I was running a ~400W load (freeze dryer) on DC battery power but noticed an audible change when I connected the AC wall plug. Checking the “AC Output” screen confirmed that the AC500 was sending 120.4V while on the battery but it only 108.2V when the unit was plugged into the wall. Is this normal? If so, why?
I have my AC500 mainly for emergencies so this was observed when I took it out of storage for my monthly checks. I didn’t have enough battery power for the freeze dryer cycle to complete so I plugged in the AC input and heard a big drop in the freeze dryer fan. Kind of alarming.
Follow up note: I took a closer look at the AC input and it is 108V also. I guess the AC500 is in bypass mode? Now I am wondering if 108 VAC in my home outlets is an issue…?
Yes, 108 VAC was your outlet voltage and the unit was in bypass mode.
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If you live in a country where your supply voltage is 120 VAC nominal from the grid, and from the grid energy meter input, with the meter output breaker switch off (no load), you probe around 120 VAC, then a voltage drop of 12 V to your outlet can be considerably high with a load of just about 400 W which is 3/4 A. This depends solely on the topology and quality of your home’s wiring.
But, if the AC500 was charging at the same time you should also consider its added load.
Yes.
If the power grid can maintain 108V, it can still carry the load normally. The quality of the power grid may be poor. If the voltage drops further, normal charging may not be possible.