Pic. 7.5. Modern maintenance-free battery: 1 - case cover; 2 - protective cover of the terminals; 3 - interelement connection; 4 - end terminal; 5 - element plugs (underneath the lid); 6 - plate holder; 7 - body; 8 - bottom amplifier; 9 - positive plate, closed by a separator; 10 - negative plate
The vehicle covered in this manual has a 12V electrical system. The body ground is connected to the negative battery terminal. The battery is located in the engine compartment or under the rear seat (models with air conditioning, as well as some diesel modifications).
The battery performs three main functions in the vehicle's electrical system:
- gives electric current to start the engine;
- stabilizes the voltage in the electrical system,
- can provide current for a short time when the power consumption exceeds the generator output power.
Sealed batteries are standard on all vehicles. They don't have filler plugs. The battery is completely sealed apart from two small side ventilation holes. These vents allow the resulting gases to escape.
Sealed batteries have the following advantages over conventional batteries:
- for the durability of the batteries, you do not need to add water;
- the battery is protected from overcharging. If too much voltage is applied to the battery, it will not take as much current as a normal battery. Increasing the voltage will continue to charge a conventional battery, resulting in gassing and loss of electrolyte;
- The battery is self-charging like a normal battery. This is very important when the car is in one place for a long time;
- with smaller dimensions and weight, the voltage and current remained the same.
The battery has two indicators:
- the battery capacity indicator is determined at 27°C, which, when fully charged, provides 10.5 V or more;
- The cold start battery rating is determined by testing at -18°C, which indicates the battery power when cranking the engine with a cold engine.
Battery backup power is defined as the maximum amount of time possible to drive at night with minimal electrical load without using generator output. Expressed in minutes, standby power (or indicator E) is the time required for a fully charged battery at 27°C and a discharge current of 25 A to reach a voltage of 10.5 V at the terminals.
Testing the current strength when starting a cold engine is carried out at -18°C. The minimum current that must be maintained by the battery at a given temperature as long as there is a minimum voltage of 7.2 V.
This indicator is measured when starting a cold engine.
Battery life is not unlimited. However, with proper care, the battery will last for many years.
If the battery tested well, but malfunctions for no apparent reason, the following factors may be the cause of the malfunction or failure:
- some appliance was left on all night;
- for short periods the car was moving at low speed;
- the electrical load of the car exceeded the output power of the generator, often with the inclusion of non-standard equipment;
- malfunction in the charging system: alternator belt slip, alternator malfunction or voltage regulator malfunction, etc.;
- improper use of the battery: failure to clean, fasten the terminals or loosen the clamps;
- mechanical malfunctions of the electrical system: shorted or pinched wires.
Sealed batteries have a built-in temperature compensated hydrometer at the top used for the following diagnostics:
– when looking at the hydrometer, make sure that the top of the battery is clean;
– During normal operation, two readings should be obtained:
- Visible green dot - the appearance of green, called «green dot» means that the battery is ready for testing;
- Dark green invisible dot - if there are complaints about starting a cold engine, the battery needs to be tested. At the same time, electrical systems and charging should be checked. Sometimes a third condition may arise:
- A clear or light yellow color is the liquid level below the tip of the hydrometer. This may cause excessive or prolonged charging, excessive or normal wear and tear of the battery. Therefore, charging and electrical systems may need to be checked if there are complaints about starting a cold engine. If the battery is the cause of the cold start complaint, replace it.
Checking the battery state of charge
The density of the electrolyte, together with the measurement of the voltage at the terminals of the battery, makes it possible to draw an accurate conclusion about the degree of charge of the battery. To check, a hydrometer is used, which can be purchased at a specialized store. The greater the density of the electrolyte, the more rises (pops up) hydrometer float. On the hydrometer scale, values are expressed in units of density (g/cm3).
When measuring the density of the electrolyte, make sure that no drops of electrolyte containing sulfuric acid, which causes corrosion and current leakage, fall from the hydrometer pipette onto the surface of the battery, body and other parts.
When measuring the density of the electrolyte, the temperature of the electrolyte should be in the range of 20–30°C. The density of the electrolyte must be measured in each cell (bank) battery. After measuring the density of the electrolyte, you can set the degree of discharge of the battery.
In all cells, the electrolyte must have the same density.
The density of the electrolyte in a fully charged battery is 1.28 g/cm3.
The density of the electrolyte battery, discharged by 25%, is 1.24 g/cm3.
The density of the electrolyte in a 50% discharged battery is 1.20 g/cm3.
A battery discharged by more than 25% in winter and more than 50% in summer should be removed from the vehicle and recharged.
When measuring the density of the electrolyte, the temperature of the electrolyte should be in the range of 20–30°C. The density of the electrolyte must be measured in each cell (bank) battery. After measuring the density of the electrolyte, you can set the degree of discharge of the battery.
In all cells, the electrolyte must have the same density.
The density of the electrolyte in a fully charged battery is 1.28 g/cm3.
The density of the electrolyte battery, discharged by 25%, is 1.24 g/cm3.
The density of the electrolyte in a 50% discharged battery is 1.20 g/cm3.
A battery discharged by more than 25% in winter and more than 50% in summer should be removed from the vehicle and recharged.
Charging the battery
A battery with a green dot indicates that charging is not needed until the battery is discharged, such as when starting a cold engine.
When charging a battery with sealed terminals outside the vehicle, install an adapter. Make sure all charger connections are clean and secure. For best results, the battery should be charged when the electrolyte and plates are at room temperature. Extremely cold batteries may not charge for several hours after starting charging.
Charge the battery until the green dot appears. During charging, the battery should be checked every 30 minutes. Tilt or agitation may be necessary for the green dot to appear.
After charging, the battery should be tested.
The time required to charge the battery depends on:
- battery size - for a fully discharged heavy-duty high-capacity battery, it takes 2 times more time than to charge a passenger car battery;
- temperature - it will take longer to charge the battery at -18°C than at 27°C. When the charger is connected to a cold battery, the state of charge will be very low at first, but as the temperature of the battery rises, the state of charge will increase;
- charger capacity - a charger with a charging current of 5 A will take longer to charge than a charger with a charging current of 30 A or more;
- states of charge - charging a fully discharged battery requires twice as much charge as charging two half-discharged batteries, because in a fully discharged battery, the electrolyte approaches almost pure water in composition and is a poor conductor. Then, as the charging current leads to an increase in the acid content of the electrolyte, the degree of charging increases accordingly.
Before charging, disconnect the positive cable and ground cable from the battery, first the ground cable.
Before charging, check the electrolyte level, top up with distilled water if necessary.
frozen battery (a battery whose electrolyte is frozen) defrost before charging. A fully charged battery freezes at -65°C, a half-charged battery freezes at -30°C, and a discharged battery freezes at -12°C.
Charge the battery only in a well-ventilated area. When charging the installed battery, leave the car hood open.
During normal charging, the value of the charging current is approximately 10% of the battery capacity. (i.e. a battery with a capacity of 50 A. h should be charged with a current of approximately 5.0 A). The charging time can be set to 10 hours.
Connect the positive terminal of the battery to the positive wire, the negative terminal of the battery to the negative wire of the charger.
During charging, the temperature of the electrolyte should not exceed +55°C, if necessary, interrupt charging or reduce the charging current.
Charge the battery until copious gas evolution begins in all battery cells and, with 3 measurements following one after another in an hour, the electrolyte density and voltage stop increasing.
After charging, check the electrolyte level, top up with distilled water if necessary.
Charging a fully discharged battery
Use the following procedure to recharge a fully discharged battery:
- measure the voltage at the battery terminals with an accurate voltmeter. If the measured value is below 10 V, the charging current will be very low and it may take some time before the battery takes on a few milliamps in excess;
- put the charger in a high place. Some chargers have a reverse polarity protection circuit that prevents charging if the battery terminals are not properly connected. A fully discharged battery does not have enough voltage to power this circuit, even if the wires are connected correctly. This will result in the battery not being charged. Therefore, follow the charger manufacturer's specific instructions to have the charger turn on and start charging the battery at low voltage;
- chargers have voltage and current regulators. The time required to charge the battery depending on the different voltages is shown below.
Battery charging time depending on the initial battery voltage
If the charge received by the battery cannot be measured after the charging time has elapsed, the battery should be replaced.
If the received charge is measured during the charging process, the battery is OK, charging should be completed as usual.
If the charge received by the battery is not measured after the charging time calculated by the above method, the battery must be replaced.
If the received charge is measured during the charge time, then the battery is good and the charge should be completed in the usual way.
Battery Care
From time to time, the following work should be done to ensure that the battery lasts longer and its capacity is maintained at maximum.
Always keep the battery and its surroundings clean. The surface of the battery must always be dry, otherwise surface leakage currents may occur between the individual banks, due to which the battery will discharge itself.
The electrolyte level must always be at the ring located on the bottom side of the filling chamber. Distilled water should be used for topping up.
In cold weather, do not leave the battery uncharged as it will (more precisely, the electrolyte in it) will freeze. Weakly charged batteries freeze already at temperatures around -10°C.
Battery storage
Batteries that are not used for a long time will discharge on their own and may be subject to plate sulfation. If such batteries are charged with a fast charger, they do not accept the charging current due to the so-called surface charging.
Before discarding a battery, check it:
- Check electrolyte density. If the density in all elements differs by no more than 0.02 g/cm3, the battery should be charged with the charger.
- Check the battery after charging under load. If the values are not correct, the battery is bad.
- Check electrolyte density. If the density of the electrolyte in one or more banks is significantly lower than in the rest (for example, in five jars the density is 1.16 g/cm3, and in one 1.08 g/cm3), the battery has an internal short circuit.
To avoid premature aging of the battery, recharge the battery in storage every 3 months.
Battery self-discharge
Depending on the modification of the car, the energy consumption of permanently operating energy consumers is added to the process of normal battery self-discharge. Therefore, the battery on a non-operating car should be charged once every one and a half months. If there is a suspicion of surface leakage currents, check the vehicle's on-board network.
Use a fully charged battery for testing.
Install on ammeter (with measuring range 0-5 mA and 0-5 A) the highest measurement limit. Connect an ammeter between the negative battery terminal and ground cable. Connect the positive wire of the ammeter to the positive terminal of the battery, and the negative wire of the ammeter to the negative terminal of the battery.
Turn off all electrical consumers, close all doors and trunk, turn off the engine compartment light.
Switch the ammeter measurement limit downward until any reading appears (allowable value is 1-3 mA). When removing fuses one by one from the fuse box, open all electrical circuits in sequence. If, when one of the circuits opens, the readings drop to 0, then the source of the malfunction should be looked for in this circuit. Possible malfunctions: corroded or dirty contacts of electrical connectors, frayed wires, internal short circuit in electrical equipment elements.
If no fault is found in the fuse-protected circuits, disconnect the wires from the unprotected devices: generator, starter, ignition system elements.
If the ammeter reading drops to 0 when one of the unprotected circuits is disconnected, repair or replace the appropriate element. In the event of current leakage in the starter or ignition system, always check (in accordance with the scheme) ignition and starter switch.
Removing and installing the battery
Pic. 7.6. Tightening of a nut of fastening of the plug of the storage battery
When the battery is disconnected from the memory of the central unit of the engine and gearbox control system, the anti-lock brake system, as well as from the memory of a number of other electrical devices, such as a radio and clock, data on the malfunctions that have occurred are erased. After connection, reprogram the relevant devices. Some standard radios have a security code. The security code prevents unauthorized use of the radio if the radio is turned off. The power to the radio and clock is cut off if, for example, the battery is disconnected, the receiver is removed or the corresponding fuse blows.
Loosen nuts and disconnect «negative» clamp and then «positive» battery terminal.
Loosen the battery support bracket nut.
Remove the battery support bracket.
Remove the battery.
Before installing, clean the battery terminals with a brass wire brush. Coat battery terminals with special grease to prevent corrosion.
Install the battery in the reverse order of removal.
Tighten the battery support bracket mounting nut to 6–8 Nm.
Tighten the nuts securing the battery terminals to a torque of 9–12 Nm.
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