Battery — design features (Renault Sandero 1)

A modern car is filled with various consumers of electricity, electronic devices, starting with a CD player and ending with controllers of electronic engine management systems, gearbox, anti-lock braking system, airbags, etc. In the damp off-season, especially in winter, all car electrics and electronics (first of all, a car battery) is taking an endurance test.

As practice shows, if problems with starting the engine in the cold season begin and to eliminate them you constantly have to recharge the battery, provided that the generator is in good working order and the tension of the auxiliary drive belt is normal, and the service life of the battery exceeds 3 years, it is quite reasonable to consider buying a new battery.

Modern batteries are usually of two types:

• maintenance-free throughout the entire service life;
• low-maintenance, requiring topping up with distilled water once or twice a year.

From a wide range of car batteries from various manufacturers presented on the market of car parts, it is advisable to choose for your car (taking into account the manufacturer's recommendations) maintenance-free battery.

It is necessary to remember that at low temperatures, due to the increase in the viscosity of the engine oil and the deterioration of the conditions for ignition of the fuel, the power consumed by the starter when starting the engine increases two to three times. The start time of a cold engine in comparison with a warmed up one in some cases increases by 10-20 times. Thus, in winter at low air temperatures, increased requirements are imposed on the starter characteristics of the battery, i.e. on its ability for a short time (10 sec according to GOST) to produce the required current necessary for the starter to operate at the nominal speed of its anchor in the cold season (-18°C according to GOST).



Table 10.3 shows the dependence of the battery capacity on the electrolyte temperature. The battery capacity is shown as a percentage of the capacity that the battery is capable of delivering at 25°C.

Dependence of battery capacity on electrolyte temperature

Table 10.3.

Electrolyte temperature,°C	Battery capacity,%
-10	80
-20	66
-30	50
-40	32

The manufacturer installs a lead-acid battery with a nominal voltage of 12 V and a capacity of 70 Ah on the vehicle.

Note. The principle of operation of lead-acid batteries is based on the electrochemical reactions of lead and lead dioxide in a sulfuric acid environment. During discharge, lead dioxide is reduced at the cathode and lead is oxidized at the anode. During charging, reverse reactions occur, to which the reaction of water electrolysis is added at the end of charging, accompanied by the release of oxygen at the positive electrode and hydrogen at the negative.

A lead-acid battery element consists of positive and negative electrodes, separators (dividing gratings) and electrolyte. The positive electrodes are a lead grid in which the active substance is lead peroxide (PbO ₂). The negative electrodes are also a lead grid with spongy lead as the active substance. In practice, 1-2% antimony is added to the lead of the grids to increase mechanical strength. Currently, calcium salts are used as an alloying component in both plates or only in the positive ones (hybrid technology). The electrodes are immersed in an electrolyte consisting of an aqueous solution of sulfuric acid (H ₂ SO ₄). The highest conductivity of this solution is at room temperature (which means the lowest internal resistance and the lowest internal losses) is achieved with its density of 1.26 g/cm³. However, in practice, in regions with cold climates, higher concentrations of sulfuric acid are used - up to 1.29-1.31 g/cm³. This is done because when a lead-acid battery is discharged, the density of the electrolyte drops and its freezing temperature becomes higher, a discharged battery may not withstand the cold.



In new battery designs, lead plates (grids) are replaced with foamed carbon covered with a thin lead film, and the liquid electrolyte is gelled with silica gel to a paste-like state. Using less lead and distributing it over a larger area, the battery is made not only more compact and lighter, but also significantly more efficient: in addition to greater efficiency, it charges much faster than batteries of previous generations.

The battery elements are located in a polypropylene monoblock (housing) 1 (Fig. 10.3) and are closed by a common cover 5, inseparably connected to the monoblock. There are no plugs in the battery cover, since adding distilled water is not required. Two ventilation holes on the sides of the battery in the upper part provide an outlet for a small amount of gas formed in it.



An electrolyte density indicator 6 can be mounted in the battery cover, the readings of which take into account the battery temperature. There are three possible indicator readings:

• green dot - battery is charged;
• dark indicator without green dot - battery is partially discharged, engine starting is difficult or impossible;
• transparent or light yellow indicator - excessive decrease in the electrolyte level due to prolonged overcharging of the battery or its natural wear and tear.

Note. Instead of the standard maintenance-free battery, you can install any battery of similar capacity and installation dimensions from other manufacturers. In this case, use and maintain the battery in accordance with the instructions attached to it.

Possible battery malfunctions, their causes and solutions

Cause of malfunction	Method of elimination
The battery quickly discharges and when starting does not provide the required engine crankshaft speed by the starter
Long-term switching on of high-power consumers (headlights, heater, etc.) when parked with the engine not running or at low crankshaft speed	Limit the number and time of switching on electricity consumers
Current leaks when the battery terminals are short-circuited by dirt or electrolyte on the surface of the cover	Clean the surface of the battery with a 10% solution of ammonia or soda ash
Short circuit in the electrical circuits of the car	Identify the circuit in which the short circuit occurred. Eliminate the short circuit
Sulfation of battery electrodes	Replace the battery
Oxidation of battery terminals and wire ends due to poor fastening at the connection points	Clean, secure and lubricate the wire ends and terminals with petroleum jelly
Malfunction of one or more batteries	Replace the battery
Rapid decrease in electrolyte levels
Damage to the battery pack	Replace the battery
Overcharging of the battery due to increased charging voltage	Check the voltage regulator for proper operation

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