Taken from the Optimate website for Optimate 4 Recommended for: AGM/MF, STD, GEL and spiral cell batteries from 2Ah to 50Ah and for Optimate 3 Recommended for: AGM / MF, STD, GEL and spiral cell batteries from 3Ah to 50Ah Alfie
I was going to suggest Motorbatt, they seem to hold their charge for an unbelievably long time, got them on 3 of my bikes and they seem very good, the Yuasa on my Triumph Thruxton has lasted 4 years before giving up the ghost a couple of weeks ago, not terrible but not class leading, I’ve got a Motorbatt on my Honda CR750 replica that’s still going strong at 6 years and I very rarely use that bike.