CyberPower CP1350PFCLCD

I recently picked up a CP1000PFCLCD and I'm running into the same error. UPS shows 12% battery remaining in Frontview and RAIDar when it is fully charged and connected to AC power. Acording to the NUT documentation, the hidups driver is extremely outdated, and the proper driver for this UPS should be usbhid-ups. I tried fiddling around with the NUT installation on my ReadyNAS Ultra to add this driver, but ended up running into issues with directory permissions, so I decided I could live with the error, at least until the firmware updates NUT (fingers crossed).

HOWEVER, once the UPS switches to battery power, it seems to report battery level correctly (still slightly inconsistent, but it at least jumps into the 80s-90s and then decreases relatively linearly).

As a test, here's how I set up the devices attached to my UPS to see if everything was working (I didn't feel like running the battery all the way down to 10-20%):
- CP1000PFCLCD usb cable plugged directly into ReadyNAS Ultra 2. ReadyNAS Frontview settings set to shut down ReadyNAS when UPS reaches 90% power, and allow network monitoring of the attached UPS from any address on my local subnet.
- PC running WinNUT. WinNUT settings set to monitor UPS at the ReadyNAS's IP address, and shutdown PC after 30 seconds on UPS power.
- Monitor and router also getting power from UPS

Here's how things went:
- Pulled plug on UPS
- about 10 seconds later got an email from my ReadyNAS saying my UPS was on battery power
- At 30 seconds mark, PC shuts down
- About 5 minutes later, get an email from my ReadyNAS saying that UPS battery level is critical and ReadyNAS is shutting down
- ReadyNAS shuts down

To further test things out, I started up my ReadyNAS and PC again (while still on battery power, which the UPS handled like a champ, FYI), and took a look at the battery level reports in RAIDar and Frontview. Started off around 82% and then continued to decrease relatively linearly for the couple minutes I had things running.

Plugged my UPS back in, started everything back up, and RAIDar reported 72% battery remaining in the UPS, increasing relatively linearly all the way to 100%. The readout then stayed at 100% for a little while, but after a few hours and a PC reboot, it's back to reporting 12%...

Moral of the story, the CPxxxxPFCLCD UPS seems to work properly with the ReadyNAS, it just reports 12% when it's full instead of 100% (which I can live with).