Battery - Overview: Other BMW Z3 E36 рестайлинг

The Battery

Model: All

Production Date: All

Scheme 42

Purpose of the Automotive Battery

The battery is the primary EMF source in the automobile. In addition the battery performs the following functions

1. Provides voltage and current for the starter motor.
2. Provides voltage and current for the ignition during cranking.
3. Supplies all electrical power when the charging system is not operating.
4. Supplies the extra power necessary when the vehicle's electrical load exceeds the supply from the charging system.
5. Acts as a voltage stabilizer in the electrical system. The battery evens out voltage spikes and prevents them from damaging other components in the electrical system.
6. Provides power to KL30, KL15 and KLR.

The battery does not store electrical energy. It stores chemical energy that is converted to electrical energy as it discharges.

Battery Construction

Modern automotive batteries are made of cases (usually plastic) containing alternating plates of Lead and Lead Dioxide (or Lead Oxide) separated by insulators. These alternating plates are connected in series to produce a voltage of 12.6 volts, or about 2.1 volts for each set of Lead and Lead Dioxide plates. The negative terminal is connected to a Lead Dioxide plate and the positive terminal to a Lead plate.

Scheme 43

The plates are covered with electrolyte which is a solution of 35% Sulfuric acid and 65% Water.

Scheme 44

1. Plastic container.
2. Positive and negative internal plates made of lead.
3. Plate separators made of porous synthetic material.
4. Electrolyte which is a dilute solution of Sulfuric acid and water better known as Battery Acid.
5. Lead terminals which are the connection point between the battery and whatever it powers.

Battery Case

Most battery cases and their covers are made of polypropylene. The case is divided into six sections or cells, shaped similar to an ice-cube tray.

The case is designed to

1. Withstand hot and cold temperature extremes.
2. Resist damage caused by mechanical shock in automotive applications.
3. Resist acid absorption and chemical damage.

The Grids

The grids are the supporting framework for the active material of the plates. They also conduct current to and from the active material plates.

Scheme 45

The Plates

Plates are grids covered with a paste mixture of Lead Oxide and Sulfuric Acid and water. An expander material made of powdered sulfates is added to the paste to produce negative plates.

A forming charge is applied to the positive plates converting the Lead Oxide to Lead Dioxide, a highly porous material which allows the electrolyte to freely penetrate the plate.

A forming charge is also applied to the negative plates converting the Lead Oxide to Sponge Lead. The Sponge Lead allows the electrolyte to penetrate freely allowing the material beneath the plate surface to take part in the chemical reaction.

The Separators

Separators are thin sheets of electrically insulating porous material used as spacers between the plates to prevent short circuits within the cells.

Fine pores in the separators allow ionic current flow in the electrolyte between the positive and negative plates.

Scheme 46

Elements

In the most common method of construction, a stack of alternate positive and negative plates are formed with separators between each positive and negative plate. The lugs of the negative plates are welded together as are those of the positive plates. The plate strap of each group of plates is used to connect them in series with the plate group of the next cell, or with a battery terminal.

The assembly resulting from placing one positive plate group and one negative plate group together, with separators is known as an element. There is one element per battery cell. More or larger plates per cell will increase plate surface area and increase capacity of the battery but will not affect the voltage output.

Electrolyte

The electrolyte is a mixture of Sulfuric Acid and Water. Electrolyte consists of 35% sulfuric acid and 65% water.

The electrolyte is the carrier for the electric current to move between the positive and negative plates through the separators.

The Lead Terminals

BMW's use a tapered top terminal. This design uses tapered terminal posts built to industry standards so that all cable clamps will fit any battery with these posts.

The positive terminal is slightly larger than the negative to minimize the danger of installing the battery in reverse. The positive terminal is 17.5mm in diameter at the top. The negative terminal is 15.9mm at the top.

Scheme 47

Battery Types

There are at least three types of the Lead-acid batteries that are currently used in the Automotive Industry.

Lead-Acid Battery

The three major contributors to battery chemistry are lead, lead dioxide and sulfuric acid. Pure lead is too soft to withstand the physical abuse of mobile applications, so a strengthener is needed. About 6% antimony, a semi metallic element produced as a by-product to copper and lead ore refining, is added to strengthen the lead.

The antimony added to the grids acts as a catalyst and makes the loss of hydrogen and oxygen through outgassing worse. These batteries require frequent water replenishing.

Lead/Calcium Battery

Introduced in the 1970's Lead/Calcium batteries have Calcium added to the positive and negative grids to reduce the outgassing. These batteries were first referred to as "maintenance free". The Lead/Calcium batteries are not resistant to deep-cycling which occurs when a battery is drained to a very low voltage before being recharged. Frequent deep-cycling renders these batteries unable to sustain a charge. Lead/Calcium batteries need to be charged at higher voltage settings or they will not be recharged to full capacity.

Hybrid Battery

Hybrid batteries use a positive grid strengthened with antimony and a negative grid with calcium. The hybrid battery is more resistant to deep cycling than the lead/calcium, but still not as good as the original Lead-acid battery. Water usage is greatly reduced in the hybrid battery, although regular checking is advisable. Most cars supplied with hybrid batteries have their voltage regulators set to 14.3 volts.

Hybrid batteries were first installed in the E30 convertible during the 1991 Model Year.

Discharging

Batteries don't store electrical energy, they store chemical energy and convert it to electrical energy during the discharging process.

Each cell of a battery contains positive and negative plates (grids). The positive plate is made of lead dioxide, the negative plate of a spongy lead. The negative plate combines with the sulfuric acid to create lead sulfate and one extra electron. The positive plate produces hydrogen ions and sulfuric acid ions (positive ions, atoms missing one electron).

The extra electrons from the negative plate are passed from the negative battery terminal and through the electrical consumer, back to the positive battery terminal. Once back at the battery, the free electrons combine with the positive ions at the positive battery terminal producing lead sulfate and water.

It is important to remember that the system is closed. For every electron generated at the negative terminal, there is an electron consumed at the positive terminal.

As the process continues, the active materials (lead and lead dioxide plates and the electrolyte) become depleted and the reactions slow down until the battery is no longer capable of supplying electrons. At this point the battery is discharged.

The discharge process changes the ratio of sulfuric acid to water in the electrolyte, as more water is produced in the discharge process. By measuring the volume of acid in the water, the state of charge of the battery is discovered.

Scheme 48

Charging

Applying voltage to the battery from an external source such as the generator or battery charger reverses the chemical action in the battery.

Reversing the chemical action in the battery, forces the free electrons at the negative terminal of the battery back into the electrolyte raising the sulfuric acid percentage. This chemical action removes the Lead sulfate that had formed on the negative plates leaving pure active material.

The electrons that were forced into the electrolyte are able to react with the lead sulfate on the positive terminal again raising the Sulfuric acid content and leaving pure active material on the positive plates.

This process enables the battery to be used over and over again.

Scheme 49

Scheme 50

1. Ah - Amp Hour Capacity This rating is derived from discharging a fully charged battery at a constant amp draw for 20 hours @ 80°F, without the voltage of the battery falling below 10.5 volts. The constant amp draw is multiplied by the 20 hours to come up with the Amp Hour Rating.
2. CCA - Cold Cranking Performance Represents the amperage capacity a fully charged battery can deliver @ 0°F for 30 seconds before the voltage of the battery falls below 7.2 volts.
3. RC - Reserve Capacity Reserve capacity is expressed in minutes and relates to the amount of time a fully charged battery can maintain a constant draw of 25 amps @ 80°F before the voltage falls below 10.2 volts.
4. W - Watts The measurement of electrical power that the battery can deliver for a cold start. It is calculated by multiplying the starter amperage draw @ 0°F times 10 volts.
5. V - Volt Unit of measure of potential difference (Electrical pressure).
6. A - Amp The current flow in a circuit. Value is proportional to the number of electrons flowing past a point in one second.
7. ohms - Ohm The measurement of the resistance of a component or circuit to current flow.
8. Electrolyte The mixture of sulfuric acid and water. 35% sulfuric acid, 65% water.
9. Specific Gravity The measurement (by weight) of the volume of sulfuric acid in the electrolyte. A specific gravity of 1.275 (the specific gravity of a fully charged battery) means that the electrolyte is 1.275 times heavier than water. The specific gravity of water is 1.000.
10. Sulfate Deposits formed on the plates of the battery as the electrolyte gives up its sulfuric acid. Excessive deep cycling of a battery can cause a hardening of this deposit and make it impossible to return sulfate to the electrolyte. A sulfated battery is one which has these hardened deposits on the plates and cannot be recharged to full capacity.
11. OCV Open Circuit Voltage The measurement of the voltage of a battery across the terminals.

Scheme 51

Tools Needed

To test a battery following tools are needed

1. DVOM Digital Volt Ohm Meter.
2. Battery Load Tester (i.e. Snap On VAT 60).
3. DISplus or MoDic.
4. Battery Draw Test Special Tool PN 61 2 300.
5. Closed Circuit Measurement Adapter PN 90 88 6 612 310.
6. Temperature Compensating Hydrometer.

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Electrolyte Level

If battery electrolyte level is allowed to drop substantially, the gas volume inside the battery grows proportionately resulting in an increased amount of flammable gas mixture. Any external or internal spark may result in an oxyhydrogen explosion. Additionally the plates are no longer covered by the electrolyte and may corrode.

The battery electrolyte level should be checked on every Inspection I and Inspection II.

Use only distilled water to top up the battery!

Tap water and electrolyte must never be used to refill or top off an automotive battery.

Workshop Hint

Electrolyte levels may drop at a higher rate in the winter months, due to higher loads and increased utilization of electrical systems.

Battery Cable Connections

The top of the battery should be clean. Check for and correct corrosion on the top of the battery and the cable connections.

Workshop Hint

Many battery problems are caused by loose or corroded connections. Insure that cables are free from corrosion and tight before continuing diagnosis.

Battery Charging

The purpose of charging a battery is to put back the energy that has been removed. A battery that is not properly charged will deliver sub-standard performance and display a shorter life span.

A battery should be charged only after performing a visual inspection on the battery case and the electrolyte levels. Never attempt to charge a battery with a damaged case or low electrolyte levels.

A state-of-charge test should be performed before attempting to charge a battery.

Always connect the positive lead of the battery charger to the positive terminal of the battery and the negative lead of the battery charger to the negative terminal of the battery.

Unplug the charger or turn it off BEFORE disconnecting the leads at the battery.

Batteries that are fully discharged should be charged according to the following table.

BATTERIES SPECIFICATIONS

The best charging method is to SLOWLY recharge the battery using the BMW approved battery charger.

A slow charging rate allows more time for the electrolyte to penetrate the plates.

Sulfated Batteries

Continuous discharging of the battery or low electrolyte levels cause crystals to form on the plates. These crystals of lead sulphate occur when a battery is discharged. The deeper the discharge the more serious the sulphation. The sulphur molecules that form the sulphate are then absent from the electrolyte, causing the electrolyte to become inefficient.

A battery relies on clean plates and strong electrolyte to both receive charging current and offer strong current discharge. A sulphated battery can do neither. Proper recharging of the battery will remove some but not all of the sulphate. Eventually the battery plates are coated with enough sulphate that it is impossible to achieve an efficient recharge.

Battery Freezing

A fully charged battery can be stored at sub-freezing temperatures with no damage. The battery is protected from freezing to a temperature of -75° F. A fully discharged battery however will freeze at +27° F.

Avoid freezing by keeping the battery fully charged.

Carefully inspect a battery which has frozen for a cracked case.

Vehicle In Storage, Battery Disconnect Switch Removed

A four week charging cycle has been established for these cases. All vehicles arrive with a color coded sticker on the windshield. The color corresponds to the week that the battery must be charged. Also the vehicle will be provided with a Battery Log Form.

The "A" portion (Vehicle Receipt) of the Log Form must be completed during the QC I Display check and then has to be filed in the Battery Charge Log Book under the applicable color coded section. All the vehicles in that color section will have to be charged that week.

Vehicle In Showroom or Display

Because of the high consumer demand on vehicles that are being displayed and not driven, a four week charging cycle is not enough. For vehicles in the showroom the battery has to be charged as frequently as necessary to ensure that the battery never drops below 12.5V. Use the "C" portion of the log form (Display Vehicle - Monitored Daily) to keep track of the charging and checking of the battery.

Vehicle In Storage, Battery Disconnect Switch Left In The Vehicle.

Since the battery disconnect switch is left installed and in the "OFF" position the 3 month charge cycle can be used. Use the "D" section of the Battery Log Form to document when the battery is charged.

Upon the sale of the vehicle, the Battery Log Form should be removed from the binder and placed in the vehicle file for future reference.

Scheme 56

Scheme 57

Note. If the battery voltage drops below 11.6v for three days or more the battery must be replaced before delivery to the customer

Scheme 58

Battery Failures

An analysis of batteries replaced under warranty shows that many claims could have been avoided had the batteries been maintained in a full state of charge.

Batteries must be maintained at all times when vehicles are at a retailer whether they are new cars, used cars, in storage (back lot), on display, or customer cars in for maintenance or repairs.

Batteries replaced due to lack of maintenance will not be covered by warranty.

Most Common Causes of Premature Battery Failures

1. Failure to maintain proper state of charge.
2. Loss of electrolyte due to overcharging or excessive heat.
3. Deep discharging (Leaving lights on or other parasitic draws).
4. Undercharging of battery.
5. Vibration (Loose battery hold down clamp).
6. Using tap water (instead of distilled water).
7. Corrosion.
8. Freezing.

Safety Tips

1. Proper Clothing: Always wear a face shield or safety goggles. Plastic gloves can prevent acid burns to hands.
2. Neutralizing Electrolyte

Any leakage or spillage of battery electrolyte should be neutralized as soon as possible to prevent damage to paint, body or trunk linings. Depending on the amount of spillage dilute some baking soda in water and apply to areas of the car that have been exposed to the battery electrolyte. The neutralizing action will create some foaming in the area where the chemical action takes place. Flush with ample amounts of water once the chemical reaction has subsided.

General Battery Hints

1. Add only distilled water NEVER TOP OFF WITH ACID.
2. Keep electrolyte level above plate separators.
3. Keep battery top clean and dry.
4. Keep open flame and metal objects away from battery top and terminals.
5. Keep vent caps tightly in place (if applicable).
6. Use proper charging equipment.

Special Battery Systems

Special battery systems are broken into two groups

1. Vibration Compensating Battery Systems.
2. Dual Battery Systems.

E36

The E36 convertible is not only an energy source. The battery is designed as a vibration dampener. Due to this additional function the battery also has a special tray with an integrated vibration absorber.

Note. E36 convertible batteries are labeled "Vibration Proof". Replacement batteries must be of the same type.

Scheme 59

E46

The E46 convertible uses the same battery as the E46 sedan, coupe and touring. The battery box is specially designed to float on the vertical axis through three articulated rods.

This allows the battery to act as an inertia mass and dampen various vibrations while the vehicle is driven.

Scheme 60

E31 (850i)

The dual battery system on the 850i was introduced to handle the higher level of electronic technology with increased functions and safety features that were added to the vehicle, as well as the added diagnostic information.

Design considerations were made to minimize electrical loads during Key Off and periods of driving with low engine speeds while certain timed operations (e.g. Glove compartment light, courtesy lights and seat heating) were active.

Special testing and charging procedures exist for the dual battery system on the 850i, refer to appropriate article for specific information.

E38 750iL

The dual battery system on the 750iL is necessary due to the addition of the E-CATs. If a single battery system was used, the E-CATs would be provided power from the single battery just after cold engine start-up when the battery is at its lowest capacity. This would increase engine loads due to charging of the single battery and cause an increase in injector "On" time during the cold engine warm-up period, which result in unnecessary tail pipe emissions.

Providing separate battery systems for the starting circuit and the vehicle circuits also minimizes the possibility of a discharged starter battery ensuring reliable engine starting.

Components of E38 Dual Battery System

1. Starter Battery: Located in the right rear trunk wheel, the starter battery is connected to the starter motor and to the heating coils of the E-CATs (via the E-CAT module).
2. Vehicle Circuit Battery: Located above the starter battery on a swing out mount, the vehicle circuit battery provides operating power for the balance of the vehicles electrical requirements and is directly connected to the vehicle generator.
3. Battery Isolation Switch: Located on the swing out mount of the vehicle circuit battery the battery isolation switch opens and closes the circuit between both batteries based on monitored conditions.

Note. The battery isolation switch is NOT used to boost a discharged starter battery with the voltage of the vehicle circuit battery to start the engine. The battery isolation switch can only withstand a maximum current flow of 60 amps.

Battery Isolation Switch

The Battery Isolation Switch provides the vehicle with separate battery systems for the vehicle circuits and the starting circuit.

When the isolation switch is open, the vehicle circuit battery is the only power source connected to the power distribution center.

When the isolation switch is closed the starter battery is charged and the vehicle circuit battery is boosted by the starter battery.

Modes of the isolation switch

Scheme 61

1. Starting Mode: Normal Starting. Safety Starting.
2. Driving Mode.
3. Charging Mode.
4. Sleep Mode.

Starting Mode

When the isolation switch recognizes KL15 via the K Bus, it determines the voltage of the vehicle circuit battery.

1. If the vehicle circuit battery IS sufficiently charged, it proceeds with Normal Starting.
2. If the vehicle circuit battery IS NOT sufficiently charged, it proceeds with Safety Starting.

Normal Starting

1. The isolation switch is open.
2. Within 0.5 seconds of engine start-up the E-CAT module energizes the E-CAT heating coils (program dependent) and simultaneously signals the isolation switch that the ECATs are "On" via signal "KATON" (low signal).
3. Upon completion of the heating period, the E-CAT module signals the isolation switch that the E-CATs are off (High Signal).
4. Under normal conditions, the isolation switch is not closed before the heating procedure is finished.

Safety Starting

1. In response to a discharged condition of the vehicle circuit battery, the isolation switch closes to momentarily boost the vehicle circuit battery and supply all systems with starter battery voltage via the power distribution center. This operation lasts for a maximum of 30 seconds or until confirmation of engine start up is received. (TD signal on the K Bus)
2. Receiving the TD signals causes the isolation switch to immediately open for the duration of the E-CAT heating cycle.
3. If the engine is not started within the 30 seconds, the isolation switch opens and remains open until KL 15 is recognized on the next start-up cycle.

Driving Mode

The vehicle circuit battery is permanently connected in parallel to the generator and is charged when the engine is running. When the isolation switch is closed, the generator simultaneously charges the starter battery.

As the vehicle is driven the isolation switch cycles between open and closed based on

1. Voltage values of both batteries.
2. Current transfer between both batteries as monitored by the isolation switch.
3. Internal temperature of isolation switch.

Conditions Causing Switch To Open While Driving

1. Sufficiently charged starter battery.
2. Current flow through switch exceeding 0.5 amps. The starter battery will supplement vehicle electrical needs during periods of high demand (e.g continuous wiper operation combined with lights and blower).
3. The internal temperature of the isolation switch exceeds programmed maximum value.

Conditions Causing Switch To Close While Driving

1. Monitored voltage of vehicle circuit battery exceeds that of starter battery by 0.7 volts.
2. The voltage of the vehicle circuit battery drops below 9 volts three times within one minute.

Scheme 62

Charging Mode (in the workshop)

The isolation switch monitors starter battery voltage during key off conditions and continues monitoring after the vehicle and the isolation switch have entered sleep mode.

1. If starter battery voltage exceeds 13.8 volts during charging in the workshop, the isolation switch comes out of sleep mode and closes. This causes the starter battery voltage to bleed off to the vehicle circuit battery, charging the circuit battery and protecting the starter battery from overcharging.

The isolation switch remains closed until the next key on cycle.

Scheme 63

Sleep Mode

The isolation switch goes into sleep mode as soon as the engine is switched off. The current draw of the isolation switch drops below 1 mA. The isolation switch comes out of sleep mode if

1. KL15 is recognized.
2. Starter battery voltage exceeds 13.8 volts (charging mode)

Failure of KATON signal

If the KATON signal is not received due to

1. Open or short to B+ - isolation switch closes for 4 seconds after start-up, TD received.
2. Short to B- - isolation switch opens 60 seconds after receiving TD.