Battery facts

Battery and Charger Basics

On this page, we would like to give you as a user some more information about batteries and chargers, as on many occasions you may be alone and have to manage on your own.

The Battery

The most common type of battery is a lead-acid battery of some sort. There are other types, such as a nickel-cadmium battery or a nickel-metal hydride battery, but the latter two are not so widespread and will therefore not be discussed below.

A lead-acid battery consists of several serially connected (open-circuit) battery cells. Each cell produces a nominal tension of two volts.

Normally, there are six cells in a (car) battery, inducing a nominal tension of 12 volts. When two 12-volt batteries are connected, the result is a tension of 24 volts. There are also 6-volt batteries with three cells, and in this case four batteries are needed to generate 24-volt tension.

For trucks, also separate 2-volt battery cells are used; they are placed in a steel sack and then connected, thus building up a truck battery for different tensions and capacities.

In a lead-acid battery electric power is stored as chemical energy of the battery cell plates. The number and size of the plates determine the capacity of the battery. The capacity is measured in ampere hours (Ah). 60 ampere hours are one of the widespread sizes; and this means that a fully charged new battery can provide 12 ampere power during 5 hours. When two batteries are serially connected, they must have the same Ah-values and be of the same type and about the same age for the charging to function properly. Besides the chemically charged plates, a lead-acid battery also contains liquid (electrolyte) consisting of diluted sulphuric acid.

Nowadays, batteries mostly belong either to the sealed type, where the electrolyte is absorbed in a porous mat or ossified to get a gel-like mass; or the conventional ”flooded” batteries.

The sealed batteries are, without exception, provided with some kind of safety valve that will open if the battery is put to incorrect use. The sealed batteries are also called valve-regulated or maintenance-free batteries; under normal circumstances they require no maintenance.

The flooded batteries on the other hand must be filled with battery water to prevent them from drying up; how often and how much water should be added depends largely on the frequency of use, but also on the choice of the battery charger.

In the course of discharging of a flooded battery, a lead sulfate layer builds on the battery’s lead plates, reducing the battery capacity; therefore a lead-acid battery should always be stored in charged condition, preferably with some kind of float charging.  Crystalline lead sulfate can be dissolved to some extent by means of a correctly dimensioned topping charge or float charge.

In case of deep discharge, the sulfation finally becomes irreversible as the amount of lead sulfate increases and the battery is exposed to mechanical corrosion that can shorten its lifetime. Try therefore always to avoid deep-discharging your battery; if you are aware of the risk for deep discharge, it is always better to pause charge the battery.

If you suspect that the battery is getting sulfated, the easiest remedy is to charge it under weak current during a lengthy period of time (0.8 – 1% of the battery’s capacity). A 600 ampere-hour battery must be charged with 5-6 amperes for at least a week, preferably 2-3 weeks. Many batteries have been submitted to unwarranted disposal because of sulfating that could have been remedied this way – depending, of course, on how far the process had developed.

Battery charger

A battery charger transforms alternating current into direct current which is then regulated with the help of advanced electronics in order to be used for charging the battery. A battery charger must charge fast, yet not yielding more current than the battery can stand under different stages of charging. This is controlled by the charging curve data stored in the microprocessor of the charger. Therefore, it is important for the charger to have a correct charging curve for each battery type, otherwise there is a risk to destroy the battery either by undercharging or overcharging.

In co-operation with battery manufacturers, we develop efficient charging curves that provide the best maintenance and charge the battery as fast as possible without damaging it. In a charging curve, there are three main charging stages – main charging (constant current charging), topping charging and float or trickle charging.

During the constant current charging, the battery is recharged with the main bulk of the power earlier discharged from it.

In the topping charging phase, overcharging of about 15% occurs in order to equalize the charges in different battery cells. In valve-regulated batteries topping charging is administered only by means of low current in order to avoid hydrogen building which causes high pressure in the battery, which in turn results in the opening of the valves to release some of the gas, so that eventually the battery will dry up and be damaged. Also it is important to avoid too high current, as the battery in this case may be damaged by heat.

Float charging compensates for the battery’s self-discharge.

For the charger to be able to charge the battery properly, it must be adjusted to all battery types and be of the right size (ampere). All our chargers are individually adjusted to each battery in order to achieve maximum effect. There are also chargers in different sizes so that accurate charging periods can be kept. As different maintenance is to be applied to almost every battery, we cannot determine an average charging time, but we can provide an example of an average battery. A freely ventilated battery of 600 Ah, which is 80% discharged, will be fully recharged in about 8 hours, using 125A Wa charger (STC) or a 80A regulated charger with chemical acid circulation (MTM, MTM-HF).

Keep in mind

Never deep-discharge a battery, pause-charge if necessary.

With valve-regulated (maintenance-free) batteries, discharge maximum 60–80%. In case of sulfation, float charge at least once a week by leaving the charger connected for an extra-long period.

Do not expose the battery for extreme temperatures if possible, let it rest between charging and operation.

Our modern chargers can read the condition of the battery and adjust the whole process of charging accordingly.

Should you connect the charger to a freshly charged battery, it will automatically shift to float charging.

The charger will always charge and maintain the battery in the best possible way to achieve maximum lifetime and capacity.