I have 4 Classic 150's. The 2 I added to the system when I expanded show much higher voltage when receiving high PV during Bulk phase. Those two will then go into absorb before the others. It is strange. It is effecting the effecency of the system. Makes me a little nervous.
Ideas?
Are the wires all the same size and length ?
You can calibrate the Classics individually for voltage drop that might be in the wiring.
You would take a voltage reading at the battery and then at the input terminals of the Classic and adust voltage compensation as needed.
It can change some depending how much power is going through too.
Maybe that will help you balance things out.
Larry
Considered that, but... It's not a drop, those two do have a greater run to the main bus bar- but they are all the same voltage in all phases- resting, absorb, and mppt/bulk when there is little amperage. As soon as the amerage gets hefty- the voltage at those two classsics is well above the others, and greater than what the battery is reading.
Quote from: jbbonnette on April 17, 2022, 10:10:50 PM
Considered that, but... It's not a drop, those two do have a greater run to the main bus bar- but they are all the same voltage in all phases- resting, absorb, and mppt/bulk when there is little amperage. As soon as the amerage gets hefty- the voltage at those two classsics is well above the others, and greater than what the battery is reading.
Maybe it is at those high current times that you need the voltage compensation set for.
Do you have your Classics in Follow Me ?
Larry
Hi jbb..,
Quote from jbbonette:
"Considered that, but... It's not a drop, those two do have a greater run to the main bus bar- but they are all the same voltage in all phases- resting, absorb, and mppt/bulk when there is little amperage. As soon as the amerage gets hefty- the voltage at those two classsics is well above the others, and greater than what the battery is reading".
OK, so, first, a stupid question: Each Classic has its own, separate PV array, correct?
Is each Classic in the same charge Mode (Solar, Legacy P&O, etc)?
Another thought, when "the amperage gets hefty', is it possible, at that point, those two Classics, have gone into Absorb ? When MPPT CCs have reached a setpoint (like reaching Absorb setpoint), the loading of the PVs connected to that particular CC is reduced, and this causes the PV input voltage to increase.
And, as you know the PV input voltage needs to be above the actual battery voltage at that time. The absolute minimum for Classic Vin, is about 5.5, or 6 volts above the battery voltage at that time. For the MPPT to work well, the input voltage headroom needs to be about 30% higher than the highest battery ever expected.
Later, Vic
You mention that on the one Classic, the PV input voltage is higher than the others...
What are the 4 Classic PV array Voc's and do any of them have any partial shading on the panels ?
What are you seeing for Vmp on the 3 Classics (BULK/MPPT) and what are you seeing for Vmp on the one Classic ?
Are they all the same amount of PV power ? How long does the one higher power generating Classic stay in Bulk before going to Absorb ?
Not sure what you mean by lower efficiency though ?
boB
going to Absorb is due to hitting the target absorb voltage so if say one classic sees the battery as 0.01v higher it will go to absorb first, This should not be any issue as the battery is essentially at absorb voltage and the controllers are needing to throttle back to prevent over charge.
I would be curious to understand how this is effecting efficiency?
It turns out the problem is with the first two 150's. They will not go above 55.4v to get into absorb 56.2. I was pulling 60A each and the MPPT wouldn't do the MPPT thing. The Voltage was just steady at 55.4.
I ran several configurations today, more often I was just using the 10KW (2 5kW arrays) for the problem 150s. I would throw on the others- they would go right to absorb but the others wouldn't.
Sounds like the batteries are getting an absorb at least. That is the important part.
Below absorb voltage, all Classics should be helping out though so you have that.
IF the voltage discrepancy is only a couple tenths of a volt from the Classic that does most of the Absorbing, then you might try adjusting the voltage OFFSET in the TWEAKS menu those tenths of a volt.
If the voltages are off by much more, then you may want to talk with support, however the feedback voltage can still be adjusted. But we'll save that option if a simple and small-ish offset adjustment is not enough.
boB 🌜