Running two units at the same time is pushing the limits of a 30A connection. Each 13,500 btu unit draws about 12.5A (25A for two). That doesn't leave much head room for any other loads like your inverter/charger, lights, etc. If you find a good solid 30A connection you should be able to run both, if virtually nothing else.
However, it's not unusual to have less than 30A service on a 30A RV connection at a campground because circuit breakers de-rate every time they trip. That means it might take a 33A load to trip the first time and 29A by the 10th time, etc. Campers routinely trip 30A services and depending on how old the breaker is you might not even get it to hold for a 20 to 25 Amp load. Accordingly, what works at one campsite (two A/C units running) might not work at the next campsite.
When connected to 30A service I turn one of our two A/C units off.
(AE5DS) & Linda Stall
1999 Tradewinds 7372 - Freightliner XC
- Caterpillar 3126B
- Generac IM-72LP
2013 Fiat 500 (Blue Ox) Visit the: National RV Club Website