check the rating
A battery should be charged ideally at 10% of it’s ampere hour rating. (60ah = 6 amps etc.)
Your vehicle alternator CAN overcharge the battery and cause damage. However , this can be overcome by using a smart battery cahrging relay, or by manual operation.
By limiting the time you charge from your vehicle you can avoid damage. (see the other thread about charging).
I have used ordinary battery chargers without any problems as long as you observe the 10% rule.
Also when you say smell of burning, this may mean a faulty cell. If you have removable cell caps, check if any are ‘gassing’ while charging. I mean excessive gas in relation to the others. You will get slight bubbling when charging, but of any are more sort of ‘fizzing’ then you have a bad cell.
Also remember you will always get a ‘rotten egg’ smell when charging any battery and is not a fault. Just chemical reaction.