UPS and Generators

I have used UPS with my onboard generator to power my TV and sat and to run my computer based GPS, when driving. It was wired into the house batteries. The first unit worked great for about 5 years. The only time I noticed it cyling between the UPS and generator was if I ran an electric heater. It went up in smoke going down I-40 in Arkansas on their "smooth" roads. The next one I used was fair. It did not like it when I was at a high voltage charge, it smoked up. I now use Samplex PSW inverter.

the issue is the hertz, mine goes between 59 and 62. i notice people not mentioning this issue . im curious why their ups is not having trouble


this has nothing to do with a rv.

A portable UPS normally has a small inverter, charger, and perhaps 5 amp hour to at the most 20 amp hour AGM style battery.

For your RV, I would recommend a inverter, and hook it up to the normal 200 - 400 amp hour battery bank. It is much less expensive, and will last much longer, and while the generator is running, the standard charger is in the 45 to 65 amps per hour rating, much higher than any portable UPS system will charge at.

You can buy a 500 watt inverter from Costco for about $40. That can be plugged into a cigarette lighter receptacle (Radio Shack sells them - along with any local auto parts store). I wired my cigarette lighter receptacle with #10 wire (for low voltage loss) and a 20 amp fuse, so if I go over about 250 watts, it will trip the fuse. I have never tripped the 20 amp fuse, even while watching TV, run the DVD, cell chargers, ect.

Your UPS might be sensing the generator output, and find it out of range by one or more parameters. It might be high voltage, not between 59 and 61 hertz, or some other reason. Many UPS systems are close tollerance on frequency, and require it to be between 59.9 and 60.1 that is to close for most generators, as the engine speed can vary by 20 RPM, changing the hertz by more than 1.

Good luck!

Fred.