A control unit for determining an electrical leakage between a first electrode pad (5050; 5150b) and a second electrode pad (5070; 5170b) of an in vivo medical device (120, 130; 4601, 4602; 4704; 4903), wherein the first electrode pad (5050; 5150b) is spaced from the second electrode pad (5070; 5170b), and wherein the first electrode pad (5050; 5150b) has an active electrode and a spaced ground electrode, and the second electrode pad (5070; 5170b) has an active electrode and a ground electrode, wherein the ground electrode of the first electrode pad (5050; 5150b) is electrically connected to the ground electrode of the second electrode pad (5070; 5170b), the control unit comprising: an input/output block for electrically connecting the control unit to the in vivo medical device (120, 130; 4601, 4602; 4704; 4903); a controller communicatively coupled to the input/output block, the controller programmed to: apply a first signal via the input/output block to the active electrode of the first electrode pad (5050; 5150b) of the in vivo medical device (120, 130; 4601, 4602; 4704; 4903), and in response, determine a measure that is related to an impedance between the active electrode of the first electrode pad (5050; 5150b) and the ground electrode of the first electrode pad (5050; 5150b); apply a second signal via the input/output block to the active electrode of the second electrode pad (5070; 5170b) of the in vivo medical device (120, 130; 4601, 4602; 4704; 4903), and in response, determine a measure that is related to an impedance between the active electrode of the second electrode pad (5070; 5170b) and the ground electrode of the second electrode pad (5070; 5170b); and use the measure that is related to the impedance between the active electrode of the second electrode pad (5070; 5170b) and the ground electrode of the second electrode pad (5070; 5170b) to determine an estimate of the electrical leakage between the active electrode of the first electrode pad (5050; 5150b) and the ground electrode of the second electrode pad (5070; 5170b). an input/output block for electrically connecting the control unit to the in vivo medical device (120, 130; 4601, 4602; 4704; 4903); a controller communicatively coupled to the input/output block, the controller programmed to: apply a first signal via the input/output block to the active electrode of the first electrode pad (5050; 5150b) of the in vivo medical device (120, 130; 4601, 4602; 4704; 4903), and in response, determine a measure that is related to an impedance between the active electrode of the first electrode pad (5050; 5150b) and the ground electrode of the first electrode pad (5050; 5150b); apply a second signal via the input/output block to the active electrode of the second electrode pad (5070; 5170b) of the in vivo medical device (120, 130; 4601, 4602; 4704; 4903), and in response, determine a measure that is related to an impedance between the active electrode of the second electrode pad (5070; 5170b) and the ground electrode of the second electrode pad (5070; 5170b); and use the measure that is related to the impedance between the active electrode of the second electrode pad (5070; 5170b) and the ground electrode of the second electrode pad (5070; 5170b) to determine an estimate of the electrical leakage between the active electrode of the first electrode pad (5050; 5150b) and the ground electrode of the second electrode pad (5070; 5170b). apply a first signal via the input/output block to the active electrode of the first electrode pad (5050; 5150b) of the in vivo medical device (120, 130; 4601, 4602; 4704; 4903), and in response, determine a measure that is related to an impedance between the active electrode of the first electrode pad (5050; 5150b) and the ground electrode of the first electrode pad (5050; 5150b); apply a second signal via the input/output block to the active electrode of the second electrode pad (5070; 5170b) of the in vivo medical device (120, 130; 4601, 4602; 4704; 4903), and in response, determine a measure that is related to an impedance between the active electrode of the second electrode pad (5070; 5170b) and the ground electrode of the second electrode pad (5070; 5170b); and use the measure that is related to the impedance between the active electrode of the second electrode pad (5070; 5170b) and the ground electrode of the second electrode pad (5070; 5170b) to determine an estimate of the electrical leakage between the active electrode of the first electrode pad (5050; 5150b) and the ground electrode of the second electrode pad (5070; 5170b).