Towing Camper with A/C Running.

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.