Is this a problem? We’re adding four new modules to our array and the installation company recommended an MPPT 100/50 as the charge controller. The modules are 320w each and after putting the specs into the calculator, it says we should use a MPPT 150/60 MC4.
How much of a difference does this make? Is there an issue with having a controller with higher capacity than the panels can generate?
The installers selection is not necessarily a problem, and if they are doing their job correctly, is probably superior choice.
The calculator is basic, and a suitably trained, and experienced installer will be able to do a better job at picking a controller than the calculator. Though the calculator is still a useful tool even for experienced installers, as it can show you the voltage under various temperature conditions that can damage an MPPT.
A few of the differences:
You didn't mention your battery voltage, I presume that it is 24V. The 150V units are required for 48V battery banks.
You didn't mention your string configuration. Though I presume 2 strings of 2 panel pairs. As a 4 panel string is likely too much for both controllers anyway.
There is no issue to have too large an MPPT for the solar array, or slightly too small and MPPT for the solar array. The cost savings can be worth the potential slight loss of peak power production of using a smaller controller. However if heat is a big factor, then the larger dissipation potential of the bigger unit might be worth it.
The MC4 vs TR, is an installers preference. I personally prefer the TR style.
Thank you, Guy. The voltage is 24 and we are replacing four 25-year-old modules and are wiring them 2 of 2. It’s a 100% off-grid house and we’re replacing a 20+ year-old Morningstar Prostar-20 PVM controller as we upgrade the modules. We’re at 5,300’ so heat isn’t an issue. Loads of sunlight in the summer, though.
My concern was whether slightly over or under sizing is an issue. We do have two other 250w modules running off another Prostar-20 and the installer suggested a 100/30 for those. I presume, based on your answer, that even though the calculator suggested a 100/25, there should be no issues?
Many thanks.
Todd
Thank you, Guy. The voltage is 24 and we are replacing four 25-year-old modules and are wiring them 2 of 2. It’s a 100% off-grid house and we’re replacing a 20+ year-old Morningstar Prostar-20 PVM controller as we upgrade the modules. We’re at 5,300’ so heat isn’t an issue. Loads of sunlight in the summer, though.
My concern was whether slightly over or under sizing is an issue. We do have two other 250w modules running off another Prostar-20 and the installer suggested a 100/30 for those. I presume, based on your answer, that even though the calculator suggested a 100/25, there should be no issues?
Many thanks.
Todd
