I don't recommend the Delta 3 Plus as a UPS
I purchased the Delta3 Plus with the intention to use it as a UPS. I ordered early and waited. The D3P showed up but for a long time no UPS software. Eventually the wait go so long I purchased an APC UPS as that was available and it actually works.
So while I have the D3Plus, I have to discharge and recharge it every 3 months. This process is another gift EF gave to me for buying and not using it, but needed to keep in god health "just in case". After a long time I became motivated to install the Power Manager software on a non-critical machine just to see how useful it could be as a UPS.
TLDR; Its not good.
The instructions are not very clear even though it is a very simple process. However, there are some issue you should know about.
- The power manager app needs to be running and you have to have have the D3P plugged into the wall, the connect USB cable and then connect the power cable...Every time you do a restart.
- The USB cable cannot be USB-C to USB-C. For some reason in 2026 EF can't figure out that many of us are living a USB-A free existence. This took me a while to figure out from a small not in the guide. Requires USB-A on the device side and USB-C into the D3P. I thankfully found a USB-A to USB-C data cable and a computer that had a USB-A port to try.
- If you close the Power Manager app while the PC is under UPS power, you lose UPS functionality and cannot recover it until you have AC power from the grid supplying the D3P again. The only way to reset is to disconnect the PC from the AC power, connect the USB cable and then connect then reconnect the power to the PC. Startup and run the power manager app again.
- There is no way to send any of the UPS info via internet to the phone app about power loss and UPS status. No emails either.
Overall I give this feature a D- compared to what it could have easily been. If you're only looking to use an EF unit as a UPS, you're better off with something else.