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Old 12-16-2020, 08:00 PM   #1
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Electrical Load Calculator

So I put together a electrical load calculator in google sheets, I have some preset loads already installed, that can be chosen or you can add your own.

Expo-Technology Electrical Load Calculator



The actual loads are stored in their own sheets, which contain a index number, load and input for watts (120 Volt) and Amps (12 Volt). You can add directly at the sheet level if you like.





So you can the choose the load for your daily use, pick the load and the amps will populate for you. You can then choose how many hours or mins the load is used for a day. For the items that are on 24 hours, but have a duty cycle like a fridge you can use the hours to get the correct daily load. 50/50 duty cycle would mean the 12 hours can be used to calculate the daily power.

There is a area to add a load, it uses a script so you would need to be logged into google for it top work.



The layout is similar for 120 volt loads, I use watts for the major input, and the amps are calculated. There are a couple of inputs for using an inverter. You need to put in your inverter efficiency (usually 85% to 95%), also put the amperage in for your inverters search mode(power saving mode), or inverting mode. If you are leaving you inverter on in one of these modes all day or partially during the day, you can add in the hours for that. If you just turn the inverter on when using it, then this won't be needed.



Most of the data is used on the misc sheet, here we add the two load inputs to get your daily electrical load. If you want a battery large enough to cover multiple days you can change the days with out charge section. This input when used to calculate the size of the battery.

We take the daily electrical load to also try and calculate the needed solar panel bank. For this I use 4 watts for each amp used a day. If you want a slightly more accurate input based on time of year, you can go on to the solar calculator.



The daily electrical load is passed directly into the sheet, you will need to change the state data , and size of your solar panel. The calculated size is not input directly from the previous sheet.

Note¹ I did put in CPAP machine power rates I found on a web page, they do not include the optional heater and humidifier.
Note² To use the add new load buttons, you will need to be logged into a google account. Other than that you should have access to the rest of the spreadsheet.


As always, any input, questions, requests are encouraged.

-greg
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Old 12-16-2020, 11:41 PM   #2
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Wow... another great addition to our community's knowledge base. Thanks for sharing all the work Greg!
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Old 12-17-2020, 08:33 AM   #3
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This is awesome! Thanks!
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Old 12-17-2020, 11:00 PM   #4
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That is an impressive piece of work. Thank you for all the time and research you put into it.
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Old 12-18-2020, 01:42 PM   #5
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Dang! This is nuts. Thanks a ton!
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Old 12-19-2020, 08:19 AM   #6
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Good work. I shared a link to this on Winnieowners.com and IRV2.com.
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Old 12-19-2020, 10:36 AM   #7
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Quote:
Originally Posted by BCam View Post
Good work. I shared a link to this on Winnieowners.com and IRV2.com.
I have no problem with that. I probably won't be checking for feedback on those forums, so feel free to bring any back here if you do see something of interest.

To that point I did just check and there was some feedback from DavidM on the winnieowners.com site

Quote:
That calculator is fine as far as it goes, but it is solely based on your estimate of how long you run the appliance each day, the DC fridge being the biggest guess.

If I were to embark on a major DC upgrade (Li, solar, etc) costing thousands of dollars, I would first install a shunt based battery monitor such as those made by Renogy or Victron (about $100) and use it to capture real amp hour usage over a couple of days camping. Then install you DC upgrade and watch how it performs using the battery monitor.

I don't really disagree with that feedback, but for many users they are doing their first electrical design and need a place to start. By all means data collected from real camping would generally be better. So I would be in no argument with that. Figuring out the run time of things can be difficult, I did think of a more complex way for things like a fridge, the reality using hours in the day is just easier. If you are not sure were to start with that I would go 50% or 12 hours, maybe 8 hours in the winter and 16 hors in the summer.

My basic philosophy in developing and using this was to cover a lot of question I get about their systems, especially as they move into the winter months or change locations and think something is wrong with there system. I much prefer to run an analysis on paper, instead charging someone to check all there wire connections for correct torque, undersized wires, and such, just to find out their using more power than expected and producing less.

Many times there is nothing wrong with their systems other than the basic math they put into developing it. Especially if they are reliant on solar, which the output will and does changes as you move thru the seasons and your location.

The added feature of my calculator was to add the feature of the solar insolation tables to help you understand what you could expect your proposed solar setup is going to provide based on the month of the year and location. This doesn't even take into account that you may camp in the shade or have snow on the panels.

So the expectation of the tool should be level set, it is only as good as the data input. Considering how long California, I could have legitimately divided it into north and south.

The engineer in me will use this for planning, and I will also use a battery monitor to check the accuracy of the projection, and update them as I go along. More importantly if I plan to add a new load, I will have some insight into what the effect of that new load on my system.

-greg
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Old 12-19-2020, 11:26 AM   #8
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I'll keep you posted.

I felt the same about his comment. Even with a shunt-based monitor, it's going to be an estimate based on a two or three day sample since every day and every trip will be different. The best approach would be to analyze meter readings are over the course of a typical camping season. Even then, who's to say what's typical.

After all, this isn't a moonshot, close is good enough. And, consider all the estimates that went into designing things for the first trip to the moon.
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Old 12-19-2020, 03:52 PM   #9
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Very cool! Thanks!
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