Towing Camper with A/C Running.

[Scubydg]

Let’s say we just got to the campsite. Started setting up the site and realized how hot it was inside the camper. The question is, in a travel trailer with no generator, can I run the A/C while I’m driving? It sure would be a lot easier on my wife while setting up camp

[CA_Traveler]

mr_andyj wrote:
This is not a practical idea.

But it's always a fun topic!

[mr_andyj]

This is not a practical idea.
Battery is not for running the AC unless you have a huge battery bank, and in that case a person with a huge battery bank would not be seeking advice from a form, he would already be knowledgeable on the subject just front the build process.
batteries will get depleted quickly from using such a huge load like AC unit. Batteries will have a short life.

The best solution presented here is to stop, turn on generator and run AC a few mins before you have the camper parked in the spot. Maybe when you stop to check in you can turn it on and by the time you get to your spot and back in the AC will have cooled it down. It is just wasteful to run an AC for hours while driving so you do not have to wait 5 or 10 mins at the campground initially to have a cool coach.

This thread is getting quite silly

[CA_Traveler]

okhmbldr post may be OK for him but there is no real context.

What's needed as others have indicated: A/C size - Is it really 12K btu, battery size and type, ambient temperature and insulation, amount of time the compressor ran vs just the fan, inverter model.

On another board a knowledgeable poster has a 5K btu A/C that he runs for 2 hours with 4x GCs or 460 Ah total.

A 12K A/C uses about 1200W or 10A AC. Thats 110A DC or 110Ah which is a significant battery draw, maybe more depending upon inverter efficiency.

[ppine]

Not possible.

[MrWizard]

okhmbldr wrote:
I'm sorry you're having a problem understanding what I did with a battery an inverter and a portable A/C. What I described is exactly what happened. The inverter would shut off when the battery power was drained too far to proceed. I don't know how all that works. I just hooked it up and it worked for me.

It Is not theory that is wrong
It is the numbers you are stating
One battery is not going to power a 12000 btu
AC for 6 hours

What was the outside ambient temperature at night
How much time did the compressor actually run per hour, 5 minutes per hour maybe 10 minutes,
Mostly just fan time,
Were the cables also connected at night so you were also connected to the boats battery system
Not just the single battery
Was the portable AC really a 4000 btu window unit
A whole lot less power consumption

[valhalla360]

okhmbldr wrote:
I'm sorry you're having a problem understanding what I did with a battery an inverter and a portable A/C. What I described is exactly what happened. The inverter would shut off when the battery power was drained too far to proceed. I don't know how all that works. I just hooked it up and it worked for me.

I'm not having a problem understanding what you are claiming.

I'm saying what you are claiming something that doesn't work.

[okhmbldr]

I'm sorry you're having a problem understanding what I did with a battery an inverter and a portable A/C. What I described is exactly what happened. The inverter would shut off when the battery power was drained too far to proceed. I don't know how all that works. I just hooked it up and it worked for me.

[valhalla360]

okhmbldr wrote:

valhalla360 wrote:

okhmbldr wrote:
It really depends on how bad you really want to cool down the trailer. One option I did for my boat about 10 years ago; I took it down the Arkansas River from Sallisaw, OK, to the Mississippi River. It was July, and very hot. I had a portable 12,000 btu A/C but no real way to power it on the boat. So, I bought a really good battery, hooked it up to a 2000/4000 watt inverter and did a test with it hooked up to the battery/inverter for power. It ran about 6 hours before the battery couldn’t power the A/C, but it was perfect for my purpose because it was long enough to cool off the cabin and make sleeping comfortable.
During the day as I traveled the river I had a set of cables that recharged the battery so I could have some cooling each night.
So, if that would work for you, just stop a few hours before you reach your destination, turn on the battery power and cool it down a little.
Note: it worked for me, your mileage may vary.

This story needs details...it is possible to run an air/con on batteries. It's just not practical.

What size battery bank? Only one battery, Interstate Batteries Deep Cycle 840 Marine Cranking Amp Battery I picked up at Academy Sports. After the trip this battery was used for the trolling motor in my small lake boat.
How big are the cables from the alternator and what size & type of alternator? The cables were about the size of my little finger, plenty large enough. I don't remember the size of the alternator, but it was on a 454 Mercruiser engine.

A lot of boats have upgraded alternators that put out 200-300amp @ 12v continous output. Assuming the cables are sized right, it's possible to continually recharge with the motor running.

Your typical truck alternator isn't designed to put out anything close to that for long periods of time. Then it typically runs thru little 12-14 gauge wires with bad connections to get to the trailer. You'll be lucky to get 20-30amp @ 12v back to the trailer.

If you are claiming a battery bank sufficient to run 6hr without the motor continually charging, you are probably looking at at least 500lb of batteries. On a big monohull power boat, not a big deal. On a typical RV, there's no where to put them and you just ate up a huge portion of the cargo capacity.

Just a couple of additional notes; the alternator on the boat while cruising during the day just ran the engine and recharged the additional battery, no additional electrical items were running.

And, the A/C was set to about 78 at night, so the compressor would cycle on and off, the fan ran continuously.

Something is seriously incorrect if you are claiming to get 6hr run time (even cycling on & off) out of a single starting battery without the motor running to constantly recharge it overnight.

Looking it up that's an 88 amp-hr battery. If you ran it down to 0% charge (it will actually cut out before hitting that point and within a couple weeks, the damage will be such that it won't hold anything close to 88amp-hr), that would be 1056 watt-hr. A 12k btu air/con unit will pull something around 1200w when running...so the battery by itself will be dead in under an hour.

I'd be surprised if you even get 1/2hr as the amp-hr rating is based on a specific amperage and Typically the 20hr rating which would imply a a 4.4amp draw. 1200w translates to 100 amp draw and the amp-hr at 100amp will be much lower.

So there is something that is being left out of the story...in reality for an RV where the charging system is in the truck and little tiny wires are run a long way back to the trailer, it's even less realistic.

[okhmbldr]

valhalla360 wrote:

okhmbldr wrote:
It really depends on how bad you really want to cool down the trailer. One option I did for my boat about 10 years ago; I took it down the Arkansas River from Sallisaw, OK, to the Mississippi River. It was July, and very hot. I had a portable 12,000 btu A/C but no real way to power it on the boat. So, I bought a really good battery, hooked it up to a 2000/4000 watt inverter and did a test with it hooked up to the battery/inverter for power. It ran about 6 hours before the battery couldn’t power the A/C, but it was perfect for my purpose because it was long enough to cool off the cabin and make sleeping comfortable.
During the day as I traveled the river I had a set of cables that recharged the battery so I could have some cooling each night.
So, if that would work for you, just stop a few hours before you reach your destination, turn on the battery power and cool it down a little.
Note: it worked for me, your mileage may vary.

This story needs details...it is possible to run an air/con on batteries. It's just not practical.

What size battery bank? Only one battery, Interstate Batteries Deep Cycle 840 Marine Cranking Amp Battery I picked up at Academy Sports. After the trip this battery was used for the trolling motor in my small lake boat.
How big are the cables from the alternator and what size & type of alternator? The cables were about the size of my little finger, plenty large enough. I don't remember the size of the alternator, but it was on a 454 Mercruiser engine.

A lot of boats have upgraded alternators that put out 200-300amp @ 12v continous output. Assuming the cables are sized right, it's possible to continually recharge with the motor running.

Your typical truck alternator isn't designed to put out anything close to that for long periods of time. Then it typically runs thru little 12-14 gauge wires with bad connections to get to the trailer. You'll be lucky to get 20-30amp @ 12v back to the trailer.

If you are claiming a battery bank sufficient to run 6hr without the motor continually charging, you are probably looking at at least 500lb of batteries. On a big monohull power boat, not a big deal. On a typical RV, there's no where to put them and you just ate up a huge portion of the cargo capacity.

Just a couple of additional notes; the alternator on the boat while cruising during the day just ran the engine and recharged the additional battery, no additional electrical items were running.

And, the A/C was set to about 78 at night, so the compressor would cycle on and off, the fan ran continuously.

[RetiredRealtorR]

time2roll wrote:

midnightsadie wrote:
going down the road all the air will be sucked out, bad idea any way.

You mean like in a motorhome where they do this all the time?

Agreed. Not a valid point at all.

[valhalla360]

okhmbldr wrote:
It really depends on how bad you really want to cool down the trailer. One option I did for my boat about 10 years ago; I took it down the Arkansas River from Sallisaw, OK, to the Mississippi River. It was July, and very hot. I had a portable 12,000 btu A/C but no real way to power it on the boat. So, I bought a really good battery, hooked it up to a 2000/4000 watt inverter and did a test with it hooked up to the battery/inverter for power. It ran about 6 hours before the battery couldn’t power the A/C, but it was perfect for my purpose because it was long enough to cool off the cabin and make sleeping comfortable.
During the day as I traveled the river I had a set of cables that recharged the battery so I could have some cooling each night.
So, if that would work for you, just stop a few hours before you reach your destination, turn on the battery power and cool it down a little.
Note: it worked for me, your mileage may vary.

This story needs details...it is possible to run an air/con on batteries. It's just not practical.

What size battery bank?
How big are the cables from the alternator and what size & type of alternator?

A lot of boats have upgraded alternators that put out 200-300amp @ 12v continous output. Assuming the cables are sized right, it's possible to continually recharge with the motor running.

Your typical truck alternator isn't designed to put out anything close to that for long periods of time. Then it typically runs thru little 12-14 gauge wires with bad connections to get to the trailer. You'll be lucky to get 20-30amp @ 12v back to the trailer.

If you are claiming a battery bank sufficient to run 6hr without the motor continually charging, you are probably looking at at least 500lb of batteries. On a big monohull power boat, not a big deal. On a typical RV, there's no where to put them and you just ate up a huge portion of the cargo capacity.

[mr_andyj]

The older Dodge Ram's with 5 speed NV4500 trannys had a PTO on both sides and you could put a keen generator on the side of the trans and make all the 120 you would ever need. I have never seen anyone use the PTO so not sure if you can drive and use it at the same time or not, and forget about tracking mpg's. Otherwise u need a gas generator and another hole in your head.

[time2roll]

midnightsadie wrote:
going down the road all the air will be sucked out, bad idea any way.

You mean like in a motorhome where they do this all the time?

[GordonThree]

six hours from a single battery is amazing. When my system was new I got about 3.5 hours from four batteries in parallel.