From specs for 5A model:
Battery capacity 1.2–110Ah up to 160Ah for maintenance.

The one I linked I have had for more than a year and my battery is monstrous 110ah AGM from Varta. The 5A model will charge battery overnight and it's very compact. 10 hours is usually enough. It also knows when to stop charging, which is the most important feature. I have never fully discharged my battery, so may take longer to charge if battery is fully discharged. It is lightweight, small and has carrying bag, so I simply keep it in car all the time.

P.S. I also purchased rubber case/bumper, which is absolutely great:

http://www.ctek.com/gb/en/chargers/Bumper

Pictures Jim. Apologies for bad lighting -- I had to use small flashlight.

I have a Ctek trickle charger on my cosworth - no complaints at all.

Theres a few cheaper alternatives about nowadays that do the same job tho. The Ctek has never let me down.

And your battery should be around 100/110aH

Thanks Sergey, that's pretty neat!:)

It's funny I was looking at chargers yesterday and came across them and was wondering about asking them about a group buy if there was enough interest from the folks on here.

I would be looking to get the 25 amp one so you could power the car during updates etc without daring the battery.