prevent damage.
 
Thanks for the great responses and confirming what I thought was the case.

Mike
 
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