Bob
What I would do is spend the time to measure the condition of the system. Start with disconnecting the charger and ALL loads from the boat and let it sit overnight. 12 hours good, 24 hours even better.
Come back the next day, with the batteries having settled overnight, and record the voltage and the hydrometer readings for each cell. This will tell you what the condition, and more importantly the REAL state of charge, of the batteries are.
Plug in the charger, and keep track of time AND voltage. If your charger is a true three stage charger, you should see the voltage rising from most likely the 12.8 or so up to 14.2 or 14.4 volts bulk phase charging for about a half an hour (depending on the condition and state of charge of the battery bank - use your house bank). The voltage will depend on what kind of batteries you have (wet or gel cell) and what the setting on your charger is (if you have a setting, some of the older Charles chargers didn't have variable settings - see
http://c34.org/bbs/index.php?topic=605.0 - read it all and the referenced links).
After that time, the charger should drop down to the absorption phase with the voltage remaining constant and the amperage tapering off.
The following describes the charging steps from the Ample Power Primer.
Only by measuring what's going on, at your boat with your instruments, will you know if the charger is malfunctioning. Understanding the following should give you an idea of what to look for.
You can download the complete Ample Power Primer, a VERY good explanation at
www.amplepower.com (click on Technical Documents)
As far as the breaker tripping, there was a recent thread about wiring and connections, which you should also check, see:
http://c34.org/bbs/index.php?topic=3700.0 Some of the recommendations may be applicable to your situation with the breaker.
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The Bulk Charge StepWhen a charge source is first applied to a well discharged battery,
charge current begins to flow, typically at the maximum rate of
the charge source. If a true 40 Amp charger is connected to an 8D
battery which is completely discharged, about 40 Amps of charge
current would flow for some period of time. Because most of the
charge is delivered at the maximum charger rate, the first step of
the charge cycle is called the bulk charge step. NOTE: During the
bulk step, battery voltage will steadily rise.
The Start of the Absorption StepAt the instant battery voltage has risen to the maximum allowable
voltage of the charge source, current through the battery begins
to decline. This simultaneous event of reaching maximum voltage
and the start of current decline marks the beginning of the
absorption step.
For instance, if the 40 Amp charger is set to 14.4 Volts, then when
battery voltage has risen to 14.4 Volts, the charger will now hold
the voltage constant. Current through the battery will begin to
decline. NOTE: The charger, (or alternator), is not limiting the
current at this point. The battery is ‘absorbing’ all it can at the
voltage setpoint.
The End of the Absorption StepThe absorption step should continue until current through the battery
declines to about 2% of battery capacity in Amp–hours as
mentioned above. Without knowing what the current is through
the battery, you can’t know when it’s full. Just because that fancy
charger, (or inverter/charger), has kicked out to float is no sign
that the battery is full . . . there is no charger on the market that
measures battery current!
It’s a given, then, that you need to measure battery current to know
when the battery is full. With a battery current meter, you can discover
some very interesting details about the charge process. For
instance, you can discover that once the charger voltage limit is
reached, battery current begins to decline. If the current decline is
rapid, either the batteries are nearly full, or they are NO GOOD!
If the current decline is slow, then either the charge source has
more output than the batteries can reasonably absorb, or the batteries
are NO GOOD! Here’s where Amp–hour instrumentation
is particularly valuable.
Given enough time at the absorption voltage, charge current will
decline to a steady–state value, that is, a low current that either
stays constant, or declines very little. At the point where charge
current has gone as low as it is going to, then the batteries are truly
full. While 2% of Ah rating is close, good batteries will reach a
steady state current at less than 1% of Ah rating.
The Float StepOnce a battery is full, a lower voltage should be applied that will
maintain the full charge. Depending on the type of battery, (liquid,
gel), and the age of the battery, 13.4 – 13.8 Volts is appropriate
as a float voltage.