Boondocking an Air Conditioner

[DaveW]

I was reading a review for the new Micro Minnie FLX and they mentioned the Truma air conditioner only used 4.6A while running (after the startup). Which is about 1/3 of the amperage of the regular Micro Minnie from what I gather. So I went looking and found that there is also a Truma air conditioner which only uses 2.8A while running!

https://autoadditionsnationwide.com/...aventa-compact

That is less running amperage than the standard 12v fridge uses. Now I'm wondering how plausible it is to swap my stock AC for this Truma Aventa air conditioner?

I already planned to purchase 8 Battleborn batteries and as much solar as I can possibly fit onto my Minnie for boondocking (without using the air conditioner, but running the fridge). I'll likely use lightweight panels to keep the weight down.

I'm pretty sure that I will still not be able to put enough solar on the trailer to completely recharge that battery bank in a single day if it is completely discharged when starting the daily charge cycle. I'm still researching for my solar setup and am by no means an expert in this field.

I could use a generator here and there to top it up. Maybe even have a separate solar kit not attached to the trailer which can be set out and also be directly pointed at the sun as needed.

Would it be enough? I believe it might be with careful monitoring of the batteries and adjusting the usage of the air conditioner as needed. Perhaps only using it in the evenings and nights, which is when I'll be in the trailer the most.

I'm looking for thoughts and suggestions from people with more knowledge in this area than I have.

[GaryKowal1]

The Truma Aventa Eco 13.5 is efficient and quiet. Unlike most rooftop air conditioners that offer only two speeds, this German import offers three efficient, low amp speeds: low 9.4 amps AC (104 amps DC); medium 9.6 amps AC (106 amps DC); and high 10.5 amps AC (116 amps DC)

[DaveW]

Originally Posted by GaryKowal1

The Truma Aventa Eco 13.5 is efficient and quiet. Unlike most rooftop air conditioners that offer only two speeds, this German import offers three efficient, low amp speeds: low 9.4 amps AC (104 amps DC); medium 9.6 amps AC (106 amps DC); and high 10.5 amps AC (116 amps DC)

That is not the Truma unit I linked to in my OP. I am assuming that is the unit in the FLX and those AC numbers are 120v? Otherwise I have no idea what your post was about.

The unit I listed in my OP uses 2.8A running on 230v. Now correct me if I'm wrong, but that is about 66 amps DC with 10% voltage drop. Which is nearly half of what you posted.

[DavidM]

Well, follow me on this from a retired engineer:

The Truma you mentioned draws 2.8 amps at 230V AC. It is not less than a DC refrigerator which draws 5 amps at 12V for a 7 cu ft model.

The output of this Truma is 1700 watts of cooling which is about 5,700 btu/hr which is about half of a typical small RV rooftop A/C.

It isn't particularly efficient. Its coefficient of performance is 1700 watts of cooling divided by 2.8 amps x 230 volts of energy input or about 2.6 which is in line with most bigger roof top A/Cs.

Compared to a typical 13,500 btu RV A/C it will run longer to do comparative cooling and may not keep up on a warm day because it is less than half of the capacity. But it should work well overnight when cooling loads are less.

It will take a huge battery bank to run it when the sun isn't shining and an equally huge solar panel farm to recharge those batteries while continuing to run it during the day on solar.

There is no free lunch.

David

[DaveW]

Originally Posted by DavidM

Well, follow me on this from a retired engineer:

The Truma you mentioned draws 2.8 amps at 230V AC. It is not less than a DC refrigerator which draws 5 amps at 12V for a 7 cu ft model.

The output of this Truma is 1700 watts of cooling which is about 5,700 btu/hr which is about half of a typical small RV rooftop A/C.

It isn't particularly efficient. Its coefficient of performance is 1700 watts of cooling divided by 2.8 amps x 230 volts of energy input or about 2.6 which is in line with most bigger roof top A/Cs.

Compared to a typical 13,500 btu RV A/C it will run longer to do comparative cooling and may not keep up on a warm day because it is less than half of the capacity. But it should work well overnight when cooling loads are less.

It will take a huge battery bank to run it when the sun isn't shining and an equally huge solar panel farm to recharge those batteries while continuing to run it during the day on solar.

There is no free lunch.

David

When I commented about the Fridge I was assuming 8 amps at 120v since I read that the 10.3 cu ft winnie fridge uses about 8 amps (but didn't specifiy the voltage). If that is only at 12v then the ac clearly does not use less than the fridge.

I know there is no such thing as a free lunch. But living completely on solar is entirely possible as many people are already doing just that in their homes, air conditioner and all. If that's what you consider to be a free lunch, then you are wrong.

Thanks for your input.


BTW, I don't mean any insult. It sounds as if you are saying it is not possible to boondock with an air conditioner (which it probably is not possible with a Micro Minnie at this time). But technologies are always advancing. 50 years ago boondocking at all with solar would have been laughed at. 50 years from now boondocking may be possible with a single solar panel. Panel technology advances, and so does air conditioning technology.

[creativepart]

Here's some info that might add to your original question.

It think at this time Truma is selling their new 12v A/C unit to OEM manufacturers in the US. This is a new effort of theirs and just getting off the ground. I'm sure they intend to make these units widely available at some point, but it's just not there yet. The Truma A/C is available in the EU and I believe in Australia as well. But it costs twice the price as current A/C units installed in RVs.

The FLX is a complete system... with 380w of solar, 320ah Lithionics smart Lithium batteries, 3000w inverter and a MSRP for all the tech of over $15,000 more than the MSRP of your 2108FBS. (FLX MSRP is $60,175, Standard 2108FBS MSRP is $44,542)

Could you spend a similar amount to get your Micro Minnie to run the A/C while boondocking? You bet. But at this moment you'd have to settle for less efficient 110v RV A/C like you have on your TT right now. And, with a less efficient A/C unit and only 320aH of battery storage you'd be looking at an hour to 1.5 hours of A/C run time.

I feel certain we'll see 12v A/C units available from multiple suppliers in the next few years. But just how long it will take and at what retail pricing remains to be seen.

[creativepart]

Originally Posted by DavidM

The Truma you mentioned draws 2.8 amps at 230V AC.

Truma is selling the Aventa A/C in Europe as a 240v appliance. But they have developed a 110v unit for the US market. You can't really get the specs on these yet as they are brand new and being sold to OEM Manufacturers only at this time.

The main selling points at this time are that they are about 25% more efficient, quieter inside and outside the RV, take up less headroom inside the RV and are not as tall as competing A/Cs.

Here's a video about the Aventa:

https://www.youtube.com/watch?v=fQP8mPXCnVE

There are 12v A/Cs available in the EU and Australia/New Zealand. And some available in the US - but they typically cost between $3000 and $4000 each.

[macnut]

Great to see some innovation!

[DaveW]

Originally Posted by creativepart

The FLX is a complete system... with 380w of solar, 320ah Lithionics smart Lithium batteries, 3000w inverter and a MSRP for all the tech of over $15,000 more than the MSRP of your 2108FBS. (FLX MSRP is $60,175, Standard 2108FBS MSRP is $44,542)

Could you spend a similar amount to get your Micro Minnie to run the A/C while boondocking? You bet. But at this moment you'd have to settle for less efficient 110v RV A/C like you have on your TT right now. And, with a less efficient A/C unit and only 320aH of battery storage you'd be looking at an hour to 1.5 hours of A/C run time.

Well, it also depends on the deals you can get. I paid just under $30,000 for my 2108FBS a couple of weeks ago, but I couldn't get a deal that good on the FLX, at least in my area ($14k under MSRP). I could do a lot with $30k to spare.

I'll also have more than 320ah, but I get your point. I was planning on 8x 100ah Battleborn batteries. But now I'm pretty certain that I'm going with 4x Silicone Dioxide (sio2) batteries due to being usable in extreme temperatures, and being cheaper while having similar performance to the Battleborn batteries. They just weigh more.

I'll run my AC sparingly if possible when needed. But I'm not expecting to be able to use it much if at all.

[Mtn Charlie]

I came across this RV solar panel/battery guide today. I realize that they are trying to sell product, but it gives you an idea of what is out there.
https://dakotalithium.com/2020/07/10...vWQkwC5kaqLoGg

[creativepart]

Originally Posted by DaveW

But now I'm pretty certain that I'm going with 4x Silicone Dioxide (sio2) batteries

Let us know how this works out. I've looked them up a number of times and I find very little real world RV experience with this battery chemistry. Almost none.

I've seen some marine reports and some of those were less than encouraging. One sailing channel I watch had to replace them in a pretty short period of time.

Soneil Technologies, in Canada, the lone manufacturer of these the last time I looked was slow to deliver batteries and all the claims of their superiority were from the manufacturer. Not a lot of real world reviews.

That may have changed - they keep being mentioned here and elsewhere - but none of those mentioning them, that I'm aware of, have actually gone ahead and purchased some and put them to use. Unlike, Lithiums which have gotten plenty of real world reviews from actual users in RVs.

[DaveW]

Originally Posted by creativepart

Let us know how this works out. I've looked them up a number of times and I find very little real world RV experience with this battery chemistry. Almost none.

I've seen some marine reports and some of those were less than encouraging. One sailing channel I watch had to replace them in a pretty short period of time.

Soneil Technologies, in Canada, the lone manufacturer of these the last time I looked was slow to deliver batteries and all the claims of their superiority were from the manufacturer. Not a lot of real world reviews.

That may have changed - they keep being mentioned here and elsewhere - but none of those mentioning them, that I'm aware of, have actually gone ahead and purchased some and put them to use. Unlike, Lithiums which have gotten plenty of real world reviews from actual users in RVs.

Ah, I see. Yeah, there's not many personal reviews on them. The 3 reviews they have on Amazon are good. But that's hardly conclusive evidence. The reviews are on the cheaper version that looks identical to the Soneil version. Both versions say Azimuth is the brand.

https://www.amazon.com/recyclable-li.../dp/B077W42CWW

https://www.amazon.com/Silicon-Dioxi.../dp/B07XH5QLQC


Azimuth website also has them but without reviews as well:
100Ah 12V SiO2 Battery G27 – Azimuth Solar Products US Website


Now I have to decide if I want to be a guinea pig or not. I may go back to the Battleborns...

[creativepart]

Originally Posted by DaveW

Now I have to decide if I want to be a guinea pig or not. I may go back to the Battleborns...

I'm looking at getting 2-200aH LiPo4 batteries this summer and I'm trying too decide which to get.

Right now I'm leaning toward the Chins "Smart" 200aH battery. They have a built in heater and below 0 degrees they stop charging and turn on heaters. Plus they have a Bluetooth App for monitoring. They are $1,079 each on Amazon. So, 400aH would be under $2,200. In your case that would be under $4,500 for 800aH. I can't imagine BBs are that inexpensive.

[DaveW]

Originally Posted by creativepart

I'm looking at getting 2-200aH LiPo4 batteries this summer and I'm trying too decide which to get.

Right now I'm leaning toward the Chins "Smart" 200aH battery. They have a built in heater and below 0 degrees they stop charging and turn on heaters. Plus they have a Bluetooth App for monitoring. They are $1,079 each on Amazon. So, 400aH would be under $2,200. In your case that would be under $4,500 for 800aH. I can't imagine BBs are that inexpensive.

Thanks, I'll take a look at them. I'm not as worried about the cold, but it is a potential issue. I was more worried about heat reducing the life of the batteries. From what I gather, lithium batteries start losing life when subjected to heat over 113 degrees fahrenheit. However, if the batteries cost 2/3 as much then it's less of a worry, lol.

it was found that when the battery is charged at 113 degrees versus 77 the lifecycle degradation was much more significant at the higher temperature. For the first 200 cycles the battery performance only degraded 3.3% at 77 degrees; at 113 degrees the performance decreased by 6.7%.

Source

[creativepart]

I'm on the fence about cold cutoffs and heated cases. Right now, my battery bank is in a compartment with a big metal shelf holding the batteries and it's open to the road underneath and along the back wall of the compartment.

It would be easy enough to have a metal floor welded on. And some kind of backing added as well. But I do camp at altitudes in the Spring and Fall and nighttime temps routinely see 25 degrees. I don't know how cold the batteries would get.

I think I can set the Victron solar controller to stop charging at 32 degrees. I don't know yet if the Magnum inverter/charger can be set to stop charging automatically at freezing - but I do know that I have an on/off button on the ARC50 remote display so I can turn it off manually when I expect an overnight freeze. And, then there is only the alternator charging to worry about - and I'm planning on adding a DC-DC charger, probably a Victron. Maybe that can be set to stop charging if I'm driving on a cold morning (that's not likely).

Heat I'm not worried about. We seek out 60's and 70's for high temps everywhere we go. And we stay home June, July and August. Plus almost all LiPo4 BMS have high temp cutoffs.

[DaveW]

Originally Posted by creativepart

Right now I'm leaning toward the Chins "Smart" 200aH battery. They have a built in heater and below 0 degrees they stop charging and turn on heaters. Plus they have a Bluetooth App for monitoring. They are $1,079 each on Amazon. So, 400aH would be under $2,200. In your case that would be under $4,500 for 800aH. I can't imagine BBs are that inexpensive.

Those look nice! I think I'm more interested in the 300ah version for $1,400. I can get two of them for $2,800 for a total of 600ah. I didn't want batteries that big of the sio2 type because I didn't want to be having to move anything over 100 pounds. These 300ah Chins batteries weigh ~67 pounds.

Edit: Actually, if I go with Chins I may get 3 of the 200ah. That way I can get up to 300A continuous discharge if I need it. Otherwise with 2 of the 300ah batteries I would be limited to 200A continuous discharge.

Originally Posted by creativepart

I'm on the fence about cold cutoffs and heated cases. Right now, my battery bank is in a compartment with a big metal shelf holding the batteries and it's open to the road underneath and along the back wall of the compartment.

I think I can set the Victron solar controller to stop charging at 32 degrees. I don't know yet if the Magnum inverter/charger can be set to stop charging automatically at freezing - but I do know that I have an on/off button on the ARC50 remote display so I can turn it off manually when I expect an overnight freeze. And, then there is only the alternator charging to worry about - and I'm planning on adding a DC-DC charger, probably a Victron. Maybe that can be set to stop charging if I'm driving on a cold morning (that's not likely).

Heat I'm not worried about. We seek out 60's and 70's for high temps everywhere we go. And we stay home June, July and August. Plus almost all LiPo4 BMS have high temp cutoffs.

I just like to try and be prepped for any situation. I'm an overthinker. I'll most likely keep my battery bank in the pass-through. Which may only be 2 batteries now, ha!

I haven't really started on the solar and charger research yet. I think I want a MPPT charger though for maximum efficiency since I don't think I'm going to be able to install enough solar to perform a full recharge of my battery bank in a single day (which I would like it if I could). So far I've really only been looking over Renogy stuff.

[tinglett]

Originally Posted by DaveW

I just like to try and be prepped for any situation. I'm an overthinker. I'll most likely keep my battery bank in the pass-through. Which may only be 2 batteries now, ha!

I did a lithium install a year or so ago and landed at 2 batteries, more by dumb luck than anything. In hindsight here is what I have observed.

First, you only need enough battery to get through a period before you recharge. I know that sounds stupid and obvious, but you really need to think about this. If you are going after 8 batteries, I can only assume one of two things: You plan on a massive consumption of power and plan to recharge somehow each day, or you plan to get through a long period of time without need to recharge at all.

I think in this discussion (so far) it's the former. Use a massive amount of power (using A/C or whatever), and recharge the next day. For me, I accidentally found that 2 batteries were just enough to eek out a full week stay boondocking if you skimp carefully (i.e, "think camping" vs. "think RVing"). As a bonus, 2 batteries gives me redundancy in case a battery fails (I did have one fail -- but don't expect that again). That bonus is a "nicety" in my opinion, but for some it may be important.

But let's talk about that little detail of recharging each day. I'd assume you'd want some reserve power, so perhaps we assume you burn through 600 Ah per day max (planned). That's 600Ah*13.2V = 7920 Wh. That's a lot of energy to replace.

Here's something I hadn't thought about when I headed down this road. If you plan for a cloudy week of bad solar, you obviously plan for a generator. I have found that about the best my charger can put into my BB batteries is about 32A. That's due to the voltage drop in the 6awg cable run. No matter how big a generator I use, that'll take 600/32 = 18.75 hours of generator runtime!

Hopefully you see where I'm going. If I have a generator running all day, well, I could also run the A/C if the generator is big enough. And then I suppose I wouldn't need so much battery.

The takeaway is that you need to balance the size of your battery bank with your ability to re-fill it -- not just your ability to drain it. This totally went over my head as I started. But, as it turns out for me, this isn't a big deal as I really want to span a length of time with no recharge at all. Any charge I get from solar is pure bonus -- not required. I like how that came out. But again, we approach boondocking as "camping" and so our energy use is very, very low. But perhaps for someone else, 8 BB batteries can span a week with a 4x energy draw than we use. Everyone is different, so this might be just the ticket for someone.

Certainly my generator scenario is solvable, but it does get challenging if you think about it. I could improve my charger situation by either replacing the charger (and cables), or by introducing a new external charger between the generator and battery for this setup. BB does state max charging rate and for my batteries that is 50A per 100Ah battery. So with 2 batteries I could increase up to 100A and charge quicker. With 8 batteries you might get to 400A, but WOW that's allota power! You'll need bus bars for that setup! Some food for thought.

[creativepart]

Originally Posted by tinglett

This totally went over my head as I started. But, as it turns out for me, this isn't a big deal as I really want to span a length of time with no recharge at all. Any charge I get from solar is pure bonus -- not required. I like how that came out.

This is so true. It's important to do a lot of research ahead of time when upgrading your electrical system (or any system) but you can never really understand all the implications upfront. It takes use and experience to fully grasp all the nuances of how it all works in the real world.

As I like to say, "You can only know what you don't know until you know it."

PS. I usually say the above quote when I've messed something up and need an excuse for my stupidity.

[DaveW]

Originally Posted by tinglett

The takeaway is that you need to balance the size of your battery bank with your ability to re-fill it -- not just your ability to drain it. This totally went over my head as I started. But, as it turns out for me, this isn't a big deal as I really want to span a length of time with no recharge at all. Any charge I get from solar is pure bonus -- not required. I like how that came out. But again, we approach boondocking as "camping" and so our energy use is very, very low. But perhaps for someone else, 8 BB batteries can span a week with a 4x energy draw than we use. Everyone is different, so this might be just the ticket for someone.

Thanks for the advise. I am aware of what you are saying. I want a large battery bank for a few reasons and as I already stated I don't believe I can possibly put enough solar on the TT to completely replenish the battery bank in a single day if it were completely drained. I don't intend to drain it to empty and the larger the bank is the less it has to be drained which will increase the life of the batteries. Having a large bank just makes sense. It can cover for cloudy days and also may negate the need for a generator at all. If I can get 1600-2000 watts of solar on the roof I'll be very happy. But I would like at least 1200 watts worth of panels and I believe that is completely possible. I may also get a suitcase setup for backup in place of a generator.

As I said, I like to be prepared for all situations. One possible situation is loss of the power grid and being able to survive without access to shore power or fossil fuels. If there's no fuel there's no way to run a generator. But at least I can have some form of power to run my fridge, lights, and other low power electronics indefinitely. I believe this is a real threat right now.

Running the AC was something I was exploring for normal situations, not extreme situations. Obviously, I'll also not be using anything requiring propane in a survival situation as well. If that happens and I need heat I'll install a small wood burning stove in the trailer. This trailer will aid me in getting away from urban areas where people will be robbing and killing each other to get food in that situation. Which is why I'm dumping money into it.

[RocknRoll]

Originally Posted by DaveW

If I can get 1600-2000 watts of solar on the roof I'll be very happy. But I would like at least 1200 watts worth of panels and I believe that is completely possible. I may also get a suitcase setup for backup in place of a generator.

I believe you may be hard pressed to get even 600W on the roof of a 2108FBS, especially if you plan to do any maintenance. Source the panels you want and take the measurements to the roof. Don't forget to give yourself some walking room.

A solar suitcase is usually 200W max unless you parallel multiple together.