I have the same clarke one, on a full battery i've had no problems on wheel nuts that have been torqued up properly. Not so much joy on the ones that have been done up with a breaker bar by some muppet doing it "as tight as it'll go".......

I always torque mine up properly and it does the job fine.
Can't complain at £100 mine was, but its still nothing on my mates snap on gun so most of the time i just use that as its in the workshop. Its like everything snap on, you think "bugger me i'm not paying that", then you get something else and eventually use or borrow the snap on equivalent and think, "i wish i'd got that now" haha.