I bought a cheap generic smart charger to keep my car battery topped up. It has a switch for 6 and 12 volts and an LED that comes on when it is plugged in and nothing else. I understand that the charger will behave differently according to the state of the battery but I cannot get any kind of measurement off it at all, 0 volts and 0 amps when no connection but also when connected to my battery booster, charged to just over 12 volts, which I am using to test. Is this normal? How can I tell if it is actually working? I would think my multimeter ought to register something, at least a brief pulse, but I don’t know enough about this to be sure.