[Nut-upsuser] Cyberpower CP850PFCLCD 120% battery charge

Charles Lepple clepple at gmail.com
Fri Apr 1 02:12:22 UTC 2011

On Mar 31, 2011, at 3:09 PM, Arjen de Korte wrote:

> Citeren Justin Ellison <justin at techadvise.com>:
>> I have a CyberPower Systems CP850PFCLCD that I'm hooking up to NUT  
>> 2.4.3
>> from apt running under Ubuntu 10.04.  Using the usbhid-ups driver,  
>> things
>> *seem* to work at first glance, but there are some odd issues.  The  
>> most
>> notable issue is that the battery.charge indicator reads 120 when  
>> at full
>> charge.  I came across this post here:
>> http://lists.alioth.debian.org/pipermail/nut-upsuser/2007-September/003222.htmlbut
>> it looks like the user never supplied the necessary data.
> 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.


in the current version of cps-hid.c, it looks like FullChargeCapacity,  
DesignCapacity and CapacityMode are unmapped. Or, it could be that the  
firmware designers confused the RemainingCapacity value with  
AbsoluteStateOfCharge, which is allowed to be greater than 100%.  
(Pages 36-38 of the PDC spec.) Are two "-D" flags sufficient to see  
the report descriptor information and relevant reports?

- Charles

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