All good quality chargers need power from the battery to ensure you have the leads on correctly (not crossed)
Some cheaper ones may not have this safe guard and will blow the fuse in the front cover if you connect up incorrectly
Sealey or Draper Chargers will be OK
Try http://www.amazon.co.uk/Sealey-Battery-Charger-12V-230V/dp/B000RA0YYU
Or E-Bay for the above chargers
I hope this is of some help
Thanks and this looks good.
But, is this a charger that does not require a residual voltage to start charging and how can you tell by looking at the description as I can't?
James EB