Solar install on a Trailer, newbie questions

red31 wrote:
panel current is either on or off, the on time tapers but not the current.

What's your point? As long as current is flowing, the battery is charging. If voltage drop prevented the battery from reaching its absorption voltage as you claimed, then no current would be flowing. But, of course, unless there's current, there's no voltage drop. And, as the battery approaches full charge, it draws less current.

PWM limits the voltage, and indirectly the current. Not the instantaneous current, which you seem fixated on, but the actual charge current - how fast coulombs flow into the battery. PWM won't taper off unless the battery is holding the desired voltage for some time after the PWM goes into the off state. The longer the battery holds at that voltage, the more fully charged it is, the lower the PWM duty cycle and the lower the current into the battery.