The website doesn’t do a great job describing the product:
Charges 6v @ 0.8A max
Charges 12v @ 3.8A max
The Aldi charger can be used to charge only a disconnected battery e.g. you can isolate your car battery and then charge it. This is explained in the manual but not shown on the outside of the packaging. An additional problem is what happens if there is a power cut - the better units will resume after a power cut. MX5 forum discusses this.
There are alternative chargers e.g. CTEK which don’t have these restriction. The better battery chargers will also switch off completely and wait for the voltage to drop before topping up the battery.
Did you know that a cold battery has a lower self discharge than a warm battery and the acids lowers the freezing point below zero? But a battery shouldn’t be placed directly in contact with a concrete floor when charging it?
Halfords have an interesting car “starter” available for £50. I bought mine with a 10% discount. It’s actually a 17 Ah car battery with a charger in a plastic case and a wall unit for charging it. There are two cigar sockets and a usb charging outlet and also a torch. The supplied wall unit will charge the battery however like many chargers it doesn’t switch off completely (unlike the CTEK).
I use it as a source of power - it costs no more than the battery that’s inside. The only catch, is that the battery needs charging every two-three months to avoid problems. Like a car battery, the life is reduced if the battery is allowed to sulphate.