"SMC" series Smart-UPS switches to battery when it encounters high input voltage.
SMC1000, SMC1500, SMC1000-2u, SMC1500-2u
The SMC series of Smart-UPS feature boost-only voltage regulation. If input voltage rises above your high voltage transfer point, the UPS will switch to on-battery operation. This is normal.
If you find your unit repeatedly switching to on-battery operation due to high input voltage, you can adjust the high voltage transfer point via Powerchute Business Edition. This gives you a wider range of acceptable input voltages and will allow your UPS to stay on-line in a wider variety of situations. Please note that this will also potentially expose your attached load to higher voltages, however it will never expose your load to anything outside of CBEMA standards for acceptable input voltage. If your application requires both boost and trim voltage regulation, we would suggest upgrading to an SMT or SMX series Smart-UPS.