A circuit for battery testing, comprising: a first connector configured to electrically couple to a positive terminal of a battery (110; 610); a second connector configured to electrically couple to a negative terminal of the battery (110; 610); a reference voltage source (140; 200; 300; 400; 620) with a positive reference terminal (142; 230; 320; 420) and a negative reference terminal (144; 232; 322; 422); a conductor connecting the second connector to the negative reference terminal (144; 232; 322; 422); a voltmeter (130; 500; 630) configured to measure voltage between a first input node and a second input node, wherein the first input node is connected to the first connector and wherein the second input node is connected to the positive reference terminal (142; 230; 320; 420); a first switch (160; 650) in series with a first load impedance (150; 660) connected between the first connector and the second connector; a second switch (162; 652) in series with a second load impedance (152; 662) connected between the positive reference terminal (142; 230; 320; 420) and the negative reference terminal (144; 232; 322; 422); and a processor (170; 640) connected to the voltmeter (130; 500; 630) and configured to: control the first switch (160; 650) and the second switch (162; 652) to selectively apply the first load impedance (150; 660) to the battery and the second load impedance (152; 662) to the reference voltage source (140; 200; 300; 400; 620), receive one or more measurements of voltage between the first input node and the second input node, and determine a condition of the battery (110; 610) based on the one or more measurements of voltage between the first input node and the second input node. a first connector configured to electrically couple to a positive terminal of a battery (110; 610); a second connector configured to electrically couple to a negative terminal of the battery (110; 610); a reference voltage source (140; 200; 300; 400; 620) with a positive reference terminal (142; 230; 320; 420) and a negative reference terminal (144; 232; 322; 422); a conductor connecting the second connector to the negative reference terminal (144; 232; 322; 422); a voltmeter (130; 500; 630) configured to measure voltage between a first input node and a second input node, wherein the first input node is connected to the first connector and wherein the second input node is connected to the positive reference terminal (142; 230; 320; 420); a first switch (160; 650) in series with a first load impedance (150; 660) connected between the first connector and the second connector; a second switch (162; 652) in series with a second load impedance (152; 662) connected between the positive reference terminal (142; 230; 320; 420) and the negative reference terminal (144; 232; 322; 422); and a processor (170; 640) connected to the voltmeter (130; 500; 630) and configured to: control the first switch (160; 650) and the second switch (162; 652) to selectively apply the first load impedance (150; 660) to the battery and the second load impedance (152; 662) to the reference voltage source (140; 200; 300; 400; 620), receive one or more measurements of voltage between the first input node and the second input node, and determine a condition of the battery (110; 610) based on the one or more measurements of voltage between the first input node and the second input node. control the first switch (160; 650) and the second switch (162; 652) to selectively apply the first load impedance (150; 660) to the battery and the second load impedance (152; 662) to the reference voltage source (140; 200; 300; 400; 620), receive one or more measurements of voltage between the first input node and the second input node, and determine a condition of the battery (110; 610) based on the one or more measurements of voltage between the first input node and the second input node.