Just sharing a little trouble shooting in advance for those who encounter it.
Quick summary of events.
Bought a new winch a while ago (Runva 11XP Prem).
Manual states a 650 cold cranking amps battery was required.
I found I had a 600 CCA battery only.
Googled for numbers on running the battery with the engine/alternator going at Melbourne temps and found it should be putting out about 900 CCA.
Initially all seemed well, so left it as it was.
A couple of months in had the first instance of when hitting the button the solenoid would just tick and the winch wouldn't reel.
No rhyme or reason to the timing. Happened hot, cold, with the engine having been off for a day and just doing a test reel in the driveway or having been driving for hours with it still running. Thought it might be a lose connection or damage wire given the random nature, but no. All checked out.
Headed to the local battery store who hooked up their test machine, found the existing "600" CCA battery was really putting out about 530 CCA. Due to the years I guess.
Bought a new Century Ultra Hi Performance battery putting out 700+ CCA, have been giving the winch a good bashing for the last month and hasn't re-occurred so seems to have done the trick.
FYI for whoever searches for this when their battery carks it next