Hi guys, this is really a minor thing, but the nut plugin in collectd is not loaded, because in sb-epel there is an old rpm which requires another collectd version.
In epel repo there is collectd-nut-5.8.0-4.el7.x86_64.rpm, but in sb-epel there is collectd-nut-5.8.0-3.el7.x86_64.rpm. So the /usr/lib64/collectd/nut.so is not present and the nut plugin is not loaded.
I installed the collectd-nut-5.8.0-4.el7.x86_64.rpm from epel and it works fine now.
Please update the rpm in sb-epel-repo.