Charging the batteries

[Doug T.]

While installing shore power on our boat, I also added a three-stage, two-bank battery charger. I also did some mods to the DC system to add a proper DC grounding buss, and some other misc stuff. Everything seems to work fine.While at the dock I started the engine just to make sure I hadn't screwed up any of the DC circuitry. It started right up. I shut it down shortly thereafter.I got to thinking: I started the engine while the shore power was still connected and the battery charger was operating. Will anything be harmed by having the alternator charge the batteries while the battery charger is operating? Obviously, the batteries are getting more amps put into them than is ideal, but this was only for about a minute.(I don't know what kind of alternator I have or how it's regulated -- I think it's original equipment, 1978, so it probably isn't very sophisticated.)

 

[J. Tesoriero]

No Problem!

I have done the same thing - over and over. I just can't seem to remember to shut down the A/C power before starting my engine. I have an A/C battery charger installed. It has not seemed to damage either the alternator, the charger or the batteries - but I worry about it each time. Good Luck

 

[Don Alexander]

Your System Will Cope

Doug,When the alternator starts the shore power charger should shut down as it thinks the increase in battery voltage is because the battery is fully charged. Also the alternator will come to a similar conclusion if the cut off voltage from the charger is higher than that of the alternator.Yes you could get charging from both sources simultaneously but this will terminate as soon as the batteries have had their fill.The chances of damaging anything are very remote - even if you ran the engine for a prolonged period.Regards,

 

[Bruce Hill]

Actually, I was taught to do it this way

Don't know if it is right or wrong, but the dealer that sold me my first sailboat taught me to always start the boat with the shore power plugged in and on. Have been doing it for 13 years and have never had a problem