The charge state of an automotive battery can be determined by measuring the acid density in kg/l. This is done using an acid siphon. The following characteristic factors apply: Acid density 1.28 kg/l: battery is fully charged. Acid density 1.20 kg/l: battery is half charged. Acid density 1.10 kg/l: battery is empty.
When charging a lead acid cell, high density acid is produced in the plates. This drops as a result of gravitation to the lower part of the cell. Over repeat cycles in which the electrolyte does not move, a sulfuric acid density gradient is therefore produced. This state must not be allowed to become permanent, otherwise it could irreversibly damage the battery. Possible countermeasures include shaking the battery, increasing the charging voltage and recirculating the electrolyte during cyclical use.
Product of the current strength (measured in amperes) and the duration (in hours) of the current. The quantity of electricity (capacity) of a battery or cell is usually expressed in ampere hours. Ah is the abbreviation.
The positive electrode at which oxidation takes place in a liquid solution, i.e. the anions (negatively charged ions) are discharged (loss of electrons). Depending on the current direction, each of the two electrodes can become an anode in secondary cells. The negative electrode is then the anode when discharging.
This term describes the test for determining the charging condition and electrolyte level of lead batteries with liquid electrolyte. The charging condition is determined by measuring of the acid density.
Battery that need not be refilled with water under normal circumstances. This term is often used for closed VRLA (valve regulated lead acid) batteries (electrolyte fixed by gel / glass mat). Product release: Automotive Battery Catalogue; See Maintenance-free battery with fixed electrolyte.
Charging method for emergency power batteries which uses a very small amount of charging current. The emergency power battery is continuously charged to compensate for possible losses in capacity. The battery is charged to 100% during the entire period of operation.
Rated capacity of the cell or battery. The charging and discharging current of a cell is often expressed as a multiple of C. (Example: The 0.1 C current for a cell with a rated capacity of 1.4 Ah is 140 mA). See Capacity.
Chemical element (Cd) that belongs to the heavy metals. In battery technology, cadmium, cadmium oxides and cadmium hydroxide are used in the cadmium electrodes found in nickel-cadmium accumulators and in normal elements.
The available quantity of electricity of a battery or cell measured in ampere hours. The capacity is dependent on the battery temperature and the discharging current. It is therefore important to state not just the capacity, but also the discharging current and temperature (e.g. cold-start capacity in seconds with cold-test current and -18°C).
The negative electrode at which reduction processes take place in a liquid solution, i.e. where cations (positively charged ions) are precipitated (gain in electrons). In secondary cells, each of the electrodes can become cathodes depending on the direction of the current. The positive electrode is the cathode when discharging.
The smallest unit of a battery, consisting of a positive and a negative electrode, a separator and the electrolyte. It stores electrical energy and forms the fundamental cornerstone of a battery if it is placed into a case and equipped with electrical connectors. The capacity of a cell is determined by its size. The cell voltage, however, depends on the electrochemical system of the element. See Element, electrochemical.
Must not exceed the limits specified for operation (system-dependent) (e.g. at -30°C, battery acid with a density of ? = 1.28 g/cm³ begins to freeze out [value determined from experiments on battery acid; the freezing point is far lower in the case of pure sulfuric acid]; temperatures above 55°C increase wear and accelerate aging).
Describes the quantity of current in ampere hours which a battery in a defined charge state can accept at a specified temperature and charge voltage within a defined period. Often, the charging current (in amperes) flowing after this period has finished is measured instead (e.g. lead batteries: charge state 50%, charging voltage: 14.4 V, temperature: 0°C, duration: 10 min, required current after 10 min: I10min ? 4 x 0.05 C20). The latter case is also known as "current acceptance".
Charging with constant current without voltage monitoring. This is only expedient for small charging currents (e.g. I20), since otherwise parasitic reactions (increased temperature, water loss) can occur.
Charging is performed with a constant current until a gassing voltage is attained. Switchover is then made to U characteristic, the cutoff voltage lying below the gassing voltage. This results in the current dropping so sharply that the battery cannot be overcharged.
Cold cranking is the discharge current given by the manufacturer. It is emitted by a battery at a temperature of -18°C with a minimum voltage of Ui=7,5 volt for a period of 10 seconds, according to the EN specifications.
Cast On Strap. Abbreviation of the designation for the manufacturing process used for the plate block which involves connecting the plate lugs of several like electrodes (parallel connection to increase the capacity) in a connecting strap made of lead alloy.
A way of switching the charging current of a battery from highest-speed charging to peak charging by means of a control circuit in the battery charger. This circuit is activated by the battery voltage or battery temperature.
The cycle stability of an accumulator is a measure of how often it can be charged and discharged. Cycle strength is particularly important in the case of solar batteries, as they are charged during the day and discharged at night.See VARTA SOLAR.
The capacity drawn from a battery divided by the rated battery capacity and expressed as a percentage (e.g. 50% discharge depth for a battery with a rated capacity of 50 Ah means that a capacity of 25 Ah is drawn).
The stored energy in a battery or a cell. It is related either to mass (gravimetrical energy density in watt hours per gram) or to volume (volumetric energy density in watt hours per cubic centimeter).
The point in the state diagram of an alloy consisting of several fully mixable alloy components at which the alloy has the lowest possible melting point (e.g. Eutetic system of a lead-antimony alloy: Pb:Sb = 88.9:11.1 with melting temperature TEutetic = 252°C.)
An additive consisting of organic and/or inorganic components (lignin, lamp black, barium sulfate) for negative mass. The expander is used to delay shrinkage of the sponge lead when the battery is in use.
Indicates the lowest allowable voltage level that a battery or cell can be discharged to. Discharging to below this cutoff voltage (deep discharge) can impair or (through pole reversal) destroy the electrochemical cell in the case of various battery types (e.g. lead, Ni/Cd, NiMH).
Battery type with an above-standard cycle stability and shock resistance. Applications: Commercial vehicles, construction and farm machinery. Product release: VARTA HEAVY DUTY, Product release: VARTA SUPER HEAVY DUTY.
A battery's initial voltage is the working voltage when discharging begins. Measurement usually follows, as soon as current has flowed long enough for the voltage to remain at a constant level, for example after 10% usage of a previously fully-charged cell.
The measurable resistance against the flow of current in a battery expressed as a drop in the battery voltage proportional to the discharging current. The value is dependent on the manner of construction, the charge state, temperature and the age of the battery.
A chemical element which belongs to the heavy metals (specific weight 11.341 g/cm³). It is used in the form of bivalent and / or quadrivalent compounds (PbSO4 or PbO2), as porous sponge lead for active masses, and as lead-antimony or lead-calcium alloys for grids in lead batteries.
A bivalent lead oxide (PbO), which can occur in two modifications: the orthorhombic, yellow high-temperature modification and the tetragonal, red modification. It is used in producing active lead masses.
Chemical compound produced on the positive and negative plates of a lead battery during discharge. It is the result of a chemical reaction between the sulfuric acid and lead dioxide of the positive electrode or the metallic lead of the negative electrode.
Chemical formula 3 PbO·PbSO4·H2O. This is formed during mixing of the active mass from lead oxide + acid + water at temperatures below 60°C and consists of flake-shaped crystallites of approx. 1 µm diameter.
General term for the non-cellulose wood component (lignin sulfuric acid or desulfonate sulfuric acid). It is the main component of the additives for negative lead masses with a component share of ?1%. It is sold under the name Vanisperse.
Lead-acid battery in which the electrolyte is held in place in a gel or microglass mat (AGM). The battery is sealed and is equipped with valves. It is highly stable and exhibits good cycling characteristics.
The material in the electrodes that takes part in the charging and discharging reactions. In the nickel-cadmium cell, nickel hydroxide and cadmium hydroxide are used as active mass at the positive and negative electrodes. In the lead cell, lead dioxide and sponge lead serve as the active mass at the positive and negative electrodes. The sulfuric acid in the lead cell which functions as an electrolyte can also be considered as an active mass, because it also takes part in the cell reaction.
Release of electrons through the cell's active mass to the external electric circuit. During the discharging process, cadmium is oxidized at the negative electrode of the nickel-cadmium cell or sponge lead is oxidized at the negative electrode of the lead cell.
Mixtures of various compounds, (e.g. lead oxide and water, sulfuric acid) that are used to coat positive and negative lead battery grids. A distinction is made between positive and negative pastes depending on the recipe. These pastes are then transformed into positive and negative cured masses. See Mass, active; see Curing.
Chemical reaction that can take place in either direction (oxidation or reduction). The cell reaction must be reversible in order to use a secondary battery (e.g. charging or discharging a secondary battery).
Increase in the number of electrons. In the case of a cell, this term refers to the electron transfer to the active mass. During the discharging operation, NiOOH (charged positive mass of nickel-cadmium or NiMH accumulators) or lead dioxide at the positive plate is reduced to a lower oxidation state (to Ni(OH)2 or PbSO4).
A device used for the physical separation and electrical isolation of electrodes of opposing polarities. In certain cases, the separator can also be used for absorbing superfluous electrolyte (microglass mat AGM). The separator for acid electrolytes generally consists of a porous PP/PE foil, while the separator for alkaline systems generally consists of PP/PE mats.
The cells can also experience an inner short circuit in the case of fine short circuits (see Tree formation). This will generally result in high self-discharging and will be reflected in a sharp reduction in capacity.
The formation of lead sulfate at the electrodes of a lead accumulator by recrystallization when the battery remains unused for a long time in deep discharge state. A coarse grained lead sulfate is produced which can only be recharged with difficulty. See Reconditioning.
Method for switching the charging current of a battery from highest-speed charging current to conservation charging current by means of a control circuit in the charger which is triggered by the battery temperature.
A simple, economical battery charger that delivers high charging currents to discharged batteries, then gradually reduces the current as the battery voltage increases and nears its fully-charged state. Not suitable for closed nickel-cadmium batteries and some other applications due to the occurrence of AC voltage fluctuations. See Charge, W characteristic.
An electrolyte's nominal temperature is a specified value which is used as a reference value for capacity tests (e.g. according to European standard EN 60095-1, Tnom lies in the region of 25±2 °C for the 20-hour capacity of lead batteries)
A slow decrease in voltage over a long period of time. Characteristic for many discharges of closed cadmium cells and closed lead cells. As a rule, the plateau extends from the first voltage drop at the start of the discharge to the bend of the curve after which the voltage drops rapidly at the end.
The working capacity of a cell or battery is the dischargeable electrical energy in watt hours [Wh] for an accumulator with average discharge voltage and corrected to Tnom. See Energy; See Temperature, nominal (Tnom).