For £12:99 it works on both 6v and 12v batteries for bikes and cars up to 120Ah. It’s probably not as good as the optimate, and doesn’t come with wires for permanent connections, but if you just want a pretty decent charger you can’t argue with the price!
Optimate and battery chargers are different things. One charges batteries, the other is for maintaining batteries. a charger won’t look after a battery properly, just as an Optimate won’t correctly give a forming charge to a new battery.
This charger actually includes a maintenance mode - it goes on to trickle charge and can be left on the battery indefinitely. As I said, not quite as clever as the Optimate (which has the trickle charge/maintenance but constantly switches between that and monitoring of the state of the battery), but it would be sufficient for sure. As for the forming charge - the Optimate 4 can be used to provide a full charge for a battery up to 30Ah (at least according to the documentation)…
Optimate 3 and earlier were designed to charge, maintain and recover a battery, but were not designed for the high amp forming charge needed for a new battery. Does the new Optimate have a special mode for new batteries/charging? Or does it do what the previous ones did and automatically start from a diagnostic mode?
The forming charge doesn’t necessarily need a high amperage - just one suitable for the capacity of the battery. What it does need is a higher than typical voltage (14.7v). I just checked, and you’re right, the Optimate only goes up to 14.3v. This cheap charger, however, does have a special 14.7v mode for initial charge, so I’m covered