Hello Gurus - I have put in a couple small 2-panel arrays and used inexpensive MPPT chargers, so while I'm not a total newb, i definitely don't know everything. My next challenge is to setup an off grid system that will be capable of running a fridge as well as a few lights and LCD tv. I am currently working on convincing the in-laws (their cabin) to purchase a DC fridge, instead of a standard AC unit.
We have been using an ancient propane fridge that is barely working (plus chewing through gas), and the cost of a new propane unit, plus the inconvenience of having to continuously refill 20lb bottles (in-laws don't want to try to deal with bigger bottles, and a permanent tank/delivery service is a non-starter given the access to the property) In the spring/summer/fall months when there is decent insolation, I think this can work. We have a small Honda generator that they are currently using to run led lights/charge phones in the evening so it won't be too much extra load to run a small inverter instead, and the generator can be just for tools and backup battery charging.
My questions start with the maximum Wattage and arrangement I can connect to the FM60. I am thinking I would like to install a 2P3S configuration, using 2 strings of 300Watt 60cell Panels. Unfortunately the roof is shaded at various times of the day in the shoulder seasons so to maximize potential production I would like to put 3 panels on the Eastern facing part of the roof, and 3 more panels on the western facing part of the roof. I am up around the 51degN so none of this is ideal but I'm just aiming to make it work the best I can. FM60 manual lists 1500W as the Max Recommended Array Size for 24V Battery Bank, but My array will technically total 1800W. It will, however, likely never ever make that kind of power given the arrangement/orientation. Anyone think this is a bad plan? I could bump up to the FM80, but we've settled on 430Ah (20Hr) 24V battery bank and so the 80A charge rate seems overkill. Due to some last-minute decisions on adding the fridge (was originally going to be a 2-4 panel array on a Chinese MPPT) I am going to have to work with this bank as it's already been purchased. (4x Crown CR430)
If I can convince them to buy a DC Fridge, I will pickup a <1000W inverter to power up the inside, if not, I guess I'll need to get a >1500W unit to handle the fridge inrush....
Related Thoughts:
Battery Bank 24V @ 430Ah (20hr) /8 = ~53A Max charge rate
430 * 24 = 10.3Kwh * 0.5 = 5160Wh @ 50% DOD
TV is ~ 30W * 2h = 60Wh/day
Lights ~5W * 4 * 4h = 80Wh/day
Cell Chargers ~8W * 2 * 2H = 32Wh/day
Tablets ~15W * 2 * 2H = 60Wh/day
Inverter Parasitic Losses ~16W * 8hr = 128Wh/day
General Loads = 360Wh/day (incl inverter losses)
DC Fridge = 600Wh/day (estimated for 13cu/ft Unique Off-Grid DC Fridge)
Total Loads = 960Wh/day but let's round that up to 1kWh/day for fun * 1.2 buffer = 1.2kWh/day (50Ah)
1.2kWh means just over 4 days runtime @ 50% DOD with no solar input.
With an AC fridge, the inverter sizing losses jump to ~400Wh/day, and the same size fridge is estimate about 1.1Kwh/day so my daily is now 1.732kWh * 1.2 buffer = ~2.1 KWh/day (87.5Ah) so I'm down to only about 2.5 days autonomy...
We have been using an ancient propane fridge that is barely working (plus chewing through gas), and the cost of a new propane unit, plus the inconvenience of having to continuously refill 20lb bottles (in-laws don't want to try to deal with bigger bottles, and a permanent tank/delivery service is a non-starter given the access to the property) In the spring/summer/fall months when there is decent insolation, I think this can work. We have a small Honda generator that they are currently using to run led lights/charge phones in the evening so it won't be too much extra load to run a small inverter instead, and the generator can be just for tools and backup battery charging.
My questions start with the maximum Wattage and arrangement I can connect to the FM60. I am thinking I would like to install a 2P3S configuration, using 2 strings of 300Watt 60cell Panels. Unfortunately the roof is shaded at various times of the day in the shoulder seasons so to maximize potential production I would like to put 3 panels on the Eastern facing part of the roof, and 3 more panels on the western facing part of the roof. I am up around the 51degN so none of this is ideal but I'm just aiming to make it work the best I can. FM60 manual lists 1500W as the Max Recommended Array Size for 24V Battery Bank, but My array will technically total 1800W. It will, however, likely never ever make that kind of power given the arrangement/orientation. Anyone think this is a bad plan? I could bump up to the FM80, but we've settled on 430Ah (20Hr) 24V battery bank and so the 80A charge rate seems overkill. Due to some last-minute decisions on adding the fridge (was originally going to be a 2-4 panel array on a Chinese MPPT) I am going to have to work with this bank as it's already been purchased. (4x Crown CR430)
If I can convince them to buy a DC Fridge, I will pickup a <1000W inverter to power up the inside, if not, I guess I'll need to get a >1500W unit to handle the fridge inrush....
Related Thoughts:
Battery Bank 24V @ 430Ah (20hr) /8 = ~53A Max charge rate
430 * 24 = 10.3Kwh * 0.5 = 5160Wh @ 50% DOD
TV is ~ 30W * 2h = 60Wh/day
Lights ~5W * 4 * 4h = 80Wh/day
Cell Chargers ~8W * 2 * 2H = 32Wh/day
Tablets ~15W * 2 * 2H = 60Wh/day
Inverter Parasitic Losses ~16W * 8hr = 128Wh/day
General Loads = 360Wh/day (incl inverter losses)
DC Fridge = 600Wh/day (estimated for 13cu/ft Unique Off-Grid DC Fridge)
Total Loads = 960Wh/day but let's round that up to 1kWh/day for fun * 1.2 buffer = 1.2kWh/day (50Ah)
1.2kWh means just over 4 days runtime @ 50% DOD with no solar input.
With an AC fridge, the inverter sizing losses jump to ~400Wh/day, and the same size fridge is estimate about 1.1Kwh/day so my daily is now 1.732kWh * 1.2 buffer = ~2.1 KWh/day (87.5Ah) so I'm down to only about 2.5 days autonomy...
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