There are a number of types of battery charger starting with the simple trickle charger.
The trickle charger has no real control and uses a very poor quality transformer and rectifier and is OK when it is monitored it will charge a battery from flat although it could take a long time and it can also over charge a battery. Normally has an ammeter to give some indication as to charge condition.
The regulated battery charger will have a float voltage the same as the car alternator and can charge a battery from flat to half charged quite quickly but then slows up and takes a long time to finish off the job. However it is safe to leave on the battery 24/7. But with a sulphated battery it is not that good at reversing the process and often they have anti-reverse polarity system so will not charge a totally flat battery.
The step battery charger comes in too main types those which switch off when complete as used with fork lifts and those using an extra third stage which continue to float charge the battery once fully charged.
The three stages are to start with constant current until a set voltage is reached this varies according to battery type but around 14.8 volts.
So second stage is a constant voltage.
It then monitors the current when this drops to a pre-set level around 5A then the voltage is reduced to around 13.2 volts (Float charge).
Because of the dropping from 14.8 to 13.2 is dependent on current which is also in turn dependent on battery size these chargers are matched to the size of battery to be charged.
From the adverts the Ctek Multi MXS 3.6 is a type of step battery charger.
The problem with using a charger that is too small is that it may never drop to a current which will put it into the final stage (Float charge) with the larger chargers I have used there is also a timer so if the battery is self discharging to an extent so the current can't drop to the pre-set level it will time out and drop anyway. They also had a sensor and if the voltage dropped below a pre-set level they would restart the sequence.
It claims to be a four stage charger but does not really say what the stages are. It says designed for 7 - 75Ah but can be used on up to a 110Ah so it would seem ample for your car.
It also however says it has reverse polarity protection so likely it will not charge a fully discharged battery.
The problem with a lot of fast chargers is they raise the voltage to over what the alternator safety system will cut in at and if big enough can burn out the Zenor Diode in the cars alternator. So normally one has to disconnect the battery before connecting to a fast charger.
The Ctek Multi MXS 3.6 claims this is not a problem. However I would not class 3.6A as a fast charger. Most of the step chargers I have used have been at least 25A.
It claims to charge a 75Ah battery in 17 hours but at 3.6A that's only 61.2Ah and with a 25% loss one would expect more like 30 hours at that rate even with no losses it would take 21 hours.
When one realises that they can't work out simple maths one starts to wonder about their other claims.
My late sister's car had the problem with batteries going flat and I re-charged it with a simple trickle charger rated 8A for couple of days then used a very small float charger to maintain it which cost me £8 from a radio rally. I would say £62.90 to maintain a battery is like using a sledge hammer to crack a nut.
A battery charger like shown
here will stop a battery going flat because of car alarms (Or get same thing for Halfords at £25) and a standard battery charger for
Halfords only costs £40 and has over double the output at 7.5A or can be selected to auto or 1.5A.
There are some very clever chargers out there Sterling do a pulse battery charger which chargers for so many seconds then monitors the battery and can recharge a 400Ah battery bank in less than 6 hours but can't really see you need a charger which is so clever. They are for things like narrow boats.
The only saving grace for the Ctek Multi MXS 3.6 is it is water proof.
