Car battery system

A car battery system comprising:

• a plurality of battery cells, each battery cell having a positive electrode terminal and a negative electrode terminal;
• a battery block that retains the plurality of battery cells in a stacked configuration and has a terminal surface that is formed by battery cell terminal surfaces established by the positive and negative electrode terminals of the battery cells;
• a circuit board which has a first surface facing the battery block and a second surface facing away from the battery block;
• and
• a battery state detection circuit that is connected to the electrode terminals of each battery cell to detect the condition of each battery cell,
• wherein the circuit board is provided with surface-mounted electronic components that implement the battery state detection circuit,
• wherein the circuit board is a single-sided board with the electronic components mounted on only the second surface of the circuit board,
• wherein the circuit board is attached to the battery block opposite the terminal surface of the battery block, and the first surface of the circuit board faces the terminal surface,
• wherein the positive and negative electrode terminals of each battery cell are connected to the circuit board and to the battery state detection circuit,
• wherein the first surface of the circuit board which faces the battery block is an insulating surface,
• wherein an insulating layer is interposed between the insulating surface of the circuit board and the terminal surface of the battery block,
• wherein the circuit board has through-holes that pass through both surfaces of the circuit board, and voltage detection lines connected to battery cell electrode terminals are inserted in the through-holes and are solder attached to the circuit board,
• wherein the circuit board has a conducting layer on the insulating surface of the circuit board at a position corresponding to at least one of the through-holes,
• wherein the conducting layer is located between the insulating surface of the circuit board and the insulating layer, and
• wherein the voltage detection lines are configured to reduce line impedance for connections between each battery cell and the battery state detection circuit, and to make line impedance uniform between the voltage detection lines for allowing high precision voltage measurements for the battery cells.