AC2A Not So Silently Periodically Cycling Fan

@BLUETTI_CARE I have a new AC2A that I am using as an EPS. There is only a 16w load (cable modem, Wi-Fi mesh node). The app shows 16w from the grid and 16w out on AC. DC is turned off. The Charging Mode is set to Silent. AC/DC-ECO is Off. (For some reason the app is showing 0.10kWh of PV Generation.)

Periodically the fan comes on for several minutes. The AC2A is in my wife’s office, so I would prefer that it remain silent.

Is the periodic cycling of the fan normal with such a light load and Silent Mode charging? If not, what can I do to stop it? If it is normal, is there anything I can do to minimize the fan run time?

@ChuckD Will this happen if the device is loaded directly without charging?

@Bluetti_Care Do you mean unplug from the wall, go onto battery power and see if the fan comes on?

How does this relate to “Silent” Charging Mode?

@ChuckD Yes. First of all, we want to check if there is a problem with the fan. Silent charging mode can only make the fan sound quieter. If the temperature reaches a certain range, the fan will still rotate.

I don’t have a AC2A but have several AC180’s which I use in UPS mode powering electronic equipment similar to what you stated, and all of the AC180’s cycle the internal fans periodically.
When these units were first released on the market there was much discussion on this forum about how the fan cycles on and off when the units have even a low output wattage draw in UPS mode.
In summary the response given by Bluetti, which makes complete sense is as follows.
The units even in UPS mode always have the internal inverter powered on ready to switch over if grid power fails within the 20ms time period requirement.
To do this the inverter draws power from the batteries causing them to cycle down to 99% then back to 100% as well.
Doing all this makes the internal circuitry increase in temperature thus causing the fan to also cycle periodically to cool the electronic circuitry.
Hope this clarifies what may be happening with your AC2A.


@DJR Thanks. I thought I saw a 99% SOC one time when the fan was running, but it was a brief glimpse and I wasn’t positive. (I did search on AC2A and the AC Series but maybe I didn’t go back far enough.)

Just to close out this thread, the power was off for several hours today during installation of a generator and the fan didn’t come on. (It will be several more weeks before I can test that the AC2A plays nice with a Generac whole-house generator.)

Side Note - The new Eaton 9SX700 double-conversion UPS on the other side of the house worked fine and shut down and booted up the QNAP NAS as expected. @BLUETTI_CARE It would be great if Bluetti added a USB communication port to some of their units that have fast transfer times so that they could be used with a NAS. The AC2A is much smaller, lighter and less expensive than a double-conversion UPS. When the time comes to replace the (lead-acid) battery in the UPS, it might make more sense to switch to a Bluetti if it had communication capability.