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Boondocking running AC 24/7 for 2-3 days. Designing a power system!

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 Hi, I thought you boondockers might be able to help.  Is anyone into the tech side of van or RV power system design?  I want to be able to travel with short muzzled dogs in the summer (outdoor temps of 85-100).  If there are no hookups, I need a way for the vehicle to run AC 24/7 for 2-3 days via a generator I assume or ?  I am starting from the ground up and am willing to buy whatever van or rv that will allow the modifications to do this, however I don’t know where to start.  Basically, boondocking with heat sensitive dogs that need to be kept in 70-71 degrees.  Let me know where I would start. Thank you!

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I'm sure someone will give advice in the technical area but I would like to advise you that you need to plan to have the dogs with you all the time - day and night.  You can't rely on any system running without issues when you're gone and have left the dogs alone.  Even getting some kind of monitoring system so you can keep track remotely as to the temperature inside and be within a short driving range to return and deal with the problem.  Good luck!

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iRV2.com also has a strong forum for technical issues on Boondocking.  Hopefully, someone here will be able to give you a start.

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40 minutes ago, lenp said:

Keep in mind that many parks/areas do not allow generator use 24/7.

Lenp

I believe he's talking about boondocking; not campgrounds.  Boondocking you can run a generator all you want but it would be socially prudent to be parked far away from others and from those using quiet solar.

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Let me give you MY personal experience, I'm still rounding up the solar leg of the system, but here is how it will look.

1st if your starting from scratch, I highly recommend a mini split for the a/c. (in fact I used 2 in my build) They are duty cycled units that don't start and stop all the time. When they due start they come on slowly so they don't hammer your inverter. In fact I can run them both on a 15 amp outlet. plus they are SUPER quiet.

2nd batteries. You can buy a 48 volt nissan leaf pack from a seller on ebay that would run a mini split for a few hours.  you would need to match that with a 48 volt inverter (which is the most efficient of the options) and a set of solar cells that will charge the batteries via an mppt charge controller.

3rd if all else fails and it's raining you can get a generator auto start that will fire up the genny when the interior temp reaches your specified temps. this will also trigger the charger side of the inverter and recharge your battery pack.

All of this needs to be accounted for before you start outfitting your van/truck. you should also add closed cell spray foam to the wall and roof cavities. That way it makes the whole package more efficient.

 

Of course the easy way would be a big battery pack and a 12volt evaporative cooler in the van. If you don't mind the dampness.

 

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Generator is going to be your least expensive option.  

A 15k AC takes uses about 150 amps of 12v power to run. 

So to run 1 if you were using solar and batteries it takes a ton.  For each 100w of solar you get about 5 amps of charging at peak so for every 1000 watts you get about 50 amp meaning you would need 3000 watts of solar, at peak to run 1 AC.  If you want to run it over night then you also need enough battery capacity for that,  150 amps x 10 hours means you would need 15,000 AH of batteries, just to run one unit.  Keep in mind, you also need more solar to charge the batterie bank the next day.  

So while this is possible, it is not practical.  While I do have a moderate battery bank, and 960 watts of solar when I need AC the generator get started. 

Edited by Nwcid

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1 hour ago, Nwcid said:

While I do have a moderate battery bank, and 960 watts of solar when I need AC the generator get started. 

So how do you manage the need for a generator when at night or in inclement weather?  I am assuming your generator is NOT auto or remote start.

Are your calculations for AC running consumption including battery storage capacity?  I read of another 5er with 2000W of solar, 8 batteries and run mini split as needed while boondocking without any need for generator, unless multiple days of insufficient sunshine.

I dont have a sufficient solar system in place and am working on moving to a fitting design, so "inquiring minds want to know"

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4 hours ago, rpsinc said:

So how do you manage the need for a generator when at night or in inclement weather?  I am assuming your generator is NOT auto or remote start.

I am not sure what you are asking here. With only parasitic loads I typically have 5 amp draw.  I have just over 300 usable ah (based on the 50% rule).  So with only parasitic loads and no charging that gives me about 60 hours.  During a typically day having TV's on, lights, computer and accessories for work, and basic "living" I draw around 20-25 amps which still would give 12 hours with no charging.  Once the sun is down it is typically only a few lights and 1 TV.  The laptops still are being used, but unplugged.  During this time the typically draw is around 11 amps, which would give me 30 hours with no charging.  I do sleep with CPAP and often with a regular fan set on low.  I have never looked at the amp use during this time.  In the morning my batteries are still usually 12.3 volts. 

4 hours ago, rpsinc said:

Are your calculations for AC running consumption including battery storage capacity?  I read of another 5er with 2000W of solar, 8 batteries and run mini split as needed while boondocking without any need for generator, unless multiple days of insufficient sunshine.

Your first question is not how it is factored.  You need to determine how many amps your load(s) draw.  I will use what is a semi common battery bank which is 4 FLA or AGM 6v deep cycle batteries that give a total of 450 AH with a cost of about $800-900.  With FLA or AGM not drawing below 50% will give the longest life of the battery bank.  This gives you 225 AH of useable power.  If you have an item that draws 10 amps  you can run it for 22.5 hours.  If you have an item that draws 100 amps you have 2.25 hours.  There are some other factors for high draw vs low draw items but I am tying to keep it basic for now.  

Back to the 100 amp load, with a full battery bank.  If your charger, solar or otherwise, puts out 100 amps, you can run continuous with no loss or gain on your batteries.  If your charger only puts out 75 amps, you now have a 25 amp deficit.  Since you had a 225 AH bank you can now run your 100 amp load for 11 hours before your batteries are at 50% because only 25 amps are being drawn from the batteries.  So you have a net loss of power. 

This is where many people get in trouble and if I understand this part of the question right.  If you run your batteries down, you need enough charging capacity to run the load and enough excess power to charge the batteries.  

Now we will do the same math with different numbers.  Let's say your battery bank is at 50% and needs 225 AH to fully charge.  You are still drawing the 100 amps, but your charger is putting out 125 amps.  Now 100 amps are going to run your load, and 25 amps are going to charge the batteries.  Since you need 225 AH it will take 11 hours to fully charge the battiest.  Now you have a net power gain. 

I see the reference to split systems but I do not know what that is and do not have time to look it up right now.  I can talk about the rest though.  With 2000 watts of solar (roughly $3000) they have just over 100 amps of charging at peak performance (only a few hours per day).  You do not say what kind of batteries, but with that kind of solar it is likely lithium which are typically 100 AH per battery.  This gives a total of 800 AH.  With lithium you can draw down to 80% giving a 640 AH of useable power.  Lithium still run almost $1000/battery so that is $8000.  So you can use the math above to see how long they can run.  Also it is very likely they do not run AC 24/7, but I could be wrong.  Also depending on what units they have the draw may vary, each of mine draw about 150 amps. 

 

4 hours ago, rpsinc said:

I dont have a sufficient solar system in place and am working on moving to a fitting design, so "inquiring minds want to know"

Typically I am only drawing down my batteries about 30% on a routine basis overnight.  At peak performance my solar puts out 50 amps of charing.  If I am only drawing 20 amps for living the other 30 amps is going into my batteries which charges them back up during the day.  In the morning we often use the coffee maker, microwave or toaster oven.  Each of these things also draw 150 amps but are only used for short periods. Again the solar makes up for this most of the time.  In the evening if we have not gotten a good charge then when we make dinner we run the generator for about an hour and my inverter has a 125 amp charger.  This allows us to use our cooking items and top off the batteries.  

Overall this is a math problem.  You need to know how much is going out (load(s), how much storage you need (batteries) how much you need to put in (charging), and how much you are willing to spend.  You can easily spend $20,000 on a full system, mine is about $5000 and I did the install, or you can buy a portable generator for under $1000.  My generator is built into the toy hauler.  All have advantages and disadvantages and you need to research what fits you needs.

 

I hope this was helpful. 

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The reference to 'split systems' is likely about mini split AC systems.  These AC systems can be very efficient and the one I use draws about 25٪ or maybe less than the power used by a RV AC and cools better.  Trying to run a RV AC with solar power is a tall order, if not impossible considering the total roof area and batteries required.  On the other hand we run our mini split AC during the day with solar power.  Here in the mountains it cools quickly when the sun goes down so it isn't needed then.  During the day we have seen temps into the lower 90's but our 12,000 btu mini split has been easily capable of keeping our 39' Teton cool.

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1 hour ago, podwerkz said:

Yeah...maybe he got rid of those expensive pampered poodles and is getting by with a misting fan.

Funny you mention that. Was  in 110 f Arizona heat last year sitting outside, Set up my misting fan, felt good, but my two rescue dogs thought it was too cool and crawled under the coach.

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If you do this on solar make sure you install an automatic transfer switch to automatically start the generator once your batteries get depleted to the point where there is enough power to start the generator.

I don’t have this type of setup yet because we made trade up in the next year or 2 and I don’t want to spend the money only to trade in or sell. I do have a mobile internet router and a Blink camera that monitors the temperature of my rig while my dog is left alone. I have it set to email me if temps get to low or to high. We are also thinking of a hide a key and posting our phone number in the event my dog needs to be rescued!

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