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DC electric air conditioners are a reality


Ray,IN

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https://polarstorm.com/  sells a 48VDC sleeper cab air conditioner that maintains cool air for 12 hours without running an engine. As battery technology leaps forward, can a version for small trailers and truck campers be far behind?

 

2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country.  John F. Kennedy 20 Jan 1961

 

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Couldn't find a price, was it listed?

White 2000/2010Volvo VNL 770 with 7' Drom box with opposing doors,  JOST slider hitch. 600 HP Cummins Signature 18 Speed three pedal auto shift.

1999 Isuzu VehiCross retired to a sticks and bricks garage. Brought out of storage the summer of 2022

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One of the most interesting aspects of anyone running a air conditioner off of battery, is the missing, most important,ingredients: how much battery you need to power it for 12 hours and how you are going to recharge the batteries.  Even a highly efficient AC is going to pull a lot of watts of DC power.  Not as  much as the typical AC on our RV's, but still a lot of watts over the 12 hour run cycle.  

But hey, in the opening post, "sleeper cab".  Well that sounds like an over the road tractor trailer where the driver needs a place to sleep for the required number of hours and then drives again.  Pretty simple, install enough battery, then recharge it off the engine alternator while you drive . 

Not so easy for most of the RV'ing community.  We don't tend to drive 10-12 hours every day to recharge the batteries. 

Then we need to think about the differences between a "sleeper cab" and a RV. In a RV, for just the living room, it would be, 12-20 feet long, 6.5' tall and 8' wide, with lots of windows.  Not exactly a sleeper cab, that is probably pretty well insulated, minimal windows, and I would guess a lot smaller than the RV living room.  The RV bedroom, that is probably more doable, but you still have to recharge the batteries. 

So the AC for the sleeper cab probably would not cool the typical RV nearly as well as the sleeper cab. 

Even with better batteries, you still need to have some way to recharge the batteries. There will need to be a similar increase in solar panel efficiency to match the battery improvements.  

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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One other point to ponder... in a sleeper cab you're generally talking about an already "cool" space obtained from the rigs AC while driving. The energy requirements to "maintain" those temps will be exponentially less than attempted to cool a heated space.

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Going to the website for the Polarstorm system  https://polarstorm.com/    provides some interesting info in the specs and FAQ sections. 

For example, in the specs, it states the compressor motor is a 6 horsepower motor and then in the FAQ's it gives details about the amount of power (watts) for 1 horsepower, specifically about 15 amps at 48V for each horse power.  Also states the system only pulls 20amps from the battery.  Not sure how that computes when their stated 6 horsepower motor would/could pull 90 amps based on 15 amps per horsepower.

The to justify the use of a 48 volt motor they (correctly I might add) state the 48V motor only pulls 1/4 the amps of a 12V motor.  Totally ignoring that the watts used would be the same, and there for the amount of power taken from the battery pack is the same for the 12V motor as the 48V motor.  AND yes I am ignoring the fact the 48V system allows smaller components to be used in the system.  This is not to question the advantages of the 48V system over a 12V system.  Just pointing out the total power draw from the battery is very close to being the same for both 12V and 48V. 

Additionally there is the following quote from the FAQ that to get the 12 hours of cooling, the system would only be running the compressor 1/3 of the time.  Depending on outside temps only having the compressor run 1/3 of the time may not be practical.

Quote

Three-phase power is a type of Alternating current that uses 3 cycles instead of the normal 1 cycle. 3-phase is perfect for running heavy duty electric motors like the ones needed for an air conditioner compressor because 3-phase motors use about 1/3 less power to do the same work.
The 48 volt 3 phase system used in PolarStorm draws power slower than the rating of the batteries, therefore allowing the batteries to reach their maximum lifetime. Some electric air conditioners can draw 80 amps from a battery bank, far above the rating of the batteries resulting in a tragically short life of just a few years. PolarStorm draws just 20 amps, and combined with the system’s efficiency, allows the system to provide continuous cooling for 12 hours while running the compressor only one third of the time.

Sounds like a bit of marketing hype.  Not that the system won't work, just that it may not work as well as the sales hype would have you believe. 

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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I have a similar system on my truck (tractor) - a battery driven apu.  It works well. It uses AGM batteries.

So when I say it "works well", there are caveats to that statement. Yes, it provides very silent air conditioning.

In any truly hot conditions, it requires that the cab be already cooled down. And not just the air- but enough conditioning that the objects in there are cooled as well....in other words, don't start with a "hot" cab. 

It requires that the curtain be drawn between the condo and the driving compartment.

And it will NEVER cool in hot weather for 12 hours. You are lucky to get 8.

All that said, it does work pretty well for my use, which is typically as a man-cave/office on shore power. Or secondarily for short duration cooling while sitting in the truck (engine off) waiting for something. It also allows us to use the truck as an RV for short overnight trips where we have power. (like camping).

We put "modified" mini-splits in trucks and these really do work well. But require shore power (or genset - Honda 2000 works well, and a 1000 should work well). They would run on a battery bank, but we have not yet done that.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
2016 smart Passion, piggyback on the truck
-------------------------------------------------------------------------
See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar power
www.jackdanmayer.com
Principal in RVH Lifestyles. RVH-Lifestyles.com

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My point to posting about this is, technology is advancing rapidly these days, mostly due to battery improvements. We aren't to the point battery-powered air conditioning is practical for RV's yet, but getting closer every day.

 

2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country.  John F. Kennedy 20 Jan 1961

 

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2 hours ago, Ray,IN said:

My point to posting about this is, technology is advancing rapidly these days, mostly due to battery improvements. We aren't to the point battery-powered air conditioning is practical for RV's yet, but getting closer every day.

You can run AC of a well sized/configured LiFePo4 battery system.

http://www.technomadia.com/2016/06/running-an-rv-ac-off-solar-batteries-and-a-hybrid-boosting-inverter/

 

 

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9 hours ago, TheLongWayHome said:

You can run AC of a well sized/configured LiFePo4 battery system.

http://www.technomadia.com/2016/06/running-an-rv-ac-off-solar-batteries-and-a-hybrid-boosting-inverter/

 

 

Yeah, for a while....but not 24/7 like you can for a conventional setup. At least not without some source of shore power.

On a properly configured solar setup AND full sun you could do it indefinitely. The problem is the "full sun" statement. 

But we are getting there. I expect that the next iteration of our trailer will have the capability of run AC with just sun - indefinitely. But it will have a pretty large solar array - about 4Kw. And at least 18Kw of lithium batteries. And NOT have RV air conditioners.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
2016 smart Passion, piggyback on the truck
-------------------------------------------------------------------------
See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar power
www.jackdanmayer.com
Principal in RVH Lifestyles. RVH-Lifestyles.com

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16 minutes ago, Jack Mayer said:

Yeah, for a while....but not 24/7 like you can for a conventional setup. At least not without some source of shore power.

On a properly configured solar setup AND full sun you could do it indefinitely. The problem is the "full sun" statement. 

But we are getting there. I expect that the next iteration of our trailer will have the capability of run AC with just sun - indefinitely. But it will have a pretty large solar array - about 4Kw. And at least 18Kw of lithium batteries. And NOT have RV air conditioners.

AND be a very well insulated trailer with double pane windows.

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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10 hours ago, TheLongWayHome said:

You can run AC of a well sized/configured LiFePo4 battery system.

http://www.technomadia.com/2016/06/running-an-rv-ac-off-solar-batteries-and-a-hybrid-boosting-inverter/

 

 

Anyone remotely interested in the ability to run an air conditioner off of battery and solar really should read the info given in the link provided by TheLongWayHome.  http://www.technomadia.com/2016/06/running-an-rv-ac-off-solar-batteries-and-a-hybrid-boosting-inverter/

Technomadia provides excellent real life details of running AC off of battery. 

I read lots of topics about people installing better batteries and/or solar to dry camp/boondock and one thing that gets ignored so very often is what it takes to recharge the batteries. 

Just tossing in a couple of 6V golf cart batteries for 200 AH of battery and planning on using the existing single stage converter in most RV's to recharge while running the generator, just doesn't work well for multi day dry camping outings.

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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Going back to the original posting:

Quote

https://polarstorm.com/  sells a 48VDC sleeper cab air conditioner that maintains cool air for 12 hours without running an engine. As battery technology leaps forward, can a version for small trailers and truck campers be far behind?

The Polarstorm sounds like a system which could do a pretty good job of cooling a truck camper, at least for a few hours.  Assuming the price of $11,000 someone mentioned is correct, it is awfully expensive.  Even then, putting enough solar on the roof to recharge or depending on a generator to recharge is not practical.

 

 

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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The DC mini splits with lithium looks promising. Problem is the 48V system. Doable though. This is likely a future project for our retirement years. Right now jobs determine our locations

2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1

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On this page of the link https://polarstorm.com/benefits/ they say it draws 25 amps, not 20 amps like it says on another page. On the solar page it says it draws 8 amps. https://polarstorm.com/options/#solar

I don't think the advertising people know much about the tech specs. 21,000 BTUs is quite a bit of cooling power, if accurate.

Using their highest amp draw figure at 48v, this gives it an EER of 17.5, which is pretty good, but not as high as this mini-split which has an EER or 21.43. http://www.geinnovations.net/HSAC_Productline.html

Batteries are the most expensive component of their system. The mini-split I linked to costs around $2k and produces 12,000 Btus of cooling - good enough for the bedroom at night, but one would need 2 of these (24,000 Btus) for the entire RV ($4k.)

16 CG-2 conventional golf cart batteries (8/ac unit) is about $1.6k. 4kw of solar is currently 50 cents/watt - $2k - less if you shop around.  

 Add a charge controller, wiring, mounting hardware, a 48v inverter charger, monitor, etc. and you are looking at about $5,500 min. (if you installed it yourself) for the first mini split/solar set-up and about $10k for two (as there is some redundancy which can be eliminated due to economy of scale), to cool the entire RV (8-10 hr run time for both) but this includes solar panels, charger and a 48v inverter/charger to charge when hooked up.

The big downside to a system like this is weight (lead/acid batteries are heavy) - a little over a ton for the whole RV system and half of that for a bedroom only system - which is much more practical, and is what I, planning to get in about a year and a half. A mini-split also provides efficient supplemental heat to stretch your propane for extended boondocking forays. On the upside when not using your AC to its max capacity you will have more than enough AC power available for other things, like that big screen TV, home theater system, sat dish, computer, microwave, etc. while off grid. Of course extended foul weather would still require some generator back-up use, but not very often.

Chip   

 

 

 

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15 minutes ago, sushidog said:

On this page of the link https://polarstorm.com/benefits/ they say it draws 25 amps, not 20 amps like it says on another page. On the solar page it says it draws 8 amps. https://polarstorm.com/options/#solar

I don't think the advertising people know much about the tech specs. 21,000 BTUs is quite a bit of cooling power, if accurate.

Using their highest amp draw figure at 48v, this gives it an EER of 17.5, which is pretty good, but not as high as this mini-split which has an EER or 21.43. http://www.geinnovations.net/HSAC_Productline.html

Batteries are the most expensive component of their system. The mini-split I linked to costs around $2k and produces 12,000 Btus of cooling - good enough for the bedroom at night, but one would need 2 of these (24,000 Btus) for the entire RV ($4k.)

16 CG-2 conventional golf cart batteries (8/ac unit) is about $1.6k. 4kw of solar is currently 50 cents/watt - $2k - less if you shop around.  

 Add a charge controller, wiring, mounting hardware, a 48v inverter charger, monitor, etc. and you are looking at about $5,500 min. (if you installed it yourself) for the first mini split/solar set-up and about $10k for two (as there is some redundancy which can be eliminated due to economy of scale), to cool the entire RV (8-10 hr run time for both) but this includes solar panels, charger and a 48v inverter/charger to charge when hooked up.

The big downside to a system like this is weight (lead/acid batteries are heavy) - a little over a ton for the whole RV system and half of that for a bedroom only system - which is much more practical, and is what I, planning to get in about a year and a half. A mini-split also provides efficient supplemental heat to stretch your propane for extended boondocking forays. On the upside when not using your AC to its max capacity you will have more than enough AC power available for other things, like that big screen TV, home theater system, sat dish, computer, microwave, etc. while off grid. Of course extended foul weather would still require some generator back-up use, but not very often.

Chip   

 

 

 

About using lead acid batteries, even if you used AGM.... With a heavy long term current draw, there is the voltage drop to be considered.  Lead acid tends to drop to 12.2-12.3V (from 12.6V) under load or even lower as the SOC goes down. Then you need to consider the need to get the lead acid battery back to 100% SOC frequently.  Using lead acid for something like this is not practical.  Additionally, I would assume if you are going to this much expense you would want the longest life possible for your batteries.  With lead acid that is only using 25-30% of your battery.  With 1600AH of lead acid that leaves you with about 400AH of usable battery. 

With lithium you don't get the voltage drop, it stays at a constant 13.1-13.3V, under load, down to 75-80% discharged. The inverter is much happier with the higher voltage.   Also Lithium is happy with only getting to 80-90% full unlike lead acid.  Not to mention the much lighter weight. Lithium is happy with being discharged to 75-80% of capacity, giving you around 1200AH of usable capacity. 

A 1600AH lithium battery pack would be the way to go for air conditioner operation. 

Al & Sharon
2006 Winnebago Journey 36G 
2020 Chevy Colorado Toad
San Antonio, TX

http://downtheroadaroundthebend.blogspot.com/

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37 minutes ago, Al F said:

About using lead acid batteries, even if you used AGM.... With a heavy long term current draw, there is the voltage drop to be considered.  Lead acid tends to drop to 12.2-12.3V (from 12.6V) under load or even lower as the SOC goes down. Then you need to consider the need to get the lead acid battery back to 100% SOC frequently.  Using lead acid for something like this is not practical.  Additionally, I would assume if you are going to this much expense you would want the longest life possible for your batteries.  With lead acid that is only using 25-30% of your battery.  With 1600AH of lead acid that leaves you with about 400AH of usable battery. 

With lithium you don't get the voltage drop, it stays at a constant 13.1-13.3V, under load, down to 75-80% discharged. The inverter is much happier with the higher voltage.   Also Lithium is happy with only getting to 80-90% full unlike lead acid.  Not to mention the much lighter weight. Lithium is happy with being discharged to 75-80% of capacity, giving you around 1200AH of usable capacity. 

A 1600AH lithium battery pack would be the way to go for air conditioner operation. 

Agreed that lithium is far superior to lead acid, but its out of my price range. The mini split AC I linked to draws 11.5 amps at 48v so if I wanted to run the AC for 8 hrs I would need 96 amp/hrs at 48v. Eight GC-2's would provide about 100 usable AH at 50% discharge which is barely sufficient for my needs, assuming the AC has a 100% duty cycle, which at night, it should be much less.  Sams sells these batteries for $85 each or $680 for the bank, which should last about 3 years (my learning bank). Later I will buy some better batteries, possibly Trojans for around $1000 which should last about 5 years. This means that my lead acid batteries will cost between 200-225/yr. Let's say I'm a little off and they cost $250/yr. for estimation purposes. 

For comparison, a 60ah 48v lithium battery bank with BMS costs about $2,500. I would need at least two of these for $5,000. Let's say they last 10 years. That's still 500/yr. They would have to last 20 years to break even, and their life is greatly reduced in excessive heat (like where AC is needed) to make a 20yr life unlikely. This does not consider the time value of money, meaning that if I would borrow the money to buy these expensive batteries that they would cost even more. http://www.electriccarpartscompany.com/48V-60Ah-br-LiFePO4-EV-Golf-Cart-br-Lithium-Battery-br-h3-2524--FOB-Salt-Lake-City-br-1980--FOB-China-h3_p_739.html

Chip

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But you can run them further down with no negative effects. Not so of lead acid. It has been proven one don't need as large as battery bank due to this. Also they should come down in price in time

2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1

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I could go with 8 Trojan T-145s which have a 260ah capacity (at the 20 hr rate) The 20 hr discharge rate for this battery is 13 amps and my AC will be discharging them at the 11.5 amp rate, less than rated capacity. Peukert won't have to be taken into account as I plan on discharging them at less than the 20 hr rate. Unfortunately they come at a hefty price of $200 each. At a 50% discharge that's 130 available ah - that's over 11 hrs of AC from a fully charged battery or 6240 watts/day. Assuming an 80% charge efficiency I would need 7,800 watts of solar power going into the batteries. To complicate matters. flat mounted panels typically only produce around 80% of their rated capacity which I would need 1950 watts of panels assuming I can get 5 hrs of sunlight/day to top them off. To add a small cushion I am considering buying 6, 350 watt panels or equiv for about 2,100 watts, which should be sufficient.  If I could afford the lithiums I could get by with about 1,600 watts of solar due to their low internal resistance, saving about $300 in solar panels, wiring and hardware.  

I would have to buy 2 -75ah lithiums at $2,700 ea. to equal the trojans usable AH's. So at today's prices I'm looking at $5400 in lithium's that last 10, maybe 15 years if I don't kill them first vs $1600 in Trojan FLAs that last 5 years. The FLAs are still a better buy, though granted they do not charge or discharge as efficiently as the mature technology of FLAs. I also recognize that a million dollar Prevost is far superior to the used $25,000 MH that I can afford. But since I can't afford $5,400 in batteries I can't consider their inherent advantages, just as I can't consider a Million dollar Prevost even if it got 100 MPG and could drive itself, as I could never afford one. Now if the price drops in half over the next year and a half then I'll consider them. Maybe after my "learner batteries" die about 4 1/2 years from now they will drop to a point that I can afford them, but I'll have to do a lot of learning in the mean time in order to figure out a way to get the advertised life out of them. Because as Technomadia found out with theirs, losing 25% of their capacity over only 3.5 years, they can be easily degraded if you are not careful. That's an expensive mistake I simply couldn't afford to make as a retiree on a very limited income.  http://www.technomadia.com/2015/02/living-the-lithium-lifestyle-3-5-year-lithium-rv-battery-update/

Here's their unfortunate experience with their LiFePo4s "Considering that our batteries are seemingly not on track to outlive an AGM bank as much as theory promised, our personal value calculation haven’t worked out nearly as well as we had hoped."

Chip

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