A battery pack (200, 200C, 700) comprising a battery protection system (202, 602, 702) for protecting a battery pack (200, 200C, 700) that comprises a first battery and a second battery, wherein said battery protection system (202, 602, 702) comprises: a first detection circuit configured to detect a status of a first voltage (V SEN; -V SEN) across a current sensing element (R SEN), and determine whether said first battery is in an abnormal condition according to said first voltage (V SEN; -V SEN), wherein said current sensing element (R SEN) is coupled between a negative terminal (P-) of said battery pack (200, 200C, 700) and a negative electrode of said first battery; a second detection circuit configured to detect a status of a second voltage (V P1 -V1; V1-V P1; V CET1; V DET1) across a first switch circuit (CET1-DET1) in a first path, and determine whether said first path is in an abnormal condition according to said second voltage (V P1 -V1; V1-V P1; V CET1; V DET1), wherein said first path is coupled between a first positive terminal (P1+) of said battery pack (200, 200C, 700) and a connection node being connected to the positive electrode of the first battery and the negative electrode of the second battery; a third detection circuit (620, 624) configured to detect a status of a third voltage (V M -V2; V P2 -V2; V M -V P2; V P2 -V M) across a second switch circuit (CET2-DET2) in a second path, and determine whether said second battery is in an abnormal condition according to said third voltage (V M -V2; V P2 -V2; V M -V P2; V P2 -V M), wherein said second path is coupled between a second positive terminal (P2+) of said battery pack (200, 200C, 700) and a positive electrode of said second battery; and a control circuit, coupled to said first detection circuit, said second detection circuit, and said third detection circuit (620, 624), wherein said control circuit is configured to turn off said first switch circuit (CET1-DET1) and said second switch circuit (CET2-DET2) if said first detection circuit determines that said first battery is in an abnormal condition, configured to turn off said first switch circuit (CET1-DET1) if said second detection circuit determines that said first path is in an abnormal condition, and configured to turn off said second switch circuit (CET2-DET2) if said third detection circuit wherein said battery protection system (202, 602, 702) is coupled to said current sensing element (R SEN), said first switch circuit (CET1-DET1) and said second switch circuit (CET2-DET2). a first detection circuit configured to detect a status of a first voltage (V SEN; -V SEN) across a current sensing element (R SEN), and determine whether said first battery is in an abnormal condition according to said first voltage (V SEN; -V SEN), wherein said current sensing element (R SEN) is coupled between a negative terminal (P-) of said battery pack (200, 200C, 700) and a negative electrode of said first battery; a second detection circuit configured to detect a status of a second voltage (V P1 -V1; V1-V P1; V CET1; V DET1) across a first switch circuit (CET1-DET1) in a first path, and determine whether said first path is in an abnormal condition according to said second voltage (V P1 -V1; V1-V P1; V CET1; V DET1), wherein said first path is coupled between a first positive terminal (P1+) of said battery pack (200, 200C, 700) and a connection node being connected to the positive electrode of the first battery and the negative electrode of the second battery; a third detection circuit (620, 624) configured to detect a status of a third voltage (V M -V2; V P2 -V2; V M -V P2; V P2 -V M) across a second switch circuit (CET2-DET2) in a second path, and determine whether said second battery is in an abnormal condition according to said third voltage (V M -V2; V P2 -V2; V M -V P2; V P2 -V M), wherein said second path is coupled between a second positive terminal (P2+) of said battery pack (200, 200C, 700) and a positive electrode of said second battery; and a control circuit, coupled to said first detection circuit, said second detection circuit, and said third detection circuit (620, 624), wherein said control circuit is configured to turn off said first switch circuit (CET1-DET1) and said second switch circuit (CET2-DET2) if said first detection circuit determines that said first battery is in an abnormal condition, configured to turn off said first switch circuit (CET1-DET1) if said second detection circuit determines that said first path is in an abnormal condition, and configured to turn off said second switch circuit (CET2-DET2) if said third detection circuit wherein said battery protection system (202, 602, 702) is coupled to said current sensing element (R SEN), said first switch circuit (CET1-DET1) and said second switch circuit (CET2-DET2).