Just noticed that the AC500 output voltage follows your house voltage when plugged in an outlet

Our normal house voltage is +121V. Every afternoon, because of heavy demand, the Grid drops as low as 107V, and the Ac500 follows it down, unless you unplug it, then it outputs 121V. I guess it has to stay in sync with the Grid for whenever it needs to draw power.
I mentioned on our Ring channel that at 107V we might be on the verge of an outage, and sure enough it started happening.
110V was the standard back in the 60s or so, but new electrical codes want 121V to be the standard as it lowers the amperage. (Watts = Voltage x Amps.) Current flow through house wiring will be a bit lower, wiring won’t get as hot, circuit breakers won’t trip as easily. But, as the voltage drops, appliances will try to draw more amps and will run hotter. This gets back to the AC500 following grid voltage drops. I don’t want that so I’ll just have to start leaving it unplugged.


As I understand it, the AC voltage that you are connecting to your AC500 is passed directly through the unit and the output is simply the same as the input because it is the same power.

It is the basic (standby) UPS implementation. It just passes through your utility power to your connected devices and takes some utility power to recharge the battery.

If you want more, you need a line-interactive UPS, which can correct a too-low/too high utility voltage or a double-conversion UPS that keeps the output voltage exactly at the designed voltage.

You can see the different UPS types in this video:


Just before you immediately call your IT supplier for an online double-conversion UPS, please note that this is not always the best UPS for all circumstances. While a double conversion UPS undoubtedly provides the most stable voltage output, the continuous AC-to-DC-to-AC conversion comes with energy loss so it is less efficient. Also, because these units are always using their inverters, they run hotter and may have noisy fans that are always on. This may not be a problem in a server room but can be a big no-no in a home setting.

Hmm, problem is I’m running Off-Grid. The AC500 only switches to Grid Power when the battery’s SoC falls to whatever I set the minimum SoC to, not before. (PV Priority mode, so that they never completely drain to 0.)
So even though it’s on battery power, the AC500 is letting the house voltage control it’s own output voltage, unless I unplug it. It could have something to do with it drawing a few watts of Grid Power even though it’s running Off-Grid.
That brings up a scenario where if the Grid was at say, 107V, then goes out, the AC500 output will then snap to 121V, all the time still running Off-Grid. I’m not sure that’s a good idea. I’m just going to leave it unplugged all the time. I’ve got the daily runtime pretty well balanced so the batteries never get too low at night before the sun starts recharging them.

1 Like


I see your post is 10 days old; have you discovered new elements in the meantime? Output voltage stability is an essential decision-making criteria in my case.

I just posted a related question in another post, where they speak of “grid enhancement”. Have you got anything like that on your device @St8kout ?

Other post:

So there is no pure sine wave when the unit is in a bypass situation?

I’m pretty sure the sine wave output is not affected, just the voltage level.

All I was pointing out was that in offgrid mode and unplugged, the voltage was the normal 120V. If I plug it back into the wall outlet, even though it’s still on battery power, the voltage will change to whatever the house voltage is at the moment. (Our grid voltage drops every afternoon, likely from people coming home from work and turning on appliances and air conditioning. It has dropped to as low as 107V. During the night it goes back up to around 120V.)

No Wave shape ,frequency and voltage are passed trough if the ac input is coveted.

Most (all i have seen) bluetti power station don’t have separate Input and output AC/DC and DC/AC converter.

they only have one that can convert in both ways.

if you connected to the grid you are by definition not “off grid” but if you go in of grid mode i assume the Power station will try to add back the same amount of power to “the grid” as your load consumes so you grid net consumption is ~0W
But you are still connected to grind and use grid power…

If you want true double conversion disconnect the input from the AC line and get a big AC to DC power supply to charge the Power station with.

Actually, I plug it in ONLY on rainy/cloudy days when it hasn’t recharged enough to run my air conditioner all night. It’s easy to calculate remaining runtime until the sun comes up for recharging. I do have to check the forecast for the next morning for rain/cloudy skies.
I use PV Priority as a backup plan in such cases, and plug it in only at night to prevent fully draining the battery bank. Otherwise it stays unplugged from the grid, which is normally most of the time.
Here’s a little tip some may find useful. I have movable panel arrays, aiming them east and west as needed. I found that on overcast/cloudy days, I get the most power from aiming them straight up instead of the sun’s hidden position. This is only if you can’t see the sun at all. I’ve had it recharge up to 70% on days where the sun never broke through.

Pass through simply means whatever ac power source you are plugged into is passed through your unit without using the inverter or other components. You will get out the other end exactly what you put into it.

1 Like

The inverter is always connected and on.
It is maybe just configured to deliver or consume no power.

It is my understanding that a relay is tripped when plugged into an appropriate AC incoming voltage and the power goes straight through to the load. If this didn’t happen, the batteries would be in a constant state of charge / discharge.