Air conditioning without a generator

jamesk

Observer
At overland expo west, the blismobil unimog was able to run an air conditioner off of its massive lithium ion bank/solar array.

Has anyone else done this and what would a realistic cost estimate for a system like that be?
 

scott7022

Nobody
FWIW.
I have run these numbers a few times over the years. Prices have changed on batt/inverters Hybrid types that will take the massive start hit. Now we have soft start caps and rooftop units with built in options. So it has all gotten easier. But it is a moot point. When the sun is up you you make more power and running AC you will use more power but the ability to replace and rates just doesn't ever come close. So a little gen is going to be required for anything past a friday night. This being said depending on the type of AC unit, tons of posts on tear drops using these smaller units, and the size of the space you can run one for a while during quite time without a gen just to cool the space before bedtime. If you're frugal and you have a decent solar setup you may only need a little bit of time on the gen.

Cheaper to use a little Gen in the long run is my opinion. If only to top off the usage after. Perhaps if one was only to camp in one distinct are say Moab or...You could build a very specific no genie system. But the effort would only be for the green factor.
Again just my opinion. There are members here that have done it back before all the new advancements, no small feat. Now it is a; "just because you can doesn't mean you should" thing!
 

Haraald

Observer
I don't know about lithium, but you need about 500Ah (20hr) (e.g. 5 of these: https://www.batteriesplus.com/battery/marine-and-boat/deep-cycle/bci-group-31m/sli31agmdpm) to run the smallest air-conditioner on the market all night and into the morning a bit. I only had 3 of them last summer and I depleted the batteries down to 20%, which you're not supposed to do, by late evening. I then charged the system back up while driving around. Mind you those batteries weigh a lot. So my guess is you need to invest $2000+ into a battery bank plus gas generator. It's my understanding that solar will never give you enough power.
 

Darwin

Explorer
It would be important to know if the "sun technologies" unit uses a variable speed compressor like what is found on the most efficient mini split units. If you cool the camper down initially and it finds its sent point it might only need 350 watts or 3000 btus to maintain temp.
 

S2DM

Adventurer
There is a fairly established thread discussing this..

http://forum.expeditionportal.com/t...oning-Units-for-non-generator-powered-campers

It is definitely possible (ask me how I know :) to run off of batteries, run all night, and not use a generator. LeishaShannon and a few others have also had success.

Key Points,

1) Very efficient unit ... Nothing commercially available and purpose built for marine or RV applications is efficient enough currently to run all night consistently without requiring a huge battery bank. You need EERs above 15 and SEERs in the mid to high 20s. This pushes you into repurposing a residential mini split. Mine uses 350-400 watts for 9k btu cooling, and a little more for 10k btu heating.

2) Efficient batteries, I.E. something that won't suffer excessively from Peukerts law, aka, Lithiums. Lead acid and AGM batteries all suffer from decreased efficiency the larger the load that you pull. So, not only do you have a battery that doesn't like to be discharged past 50%, you also have a battery that doesn't like to have large loads drawn quickly.

3) Relatively large battery array - atleast 400ah in a lithium at 12v, but 600-800 is better.

4) Well insulated, smaller camper. - it can work in a larger rig, but everything needs to scale accordingly.

That said, a number of folks have had success with smaller banks, AGMS, and less efficient units, just used more judiciously.

-S
 
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Darwin

Explorer
This pushes you into repurposing a residential mini split. Mine uses 350-400 watts for 9k btu cooling, and a little more for 10k btu heating.
Did you end up with a 220 volt unit? IF so, what step up transformer thing are you using?

On a side, I think in the future more and more RV's and boats will see 48 volt systems for the electrical side as lithium becomes more mainstream and it allows the use of higher current electrical appliances, there is already pure 48 volt mini splits on the market for "off grid" use.
 

S2DM

Adventurer
Did you end up with a 220 volt unit? IF so, what step up transformer thing are you using?

On a side, I think in the future more and more RV's and boats will see 48 volt systems for the electrical side as lithium becomes more mainstream and it allows the use of higher current electrical appliances, there is already pure 48 volt mini splits on the market for "off grid" use.

I did use a 230v unit. I originally ran it with a step up transformer from outback, but for a couple reasons, switched directions. Its now being run with a small phoenix, 1000watt inverter from Victron. The separate inverter was a little higher efficiency, but the big advantage is that it had its own data port for my electronics monitoring set up (CCGX and the victron app), which allowed me to see direct usage amounts, rather than extrapolating what percentage of my 115v load was actually 230v through the transformer.

We have yet to install the phoenix, and have just done some bench testing with the unit thus far. I am in the midst of rebuilding the housing on the daikin unit out of 80/20 and working on a vibration mount for it.
 

S2DM

Adventurer
As an aside, I think the 48V DC units may end up being a great option. Some of them are quite efficient. Most 12-48V DC-DC convertors still only operate at 90% efficiency though.
 

Darwin

Explorer
As an aside, I think the 48V DC units may end up being a great option. Some of them are quite efficient. Most 12-48V DC-DC convertors still only operate at 90% efficiency though.
Ya, I am still trying to figure out and decide if it would be better to go with dual inverters one dedicated 230 volt for a standard high efficiency mini split or the pure 48 volt version. I know there are also losses going from DC to AC. I was planning on skipping 12 volts all together and going with 48 volts for the DC side with step down converters for the minimal 12 or 24 volt appliances.

Here is the 48 volt unit
http://www.hotspotenergy.com/DC-air-conditioner/
 

adam88

Explorer
Ya, I am still trying to figure out and decide if it would be better to go with dual inverters one dedicated 230 volt for a standard high efficiency mini split or the pure 48 volt version. I know there are also losses going from DC to AC. I was planning on skipping 12 volts all together and going with 48 volts for the DC side with step down converters for the minimal 12 or 24 volt appliances.

Here is the 48 volt unit
http://www.hotspotenergy.com/DC-air-conditioner/

I have done extensive research on Hot Spot Energy and their 48v mini-split, and suffice to say, I am convinced it is one of the best built units in the world. The quality of it actually seems to be better than you'd find with a residential mini-split like Mitsubishi or Fujitsu. The company was founded by some really brilliant engineers and they go to great lengths to make everything perfect. In particular, their 48v unit operates entirely off 48v - everything! All the fans, valves and solenoids inside are 48v. They seem obsessed with squeezing out every last drop of efficiency. I am definitely excited about the prospects of using this in my build.
 

S2DM

Adventurer
I have done extensive research on Hot Spot Energy and their 48v mini-split, and suffice to say, I am convinced it is one of the best built units in the world. The quality of it actually seems to be better than you'd find with a residential mini-split like Mitsubishi or Fujitsu. The company was founded by some really brilliant engineers and they go to great lengths to make everything perfect. In particular, their 48v unit operates entirely off 48v - everything! All the fans, valves and solenoids inside are 48v. They seem obsessed with squeezing out every last drop of efficiency. I am definitely excited about the prospects of using this in my build.

I've been looking at it pretty closely as well, and am considering moving my daikin over into our new workshop build, and purchasing this for the camper. I'm still torn on the power supply though, and havent finished researching the relative efficiencies of a 12-48v DC to DC converter, vs a 12-230 DC to AC inverter.

What are you using?

I was tempted to switch to a 48V native system, as I have very little that requires 12v, but that makes the AC inverter more complicated and requires all of my batteries to be always operational (I have 4 12V, 200AH, lithiums). I've got too much in my batteries to switch to 24V batteries, but that would be easier, 2 in parallel and 2 in series.
 

adam88

Explorer
I've been looking at it pretty closely as well, and am considering moving my daikin over into our new workshop build, and purchasing this for the camper. I'm still torn on the power supply though, and havent finished researching the relative efficiencies of a 12-48v DC to DC converter, vs a 12-230 DC to AC inverter.

What are you using?

I was tempted to switch to a 48V native system, as I have very little that requires 12v, but that makes the AC inverter more complicated and requires all of my batteries to be always operational (I have 4 12V, 200AH, lithiums). I've got too much in my batteries to switch to 24V batteries, but that would be easier, 2 in parallel and 2 in series.

My intention is to go with a 48v native system, lithium ion batteries. If you look in the "12v / Solar" forum down below on the forums mainpage, there's a post there I made about LG RESU Lithium ion batteries. These battery packs are naturally 48v. So they jive perfectly with this air conditioner, it's a match made in heaven. But that being said, if I wasn't going with lithium then I would just get (4) 12v batteries or (2) 24v batteries, probably Lifeline AGM, and run them at 48v.

Ill then have a 48v inverter (like Magnum MS4448) that will power most of the stuff, like the induction stove, microwave, hot water tank, etc. I will then use a 48v to 12v converter to power some things in the vehicle like lights, pumps and maybe a fridge. This way I can turn off the inverter at night.

The only thing I haven't found a really good way to do yet is to charge the batteries using my truck's 12v alternator, which is kind of a problem. I am sure there's a reasonable solution out there though.
 

S2DM

Adventurer
My intention is to go with a 48v native system, lithium ion batteries. If you look in the "12v / Solar" forum down below on the forums mainpage, there's a post there I made about LG RESU Lithium ion batteries. These battery packs are naturally 48v. So they jive perfectly with this air conditioner, it's a match made in heaven. But that being said, if I wasn't going with lithium then I would just get (4) 12v batteries or (2) 24v batteries, probably Lifeline AGM, and run them at 48v.

Ill then have a 48v inverter (like Magnum MS4448) that will power most of the stuff, like the induction stove, microwave, hot water tank, etc. I will then use a 48v to 12v converter to power some things in the vehicle like lights, pumps and maybe a fridge. This way I can turn off the inverter at night.

The only thing I haven't found a really good way to do yet is to charge the batteries using my truck's 12v alternator, which is kind of a problem. I am sure there's a reasonable solution out there though.

That energy density looks borderline unbelievable. Its almost 4x the total energy of my bank and less than half the weight and size. Not that I'm doubting you, that's just a huge difference, and Victrons are pretty much top of the line when it comes to lithium arrays for mobile applications. We are currently disconnecting our home and work shop from the grid and had been planning on the simpliphi, but I'll have to give these a closer look for that application.

Have you delved into their rating for off-road use? Looking that installation video, it seems they might be a riskier proposition, just eyeing the way that circuit board is laid out up top.

-S
 

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