Passive cell balancing

A vehicle comprising:

• an electric motor configured to provide motive torque;
• and
• a battery system operatively connected to the electric motor and operable to provide electrical power to the electric motor, wherein the battery system comprises:
• a high voltage rechargeable battery including battery stacks comprising battery cell groups, wherein:
• each battery cell group has a desired cell balancing window defined between an upper limit voltage V1 and a lower limit voltage V2;
• each battery cell group has a minimum idle voltage V3;
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• and
• each battery cell group comprises at least one battery cell;
• and
• each battery cell independently has a self-discharge current less than or equal to a maximum self-discharge current ISD;
• and
• a diode arrangement configured to passively reduce a difference in voltage between battery cell groups, wherein:
• the diode arrangement comprises diodes;
• each diode is connected electrically in parallel with a respective battery cell group;
• each diode is configured to drain the respective battery cell group with a same first diode current ID1 at voltage V1, with a same second diode current ID2 at voltage V2, and with a same third diode current ID3 at voltage V3;
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A method for cell balancing a battery, the method comprising:

• connecting battery cell groups electrically in series in a battery stack, wherein:
• each battery cell group has a desired cell balancing window defined between an upper limit voltage V1 and a lower limit voltage V2;
• each battery cell group has a minimum idle voltage V3;
• V
• 1
• >
• V
• 2
• >
• V
• 3
• ;
• and
• each battery cell group comprises at least one battery cell;
• each battery cell independently has a self-discharge current less than or equal to a maximum self-discharge current ISD;
• and
• interconnecting a diode arrangement with the battery cell groups, wherein the diode arrangement is configured to passively reduce a difference in voltage between battery cell groups, wherein:
• the diode arrangement comprises diodes;
• each diode is connected electrically in parallel with a respective battery cell group;
• each diode is configured to drain the respective battery cell group with a same first diode current ID1 at voltage V1, with a same second diode current ID2 at voltage V2, and with a same third diode current ID3 at voltage V3;
• I
• D
• ⁢
• 1
• >
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• D
• ⁢
• 2
• >
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• D
• ⁢
• 3
• >
• 0
• ;
• and
• I
• D
• ⁢
• 1
• >
• I
• D
• ⁢
• 2
• +
• I
• SD
• .