I am expanding my array, wanting to add four 230-watt 24-v. panels, 29.6 volts. I want to wire them in series pairs, so that would be two strings of just less than sixty volts. I am purchasing a used Classic 150 as I move away from Outback MX60s, so I am not familiar with Midnite controllers I have used the Midnite array-sizer and it appears I am well within limits with the four panels, the limits for one Classic 150, I mean, or could even go to six panels [two strings of three in series].
The reason for the post here is that the dealer selling me the controller says he thinks that the 150 might not work at an input voltage of much less than 59 volts, and it that's true, I would need two more panels to give me two strings wired to around 90 volts. He is afraid I might end up having to order two more panels to make the 150 work on warmer days.
The Outbacks will work, turn on so to speak, at an input voltage of battery voltage plus 2 volts. So, 14 volts or whatever. I have done a search and not found the answer to my question. The dealer is a battery and panel seller and is not up on Midnite stuff, he just has a used controller he's selling me.
My battery bank is a 12-volt set.
So, to sum up, anyone know the minimum input voltage needed for the Classic 150 to wake up and start working??
If you are using a 12volt battery then you are fine. The Classic basically needs say 33% higher than the battery voltage to wake up in solar mode. If you use Legacy mode (more like the MX60) it will turn on down much closer to the battery voltage.
Of course you really would not want to design that way as you would be way below the MPPT voltage of the array and you would be loosing a lot of power.
Ryan
Thanks, perfect.
Quote from: JesseCrane on September 02, 2013, 06:19:35 PM
I am expanding my array, wanting to add four 230-watt 24-v. panels, 29.6 volts. I want to wire them in series pairs, so that would be two strings of just less than sixty volts. I am purchasing a used Classic 150 as I move away from Outback MX60s, so I am not familiar with Midnite controllers I have used the Midnite array-sizer and it appears I am well within limits with the four panels, the limits for one Classic 150, I mean, or could even go to six panels [two strings of three in series].
How far are your panels from the controller? If they are reasonably close you will benefit from putting all the panels (four or six panels) in parallel. The classic is more efficient and runs cooler if it doesn't have to down convert the voltage so much. in other words, the classic will be happier converting 29.6 volts to 12 volts, rather than 60 or 90 volts to 12 volts.
The down side of a lower voltage array configuration is that you need thicker wire to carry the current between the combiner and the controller. That's why my first question is "How far are your panels from the controller?"
--vtMaps