[Nut-upsdev] UPS (Megatec) with strange voltage values

Arjen de Korte nut+devel at de-korte.org
Thu Oct 9 05:59:20 UTC 2008


Citeren Carlos Rodrigues <cefrodrigues at gmail.com>:

> So the actual problem is the nominal battery value being used to scale
> the graphics?

Yes. If 'battery.voltage.nominal' is not provided by the driver, it  
attempts to guess this based on the 'battery.voltage'. But the latter  
doesn't work for higher battery voltages, since the battery low and  
high voltages don't overlap. This is not the case here.

> I don't think there's anything that the driver can do about this.

There is. If the reported battery voltage is only part of the total  
battery voltage, you should allow a manual override to set a  
multiplication factor. Note that 'battery.voltage' and  
'battery.voltage.nominal' are supposed to report the voltage of the  
total battery string and at the very least, should use the same for  
both.

> Perhaps the graphics should use a dynamic scale instead of a fixed
> scale (there are many other models out there reporting nominal
> voltages of 12V and then ~2V for the current battery voltage).

This is the case. The problem here is that in this case the megatec  
driver reports 'battery.voltage' as single cell and  
'battery.voltage.nominal' as the total string voltage.

Best regards, Arjen
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