I assume that you have the MD18559, as this is the one currently available for £12.99.
If so the manual is available
here
If this is the one, page 9 states this below:
"Proper use
This appliance is a primary-side switched charging appliance
with pulse trickle charging. It is suitable for charging and trickle-
charging the following rechargeable 6 V or 12 V lead batteries
containing an electrolyte solution or gel as well as AGM batteries,
which are used in motor vehicles:"