I am in the final stages of moving to an off grid house in Sacramento, CA area and am starting my upgrade planning.
Calculated winter daily loads are 15.5kwh
Weekly loads that can be shifted 46kwh/wk and run with generator if needed
Optional load for summers 12kwh (Hybrid car, gas and charge at work in the winter)
Calculate for Winter 15.5kwh*2 days*1.5 losses= 46.5kWH
Calculate for Winter 15.5kwh*3 days*1.5 losses= 70kWH
46.5kwh/48v = 968AH needed for 2 days
70kwh/48v = 1458AH needed for 3 days
Trojan SIND 04 1685 has a 1293ah * 48v 20hr rate = 62,064 kWh
Trojan SIND 02 2450 has a 1489ah * 48v 48hr rate = 71,472 kWh
Trojan SIND 02 2450 has a 1594ah * 48v 72hr rate = 76,512 kWh
2 days @ 20hr rate => 968ah/1293ah => 75% discharge => 25% charge
2 days @ 48hr rate => 968ah/1489ah = 65% discharge => 35% charge
Days of charge to 20% = 1594ah/484ah = 2.63 days
Not ideal, but stays above 80% discharge in emergency, and a generator can be used to help as needed. To increase to 3 days or staying about 50% batteries requires doubling the inverters, panels, etc. to meet the min charge rates. This would translates to a 50% increase in an already expensive system, and 50% more in battery replacement costs forever.
http://www.trojanbattery.com/pdf/dat...04_1685_DS.pdf
So, assuming 1293ah batteries that puts me at a max discharge of c/8 = 161.6amps, and min. charge rate of 129 amps.
Min. Generator size is 129amps*48v = 6.2kW @80% load = 7.7k round up to 8k generator
min. solar array is 129amps * 48v = 6.2kWh
Max draw is 161amps =>7.7kW
Solar array is at 150 degree angle, due to shading and pvwatts says
Existing system
Solar Array: 2.5kW panels
Inverter/Charger: Magnum MS4448PAE
Batteries: 48v 370ah and 7 years old.
Generator: Champion DuelFuel 7k continuous
Proposed System
1x Schneider Electric Conext XW+ inverter rated at 6800watts
2x Midnite Classic 150
12x 4v Trojan 1685AH batteries
1x top of pole mounts holding 15 60cell panels
15x 295watt mono Solarworld panels (input needed)
12x 205watt poly panels (existing panels)
8k Diesel or LP liquid cooled low rpm generator
1x residential fridge is in the daily load calc (The main fridge, not willing to compromise to propane)
1x 48v Sunfrost RF18 is in the daily load calc (may not happen, but including in loads)
Once I pin down the proposed system, I will then be trying to figure out the best order to do things. The generator brand doesn't instill confidence and the batteries are on their last legs. I don't dare get an expensive set of batteries without a large enough inverter/charger to maintain them. The existing Magnum invertor could charge them, but not avoid stratification.
Proposed order of purchase / install
1. Generator 8k
2. Solar Panels -> upgrade existing system to 4.4kW with the new panels
3. Forklift upgrade the Inverter and chargers / Upgrade to full 11.4kW
?? Batteries
Batteries should be replaced soon, so possibly step 1.5 if I can survive 6-12 months with the existing charger and not kill them. Otherwise step 4 and I hope I can avoid buying a temp cheap set of batteries in the meantime. Possibly a lot of generator time, which is cheaper than a cheap set of batteries
Calculated winter daily loads are 15.5kwh
Weekly loads that can be shifted 46kwh/wk and run with generator if needed
Optional load for summers 12kwh (Hybrid car, gas and charge at work in the winter)
Calculate for Winter 15.5kwh*2 days*1.5 losses= 46.5kWH
Calculate for Winter 15.5kwh*3 days*1.5 losses= 70kWH
46.5kwh/48v = 968AH needed for 2 days
70kwh/48v = 1458AH needed for 3 days
Trojan SIND 04 1685 has a 1293ah * 48v 20hr rate = 62,064 kWh
Trojan SIND 02 2450 has a 1489ah * 48v 48hr rate = 71,472 kWh
Trojan SIND 02 2450 has a 1594ah * 48v 72hr rate = 76,512 kWh
2 days @ 20hr rate => 968ah/1293ah => 75% discharge => 25% charge
2 days @ 48hr rate => 968ah/1489ah = 65% discharge => 35% charge
Days of charge to 20% = 1594ah/484ah = 2.63 days
Not ideal, but stays above 80% discharge in emergency, and a generator can be used to help as needed. To increase to 3 days or staying about 50% batteries requires doubling the inverters, panels, etc. to meet the min charge rates. This would translates to a 50% increase in an already expensive system, and 50% more in battery replacement costs forever.
http://www.trojanbattery.com/pdf/dat...04_1685_DS.pdf
So, assuming 1293ah batteries that puts me at a max discharge of c/8 = 161.6amps, and min. charge rate of 129 amps.
Min. Generator size is 129amps*48v = 6.2kW @80% load = 7.7k round up to 8k generator
min. solar array is 129amps * 48v = 6.2kWh
Max draw is 161amps =>7.7kW
Solar array is at 150 degree angle, due to shading and pvwatts says
Month | 6.9k DC array Output (kWh) | per 30 days kWh |
Jan | 488.0 | 16.3 |
Feb | 658.9 | 22.0 |
Mar | 871.4 | 29.0 |
Apr | 1017.0 | 33.9 |
May | 1085.9 | 36.2 |
Jun | 1054.5 | 35.1 |
Jul | 1117.8 | 37.3 |
Aug | 1146.7 | 38.2 |
Sep | 1077.5 | 35.9 |
Oct | 936.6 | 31.2 |
Nov | 603.9 | 20.1 |
Dec | 471.7 | 15.7 |
Existing system
Solar Array: 2.5kW panels
Inverter/Charger: Magnum MS4448PAE
Batteries: 48v 370ah and 7 years old.
Generator: Champion DuelFuel 7k continuous
Proposed System
1x Schneider Electric Conext XW+ inverter rated at 6800watts
2x Midnite Classic 150
12x 4v Trojan 1685AH batteries
1x top of pole mounts holding 15 60cell panels
15x 295watt mono Solarworld panels (input needed)
12x 205watt poly panels (existing panels)
8k Diesel or LP liquid cooled low rpm generator
1x residential fridge is in the daily load calc (The main fridge, not willing to compromise to propane)
1x 48v Sunfrost RF18 is in the daily load calc (may not happen, but including in loads)
Once I pin down the proposed system, I will then be trying to figure out the best order to do things. The generator brand doesn't instill confidence and the batteries are on their last legs. I don't dare get an expensive set of batteries without a large enough inverter/charger to maintain them. The existing Magnum invertor could charge them, but not avoid stratification.
Proposed order of purchase / install
1. Generator 8k
2. Solar Panels -> upgrade existing system to 4.4kW with the new panels
3. Forklift upgrade the Inverter and chargers / Upgrade to full 11.4kW
?? Batteries
Batteries should be replaced soon, so possibly step 1.5 if I can survive 6-12 months with the existing charger and not kill them. Otherwise step 4 and I hope I can avoid buying a temp cheap set of batteries in the meantime. Possibly a lot of generator time, which is cheaper than a cheap set of batteries
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