[Nut-upsuser] ordered shutdown

[Arjen de Korte]

Citeren Julian Stacey <jhs op berklix.org>:

> As batteries age, they might (or not) retain most of their Amp Hour
> capacity, but as their internal resistance increases, can't deliver
> same peak current load as a newer lower internal resistance battery.

The internal resistance usually increases because of loss of active  
surface area in the cells (shedding lead from the plates and  
sulfatation) and (for VLRA cells) by drying out. All these effects not  
only cause higher resistance, but also lower the Amp hour rating.

> An on line battery test does not tell much, just a binary Worked/
> Failed, (unless it tells more by comms port to NUT?) I would guess
> few (if any ?) UPS might have current measuring, for prediction ?
> None of the 5 or 6 UPS I have serviced have individual voltage
> sensors to individual batteries, so UPS & Nut can only measure the
> whole stack, & as some UPS use eg 4 x 12V 17AH @ 60 Euros, replacing
> all 4 when only some need it, is expensive.

The only reliable way to determine this, is by running a (periodic)  
deep discharge test, either through a build in command or by pulling  
the plug. There is no need to remove batteries out to do this.

Best regards, Arjen
-- 
Please keep list traffic on the list