Two IC "Integrated Circuit "inside your laptop charging system,
One inside your battery and other one inside your laptop for fully protection. That's to protect the battery from over charging.
If one of them fail the other will protect it.
These days there is third protection inside the batteries: A thermostat sensor.
If your battery over heated the charger will be disconnect.
all that to protect the battery from over charging or heating.
In your case the voltage is the same but the amps is different, and that's will make your battery over heated.
Keep in mind some laptop vendors build there laptop chargers by measuring the Amps, so they know when the battery is fully charged by knowing the Amps, if you used other charger with different Amps actually your charger will continue charging or discharging before the right values.
and that's will cause a heat, if your battery not contain a temperature sensor or the sensor have fail for some reason that's will cause problems.
I have a more detailed article about how it works on my blog here here.