40 amp battery charger work with 30amp shore power?

Don S/V ILLusion · Feb 22, 2012

You can't compare the amp rating because one is at 120VAC and the other (the charger) is rated at 12V. The charger will draw 40 amps at 12V or 480 watts (actually a bit more but this is good for comparison sake).

Your shore power is rated at 30 amps at 120V or approx 3600 Watts - way more than your charger will ever require.

Remember the rating numbers used on circuits is meaningless unless you convert power demand from 120V to 12V.

alexco38 · Feb 22, 2012

Ohm's law:

40 Amp * 14 volt = 560 Watt (when the batteries are all discharged)
30 Amp * 120 volt = 3,600 Watt

It the watts that count.

mitiempo · Feb 22, 2012

I agree with the others - it is not a problem on shorepower.

But it is not overkill. If your batteries are down to 50 or 60% SOC they will accept between 80 and 100 amps, for a while anyway. And a charger cannot be too large - the batteries will determine their acceptance of current.

Ron20324 · Feb 22, 2012

I don't believe the unit "draws" any 12v volts. The book says it draws 8.5 amps AC, but usually has a 15-amp circuit breaker.

Blitz · Feb 22, 2012

My victron 30 amp charger draws less than 5 amps per the manufacturer and observed upon startup. Victron told me to use a 15 amp breaker.

Benny17441 · Feb 23, 2012

The charger's 40 amp rating is for the 12V output to the batteries. Ron states the book indicates a draw of 8.5 amps at 120V and that should be a maximum at bulk rate charge. Your 30amp shorepower will adequately accomodate the charger.

Maine Sail · Feb 23, 2012

Blitz said:
My victron 30 amp charger draws less than 5 amps per the manufacturer and observed upon startup. Victron told me to use a 15 amp breaker.

The Victron chargers are very efficient compared to many others. The Sterling Pro Charge Ultra and ProMariner ProNautic P are also very efficient at about 90%. Some chargers are as little as 60% efficient while others are in the 90% range.

Maine Sail · Feb 23, 2012

Jared1048 said:
Hello all!

Im upgrading my battery bank and am starting with a bigger shore charger. The unit I want to get is an older xantrex 40. Im worried though that it might exceed my shore power connection being only 30amps?

The battery bank I want to get would be around 450 ah. So this charger is a little overkill but it's a good deal.

What do you guys think?

Thanks,
-Jared

Jared,

As others have said DC/OUT does not equate to AC/IN.

Feel free to read this article before installing your charger...

Installing A Marine Battery Charger (LINK)

Charles Erwin · Feb 23, 2012

Maine Sail -

Have an identical inquiry about charger replacement - ie replace a ferroresonant (old Guest 2520) charger with IOTA DLS 30 instead of of Promariner or Stering - which you documented in your charger intall discussion. IOTA are less cost - but no 20 amp option. Apart from ABYC/UL compliance certification - are IOTA chargers still on your radar as an option?

Charles