I recently got a UPS (AWP AIDE PRO 1500VA) and fully charged it. Out of curiosity, I tested its battery backup by unplugging it from the wall, and it worked properly. However, when I plugged my phone into the UPS and touched it while charging, I felt a small electric shock in my fingers. It was just a tingly sensation, but it freaked me out enough to unplug it immediately. For context, I live in a house with no grounded outlets (only two-prong sockets), so even though my UPS has a three-prong plug, I can't connect the ground. I'm renting, so I can't really modify the wiring. My UPS is a line-interactive model, not an online or double-conversion type. I'm wondering:
1. Why did I feel a shock from the UPS when it wasn't plugged in?
2. Is this a fault of the UPS, or is it just due to the lack of grounding?
3. Is it safe to continue using this UPS, or should I stop immediately? Any insights from those with electrical knowledge would be appreciated—thanks!
2 Answers
A little leakage current through your phone's charger is pretty normal, especially with a non-pure sine wave UPS. It's not supposed to do that, but it usually isn't dangerous. Still, these UPS systems are meant to be used with grounded outlets, so be careful!
It sounds like your UPS is outputting a floating voltage when it's on battery, which means it's not referenced to a ground. While this can be potentially dangerous, it's pretty rare. Just be cautious!
So does that mean my UPS is basically not safe to use since my outlets aren't grounded?