What's a possible cause of battery drain?

[SailingHarmonie]

Originally Posted by Bowdrie

I could be wrong, but I don't think you can use a multimeter to check for that.
The charger I took to a shop was connected to an O-scope.

Testing for ripple with a multimeter is very easy. You switch its measurement mode to AC Volts and measure across the battery terminals. In an ideal world it measures Zero. Anything over 0.5% of battery voltage is quite high. Most decent battery manuals will have a specification for a not to exceed number.

[Boatwright]

Junk your cheap on the inside, flashy on the outside NOCO charger. Go to Defender Marine or other reputable dealer and buy a real marine charger designed for a hard-wired connection to a properly wired marine shore power breaker panel.

Study up on how to do this safely. If you are unsure about this, please do yourself a favor and hire a qualified marine electrician.

[Icarus]

Originally Posted by Russian007

two newish Duracell AGM's. New 10+10 Genius Noco charger. One battery has the starting circuit and nothing else except the voltmeter and charging cable. The #2 battery has the accessories and drains down to 7 volts in a day or two if not connected to charger. I have switch !,2, both, OFF. Also have a combiner.

Only one piece of evidence: With the VHF off, the VHF's mic speaker emits an audible and steady POP POP POP POP every second. If I dq the power supply to the VHF the popping sounds stops immediately.

Anyone want to venture a guess? A Whale bilge pump was cycling ON periodically, thought that the culprit. it wasn't.

This is all happening in the slip when connected to shore power. 110v
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Disconnect the Negative battery terminal and measure the voltage and Amp between Battery post and disconnected Neg cable with everything switched on. If you have lets say 3amp drawing while everything is off. Switch off each individual accessory till the DC draw disappears....the last accessory is the culprit...
Shorepower shouldnt have anything to do with DC current draw, check your AC battery charger