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TimCA · 08-31-2021, 08:38 AM

Hello, Air Forums,

I am new here and tried to search for an answer to my question but could not find it so I am making my first post.

I am looking into installing a 12V DC rear air conditioner on our 2017 Interstate Lounge so we can run rear air conditioning while driving without having to run the generator. I travel with our family of 6 and it is always a battle with the people in the back between noise and temperature. I have set up many fans to move the cold air from the cab air conditioning to the rear and that has gotten us through 3+ years, but now I am looking for a more permanent solution. I have found 3 options that I am looking into:

KingTec KTD-2 Rooftop unit
The B-COOL9000RM Rooftop unit
Webasto Vancouver

With the rooftop units I would be replacing the Dometic 120V AC unit and running new wires down to the batteries for the 12V DC unit. With the Webasto I would be installing it separately and keeping the Dometic 120V AC unit. I like the plan of having both but having trouble getting manager approval (from my wife) to cut in the Webasto's vent somewhere.

Has anyone ever installed a 12V DC rear air conditioner and if so, what model did you use and how is it working? I realize this type of solution is not ideal for most people, but we have a perhaps strange use having so many rear passengers all the time.

Thank you for your time,
Tim

**richard5933** · 08-31-2021, 09:24 AM

Check out the units used in the trucking world. Lots of newer semi tractors are using DC powered a/c units to keep the sleeper area cool. They run off a designated set of batteries (similar to our house systems) and are set up so that they can be used with the engine off. When the batteries get below a set voltage the engine starts automatically to recharge.

With the size of a class B not being that much different from a sleeper cab, they likely will have something which will work.

uncle_bob · 08-31-2021, 10:26 AM

Hi

While it's not ideal, I'd fire up the generator and run it and the existing A/C as you rumble down the road. See how well that does at "solving" the problem. That will give you some idea of how many BTU's of cooling you need.

Next up is the question of needing "more" while out camping (since this will now be your only A/C unit). If the van isn't used that way then cross that off the list ...

No matter how you do it (12V or 120V) a 13,000 BTU A/C is going to pull some power. If it pulls 12A to 15A off of 120V, it's likely to pull 120 to 150A off of 12V. That's a lot of juice. It's more than many versions of the Sprinter have "to spare" according to the MB up fitter documentation. (like by 2 or 3X). You may need to drop in another alternator ....

Next wrinkle in the plan is actually *getting* a 12V A/C unit right now. Like a lot of things, they seem to be impacted in some obscure way by the virus. People have reported not even being able to get a projected delivery date on some models .....

Fun !!!

Bob

TimCA · 08-31-2021, 10:59 AM

Thank you for the suggestions!

I will look into the truck sleeper cab units.

I agree, I am probably going to have to wait a while to get whatever we choose due to supply chain issues.

We do run the generator and stock Dometic unit while driving periodically to get the temperature down and then we try to maintain from the cab air conditioning with fans, but my picky family doesn't like running the generator at all and they don't think the fans and cab unit keep it cool enough even after getting down to reasonable starting temp with the generator/Dometic unit.

The KingTec KTD-2 only draws 48A @ 12V DC so I think that should be workable to run for a decent number of hours (with enough batteries and the alternator charging).

We have generally never use the air conditioning while parked so we are willing to sacrifice having 120V AC powered air conditioning although having both the AC and DC units would be perfect if I can get my wife to agree to the vents being cut in (did I mention the picky part?)

Thank you again,
Tim

uncle_bob · 08-31-2021, 12:46 PM

Hi

The way A/C works is that half the power in is going to be less than half the cooling coming out. A unit that pulls 1/3 the power is not going to be close to what your existing unit does. Is this an issue? Only you can answer that question. If the existing unit runs more than about 1/5 of the time, I'd be concerned. ( = doing all this and coming up short would be a major bummer ....).

48A is right at the 50A limit in the MB up fitter specs for the "typical" Sprinter from 2017. They change things a bit from time to time so it's best to dig into the exact numbers for your model chassis. The power they allow runs all the stuff AS has added so "at the limit" could easily be "over the limit" depending on what's running.

One also could easily debate just how meaningful the MB specs are. That gets off into all sorts of rabbit holes .... (do you run the power door and the A/C at the same time kinds of questions ....).

Bob

goldenchase · 08-31-2021, 01:12 PM

A few years ago I did a deep dive into the differences between DC compressor and AC compressor air conditioning units. The DC compressor units back then mostly came from Europe having been developed for the trucking market. Back then these units cost 4X per BTU, the cost of AC compressor RV units in the US. However, the DC compressor units were 2X as efficient (watts/BTU) as the AC powered compressors found on RV air conditioner units in the US.

I have no idea if these DC compressor units being sold now into the RV market use the same technology of those I studied several years ago.

The other advantage of a DC compressor air conditioner for an RV is that they can be driven directly from the batteries without involving the inefficiencies of converting DC to AC via an inverter.

JohnTF · 09-01-2021, 10:11 AM

What are you going to use for battery bank ?

jimdelane · 09-01-2021, 11:30 AM

Like uncle_bpb says, regardless of whether you are using 120v or 12v - you will draw a lot of amps. A unit may draw only 48A while running but you need to consider the startup amps. Perhaps the unit has a type of soft start to soffen the blow. You might consider installing a lithium battery bank to support it. I am aware of many people who use multiple AMPS 400ah battery or multiple 200Ah batteries to provide the reserve energy and the higher amp BMS to handle surges. You have a lot of choices to pick from. Depending on how much space you have - you may be able to put in multiple smaller batteries or larger single batteries. Lithium batteries generally can be installed on their sides, ends or upright.
AMPS Lithium
https://lithiummarinebattery.com/shop

Battle Born Batteries
http://www.battlebornbatteries.com/

LiFeBlue Battery
http://www.lifebluebattery.com

ReLion
https://relionbattery.com/products/lithium

Chargex
https://www.lithiumion-batteries.com...-rv-deep-cycle

MountainLife · 09-01-2021, 04:14 PM

We also have a 2017 AI Lounge Ext and good for you for using it as we like to call it "party bus" style. We have mad a few short jaunts with full capacity, but most of the time it is just the hubby and I going on both long and short trips.

I do not like the idea of using the generator while driving. It is a safety issue and not to mention illegal to have the propane on while driving. Enough said.

Have you considered using the Sprinter's AC and add ducting to get cold air to the back? It might require adding inline fans and dampers to push the air where it is needed. Just a thought. I like the idea of investigating what truckers do in their sleeper cabs.

Enjoy the joyous sounds of chaos with your kids. I know I miss those days.

**richard5933** · 09-01-2021, 05:00 PM

Quote:

Originally Posted by MountainLife

We also have a 2017 AI Lounge Ext and good for you for using it as we like to call it "party bus" style. We have mad a few short jaunts with full capacity, but most of the time it is just the hubby and I going on both long and short trips.

I do not like the idea of using the generator while driving. It is a safety issue and not to mention illegal to have the propane on while driving. Enough said.

Have you considered using the Sprinter's AC and add ducting to get cold air to the back? It might require adding inline fans and dampers to push the air where it is needed. Just a thought. I like the idea of investigating what truckers do in their sleeper cabs.

Enjoy the joyous sounds of chaos with your kids. I know I miss those days.

From where do you get that it's illegal to run propane appliances while driving? Other than a very few tunnels where propane must be off (or is outright banned) please let us know what law/regs/rules prohibit the use of propane appliances while an RV is on the road.

MountainLife · 09-01-2021, 05:49 PM

Quote:

Originally Posted by richard5933

From where do you get that it's illegal to run propane appliances while driving? Other than a very few tunnels where propane must be off (or is outright banned) please let us know what law/regs/rules prohibit the use of propane appliances while an RV is on the road.

I stand corrected. Maybe not explicitly illegal, but a risk nonetheless. I had a friend lose their whole motorhome to a propane fire so I am extra cautious. We were instructed by our dealership when we took delivery to turn the propane off for travel. I think both things just stuck with me. I'm a bit risk averse.

uncle_bob · 09-02-2021, 09:38 AM

Quote:

Originally Posted by MountainLife

I stand corrected. Maybe not explicitly illegal, but a risk nonetheless. I had a friend lose their whole motorhome to a propane fire so I am extra cautious. We were instructed by our dealership when we took delivery to turn the propane off for travel. I think both things just stuck with me. I'm a bit risk averse.

Hi

There are a *lot* of RV's running absorption fridges while bumping down the road. They all have the propane turned on while in motion. Turn it off and you have melted ice cream when you get to the campground .... I have data on this ....

Bob

MountainLife · 09-03-2021, 04:44 AM

Quote:

Originally Posted by uncle_bob

Hi

There are a *lot* of RV's running absorption fridges while bumping down the road. They all have the propane turned on while in motion. Turn it off and you have melted ice cream when you get to the campground .... I have data on this ....

Bob

The propane fridge is what caused the RV fire. Went up so fast they lost their tow vehicle as well. I’m scarred (and scared &#128518

for life but understand about keeping food cold. I’m glad our unit has a 12v fridge.

**Rocinante** · 09-03-2021, 07:11 AM

What in the world do propane-driven absorption fridges have to do with this discussion about 12-volt air conditioners? C’mon, folks, get a grip. [emoji57]

MountainLife · 09-03-2021, 09:28 AM

Quote:

Originally Posted by Rocinante

What in the world do propane-driven absorption fridges have to do with this discussion about 12-volt air conditioners? C’mon, folks, get a grip. [emoji57]

The recommendation was to run the propane generator to use the roof AC. Not exactly that off topic. Of you’re not interested that’s fine. I’m sad that people on this forum get attacked if they ask a question that was previously answered. Aren’t we all here to help and support each other? I get it’s frustrating when people with trailers chime in on this forum but sometimes they have useful information to share. If it doesn’t interest you just keep scrolling. If seen posts where people start with apologizing for asking a question and that they did look for the answer. Searching on this forum isn’t that easy and I just wish we could all be more tolerant.

**Rocinante** · 09-03-2021, 10:59 AM

No worries. My comment wasn't anti-trailer. Was simply calling out that the purpose of the thread was to discuss installation and availability of 12V AC units.

To quote from the OP, "Has anyone ever installed a 12V DC rear air conditioner and if so, what model did you use and how is it working?"

See nothing at all about propane or absorption fridges.

So, you're actually not helping the OP with this digression. Feel free to carry on, though, driving off new members who ask a specific question, but who instead receive a bucket of random discussions about things in which they have zero stated interest.

MountainLife · 09-03-2021, 03:22 PM

Quote:

Originally Posted by Rocinante

No worries. My comment wasn't anti-trailer. Was simply calling out that the purpose of the thread was to discuss installation and availability of 12V AC units.

To quote from the OP, "Has anyone ever installed a 12V DC rear air conditioner and if so, what model did you use and how is it working?"

See nothing at all about propane or absorption fridges.

So, you're actually not helping the OP with this digression. Feel free to carry on, though, driving off new members who ask a specific question, but who instead receive a bucket of random discussions about things in which they have zero stated interest.

That wasn't me. The sidebar was about the safety of using propane while driving. For example, to run the generator to then run the roof AC. I just said I wasn't comfortable with using propane while driving which lead to the fridge comment. I do hope we hear what solution they came up with. I would be interested in hearing.

don000 · 09-08-2021, 09:55 AM

Quote:

Originally Posted by TimCA

Hello, Air Forums,

I am new here and tried to search for an answer to my question but could not find it so I am making my first post.

I am looking into installing a 12V DC rear air conditioner on our 2017 Interstate Lounge so we can run rear air conditioning while driving without having to run the generator. I travel with our family of 6 and it is always a battle with the people in the back between noise and temperature. I have set up many fans to move the cold air from the cab air conditioning to the rear and that has gotten us through 3+ years, but now I am looking for a more permanent solution. I have found 3 options that I am looking into:

KingTec KTD-2 Rooftop unit
The B-COOL9000RM Rooftop unit
Webasto Vancouver

With the rooftop units I would be replacing the Dometic 120V AC unit and running new wires down to the batteries for the 12V DC unit. With the Webasto I would be installing it separately and keeping the Dometic 120V AC unit. I like the plan of having both but having trouble getting manager approval (from my wife) to cut in the Webasto's vent somewhere.

Has anyone ever installed a 12V DC rear air conditioner and if so, what model did you use and how is it working? I realize this type of solution is not ideal for most people, but we have a perhaps strange use having so many rear passengers all the time.

Thank you for your time,
Tim

In the custom Sprinter build that replaced my Interstate I utilized a ProAir ElectraKool unit, powered by a 400 a/h Lithionics battery charged by a 280 Amp second alternator by Nations. My DIY installation was guided by David Flather at Pinnacle Innovations. After two years of sporadic use, including outside temperatures reaching 105°, I could not be happier (nor could our dogs).

Don

TimCA · 09-08-2021, 10:49 PM

Don,

Thank you very much! I will check out the ProAir Electra Kool and the extra alternator. I am definitely going with lithium iron phosphate battery bank with 400Ah+ capacity so that will work out nicely, and the extra alternator would be a big help to keep it charged. From a quick glance the Electra Kool looks like it could fit where the existing Dometic rooftop unit is. I decided if I replace the Dometic rooftop unit that I will cap off and try to leave all the existing 120V AC wiring in case I change my mind in the future and want to revert back to the Dometic or another AC unit.

I will let you all know once I decide on a unit and perform the upgrades and how it turns out, although it might be a long time given general supply shortages.

Thank you,
Tim

don000 · 09-09-2021, 07:20 AM

Quote:

Originally Posted by TimCA

Don,

Thank you very much! I will check out the ProAir Electra Kool and the extra alternator. I am definitely going with lithium iron phosphate battery bank with 400Ah+ capacity so that will work out nicely, and the extra alternator would be a big help to keep it charged. From a quick glance the Electra Kool looks like it could fit where the existing Dometic rooftop unit is. I decided if I replace the Dometic rooftop unit that I will cap off and try to leave all the existing 120V AC wiring in case I change my mind in the future and want to revert back to the Dometic or another AC unit.

I will let you all know once I decide on a unit and perform the upgrades and how it turns out, although it might be a long time given general supply shortages.

Thank you,
Tim

One important caveat: the most challenging aspect of the conversion will be running the heavy gauge cables needed for 12v through an Interstate, and finding room for fuses, terminal blocks and ideally a warm location for the lithium battery. You should have 1/0 cables to the air conditioner from your bus bar / fuse block, and 4/0 cables from the second alternator to the battery. Professional advice is worth the additional expenditure.

Don