I've used a CTEK for years with a spare battery in the garage. Safe to leave it for months on end ... it will trickle charge if there's a voltage difference and if not it does not charge. Very happy with it.

I just swap batteries over very 3 months or so and keeps them fresh as a daisy !!

It goes through a charge cycle which helps maintain the battery (de-sulphation when sulphur from the sulphuric acid accumulates on lead surfaces).

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2007MY Freelander 2GS 2.2 TD4