The task of the battery charger.

The task of the charger is to recombine the active material; sulphuric acid (H2SO₄), lead (Pb) and lead oxide (PbO₂) from the lead sulphate (PbSO₄) that has been generated during discharge. Indeed, lead sulphate is the same material that causes the fault known as sulphating. Lead sulphate is necessary throughout the entire process, but it is when the crystals of lead sulphate grow larger that the trouble begins.

A charge graph, or to be more precise a charge algorithm, shows how the battery acquires energy over the full charging process. A DIN-standard, 41773, provides guidelines on how an algorithm of this type is structured, but the most important thing is the know-how associated with the treatment of a battery in order for it to remain in the best possible shape so as to achieve the goal of the longest service life and highest capacity. Bear in mind that there is no universal method to solve all the problems in an optimum way. The battery can be manufactured in a number of ways, and you need to consider both the battery itself together with the way it is used, which gives rise to a great number of algorithms. These differ sharply between a modern multi-step switch mode charger and a linear transformer battery charger of the type you will find at a car spare parts dealer or a discount store.

• The linear battery charger is indeed marked with a high Ampere number, but this is often measured using a battery that is as low as 5-6V. A more realistic number is 75% of the rated current power, but this drops quickly when the battery voltage starts to rise.
• The switch mode battery charger falls a little behind at the start as regards the amount of energy given to the battery but soon catches up.
• The linear battery charger has difficulty filling the battery despite being at a high voltage with the battery charger emitting little current but a lot of heat without providing that much charge to the battery.
• A battery charger that cannot provide a constant voltage cannot fully charge a battery without reaching a range where the battery starts to gas and loses fluid. A rule of thumb is that you will get 80% of the charge during the initial phase. Some battery chargers with a more basic control go down to a lower voltage when 14.4V has been reached, but then it can take weeks to get the remaining 20% of the charge.