A battery protection system comprising: a plurality of protection modules (302, 312), 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 operable for outputting a protection signal (Sovi, 434, S OV2) if an abnormal condition in said battery cells is detected; a switching terminal operable for receiving a switching signal; and detection circuitry, coupled to said monitoring terminals (BAT1,...., BAT5), said output terminal, and said switching terminal, 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 (302, 312) 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 of said first protection module and a first monitoring terminal of said first protection module are coupled to said second protection module and operable for receiving a signal (S OV2) from the output terminal 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 operable for outputting a protection signal (Sovi, 434, S OV2) if an abnormal condition in said battery cells is detected; a switching terminal operable for receiving a switching signal; and detection circuitry, coupled to said monitoring terminals (BAT1,...., BAT5), said output terminal, and said switching terminal, 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 (302, 312) 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 of said first protection module and a first monitoring terminal of said first protection module are coupled to said second protection module and operable for receiving a signal (S OV2) from the output terminal of said second protection module.