DIY Manual

48 | P a g e 10-543-1 REV A
DIY Manual
When designing a solar system, ensure you select the correct Classic controller to handle the
maximum current. For example, say you plan to install 4000W of PV and you want to charge a
24V bank. Which Classic should you purchase? Answer – 4000W / 24V = 166.7A. None of the
Classics will support this system design. Too much current. You either use two controllers and
split the 4000W into two separate PV arrays, or you change the battery bank voltage to 48V:
4000W / 48V = 83A. In that case, the Classic 150 is the right model.
Classic Charging Stages
Figure 15 shows a perfect 3-stage charge if the sun were out and loads are small. The Classic
wakes up on the left side in “BULK MPPT” and starts charging as hard as it can. It pushes the
battery voltage up until it reaches the “ABSORB” voltage set point. The Classic regulates the
battery voltage in Absorb by lowering the current and maintains the Absorb voltage for the
amount of time set in the Absorb Time menu or until End Amps is reached. At this point the
Classic transitions to “FLOAT” and maintains the Float voltage as long as there is sufficient power
from the PV. When the power from the PV becomes too low, the battery voltage will drop below
the Float voltage set point, the Classic will go into Float MPPT, and push as hard as it can to get
back to the Float voltage.
Figure 16 shows two cycles in time where a large load came on (the dips). You can see the Classic
came out of Absorb or Float and went into an MPPT mode. Anytime the Classic shows MPPT on
its display it is doing the absolute most it can to produce power. If MPPT is not present that
means the Classic is holding back and not putting out what it can to keep the voltage from rising
above the set point.
Figure 15