To check the wires between the leads and the battery:
1) Disconnect A/C power from the outlet.
2) Disconnect one end of the red (positive wire) out of the contact on the panel, and then disconnect the other end of the red wire from the battery.
3) Use a multimeter to check for resistance in the wire. If the meter reads zero resistance, or a very small amount, than the wire should be in working condition. If the meter read very high resistance or infinite resistance, that means that the wire is broken/defective.
4) You can also check the black (negative) wire in the same way.
5) Reattach the wires between the panel contact and the battery.
6) Plug the A/C transformer back into the A/C wall outlet.