Wich battery tester brand do you recomend me ?

get a Fluke.

Any Digital Volt Meter will do the job. Get at east one lead with Crockodile clip on,
Goes over 14.5 Volts when revved = Voltage Regulator blown, May havealso Cooked the Battery.
Goes up to 14.5 Voltes, Alternator OK
Switch Off engine
Should read 12 Volts
Leave for 20 minutes
Still reads 12 Volts Battery OK
Reads below 12 Volts you need new Battery

Schumacher is pretty good for the money. Good feature set for <$50.

Pep Boys

Interstate.

Your dogs tongue. If it hyper yells it means the battery is fully charged