If you’re getting a maximum voltage of 12.4V from the multimeter before starting the car, it means your car isn’t fully charged and that could be the result of a malfunctioning cell. Start by checking the level of water if you can take off the caps of your car battery.
The main reasons behind a car battery has voltage but no amps are a dying battery, bad contact between rectifier and load, loose connection, malfunctioning battery cell, and high resistance. You’d have to replace the battery to solve this problem in most cases.
The amperage on the meter will rise when the charging process starts. It may stay at zero when the battery is fully discharged. But eventually, the readings will increase. However, the amps will gradually fall as the charging process approaches the final stage. The amps hit zero once the battery is fully charged. 4). Dead Battery
Poor contact between the rectifier and load can produce zero amps even though the voltage is present. Some people dismiss the possibility of a bad battery because the charger shows a voltage. However, a defective battery can still show a decent voltage on the display. The voltage doesn’t mean your battery is healthy.
Unfortunately, when your Lithium-ion battery can not be fully charged, there could be a variety of reasons behind the problem. The issues might stem from a damaged battery or external factors unrelated to the lithium battery itself. It may require some trial and error as well as battery troubleshooting to uncover the underlying cause.
It also changes according to the weather; a 12V car battery’s voltage falls in low temperatures. As a result, then, if you measure could be that your vehicle battery’s voltage is 12.5V and yet it’s actually fully charged. The same applies if your battery has been around the block a few times ie. it’s getting old.