Reply
 
Thread Tools Display Modes
 
Old 03-28-2017, 11:41 AM   #1
New Member
 
Join Date: Mar 2017
Posts: 2
Confused on air conditioning.

Hello everybody, I've been lurking here for awhile learning what I can. I have been planning on building a skoolie for a couple of years now, and now that I am going to retire in the next year or 2 I'm about to start getting serious and start buying what I need. Me and my wife have been thinking about what we wanted, and we have figured that we are most interested in boondocking and being very independent. Now we are happy with the smaller space, but we are not willing to give up our creature comforts. For us that means AC among other things. So I have been looking for info on running an AC on solar power, but it seems that the general consensus is that it's not possible/not worth it on a schoolie or rv. Now I'm planning on designing around my planned electrical loads, and I'm earmarking up to $7000 on the power system, tho hopefully it won't run that much.

So here is my idea so far. I want to use household appliances on a 115v system, I don't see much or any need for dc appliances. My plan is a 48v system based on 8 6v batteries(leaning towards the t105 re's atm) and an inverter feeding a 115v power panel that has the place set up like a traditional house. I plan on at least 1000w of panels or more if needed. I do plan on having a small generator, but I want it more as a emergency backup and not something I have to use very often. I have in my house a small 5000btu window ac that says it uses 550 watts. It keeps my livingroom, kitchen and hall area fairly cool here in west TN. So I'm thinking that will probably be enough to keep us reasonably cool when we get caught in hot weather.

Now if I have 8 t105's I'm looking at about 900 amp hours at 50% of my battery capacity. Figure 10% resistance and inverter loss gives me about 800 amp hours. My ac(or one like it) would be pulling say, 600 watts. So 600/48=12.5, and I believe the numbers they give you is 100% duty cycle. So if I understand right, the most it would draw in a day, running full blast is 300 amp hours from my batteries. But that seems awful low for everybody to be saying that AC on solar is just not practical, so I feel like I'm missing something. Could somebody please tell me if I'm all messed up on figuring out how this works.

Thanks in advance for any help.
Anzid is offline   Reply With Quote
Old 03-28-2017, 11:57 AM   #2
Almost There
 
Join Date: Jan 2016
Location: Tepme AZ
Posts: 97
Year: 1976
Coachwork: Crown
Engine: Detroit Diesel 6-71
Rated Cap: 52 pax
Quote:
Originally Posted by Anzid View Post
Hello everybody, I've been lurking here for awhile learning what I can. I have been planning on building a skoolie for a couple of years now, and now that I am going to retire in the next year or 2 I'm about to start getting serious and start buying what I need. Me and my wife have been thinking about what we wanted, and we have figured that we are most interested in boondocking and being very independent. Now we are happy with the smaller space, but we are not willing to give up our creature comforts. For us that means AC among other things. So I have been looking for info on running an AC on solar power, but it seems that the general consensus is that it's not possible/not worth it on a schoolie or rv. Now I'm planning on designing around my planned electrical loads, and I'm earmarking up to $7000 on the power system, tho hopefully it won't run that much.

So here is my idea so far. I want to use household appliances on a 115v system, I don't see much or any need for dc appliances. My plan is a 48v system based on 8 6v batteries(leaning towards the t105 re's atm) and an inverter feeding a 115v power panel that has the place set up like a traditional house. I plan on at least 1000w of panels or more if needed. I do plan on having a small generator, but I want it more as a emergency backup and not something I have to use very often. I have in my house a small 5000btu window ac that says it uses 550 watts. It keeps my livingroom, kitchen and hall area fairly cool here in west TN. So I'm thinking that will probably be enough to keep us reasonably cool when we get caught in hot weather.

Now if I have 8 t105's I'm looking at about 900 amp hours at 50% of my battery capacity. Figure 10% resistance and inverter loss gives me about 800 amp hours. My ac(or one like it) would be pulling say, 600 watts. So 600/48=12.5, and I believe the numbers they give you is 100% duty cycle. So if I understand right, the most it would draw in a day, running full blast is 300 amp hours from my batteries. But that seems awful low for everybody to be saying that AC on solar is just not practical, so I feel like I'm missing something. Could somebody please tell me if I'm all messed up on figuring out how this works.

Thanks in advance for any help.
I too will be using a 48 volt system. as you have calculated, the higher the voltage of the system the more storage you get out of the same batteries. To be honest, I know nothing of solar design and have a solar guru designing my system. He has designed off grid systems for my cabins and a solar well pump with battery backup for my dads ranch. He explained it all really well but was using all these big works and calculations with big numbers and he was talking fast.... I understood little but he's the pro. I'm interested in following this thread to see how you build yours.
__________________
-Chevy
Chevydude01 is offline   Reply With Quote
Old 03-28-2017, 12:37 PM   #3
Bus Geek
 
Join Date: May 2016
Location: Eastern WA
Posts: 6,363
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
Quote:
Originally Posted by Anzid View Post
Hello everybody, I've been lurking here for awhile learning what I can. I have been planning on building a skoolie for a couple of years now, and now that I am going to retire in the next year or 2 I'm about to start getting serious and start buying what I need. Me and my wife have been thinking about what we wanted, and we have figured that we are most interested in boondocking and being very independent. Now we are happy with the smaller space, but we are not willing to give up our creature comforts. For us that means AC among other things. So I have been looking for info on running an AC on solar power, but it seems that the general consensus is that it's not possible/not worth it on a schoolie or rv. Now I'm planning on designing around my planned electrical loads, and I'm earmarking up to $7000 on the power system, tho hopefully it won't run that much.

So here is my idea so far. I want to use household appliances on a 115v system, I don't see much or any need for dc appliances. My plan is a 48v system based on 8 6v batteries(leaning towards the t105 re's atm) and an inverter feeding a 115v power panel that has the place set up like a traditional house. I plan on at least 1000w of panels or more if needed. I do plan on having a small generator, but I want it more as a emergency backup and not something I have to use very often. I have in my house a small 5000btu window ac that says it uses 550 watts. It keeps my livingroom, kitchen and hall area fairly cool here in west TN. So I'm thinking that will probably be enough to keep us reasonably cool when we get caught in hot weather.

Now if I have 8 t105's I'm looking at about 900 amp hours at 50% of my battery capacity. Figure 10% resistance and inverter loss gives me about 800 amp hours. My ac(or one like it) would be pulling say, 600 watts. So 600/48=12.5, and I believe the numbers they give you is 100% duty cycle. So if I understand right, the most it would draw in a day, running full blast is 300 amp hours from my batteries. But that seems awful low for everybody to be saying that AC on solar is just not practical, so I feel like I'm missing something. Could somebody please tell me if I'm all messed up on figuring out how this works.

Thanks in advance for any help.
The T-105 is rated at (20hr reate) 225AH. So, 8 T-105's in series will yield a 48 volt 225AH bank. Assuming a max 50% discharge you would have 112AH @ 48v available.

If you connected 8 T-105's in parallel then you would have a 6 volt 1800AH bank.

Series=Add voltage of each battery. AH rating stays the same.
Parallel=Add AH rating of each battery. Voltage stays the same.

To get 48v @ 1800AH you would need 8 series strings of 8 T-105's connected in paralell. 64 T-105's... That is A LOT of batteries...

I would suggest that you start with the AC and an https://www.amazon.com/P3-P4400-Elec...ds=kill+a+watt .

Run the AC for a few days in conditions that approximate what you expect to see when traveling and see how much power the AC REALLY uses in a day. Then size your solar & battery bank accordingly.

for most of us, running AC from batteries is not practical because of the size of battery bank required.

I did see one AC install that they called "hybrid". They had a solar install big enough to run the AC on its own when the sun was shining strong and a smaller battery bank to "buffer" during the occasional cloudy spot. The AC was a 12 volt mini-split and only 6k btu.
PNW_Steve is offline   Reply With Quote
Old 03-28-2017, 02:38 PM   #4
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,628
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
For your use model it might be worth considering LiFePo (lithium, but this is not the same as Li-Ion) chemistry instead. It endures much lower depth of discharge, faster recharge, and may yield more cycles aka longer lifetime than the lead batteries would. It's worth investigating.

The adequacy of a 5000 BTU air conditioner is suspect. Factory insulation and air sealing in a bus are terrible in comparison to a conventional home. To achieve the temperature control you're accustomed to through an entire bus you'll need much more than a 5000 BTU air conditioner or to substantially improve the insulation and air sealing.
family wagon is offline   Reply With Quote
Old 03-28-2017, 03:04 PM   #5
Skoolie
 
bubb, the real one's Avatar
 
Join Date: Dec 2014
Location: central texas
Posts: 149
Year: 1990
Coachwork: Thomas/International
Chassis: 3700
Engine: 7.3
Rated Cap: 72
the issue is AC vs DC, your 5000btu unit probably pulls 4.5 amps AC but,
1 amp AC equals about 10 amps DC, which means the unit will pull around 45amps DC to run,
Lets not even talk about electric motors LRA on startup,
__________________
my bus thread, https://www.skoolie.net/forums/showthread.php?t=8860&highlight=bubb
bubb, the real one is offline   Reply With Quote
Old 03-28-2017, 03:06 PM   #6
Bus Geek
 
brokedown's Avatar
 
Join Date: Dec 2016
Location: Weeki Wachee, FL
Posts: 3,028
Year: 1997
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: Cummins 5.9
Rated Cap: 72
Running air conditioning from solar is pretty unreasonable. Your entire build will end up being designed to support it, at the expense of other features. Look into generators or engine driven solutions. Electricity is terrible for heating or cooling.
__________________
Keep up with us and our build!
Follow us on Facebook, Instagram, YouTube, and Twitter
brokedown is offline   Reply With Quote
Old 03-31-2017, 04:25 AM   #7
New Member
 
Join Date: Mar 2017
Posts: 2
Thanks PNW_Steve, that was the mistake I was making. I was thinking the amount of battery power my math was getting me looked too good, I don't know why I was multiplying amps with voltage. So it looks like ac will be genny or shore power only.
Anzid is offline   Reply With Quote
Old 03-31-2017, 07:02 AM   #8
Bus Nut
 
Phatman's Avatar
 
Join Date: Jan 2015
Location: Brazoria County, Texas
Posts: 552
Year: 1997
Coachwork: Carpenter
Chassis: International
Engine: T444E
Rated Cap: 32 Passenger
As an electrician for the last 42 years, I will tell you electricity is the most inefficient way of doing anything. It's not to say that electricity is not good, sometimes it is the only way. Family Wagon is right though about the 5000btu a/c. GOOD LUCK ANZID
Phatman is offline   Reply With Quote
Old 03-31-2017, 08:34 AM   #9
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 1,721
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford e350 2 mercedes
Engine: 7.3 powerstroke & MBE906
Besides the technical correction PNW and the practical recommendation from family wagon regarding insulation and lithium only more solar will help.
I think the 90% inverter efficiency/ losses are a little optimistic. I would take 85% . That is a real life number from out battery backup solar at our home. the inverters are outback gvfx3648.
Some inverters "without heavy" 60Hz transformers can be more efficient .
Not sure what bus you are looking for but we used to have 600 watt on an ambulance econoline van and ran a 500 btu window unit at 30% duty cycle during the day.

Our current built will support 900 watt of solar and we are set up for 48 volt lithium at 120 Ah from a Nissan Leaf.
Depending on in what climate you are I think it is very well possible to run your AC on solar... and solar is very cheap nowadays. generators, fuel tanks, maintenance, noise... just not from this time anymore.
Check out small split heat pump systems so you can use some of the heat as well.
Later J
joeblack5 is offline   Reply With Quote
Old 03-31-2017, 09:24 AM   #10
Bus Nut
 
dredman's Avatar
 
Join Date: Dec 2014
Location: Birmingham Al
Posts: 600
Year: 2003
Coachwork: Blue Bird
Have you ever thought of simply MOVING towards cooler, dryer weather when things heat up? That has been my strategy for the last 2 years, and I am rarely uncomfortable. Mountains do a hell of a lot for temps, and those wheels come in handy for moving around. Chasing weather sounds extreme, but nowhere near as extreme as trying to cool a school bus with batteries?
__________________
My Skoolie Story on YouTube
dredman is offline   Reply With Quote
Old 04-01-2017, 06:40 PM   #11
Bus Nut
 
Join Date: Mar 2017
Location: iowa
Posts: 426
Year: 1998
Coachwork: bluebird
Chassis: chevy
Engine: 3116 catapillar
Rated Cap: formerly 71 now 2 or 4
first and foremost learn about super insulating im looking to do the same and in process of designing my system as when its hot sunshine is abundant i feel that is is possible and will pursue this however the solar panels will be my last purchase as they are evolving so fast raising my ceiling is a great start also
mmoore6856 is offline   Reply With Quote
Old 04-01-2017, 06:56 PM   #12
Bus Nut
 
Join Date: Mar 2017
Location: Greenwood, Indiana
Posts: 669
Year: 1999
Coachwork: New Flyer
Chassis: D45HF "Viking"
Engine: 11.1L Detroit Diesel S60
Rated Cap: 51,600
A/C Inrush Current

And don't forget that the compressor motor's inrush current draw (i.e. motor startup) is anywhere from 2x-6x it's running current draw. Most inverters can only handle up to 2x its rating in surge before it shuts down to protect itself.

That's generally why A/C isn't battery-driven - the compressor motor kills the batteries/electronics from the inrush. Also, that's why the refrigeration cycle used in most mobile applications (i.e. Dometic's motorhome refrigerators) is different than the refrigeration cycle used in standard home-based refrigerators (and why those blasted mobile refrigerators have to be level to work right).
MarkyDee is offline   Reply With Quote
Old 04-01-2017, 07:39 PM   #13
Bus Geek
 
Join Date: May 2016
Location: Eastern WA
Posts: 6,363
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
Here is an "exception". It is a 12v mini split.
Attached Images
File Type: jpg Catch7576.jpg (98.2 KB, 23 views)
PNW_Steve is offline   Reply With Quote
Old 04-01-2017, 07:56 PM   #14
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 1,721
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford e350 2 mercedes
Engine: 7.3 powerstroke & MBE906
MarkyDee, yes inrush is a problem but modern inverter ( variable speed) based AC systems have a much lower inrush current.
Not sure what you are referring to with mobile refrigeration cycle that need to be level, i assume you mean the Ammonia based systems that are 120VAc, 12VDC and propane, those systems beside he convenience of tri-fuel are very inefficient.
A lot of mobile refrigerant systems use ordinary R134 or similar compression / expansion cycles with help of 12 volt compressors.
A common compressors is BD35F made by Danfoss but there are more .
Regarding inrush on older compressor systems.... a 5000BTU $99 AC inverter that pulls 600 watt and 3600 watt inrush can be supplied by an $300 inverter. Your vehicle starter motor at 12 v and 500 amp is about the same peak load .

Later J
joeblack5 is offline   Reply With Quote
Old 04-01-2017, 08:07 PM   #15
Bus Nut
 
Join Date: Mar 2017
Location: Greenwood, Indiana
Posts: 669
Year: 1999
Coachwork: New Flyer
Chassis: D45HF "Viking"
Engine: 11.1L Detroit Diesel S60
Rated Cap: 51,600
Quote:
Originally Posted by PNW_Steve View Post
Here is an "exception". It is a 12v mini split.
Interesting. I'd hate to see what the surge is for starting the heat pump. Do you have a link for that system?
MarkyDee is offline   Reply With Quote
Old 04-01-2017, 08:44 PM   #16
Bus Nut
 
Join Date: Mar 2017
Location: Greenwood, Indiana
Posts: 669
Year: 1999
Coachwork: New Flyer
Chassis: D45HF "Viking"
Engine: 11.1L Detroit Diesel S60
Rated Cap: 51,600
Quote:
Originally Posted by joeblack5 View Post
MarkyDee, yes inrush is a problem but modern inverter ( variable speed) based AC systems have a much lower inrush current.
Not sure what you are referring to with mobile refrigeration cycle that need to be level, i assume you mean the Ammonia based systems that are 120VAc, 12VDC and propane, those systems beside he convenience of tri-fuel are very inefficient.
A lot of mobile refrigerant systems use ordinary R134 or similar compression / expansion cycles with help of 12 volt compressors.
A common compressors is BD35F made by Danfoss but there are more .
Regarding inrush on older compressor systems.... a 5000BTU $99 AC inverter that pulls 600 watt and 3600 watt inrush can be supplied by an $300 inverter. Your vehicle starter motor at 12 v and 500 amp is about the same peak load .

Later J
Heh, I was talking about the ammonia-based systems. But the last time I dealt with one of those old refrigerators was in a Pace Arrow from the late '80s. Man that thing drove my father and me absolutely bug-nuts crazy trying to get it level so it would cool off.

As for the 12v compressor-based refrigerators, I'd love to see one. Do you have a link to one? I want one for my conversion but I've never been able to find a full-up refrigerator that runs on 12v.

As for inverters, all I've seen have limited surge before shutdown. Also, most cheap inverters are modified-sine and ultimately will destroy AC motors with the additional harmonics. Pure-sine inverters are quite a bit more money. At least, that's been my experience from my electrical engineering/IT/computer perspective.
MarkyDee is offline   Reply With Quote
Old 04-01-2017, 08:57 PM   #17
Bus Geek
 
Robin97396's Avatar
 
Join Date: Feb 2016
Location: Willamina, Oregon
Posts: 6,409
Coachwork: 97 Bluebird TC1000 5.9
https://www.amazon.com/Solar-Powered.../dp/B00K7KAC1K

DC Solar Air Conditioner Heat Pump | Solar Air Conditioning | Solar Heating | Manufacturers

World’s First DC-Powered, Ductless Mini-Split Air Conditioner Unveiled by Solar Panels Plus | Business Wire

https://sunshineworks.com/pages/sola...oner-heat-pump

It sounds like 12 volt systems have been out there for a while.
__________________
Robin
Nobody's Business
Robin97396 is offline   Reply With Quote
Old 04-01-2017, 11:43 PM   #18
Bus Nut
 
Join Date: Mar 2017
Location: Greenwood, Indiana
Posts: 669
Year: 1999
Coachwork: New Flyer
Chassis: D45HF "Viking"
Engine: 11.1L Detroit Diesel S60
Rated Cap: 51,600
Sweet, thank you very much! I'm bookmarking especially that last link for when I finally get started on a conversion....

Its nice to be at least partially wrong on this (no inverter showing in any of the pics - at least external to the system). I've been "sweating" the AC system on my so far hypothetical bus....

I'm betting that if DC HVAC is available that DC refrigerators are, too.
MarkyDee is offline   Reply With Quote
Old 04-02-2017, 06:24 AM   #19
Bus Nut
 
superdave's Avatar
 
Join Date: Mar 2015
Location: hills of sw virginia
Posts: 889
Year: 1996
Chassis: thomas
Engine: 8.3 cummins
Rated Cap: 11 window
that unit requires a 220 volt inverter or 220 volt shore power. the thing I hate the most about this unit, when your not using it your not getting any power from the panels. the compressor uses 10 amps and 4 amps for the outside fan . little bit of cloud cover or in the afternoon and its worthless. AGAIN you will need a big bank of batteries and lots of panels to run ac. remember you need enough panels to run the unit and enough to charge your huge battery bank at the same time. plan on spending 5 or 6 grand for your ac or you could just suck it up!
__________________
living in a bus down by the river.
my build pics
https://www.skoolie.net/forums/membe...albums942.html
superdave is offline   Reply With Quote
Old 04-02-2017, 07:28 AM   #20
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 13,485
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
there are plenty of soft start units that dont require 220 volts... there are mini splits.. there are also fully packaged units that are designed for teardrop campers that can be basement mounted and ducted easily which could be made to run from solar..

I like dred's idea of going to the weather you desire.. I myself do the ooposite as i love summer heat outside but want ot sleep ice cold inside.. However I play reality here and I dont try to cool a bus with batteries.. sure i can cool my bus for a few hours during the day with my 12k BTU inverter A/C .. and with it running low speed it will run close to through the night.. but REALITY says I use an ENGINE to charge up the batteries or run it when I want to really be cool..

when im running the full DEV bus lab I leave the bus idle with 65,000 BTU of A/C blasting ...

you can easily alter the weather inside your bus but it takes energy to do so.. and at what point is being "green" and "off-grid" really those things when you want to have all the creature-comforts of On-Grid living? and at what cost?

why not do a hybrid system... sure set up your solar and your batteries and an efficient 5,000 BTU A/C unit in a well insulated bus will cool you on Many days.. esp if you 'tent' your bus or park it in the shade.. (yes you may need to be able to detach and move your solar panels to the sun while your bus is shaded.. ),,

but for those oppressively hot days you have a fossil fuel alternative.. an ENGINE.. a generator that could run a Bigger A/C unit..

85% of the time you never need to use it.. but those really hot days you crank it up...

keeps you from needing extreme solar and battery packs to find you'd only need them a small portion of the time compared to a reasonable set up..

-Christopher
cadillackid is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 01:44 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×