A battery protection system comprising: a plurality of protection modules , each protection module of said protection modules comprising: a plurality of monitoring terminals (BAT1, ...., BAT5) operable for monitoring a status of a plurality of battery cells; an output terminal (OV) operable for outputting a protection signal (Sovi, 434, S OV2 ) if an abnormal condition in said battery cells is detected; a switching terminal (VCC) operable for receiving a switching signal; and detection circuitry , coupled to said monitoring terminals (BAT1, ...., BAT5), said output terminal (OV), and said switching terminal (VCC), and configured to switch from a normal-working mode to a fast-test mode in response to said switching signal, wherein in said fast test mode a series of tests are performed on the protection module to make sure that the protection module works properly, delay outputting of said protection signal (S OV1 , 434, S OV2 ) for a first time interval (ΔTN) if said abnormal condition is detected in said normal-working mode, and delay outputting of said protection signal (S OV1 , 434, S OV2 ) for a second time interval (ΔTF), less than said first time interval (ΔTN), if said abnormal condition is detected in said fast-test mode, wherein said protection modules comprise a first protection module for generating a first protection signal (S OV1 ) to protect a first set of battery cells and a second protection module for generating a second protection signal (S OV2 ) to protect a second set of battery cells , and the switching terminal (VCC) of said first protection module and a first monitoring terminal (BAT5) of said first protection module are coupled to said second protection module and operable for receiving a signal (S OV2 ) from the output terminal (OV) of said second protection module . a plurality of monitoring terminals (BAT1, ...., BAT5) operable for monitoring a status of a plurality of battery cells; an output terminal (OV) operable for outputting a protection signal (Sovi, 434, S OV2 ) if an abnormal condition in said battery cells is detected; a switching terminal (VCC) operable for receiving a switching signal; and detection circuitry , coupled to said monitoring terminals (BAT1, ...., BAT5), said output terminal (OV), and said switching terminal (VCC), and configured to switch from a normal-working mode to a fast-test mode in response to said switching signal, wherein in said fast test mode a series of tests are performed on the protection module to make sure that the protection module works properly, delay outputting of said protection signal (S OV1 , 434, S OV2 ) for a first time interval (ΔTN) if said abnormal condition is detected in said normal-working mode, and delay outputting of said protection signal (S OV1 , 434, S OV2 ) for a second time interval (ΔTF), less than said first time interval (ΔTN), if said abnormal condition is detected in said fast-test mode, wherein said protection modules comprise a first protection module for generating a first protection signal (S OV1 ) to protect a first set of battery cells and a second protection module for generating a second protection signal (S OV2 ) to protect a second set of battery cells , and the switching terminal (VCC) of said first protection module and a first monitoring terminal (BAT5) of said first protection module are coupled to said second protection module and operable for receiving a signal (S OV2 ) from the output terminal (OV) of said second protection module . <EOS>