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Living Legend
Get an optimate charger, these not only charge the battery but cycle it by discharging and then recharging which keeps the battery in good condition and it will last for years. They are especially useful if the bike is going to be sat for a couple of weeks/months at a time with no use and also prevents it from discharging to levels that damage the structure. In warmer climates this is not as necessary but in the UK...Yeah, go for it!!
That's what came with my 3T but I'd never heard of it and have always used Battery Tenders. The previous owner kept it on the Optimate year around. It's good to know that I have a worthwhile charger. The battery was 8 years old but it started right up and got me home from the seller's house. I still replaced the battery within a few days.