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Old 08-09-2017, 06:41 AM   #1
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Running AC off grid ??

What kind of AC and how big is my battery bank/solar panels to run AC for at least 3 hours?
Thank you so much.
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Old 08-09-2017, 07:36 AM   #2
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Trying to finalize my power needs for my family's upcoming build and I, too, am heavily interested in this topic. Spent all day yesterday trying to learn what I don't know. Only ended up more dazed and confused... xD

So yeah, if anyone has some great resources, please do share!
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Old 08-09-2017, 07:39 AM   #3
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How much AC is needed?

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Old 08-09-2017, 07:42 AM   #4
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Minimum AC wattage consumption available. Is it the mini split?
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Old 08-09-2017, 07:44 AM   #5
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Square feet to be cooled?

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Old 08-09-2017, 08:05 AM   #6
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Originally Posted by Tootalltechie View Post
Square feet to be cooled?

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Air conditioning but calculator
BTU Calculator
For me, it's about 200sqft, if that. We need the setup to run the AC for 3-5 hours midday two or three times a week, but still last about 7 hours overnight throughout the week. I'm looking at about 2000w of solar on the roof and I live in Florida, so plenty of sun... xD

Not sure if this is enough information to work with, so sorry if that's the case!
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Old 08-09-2017, 08:08 AM   #7
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Originally Posted by willvalenton View Post
Minimum AC wattage consumption available. Is it the mini split?
Hmm... I don't think so. I'm looking up some of the lower end mini splits now and I think that's higher than a window unit we're looking at. I'll get the information and let you know!
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Old 08-09-2017, 08:16 AM   #8
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Originally Posted by willvalenton View Post
Minimum AC wattage consumption available. Is it the mini split?
Here ya go. Pretty close between the two, actually.

https://www.amazon.com/Pioneer-Air-C...plit%2Bac&th=1

That unit pulls about 782w (292 to 1087 min/max).

The window unit I was looking at is this:

https://www.amazon.com/Frigidaire-FG...ir+conditioner

This unit pulls about 665w.
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Old 08-09-2017, 08:57 AM   #9
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Quote:
Originally Posted by Tropf View Post
For me, it's about 200sqft, if that. We need the setup to run the AC for 3-5 hours midday two or three times a week, but still last about 7 hours overnight throughout the week. I'm looking at about 2000w of solar on the roof and I live in Florida, so plenty of sun... xD

Not sure if this is enough information to work with, so sorry if that's the case!
That would be my guess too.
2000 watt divided by 12 volt equals about 170 amp hour. 170 x 3 hrs = 510 amp hour of run time. You don't want your battery bank to run down to 50% so multiply the 510 by 3 you get a battery bank of 1500+ amp hour.

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EDIT
I think that it would give you a run time of about 4 hrs. If you were using a 1800 watt AC unit at full blast.
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Old 08-09-2017, 09:03 AM   #10
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That would be my guess too.
2000 watt divided by 12 volt equals about 170 amp hour. 170 x 3 hrs = 510 amp hour of run time. You don't want your battery bank to run down to 50% so multiply the 510 by 3 you get a battery bank of 1500+ amp hour.

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Hah. I knew I was leaving something important out. I'm debating a 24v or 48v system because there's two of us, we own an educational video game company so technology is always prevalent, and we're going to have our two shepherds with us.

The other piece of information I left out is I'm looking at using lithium phosphate batteries. I assume I can still follow your formula, just swap voltage based on the system I decide on and account for the additional utilization of the lithium?

EDIT: I put this information in another post, but it's being reviewed by mods I guess... I intend on using a frigidaire window unit that uses around 665w when cooling.
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Old 08-09-2017, 09:05 AM   #11
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Originally Posted by Tootalltechie View Post
Square feet to be cooled?

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BTU Calculator
I tried to make a post with links and information regarding a split unit vs the window unit I intend on buying, but I got a message about mods looking at it or something... I compared a 8000 btu Window Unit to a 9000 but mini split and the window unit came out about 100 and change less wattage.

Anyways, hopefully it pops up soon. xD
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Old 08-09-2017, 09:08 AM   #12
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Quote:
Originally Posted by Tropf View Post
I tried to make a post with links and information regarding a split unit vs the window unit I intend on buying, but I got a message about mods looking at it or something... I compared a 8000 btu Window Unit to a 9000 but mini split and the window unit came out about 100 and change less wattage.

Anyways, hopefully it pops up soon. xD
I just copy and paste the link. The mobile Tapatalk app I think does the rest.

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Old 08-09-2017, 09:11 AM   #13
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unfortunately this needs to be addressed during the early stages of a build with superinsulation so you can run a smaller one for less time. 2 types of heat transfer going on here convection from the sun going thru what poor insulation they originally put in and conduction thru the metal as metal brings it in so if you foam it still follows the metal in i considered adding 3-4 inches to the outside of my roof and fiberglassing over it but opted on a 20" roof raise and using 5-6 on the inside got a portable ac so after insulation is done ill run it and see what b t u s i need i want to run off a battery bank using solar also.
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Old 08-09-2017, 09:14 AM   #14
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Quote:
Originally Posted by Tropf View Post
Hah. I knew I was leaving something important out. I'm debating a 24v or 48v system because there's two of us, we own an educational video game company so technology is always prevalent, and we're going to have our two shepherds with us.

The other piece of information I left out is I'm looking at using lithium phosphate batteries. I assume I can still follow your formula, just swap voltage based on the system I decide on and account for the additional utilization of the lithium?

EDIT: I put this information in another post, but it's being reviewed by mods I guess... I intend on using a frigidaire window unit that uses around 665w when cooling.
If I'm correct your batteries will be 12 volt either way. The charge voltage will be stepped down by your charge controller.
I was trying to point out that your battery bank will need to be huge to run AC for just a short time.

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Old 08-09-2017, 09:14 AM   #15
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Originally Posted by mmoore6856 View Post
unfortunately this needs to be addressed during the early stages of a build with superinsulation so you can run a smaller one for less time. 2 types of heat transfer going on here convection from the sun going thru what poor insulation they originally put in and conduction thru the metal as metal brings it in so if you foam it still follows the metal in i considered adding 3-4 inches to the outside of my roof and fiberglassing over it but opted on a 20" roof raise and using 5-6 on the inside got a portable ac so after insulation is done ill run it and see what b t u s i need i want to run off a battery bank using solar also.
Totally agree

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Old 08-09-2017, 09:19 AM   #16
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If I'm correct your batteries will be 12 volt either way. The charge voltage will be stepped down by your charge controller.
I was trying to point out that your battery bank will need to be huge to run AC for just a short time.

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Well, I'm going to be honest...I really don't know anything about any of this... xD

I was looking at these SIMPLIPHI batteries and they offer them in 12, 24, and 48v variants. My understanding is that to run, say a 24v system, I would need a 24v inverter,batteries would have to be working at 24v, and the panels would have to be operating around 36v... for reasons completely unknown to me...

But yeah, I've been coming to same conclusion. My target goal is to get about 1000ah bank going, but then I need to figure out what the solar requirement to keep it going is. Math and science are hard...
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Old 08-09-2017, 09:20 AM   #17
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im also working up a plan to have a metal frame slide out from under my solar panels with more solar panels to double my power and give shade also (also a 10' roll up on the end of it)
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Old 08-09-2017, 09:21 AM   #18
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Originally Posted by mmoore6856 View Post
unfortunately this needs to be addressed during the early stages of a build with superinsulation so you can run a smaller one for less time. 2 types of heat transfer going on here convection from the sun going thru what poor insulation they originally put in and conduction thru the metal as metal brings it in so if you foam it still follows the metal in i considered adding 3-4 inches to the outside of my roof and fiberglassing over it but opted on a 20" roof raise and using 5-6 on the inside got a portable ac so after insulation is done ill run it and see what b t u s i need i want to run off a battery bank using solar also.
Haven't even bought a bus yet, so the planning is definitely happening upfront... xD

One question I was curious about...please tell me if I should quit trying to use my brain and just go to someone who knows better, but... rather than insulating the inside and losing headroom, I was curious if insulating the outside of the roof was a feasible option.

It sounds like you're saying it is, but only if I create a fiberglass housing for it externally?
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Old 08-09-2017, 09:22 AM   #19
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im also working up a plan to have a metal frame slide out from under my solar panels with more solar panels to double my power and give shade also (also a 10' roll up on the end of it)
My God.... you figure that out, and I'm gonna need the rundown on the achievement...I love it!
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Old 08-09-2017, 09:30 AM   #20
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something like a big drawer slide but must be secured good while moving to keep it from rattling hat will be stage 2 ork added after im living in it also google recycling shower systems i designed a system to filter (particulate,chemical and biological) using a 10 gal self contained system man was i proud then.......found out they are commercially available and common on boats and in europe
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