Confusing the MPPT controller
Here I go with my ignorant self again, seeing something and thinking I can figure it out. ;) When I first got my original panels I talked to quite a few people including Mark at Rogue saying to run...
Forum Discussion
Not sure if this is related or helps any, but I have this data so might as well use it!
The controller adjusts Vmp to suit circumstances. If things are getting tight as in the following example, where it had to raise Vmp as "overhead" shrank, then I suppose mixed panels would make it tighter/more critical?
In this case, the 60 cell panel ran out of "overhead" on a 24v battery bank when it got Vbatt to 30v, but the neat thing is to watch the Vmp climb. (Or maybe the controller ran out of Vmp it could go up to while in MPPT?--panel voltage would go to 35v or whatever once in Float)
THE TEST
The bank was full, in Float (as set) at 14.4v as 12v bank, so knocked that down with microwave on inverter for three minutes, disconnected solar, put batts in 24v mode, connected solar controller but not array yet, and set Absorb to 31v (max setting) and Float to 29v (max setting) By now battery holding at 25.6v ready to start, so connected array
I measured Vmp at the controller array terminals and took battery voltage and amps from the controller's display. I did not note the times. Controller was in Bulk and doing MPPT-- So here is how it went with Vmp, V batt, Amps, output watts
29.0, 26.3, 6.0
29.8, 27.4, 5.01, 138
30.1, 27.7, 3.52
30.4, 28.7, 4.64
30.4, 29.3, 4.81, 142
30.7, 29.9, 4.66
31.0, 30.2, 4.52
31.1, 30.3, 4.04, 137
It stayed at 30.3 saw 30.4 but fell back to 30.3 again so stuck there, still; showing Bulk ( not yet to the 31v Vabs setting)
The key seems to be the MPPT finds an ever higher Vmp as Vbatt gets higher, so the amps keep coming.
The controller adjusts Vmp to suit circumstances. If things are getting tight as in the following example, where it had to raise Vmp as "overhead" shrank, then I suppose mixed panels would make it tighter/more critical?
In this case, the 60 cell panel ran out of "overhead" on a 24v battery bank when it got Vbatt to 30v, but the neat thing is to watch the Vmp climb. (Or maybe the controller ran out of Vmp it could go up to while in MPPT?--panel voltage would go to 35v or whatever once in Float)
THE TEST
The bank was full, in Float (as set) at 14.4v as 12v bank, so knocked that down with microwave on inverter for three minutes, disconnected solar, put batts in 24v mode, connected solar controller but not array yet, and set Absorb to 31v (max setting) and Float to 29v (max setting) By now battery holding at 25.6v ready to start, so connected array
I measured Vmp at the controller array terminals and took battery voltage and amps from the controller's display. I did not note the times. Controller was in Bulk and doing MPPT-- So here is how it went with Vmp, V batt, Amps, output watts
29.0, 26.3, 6.0
29.8, 27.4, 5.01, 138
30.1, 27.7, 3.52
30.4, 28.7, 4.64
30.4, 29.3, 4.81, 142
30.7, 29.9, 4.66
31.0, 30.2, 4.52
31.1, 30.3, 4.04, 137
It stayed at 30.3 saw 30.4 but fell back to 30.3 again so stuck there, still; showing Bulk ( not yet to the 31v Vabs setting)
The key seems to be the MPPT finds an ever higher Vmp as Vbatt gets higher, so the amps keep coming.
