Batteries, charging and 12 V electrical

12 V battery testing and terminal care with a multimeter. Low-voltage direct current only.

Common failure modes

• Corroded terminals read as a dead battery
• A battery tested immediately after a drive
• A parasitic drain never traced

Procedures

• What battery does my car take, and how do I read the group size and CCA rating before I buy a replacementA replacement car battery has to match the vehicle in five separate ways at once, and the sticker on the case spells out
• Work out why a battery is flat every morning when the battery itself tests goodA battery that reads a normal voltage on a multimeter and is still flat the next morning usually has one of two explanat
• Find the date code on a vehicle battery and work out how old it actually isNobody looks up a car battery's age for fun. The question comes up when the battery is slow to start the engine, when a
• How to find and replace a blown fuse in your carWhen one thing in a car stops working and everything else is fine — the cigarette lighter socket, the radio, one interio
• How to change the battery in a car key fobA key fob that only works when you are standing next to the car is usually a flat coin cell rather than a broken remote.
• How to test a car battery with a multimeterA multimeter across the two terminals of a car battery gives you one number, the open circuit voltage, and that number i

Where this stops

Charging system repair and any work on a high-voltage traction system is never covered.