[Nut-upsuser] Cyberpower CP850PFCLCD 120% battery charge

Justin Ellison justin at techadvise.com
Fri Apr 1 02:24:56 UTC 2011

Good news, this model appears to work perfectly, save for an odd
factory default.  I only have 55% of a load on this thing, but the
minute I unplug it, I have right around 5 mins of battery time.  That
was causing the LB flag to be set almost immediately(because the
factory default for low runtime was 300).  I was able to set a new
bettery.runtime.low of 120 using upsrw.

On Thu, Mar 31, 2011 at 2:09 PM, Arjen de Korte <nut+users at de-korte.org> wrote:
> For whatever reason the people that made the UPS firmware decided that they didn't need to follow the USB HID PDC specifications. From the data you sent, it looks like the value for battery charge that is reported by the UPS needs some conversion (coefficient and/or offset) to get to the true battery charge. Most likely, this is present in the bundled software for the UPS, but sadly we don't know them. So unless you're going to change that, the situation is unlikely to improve. It looks like '120' means 100% charge, but one data point is not enough to find (at least) two missing parameters.

When I tested it out tonight, I made a point to watch the LED on the
unit in comparison to the battery.charge indicator from nut.  Almost
instant I unplugged it, battery.charge went from 120 to 91, and
immediately fell in sync with what the LED was showing.

>> The other issue that I found was that the LB flag is sent way to early when
>> I unplugged the UPS from the outlet.
> I don't think so. The data you posted indicated that about the time the UPS started reporsing LB (low battery), the runtime fell below the battery.runtime.low, so this is about right. If you don't need 5 minutes to shutdown your system, you might try lowering this value (if the UPS supports that) and see if this increases the useable time on battery.

Aside from the minor annoyance of the 120 battery.charge when full,
this UPS works perfectly with Nut.  Nice work guys!


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