Solar Controllers--Don't be a Sucker! :(

Salvo wrote:
12th- OK, I agree my 20% in boost mode is too low. I have my current solar setup for 6 years now. I have been going consistently out of boost by noon or 1 pm. I think you'll find that most RV'ers will have similar results. That means mppt production is more like 50%. The moment you're out of boost, battery current will taper.

You mentioned running tv and going back into mppt. You may have an old fashioned tv that consumes 20A, but probably not. My tv consumes 2A. Your solar has the potential of more than 20A. A 2 or 5A load will not cause mppt when battery charge current has already appreciably tapered. A coffee maker operated in the afternoon may cause mppt for a few minutes, but nothing substantial. At sunset or an hour before, you may or may not go into mppt. But there's no punch behind the sun's power. There's so much atmospheric diffusion that you can look at the sun with the naked eye. The couple of hours before sunset or after sunrise are more or less meaningless solar production. Also, at those low sun altitudes, there's usually some obstruction (trees, hills, etc).

Sal

You apparently know a lot, but not how the Rogue MPT-3024 operates. I just went out and performed a little test. The system has been sitting idle in float for more than a week so I know beyond a shadow of doubt that the batteries are bursting full by anyone's definition. This test was at 6pm. I turned on the inverter and the TV. I also had a MaxFan running at 50%. The controller immediately reverted to MPPT.
Voltage input: 32.2
Amperage input: 4.2
Watts: 135
Voltage output: 14.1
Amperage output: 9.6
The numbers were actually fluctuating a little while I wrote them down so the output wattage appears higher than input (maybe that's the magic of MPPT:)). Next time I will have to take a picture.
There was also 1.9 amps going to the batteries according to the Trimetric. So the inverter, TV, fan and parasitic loads were consuming 7.7 amps. The system stayed in MPPT mode until I turned the TV and inverter off.

Several quotes from the Rogue Owner's manual for your reading pleasure.

"2) ABSORB: . . . In general, if the charger is supplying current to loads as well as charging batteries in this mode, the FLOTR setpoint will never be met because the loads will almost always be demanding a current greater than that of the FLOTR setpoint. The timer will instead elapse and force a transition to the full state. If the controller cannot maintain the battery voltage within 0.2 volts of the absorb setpoint (because of insufficient current from the PV array and/or excessive loads), it will revert back to the MPPT mode and will once more begin charging up to the absorb setpoint. The absorb timer will be reset and will begin counting down again when the controller next enters the absorb mode. This transition between MPPT and ABSORB modes may occur back and forth a number of times when the battery voltage is near the absorb setpoint on partly cloudy days. . ."

and

"4) FLOAT: . . . If the controller cannot maintain the battery voltage within 0.2 volts of the float setpoint (because of insufficient current from the PV array and/or excessive loads), it will revert back to the MPPT mode and the charge routine starts over. As the sun sets at the end of the day and/or the PV array becomes shaded, the controller will exit float mode and will return to MPPT mode, where it will remain until the PV array is unable to provide at least 100mA of current to the charger. At less than 100mA, the controller will enter sleep mode. . ."

From this it obvious that a much higher percentage of time will be spent in MPPT rather than your estimated 20% or 50%, especially if one is creating demand loads. It's a shame if other controllers don't operate this way.