[Nut-upsdev] Mustek PowerMust 848

Arjen de Korte nut+devel at de-korte.org
Wed Jan 21 19:33:36 UTC 2009

Citeren Marian Ciobanu <ciobi at inbox.com>:

> The blazer manual warns that using a linear approximation based on
> voltage is quite inaccurate. So I think it is improvable.

Indeed. It also explains the reason why you can't use battery voltage  
in that calculation. Although you efforts to improve this are heart  
warming, you don't seem to grasp the background behind the way battery  
charge needs to be calculated under load (which doesn't use the  
battery voltage at all). Please go and Google for 'Peukert equation'.

> True, it's not
> going to get very accurate, but is the current implementation the best
> that can possibly be done? The UPS reports a "load", which is related to
> current.

Output current can't be correlated to the battery current that you  
need for a better battery charge calculation. Let alone the fact that  
a driver will never be able to monitor this with the near real-time  
accuracy that would be needed in the calculations. You'd need a lot  
more than one measurement every two seconds for that.

> I think it should be used when determining a charge. (A
> calibration program would be nice too.)

Not at all. :-(

> Anyway, I have to run my experiments first. My goal is to have a variable
> that goes from 100, when the battery is fully charged and the AC power is
> lost, to 0, when the UPS starts to warn that it has reached the "low
> battery" level. This should work for dynamic loads, decreasing faster as
> the load increases. If I make significant progress, I'll report back
> sometime next week.

Feel free to do so, but don't expect that the results of your hard  
work will be incorporated in NUT.

Best regards, Arjen
Please keep list traffic on the list

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