A Quick Post Mortem on the Battery Issue

Editors Note:  This post is for my future self to remember and read the next time I arrive at a dead boat.

First, for context, our previous boat, Seas The Day (315), was set up to be on a mooring ball.  So I rarely used the plug in charger (maybe once or twice a season).  She had a small flexible solar panel that kept up with the daily battery drain and all her systems were usually kept "off" when we weren't using her.  As a result, her battery switch was usually kept in the 1+2 position so that the alternator would charge both batteries when she was under power.

Seas The Day (425) has two banks of batteries, a generator and of course shore power, so her electrical system is a lot more complex.  Here are some photos...

The battery switches are located in one of the starboard hatches.
Note the little circuit breaker between the circular switches.
(It feeds the power to the main panel.)

The main panel in the Salon.
Battery and bilge are at the left.
DC section in the center and AC section at the right.

The battery charger showing output voltage and current
(This was reading 0 and 0.)

The Problem:  

I'm guessing I had left the boat with the battery charger switched off.  (Editor's note, we have since had the dock pedestal looked at... we're pretty sure there was a bad connection in one outlet that probably caused a breaker to trip.)  The refrigerator and freezer were running, which drained the batteries.  Once the batteries drained below a safe point, the panel breaker between the circular switches tripped shutting off power to the DC distribution panel.  At that point, the batteries were below the voltage where they would be recognized by the charger.

Of special note is the fact that the charger manual DOES NOT MENTION this possibility... I probably would have returned the charger or purchased another one if not for the Facebook 42/425 group and Andy's response.

Solutions:

My solution (after some internet research) was to power cycle the charger and quickly (by pressing the up arrow within 7 seconds) put the charger in PS (power supply) mode.  This outputs power to the system (intended to power the boat without any batteries installed) but DOES NOT MONITOR BATTERY CHARGING.  I left it in that mode for 30 min to put some voltage into the system.  With the voltage up above 11 V, I switched it back to BC (battery charger) mode and resumed charging.  Note that it took overnight to reach full charge from this state.

An alternate solution would be to remove the house battery hatch and using a portable (book-style) jumper pack, jump the batteries so that the charger sees a usable voltage... then power cycle the charger and leave the jumper pack on the battery for the first hour or so.  

From the Owner Manual:

For quick and easy reference next time this happens, here are some diagrams from the owner manual that pertain to Seas The Day (425).  Note that we do not have the dedicated starting battery option, but we do have the generator.  Note that there's a difference between system drawings and schematics.

Discussion:

Some key points...

The output of the charger is independent of the battery switch position!  The output of the charger always is available to both battery banks.

Battery switch position 1 feeds the forward (single) battery bank to the distribution panel.

Battery switch position 2 feeds the house (double) battery bank to the distribution panel.

The battery switch position DOES determine which batteries are charged by the alternator while underway.  For that reason, NEVER run the engine with the main battery switch in the OFF position.

Watch for the little circuit breaker between the circular switches... if the main panel is off, this is the likely culprit.

The bow thruster and windlass are independent of ALL switches in the salon... they are only controlled via the small panel under the right edge of the forward berth.

My Thoughts on Best Practice:

Leave the battery switch in position 2 while at the dock.  If you end up with a discharge, you can switch to position 1 and still go sailing with use of bow thruster, etc.

Switch to position 1+2 while underway... that way the alternator keeps the forward battery full and ready for the bow thruster and windless.