Midnight Solar Classic 150 Issues Summary

I installed a solar system in September 2014. The Classic 150 (C150) Charge controller and inverter came premounted and wired on a Magnum panel from Northern Arizona Wind and Sun. After learning the system, I realized there were several problems with the controller not all listed here. Two issues are annoyances more than anything but problem #1 resulted in unnecessary battery drain and I’ll describe that first. This is an off-grid, stand-alone system without generator or other back-up. All power comes from 3 kW of panels with a 470 Ah, 48V battery bank. The C150 is paired with a Magnum 4448 PAE Inverter and RC-50 Remote display.

1) Sometimes, there is a significant time lag (ranges from seconds to more than a minute) after a load is added to the system before the C150 adjusts and allows more power from the panels in to cover the load. During that lag, the batteries are carrying a large load even though there is an abundance of solar energy that is not being used. Then, suddenly, the C150 kicks in and the solar power soars and covers all the load and starts recharging the batteries (there is no change in sun availability during this time). Other times it works perfectly; i.e. power loads are met as they occur, no lag. The problem appears to be random in terms of when it will occur and a user will likely not know the problem exists without spending a lot of time watching the system monitors.

2) The “Status” display on the C150 often (some days it’s perfect all day, other times it comes and goes throughout the day) shows incorrectly low values for Wattage and Amperes. For example, the C150 shows 500W at 50V, 10A as the total energy available in the system but the RC-50 monitor indicates the same voltage with batteries charging at 12 or 13A. I have verified with a meter that the RC-50 values are correct. It is especially obvious when the C150 shows 0 watts in the system, yet the batteries are charging. If a load kicks in, the C150 displayed values increase but still under-report the amount of energy that is being used. This is annoying but also means the cumulative power calculated by the 150 is under-reported. The C150 appears to be diverting power correctly, just not displaying it. Midnite Solar has been responsive even though they say they have never seen this problem before. They sent a new display, which did not correct the problem and now an entire new charge controller that they sent does the exact same thing. This indicates to me a widespread quality issue.

3) A small glitch but I’ll mention it anyway: as you scroll across the maximum power data under the Daily Graph mode (in Logs), the displayed values truncate the thousands so all you can see is the last three digits. I made Midnite Solar aware of this and they said they would fix it in the next Firmware Update.

Midnight Solar doubted this problem #2 existed until I recorded it while it was occurring and sent them the video. Then they acknowledged the problem and said they were working on a fix. The “new” Classic 150 they sent me was a better functioning controller – did not experience the serious Problem #1 above, but had the identical display issue to the original Classic 150. More troubling was that I discovered old data files on the controller and upon pressing Midnight Solar, confirmed that they has sent me a refurbished unit. That is unacceptable in my opinion unless I agreed to that.

Months later no fix had emerged for the Classic 150 and Northern Arizona Wind and Sun graciously sent me a Morningstar Tristar MPPT 60 and I returned the Classic 150 to them. The Morningstar has performed flawlessly for more than a year. Thanks NAWS for taking care of me!

What struck me most in using the Midnight Solar Classic 150 versus the Morningstar Tristar 60 is that each of three Classic 150s had a “personality”, with its own strengths, weaknesses, inconsistencies, and oddities. They were all different. It seems to me that electrical equipment should perform the same way, as intended, each time. Lack of uniformity means lack of quality control, whether it is in hardware or software or both. The Morningstar has been completely consistent and reliable with no performance oddities or surprises, a much higher quality unit and satisfying experience in my opinion. I also appreciate the silentness of the Tristar versus the constant clicking and fan noise of the Classic 150. Seems to me that noises indicate efficiency loss and mechanical parts that will eventually wear out.