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Old 05-11-2018, 01:47 PM   #1
Mini-Skoolie
 
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Help! Solar electrical system

So I haven't posted in a while, we're in the middle of our conversion. Almost done insulating, so now is the time to set up the electrical system. And I have no idea what I'm doing. Here's what I researched and wrote down, could anyone look over it to tell me if I'm on the right path?

System size:
Trying to calculate how much power we need.
  • 2 USB charged Phones / 5W
  • 2 Laptops / 60W
  • Dometic fridge / 100W
  • Roof Fan / 32W
  • Wifi Hotspot

    Stuff that runs occasionaly
  • Blender / 1380W
  • Hair dryer
  • USB charged camera
  • USB charged speakers
  • USB charged Bike lights
  • USB charged power bank for phones

Looking at these Renogy Solar panel kits, unsure if 300W, 400W or 500W.


Looking at Batteries, Walmart has deep cycle batteries with up to 235 Amp hours. How much do I need?

Do I need a 12V or 110V, I think some devices will require one, some the other. How do I solve this?

Thanks!!
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Old 05-11-2018, 01:57 PM   #2
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How about water pump, TV, microwave, coffee maker, smoke detector, CO2 detector, etc...

The next step is to add a time component. How long does each of those items operate each day? From that, you can determine amp-hours (or watt-hours) needed. Longer description here: Energy Audit - Watt For? - JdFinley.com

Assuming you are not connected to shore power. You can generate 110VAC power using an inverter (uses stored energy from the batteries) or a generator.
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Old 05-11-2018, 02:24 PM   #3
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Quote:
Originally Posted by JDOnTheGo View Post
How about water pump, TV, microwave, coffee maker, smoke detector, CO2 detector, etc...

The next step is to add a time component. How long does each of those items operate each day? From that, you can determine amp-hours (or watt-hours) needed. Longer description here: Energy Audit - Watt For? - JdFinley.com

Assuming you are not connected to shore power. You can generate 110VAC power using an inverter (uses stored energy from the batteries) or a generator.
Foot water pump, no TV, no microwave, coffee on gas stove, smoke and CO2 detector on batteries.

fan running during the day, fridge all the time. phone, laptops etc when charging.
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Old 05-11-2018, 03:47 PM   #4
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Super interested to see if you get any answers to this thread because it sound like we have very similar solar needs. We're looking into having a foot pump water system as well to save water and electricity and your other electric needs or lack of them are pretty close to yours. Ive looked into a 300 water solar panel from northern arizona wind and sun. Trying to decide to if it would be worth it to put a second one on there
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Old 05-11-2018, 04:29 PM   #5
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I am also interested in the results. sub'd for future...
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Old 05-11-2018, 04:44 PM   #6
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You really should still do the energy audit. It will "quantify" your "quality" answers, as no one can really design to "qualities" (I'm an engineer and get asked to "oh, can you make this a little 'fancier', please?" all the bleeping time - what does 'fancy' mean to you, and now what does it mean to the customer? yep - not the same thing...).

In other words, it will force you to think not only about the items you are running, but for how long each will be running. It will put numbers to your desires - numbers that can be acted on and designed for. Without those numbers (even if they are rough estimates) you cannot design anything as you don't know what your goals are.

Furthermore, how long you can live as you please without the grid does factor in to how satisfied you are with your build long-term. However, only you can decide how important that is to you....
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Old 05-11-2018, 08:39 PM   #7
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What I have not found yet is what is panel output in less then optimal conditions, like a cloudy day. Or low sun angle?

So let's look at my fridge. It takes according to the manufacturer 75 watts when running. If in a 70 degree room it runs 30 % of tbe time. So in 24 hours that is 8 hours run time at 75 watts. 600 watts then for a day. Great 8 hours of optimal sun with a 75 watt panel would do. Well no margin for error or even opening the door. Now what if cloudy? The panel still has some output. But how much? This info I have not found yet.

The above asumes a battery would store the excess during the day and give back at night. Again no loss of power taken into account


I see lights are not included in the list from the original post. I changed to all led 12 volt bulbs and with all lights on I am using 60 watts. Of all would be on all the time.
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Old 05-12-2018, 12:28 AM   #8
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Thank you all! I did the energy audit and read the link posted above. Mine looks like this:

Dometic Fridge: 0,75kwh/24h = 750W/24h
iPhone 5W/h x 3h daily = 15W/24h
Sony Phone 5W/h x 3h daily = 15W/24h
Hotspot = ?
LED Lights 8,5W/h x 5h daily = 42,5W/24h x 3 lights = 127,5W/24h
Maxxfan 31,2W/h x 12h daily = 378W/24h
USB stuff 5W x 3h daily = 15W/24h
= 1300,5W/24h

Also included the Lights, I had completely forgotten about those. Using the math suggested in the link, going by a 5h day of solar power, I would need a 300W system to generate 1500W of power per 5h day. Guessing I might be off in the audit, a 400W system should do, considering we're in California where it gets a lot more than 5h of sunshine per day.

The only questions I have left are:
  • How big of a battery bank do I want and/or need?
  • Can I run every 12V device off 12V and just add an inverter between the battery bank and a few 110V outlets for devices that need 110V?
  • Can anyone point me towards good installation guides to set it all up?
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Old 05-12-2018, 06:04 AM   #9
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I plan on 4 batteries. Because my battery box holds 4. I also know from practical experience that 2 batteries is just not enough if to many cloudy days. My load is about the same as yours, but add water pump. Fridge is 120 volt and using inverter, so adding a little bit for that as well.

I have used Renogy panels and charge controller on several boats with good success, so plan on the same for the bus. 4, 100 watt panels with there charge controller. I have 6 gauge wire to the batteries to the 12 volt fuse panel. 8 Guage to the charge controller from the fuse panel. Everything is set up and working however I just have a few HF panels bungee corded on for now. Will change them when ready to start using the bus sometime this summer.

I have multiple 12 volt outlets around the bus, and 120 volt as well plus 2 rooftop ac. Right now that only works from shore power.
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Old 05-12-2018, 06:06 AM   #10
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Oh another point to make, I am by no means an expert on solar, just making my through it like you.
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