[Nut-upsuser] Unsupported UPS using megatec_usb

Arjen de Korte nut+users at de-korte.org
Sat May 17 09:14:48 UTC 2008

> The apparent maximum voltage of the battery is 12.8v.

Is this the value reported by the UPS or did you measure it with an
external measuring instrument? A UPS is not a calibrated measuring
instrument and the values reported by some models are way off the 'real'
values. In other words, the accuracy is usually lousy.

> I've hooked up a monitor to drain it, and once the battery voltage gets
> down below 11v the overload beeper starts up (which cannot be disabled),
> and
> after a very short period of time the ups shuts off the monitor, upon
> which the voltage jumps back up to 11.30v, and then again after a short
> interval
> the UPS shuts off.
> Is it normal for the UPS to have trouble with voltages so close to the
> full capacity of the battery?

The UPS powered the load without mains present, started beeping when the
battery was almost empty and switched off the load (to protect the battery
for deep discharge). Short of the voltage readings, nothing wrong here.

Also note that some UPS'es will only allow you to shutdown the load when
running on battery. Try if the 'load.off' command works in the absence of

Best regards, Arjen
Eindhoven - The Netherlands
Key fingerprint - 66 4E 03 2C 9D B5 CB 9B  7A FE 7E C1 EE 88 BC 57

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