Batteries - charging - normal?

[hippieforever3]

Boy, its amazing the range of reactions you get when you play the
musical horn.

Alternator charging and battery health questions.
In the morning the voltmeter may be showing between 10.5 and 11 volts,
Engine turns over nice and easy and settles into idle.
Voltage now reads around 10 volts and charging meter is dead on zero
and continues until we tap the accelerator. Rev up to around 1200rpm
or more and then the charging meter jumps to 60-75a and the volt
meter pops up to 11.5 or so.
Continue to idle and charging drops to 20ish and voltage climbs to 12-
12.5v in 10-15 minutes.

The first question is what is going on until that initial tap on the
accelerator?

We've got 4 Kirkland Marine deep cycle batteries about 20 months into
a 30 month warranty.
While we were at Walmart the other day we tried to get them to check
the batteries but they did it with all four connected and only
checked for the cold cranking spec (550a). I didn't think that test
was worth squat but that was all they would do.

Just running and hour or two of two mini-spots, the night light, the
water pump sporadically and the heater fans intermittently at night
drops us from full charge voltage to around 11v or into dangerous
cranking territory.

The second question is, do those reading and times sound like a
healthy battery bank?

Regards,
GPSGary
On our way to registering in South Dakota
84FC35 (with a personality)