Battery powered rooftop AC installed in my sleeper.

So for its working great. It didn’t get much below 80 degrees in Kansas City last night (outside) and I had it set at 70 overnight. I had to bump up the temp from 68 because it was getting cold in the truck. This was on the eco-mode setting which is the most efficient for the battery. It blows most of the air directly down on the bunk and draws the air from just in front of the blower vents so there is some efficiency loss. The cab is noticeably warmer as the air is not flowing to the front. It would not work very well as a all around AC unit while driving unless you mounted it directly over the driver seat.
If I had to do it over I would mount it further forward so the air would circulate better.

 

Im not a fan of the batteries in living compartment, offgassing from charge/discharge, maybe case it off and add a vent fan?

Clean install though, i need to truly test how long my electric ac system lasts on existing batteries

 

The roof mount location is best. Cold air flows down.
Your insulation is key. Were you able to get any insulation in the roof where most of the heat loss is?
Check to make sure there is plenty of circulation around the condenser unit outside on the roof.
I don't see a problem but the harder the unit works to get rid of heat the more electricity it requires.
Because you have a moderate sized flat top sleeper, 6800 BTU's may be adequate for the cubic feet you are trying to cool. Keeping the curtains closed and only cooling the sleeper area will help even further.
Guys with a high roof sleeper wide open, 6800 BTU's likely won't be enough.

We will see how long that stock alternator puts up with the extra load day after day. There are many other heavier duty options available when that one gives it up. Look into the emergency services (fire truck, ambulance) upfitters for good alternatives. Keep in mind the charging rates of your flooded cell SLI( Starter Lights Ignition) truck batteries are different than the AGM batteries. One or the other is going to suffer from using the same charging system. Lots of info here from Deka Battery:
Frequently Asked Questions - East Penn Manufacturing

Good luck

 

They are AGM (Absorbed Glass Mat) batteries. They are completely sealed.
Here is the FAQ section about AGM batteries from Deka, East Penn Battery. Lots of cool information here;

Frequently Asked Questions - East Penn Manufacturing

 

Ah, well, glad to be mistaken

 

About alt, carry a spare, even at 500$ a year should be a cheap date vs fuel/road call

 

Absolutely a good choice.
I used to buy brand new ones. When you have to the time you can source them cheaper than any rebuilt unit from fly-by-night service truck.

 

The only concern is the batteries and keeping them charged, the charger should be setup for agm batteries, then they last a long time.

 

Those new batteries are amazing. Lot of cars have them mounted under a seat. The part that got my attention is being able to mount them sideways, upside down. Lol

 

Having a spare alternator on hand is a great idea. I can get a 200 amp from my local truck repair shop for $400. I have heard you can get one over 300 amp but they are not able to find one. I will hit the goog for that. It was 90+ driving to Minneapolis today and it took a lot longer to charge the batteries. This was the first time I ran the air continuously all night for 10.5 hours in hot weather.
The Victron is a 3 stage charger with specific settings for AGM and Lithium type batteries. The bulk charge (up to 80% capacity) took 5.5 hours. The Absorption stage finishes it off, then switches to float mode. I drove for 8 hours and this is the first time it did not reach float stage. I did not install a digital battery monitor but I think I will need one. Victron makes a bluetooth shunt ($135) so you can read the actual discharge rate in real time. That is the only way to know if I have discharged the capacity below 50%.