hclarkx
New Member
I've assembled a spreadsheet to size my RV solar/battery system. I didn't find anything like it on the internet so did the DIY thing.
I'm now on my second system upgrade planned using this spreadsheet. I don't like running my generator so used the spreadsheet to size my battery and solar array to eliminate generator run events where and when I camp. It has worked well as I've come close to needing the generator (inclement weather) and have seen my battery hit 20%, but so far the generator has not run in several years. My current upgrade covers a mini split A/C.
While the spreadsheet is designed for RVing, it should work fine for residential off-grid or cabin situations. Maybe marine as well.
Currently the spreadsheet is in Excel but users I've shared it with have used other spreadsheet programs that can import a *.XLSM Excel file, including Google Sheets.
There is no charge. The spreadsheet is in the public domain.
I am not able to make the spreadsheet file available via DIYSolarForum.com because it is a *.XLSM file which is not supported. So, for now, if you would like a copy, PM your email address to me and I'll send it to you.
Overview .......
Extensive documentation (yes, I have a writing problem)
A day/night load calculation worksheet (you can enter totals directly)
Paste-in of representative yearly hourly solar data from PVWatts
Simulation of day to day evening and morning battery SOC
Supports two mini-split or heatpump A/C units and electric fridge
Designed for LiFePo4 batteries (user can approximate AGM with some effort)
Results include ......
Evening generator run events (solar and/or battery falls short)
Daytime generator run events (solar and/or battery falls very short)
Generator Ah use at each generator run event
Evening battery SOC (sundown)
Morning battery SOC
Data Required ...... (enter for each month)
Day and night load data by season (summer & winter)
Refrigerator energy use at 70F (amps and duty cycle) (12V or Residential)
Space heater amps and duty cycle
A/C 1 rated Watts plus day and night duty cycle
A/C 2 rated Watts plus day and night duty cycle
Minimum battery morning SOC in percent
What-if analysis ........
Enter PVWatts for a location
Enter trial battery and solar array sizes
See annual generator run events
Adjust battery and solar array sizes for tolerable generator run events
The main focus of the spreadsheet is to size the battery and solar array for the number of generator run events you can tolerate. If you see more generator run events in the months and locations you will camp or be at your cabin, you will need more battery (mostly) and possibly more solar (second order effect). If you can tolerate more generator run events, you can reduce system size. Once you are close, you can look at the trade-off between battery and solar capacities. Costs suggest more solar and less battery, though there are definite constraints on minimum battery size.
Future Upgrades: ... The solar data that comes from PVWatts includes hourly temperature. At some point in time I expect to adjust A/C duty cycle based on temperature.
I'm now on my second system upgrade planned using this spreadsheet. I don't like running my generator so used the spreadsheet to size my battery and solar array to eliminate generator run events where and when I camp. It has worked well as I've come close to needing the generator (inclement weather) and have seen my battery hit 20%, but so far the generator has not run in several years. My current upgrade covers a mini split A/C.
While the spreadsheet is designed for RVing, it should work fine for residential off-grid or cabin situations. Maybe marine as well.
Currently the spreadsheet is in Excel but users I've shared it with have used other spreadsheet programs that can import a *.XLSM Excel file, including Google Sheets.
There is no charge. The spreadsheet is in the public domain.
I am not able to make the spreadsheet file available via DIYSolarForum.com because it is a *.XLSM file which is not supported. So, for now, if you would like a copy, PM your email address to me and I'll send it to you.
Overview .......
Extensive documentation (yes, I have a writing problem)
A day/night load calculation worksheet (you can enter totals directly)
Paste-in of representative yearly hourly solar data from PVWatts
Simulation of day to day evening and morning battery SOC
Supports two mini-split or heatpump A/C units and electric fridge
Designed for LiFePo4 batteries (user can approximate AGM with some effort)
Results include ......
Evening generator run events (solar and/or battery falls short)
Daytime generator run events (solar and/or battery falls very short)
Generator Ah use at each generator run event
Evening battery SOC (sundown)
Morning battery SOC
Data Required ...... (enter for each month)
Day and night load data by season (summer & winter)
Refrigerator energy use at 70F (amps and duty cycle) (12V or Residential)
Space heater amps and duty cycle
A/C 1 rated Watts plus day and night duty cycle
A/C 2 rated Watts plus day and night duty cycle
Minimum battery morning SOC in percent
What-if analysis ........
Enter PVWatts for a location
Enter trial battery and solar array sizes
See annual generator run events
Adjust battery and solar array sizes for tolerable generator run events
The main focus of the spreadsheet is to size the battery and solar array for the number of generator run events you can tolerate. If you see more generator run events in the months and locations you will camp or be at your cabin, you will need more battery (mostly) and possibly more solar (second order effect). If you can tolerate more generator run events, you can reduce system size. Once you are close, you can look at the trade-off between battery and solar capacities. Costs suggest more solar and less battery, though there are definite constraints on minimum battery size.
Future Upgrades: ... The solar data that comes from PVWatts includes hourly temperature. At some point in time I expect to adjust A/C duty cycle based on temperature.