Type of car battery charger

I am trying to assess what type of electric circuit my 12V car battery charger is using.

It is 2.7A DC (it also says its 4A rms)

i just charged my car battery with this £18 charger and when i scoped the battery terminals while it was being charged i saw the following type of waveform



....this looks like the waveform you get on a capacitor following a diode bridge with a smoothing capacitor after it ?

....the ripple was about 200mV pkpk.

...do you think this means that my charger is just like this ?.....

mains transformer -> diode bridge -> capacitor-> power resistor -> battery

?

i can't open the charger as it has "safety" screws which i dont have a driver for.

i have limited view through the vents in the top.

..all i can see is a transformer and some quite chunky diodes.

In operation the outside of the plastic case gets pretty warm.

When the green LED comes on to say its fully charged.....it still feels warm and i'm wondering if its still forcing current in and damaging the battery ?

tried an ammeter in series?

I doubt those cheap k-mart chargers you can leave connected permanently to a battery, they work good a charging up a flat auto battery, just don't leave it connected > 8 or so hours.

Measure the battery voltage while charging.
If stays between 13.5V and 14V, it is fine, warm or not.

If it has more than 1 diode, it is full wave. There is no need of capacitor to filter, the battery behaves like one.