rightjake
New Member
I have a 10 year old off grid system at a cabin in Canada which I use off and on from April to mid October. I had two strings of 3x250 watt (ET Solar) panels in series (south facing ground mount) but two of the panels failed last year; one failed completely and the other has very erratic output. I am looking to replace the panels and upgrade to a larger system.
The old system was installed by a very knowledgeable friend but he is no longer active. I understand the basics of solar systems but with gaps, only some of which I know. With some guidance from an electrician I wired my cabin to code thinking I would eventually connect to the grid but the utility wanted, and still wants, an arm and a leg to connect and the grid is unreliable so I’ll stick with solar.
My system as it stands:
Midnight MNPV3 combiner with two circuits in use, each with a 10 amp 150V DC breaker
Magnum 4024 PAE inverter - 4000 watt, 24volt.
Schneider/Xantrex 150/60 MPPT charge controller
8 Rolls 6V 430 ah deep cycle lead acid batteries in two strings of four. The 250 watt panels I will replace had these ratings:
Open circuit voltage 37.4 volts
Working circuit voltage – 30.3 volts
Isc – 8.74 amps
When the system was new the Schneider controller, rated at 60 amps, put out up to 1600 watts at peak. The Magnum inverter has performed well - I have used a 2HP table saw for 10 years with no starting problems and I have the option of tying in a generator if I ever want to use the cabin in winter. The inverter has been reliable and ample for my needs and Magnum gear seems to have a good reputation so I am thinking to stick with it. That locks me in to a 24 volt system. In the past I’ve used about 3-5 kwh daily with a small freezer, fridge, lights, computer, microwave. With a larger system I’d use a small 110v electric hot water heater (on a switched circuit), electric kettle, toaster oven.
I’m thinking of using:
Six Longi bifacial 545 watt panels in 2 strings each with 3 panels in series, total capacity of 3270 watts
Victron 250V/100 amp controller. Victron rates it at 2900 watts nominal power in a 24 volt system.
The Longi panel specs are:
Open circuit voltage 49.5
Isc – 13.85 amps
Current at max power -12.97 amps
My lead acid batteries are tired and I’m thinking to replace them with two Eco Worthy 12 volt 280ah LFP batteries in series but the battery replacement is probably going to be next year. In the past I've shut the inverter down for winter and kept the CC going to keep the batteries topped up. If I go to LFP batteries I will store them indoors at a friends place over the winter.
Questions
The old system was installed by a very knowledgeable friend but he is no longer active. I understand the basics of solar systems but with gaps, only some of which I know. With some guidance from an electrician I wired my cabin to code thinking I would eventually connect to the grid but the utility wanted, and still wants, an arm and a leg to connect and the grid is unreliable so I’ll stick with solar.
My system as it stands:
Midnight MNPV3 combiner with two circuits in use, each with a 10 amp 150V DC breaker
Magnum 4024 PAE inverter - 4000 watt, 24volt.
Schneider/Xantrex 150/60 MPPT charge controller
8 Rolls 6V 430 ah deep cycle lead acid batteries in two strings of four. The 250 watt panels I will replace had these ratings:
Open circuit voltage 37.4 volts
Working circuit voltage – 30.3 volts
Isc – 8.74 amps
When the system was new the Schneider controller, rated at 60 amps, put out up to 1600 watts at peak. The Magnum inverter has performed well - I have used a 2HP table saw for 10 years with no starting problems and I have the option of tying in a generator if I ever want to use the cabin in winter. The inverter has been reliable and ample for my needs and Magnum gear seems to have a good reputation so I am thinking to stick with it. That locks me in to a 24 volt system. In the past I’ve used about 3-5 kwh daily with a small freezer, fridge, lights, computer, microwave. With a larger system I’d use a small 110v electric hot water heater (on a switched circuit), electric kettle, toaster oven.
I’m thinking of using:
Six Longi bifacial 545 watt panels in 2 strings each with 3 panels in series, total capacity of 3270 watts
Victron 250V/100 amp controller. Victron rates it at 2900 watts nominal power in a 24 volt system.
The Longi panel specs are:
Open circuit voltage 49.5
Isc – 13.85 amps
Current at max power -12.97 amps
My lead acid batteries are tired and I’m thinking to replace them with two Eco Worthy 12 volt 280ah LFP batteries in series but the battery replacement is probably going to be next year. In the past I've shut the inverter down for winter and kept the CC going to keep the batteries topped up. If I go to LFP batteries I will store them indoors at a friends place over the winter.
Questions
- Does my upgraded system plan make sense? What am I missing? Are there more sensible equipment/$alternatives than what I’ve penciled out here?
- I’m thinking to use 20 amp DC breakers in the two circuits at the combiner. The solar system is off in the dead of winter but in April and October the temperature can hit 15 degrees F. Also I’m not quite sure how to size the DC breakers between the charger and batteries and the batteries and the inverter. I’ve been given contradictory sizing recommendations.
- Over paneling? – I figure the excess panel capacity would help in the fall season shorter days and in mid summer when forest fire smoke can last for weeks and drastically reduce panel output (forest fires have become much worse over the last 10 years). As I understand it the CC will handle up to its maximum 100 amp rating regardless of whether the panels are rated for more and the critical limit is to make sure the input voltage never exceeds the CC voltage input rating (250 volts for the Victron).
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