Autoelectrics tech pages

Vehicle Breakdown call out + replacement battery supply & mobile fitting at a competitive price !

A.M.P.S breakdown supply & fit a range of Brand New Premier Quality vehicle batteries with warranty from Budget battery 24 months to Premium Quality 4 years to replace your flat or worn out battery

Car Van HGV Truck Tractor Batteries

Autoelectrics Mobile Product Services has Bosch professional battery diagnostic test equipment to check batteries are not replaced unnecessarily.

Our online product range includes :

  • Jump Leads - Battery Booster Cables
  • Battery isolator switches
  • Battery Terminals
  • Battery Cable
  • Battery Specification

    Use the correct specification of battery recommended for your vehicle. The original equipment vehicle battery may often be identified by a product code, typical examples are: 002 , 005 , 015 , 017, 027, 037 , 038, 048 , 049 , 054 , 063 Car battery, 065 Car Battery , 067 , 069 , 072 , 075 , 077 , 085, 088 , 089 ,093 , 096 , 097 , 110 , 154, 334 ,335 , 421 ,622 , 627 Truck Battery , 629 , 643 Truck / Tractor Battery , 644 , 647 , 648 , 655 , 656 , 663 , 664 , 678 , 895, 896

    Batteries can be identified by :-
    System voltage eg 6 volt, 12v , 24v ,
    Capacity in Ampere hours Ah
    by Cold Cranking current CCA
    Terminal layout position
    Size : Physical dimensions

    The correct battery application for your car, van, truck, or tractor is designed to take account of factors such as :

    *Engine capacity and starter current draw (higher cylinder capacity or greater compression ratio requires more effort to rotate it)

    *Reserve power requirement (additional systems such as lights, air conditioning, (which can use up reserve power) .

    *Location ( special batteries for specific mounting position)

    *Climate (Cold temperatures can naturally discharge the battery and also increase loads encountered during starting) A battery with a higher CCA rating (Cold Cranking Amps) will make cold starting easier. CCA is the number of Amps a battery can deliver, over a specified period of time, to a specified voltage.

    *Vibration & chemical attack (eg: encountered on industrial machines )

    *Charge-Discharge cycle.

    Batteries with various cycle times are avaliable

    Vehicle batteries come in many types and sizes. Batteries are the chemical energy store at the heart of the vehicle electrical system. Batteriues are the energy source for starting the vehicle. A discharged car battery is one of the most common causes of vehicle breakdown.

    Starter batteries

    Vehicle Starter batteries are for high output short duration cycles,

    Deep cycle (leisure) batteries

    Leisure batteries are designed for lower output longer operation and are usually used on caravans or motor homes for auxilliary electrics.

    Amp Hour Rating

    The Amp hour (Ah) rating of a battery defines for how long it will deliver current (eg 240 Ah will deliver 10amps for 24 hours, or 24 amps for 10 hours etc...)

    Safety procedures

    Safety procedures should be undertaken when storing , charging, fitting and removing vehicle batteries

    Dangers associated with vehicle batteries include Sulphuric Acid and Explosive gases. Eye protection and gloves should be worn during battery handling and fitting. Arcing may occur if terminals are shorted with metallic objects.

    Always remove the chassis ground terminal first when disconnecting a vehicle battery.

    Batteries should only be charged in a well ventilated area. Refer to for further guidance.

    Vehicle Battery charging during vehicle operation

    Lead Acid vehicle batteries require direct current (dc) to recharge.
    In use, the vehicle battery is recharged by generator either engine driven alternator or dynamo whilst the engine is running.
    The charging voltage must be slightly above the battery voltage, for example a 12 volt car battery would be recharged at around 13.5 volts.
    Alternative additional methods exist of recharging vehicle batteries whilst a vehicle is moving including regenerative braking as used in modern hybrid vehicles.
    Any method of generating electricity and rectification to direct current (dc) could be used to recharge a car battery providing the voltage is regulated and sufficient current provided.
    Possible battery charging sources are solar panel ( Photovoltaic ) battery chargers, wind generators, mains powered battery chargers etc.

    Poor connections of wiring leads to high resistance to current flow causing battery charging problems

    Vehicle Battery Construction

    A conventional Lead-Acid car battery consists of a container holding terminals connected to a series of lead plates immersed in a sulphuric acid electrolyte. Other types include Dry cell , Gel filled cell, AGM (advanced glass mat)

    Battery Reserve Capacity

    Starter Battery reserve capacity (capacitance) must be sufficient to allow a high flow of current to the engine starter motor of the vehicle when cranked and also supply some of the current for other major components such as heater fans, lights, fuel injection, etc.

    Reserve capacity (RC) is the amount of time a vehicle can run on battery power only without charging system operating. Reserve capacity specification assumes the vehicle requires 25 amps to support basic electrical function at operating temperature of 25 degrees centigrade and is the time in minutes taken for the battery to reach a final voltage of 10.5v whilst disharging without generator operation

    Vehicle Battery Maintenance

    Lead-Acid battery maintenance involves:

    Visual check
    Condition of the battery casing for cracks, and security of the battery hold down device.

    Electrolyte level check involves identifying amount of electrolyte fluid in the cells, this should just cover the plates, top up with distilled water as necessary.

    Specific Gravity of Electrolyte
    A hydrometer may be used to check the specific gravity of electrolyte in each cell. (avoid flames & sources of ignition because batteries can emit hydrogen gas which is highly flammable).Specific gravity of battery electrolyte can be tested Charged battery (12.7 volts) : 1.28 SG Discharged battery (10.8 volts) : 1.12 SG

    Battery and charging system performance tests can be carried can be carried out using dedicated test equipment such as Midtronics or Bosch BAT121 battery tester.

    Cable and Connections

    *Check battery terminals are clean , secure and in good order .

    *check the cables for condition.

    Engine Won't Start?

    Battery failure is the most common cause of vehicle breakdown.
    Vehicle Battery Failure Symptoms :

    Ignition key turned to the "IGN" position : No ignition lights on the dash panel when the key is turned to the "IGN" position may indicate battery failure.Try switching the headlights on ,if they operate brightly, this could be an electrical fault requiring further investigation and repair.

    Ignition switch on, dash warning lights come on, when you turn the key to the crank position the warning lights go dim and nothing happens. This could also be a starter motor or wiring fault. Ignition switched on, dash warning lights come on , turn the key to the crank position, nothing happens, but lights do not dim: Could be an electrical fault with switch, relay, wiring, or starter. Ignition switched on, dash warning lights come on, turn to crank position and you just hear a click from the starter motor; Possible low battery volts, starter solenoid fault, or wiring etc. Ignition on , turn to start position and starter motor cranks engine over slower than normal; Could be a starter or wiring fault, but if this happens on a cold winter morning its a fair bet the battery is failing.

    Vehicle Electronics : Computer fault codes particularly present in airbag module for low battery volts can be a sign of a failing starter battery For more information on vehicle starter faults see the table on our starter motor page Causes of Vehicle Battery failure Battery at end of service life : During its natural cycle material is transferred through electrolyte from one plate to another in each cell of the battery, this causes degradation until the cell fails. The battery can also fail due to internal short circuit. Most batteries are stamped with a date code and have an expected lifespan.

    Self discharge:

    Car Battery draining or not holding charge ?
    A battery loses a percentage of surface charge even when disconnected .A Lead Acid battery will generally become weaker as it ages. 12v vehicle batteries with a voltage of 12.4v or below should be recharged Low electrolyte level : The electrolyte is the medium through which the electrons pass during the battery cycle. Low electrolyte can cause premature failure. A cracked battery casing can allow electrolyte to leak causing advanced corrosion to surrounding structures. Severe cold temperature can freeze battery electrolyte.

    Poor connections: Loose or corroded battery terminals or defective wiring cause high resistance resulting in either the battery not being charged properly or not being able to deliver its current when required. Sulphate around battery terminals leads to poor connection. Severely corroded battery clamps should be renewed. Battery Current drain: Each time a vehicle electrical consumer is switched on eg, lights, current flows from the vehicle battery and causes it to discharge.

    Car battery draining overnight ?
    Faulty components can cause the battery to drain unintentionally ,examples are wiring shorts, defective alternator diodes, lights left on , etc.

    Charging system failure

    Dashboard Battery light On ? Breakdown coming soon !
    If the battery is not being recharged as the vehicle is operated it will gradually drain until breakdown occurs.
    Charging system failure can be caused by a faulty battery, loss of alternator drive due to fan belt failure , faulty alternator, incorrect voltage regulator setting, defective wiring, loose connections. Frequent short journeys can result in a vehicle battery becoming discharged due to insufficient recharge time following heavy discharge by vehicle starter motor.
    For more information on battery charging systems see our Alternator page

    Battery OverCycling
    Each time a lead acid battery is discharged ,its plates expand and contract resulting in excess material being released and deposited at the bottom of the battery casing. This will eventually build up and cause a short circuit and premature failure.
    The most common causes of battery overcycle are :
    Incorrect battery for application.
    Vehicle electrics fault (eg diesel glow plugs relay stuck on) Taxi or multi-drop vehicle use. Starter battery used for leisure application.
    Some batteries are manufactured for this type of operation by fitment of glass wool between plate separators which holds active material in place to be absorbed back on to the plates when the battery is recharged.

    Overcharging of the vehicle battery:
    When the vehicle engine is running, it is the alternator which supplies power to recharge the battery. A failure in the alternator voltage regulation circuit can cause excess voltage to be applied to the battery. This causes decomposition of active material forming the battery plates , and also loss of electrolyte. It is often first noticed by a smell of 'rotten eggs' (hydrogen sulphide) , or by vehicle bulbs continuously failing. Fault codes may be logged in vehicle computer modules (particularly the SRS airbag module) referring to battery overvoltage.

    Battery Recovery
    A build up of Lead Sulphate crystals on the Lead plates can reduce surface area in contact with electrolyte inside the battery leading to loss of performance.
    Use of a battery desulphator, which is a special type of battery conditioner developing a pulsed charging current may reverse the effect of sulphation.

    Battery fitting guidelines

    Installation Safety first

    Safety procedures should be undertaken when storing , charging, fitting and removing vehicle batteries.

    Dangers assosciated with vehicle batteries include Battery Acids and Explosive gases.

    Eye protection and gloves should be worn during battery handling and fitting. Batteries should only be charged in a well ventilated area. Refer to for further guidance.

    Fitting a vehicle battery incorrectly can damage or destroy a vehicles electrical system.

    Be Prepared : Have the radio code available and take note of any special procedures recommended by the vehicle manufacturer. Use a memory saver device to prevent loss of computer memories if possible. Disconnection of vehicle batteries can result in memory loss from some computerised vehicle systems for example body control modules.

    Ensure all battery terminal clamps are clean and in good condition. Corroded or damaged battery terminal clamps should be cleaned or renewed depending on condition. On Negative ground systems always disconnect the Negative terminal first . When installing the new battery first fit the battery securing device. Then fit the Positive terminal first and ensure the terminal clamp is fully tightened before fitting the Negative terminal and tightening. Anti corrosion spray may be applied to the terminals according to manufacturers recommendation.

    Safety reminder :

    Vehicle Batteries may contain Sulphuric acid which can cause burns. Car batteries can emit hydrogen gas which is an easily ignited and explosive gas. Metallic objects in contact with battery terminals, and terminal disconnection / connection can cause sparks which may ignite hydrogen gas causing explosion. Avoid smoking and other sources of ignition. High currents can be discharged through metal objects such as jewellery causing burns. Batteries contain Lead and can be heavy.

    Dispose of correctly.

    Battery Charge Warning light operation

    The battery charge warning light should illuminate when the ignition key is turned to on, but the engine is not running. Once the engine is running the battery charge warning light should go off.

    Low battery voltage due to a failed battery or charging system may cause computer system fault codes to be logged which may need to be cleared using diagnostic equipment. Some vehicle computer memories are reset to basic setting by battery disconnection and may have an adaptive learning period after the vehicle is restarted . Dual Batteries, Split Charge, Battery Backup etc. Link: For more information about auxiliary battery charging systems visit our Onboard Power page

    Battery Banks

    There are times when just one vehicle battery is not enough.

    24 Volt Systems

    Linking of two 12 volt heavy duty batteries in series is commonly used to attain 24 volt system requirements on hgv heavy goods vehicles and heavy plant hire equipment.
    Advanced battery charge management equipment is often fitted to specialist vehicles such as ambulances ,fire fighting , breakdown vehicles, leisure and marine equipment. This may involve fitment of advanced voltage regulation devices, to optimise battery charging, together with additional batteries and switchgear.

    Typical situations when an extra battery is useful:
    Commercial vehicle on multi drop distribution fitted with a tail lift :
    Extra batteries are fitted recharged by a split charge system via voltage sensitive relay to power the tail lift equipment which is isolated from the main vehicle starter batteries whilst in use.
    Should the Auxiliary batteries become discharged the vehicle can still be started on its normal batteries and the auxiliary battery be recharged with the engine running. Caravan fitted with deep cycle leisure battery for internal lighting etc: The towing vehicle is fitted with a split charge relay to enable the leisure battery to be recharged as the vehicle is driven. An inverter may also be fitted to supply electricity at higher voltage for mains appliances, and possibly mains or solar powered battery charging equipment. Breakdown vehicle fitted with auxiliary batteries to enable dead vehicles to be boost started without leaving the breakdown vehicle immobilised due to a discharged battery. Marine craft fitted with a dual battery system so that the vehicle can still be started should one battery become discharged or fail whilst out at sea.

    Battery Management System

    Battery management systems may be fitted to certain vehicles eg BMW idrive. An Intelligent Battery Sensor (IBS) may be fitted in the Negative lead to monitor battery condition including State of charge and battery health, voltage , current, temperature, sometimes resulting in increased battery discharge message to be displayed. Configuration may be required if a battery is replaced to "register the new battery" so the battery charging system operates correctly.

    Removal of vehicle battery may cause computer coding to be lost and require vehicle configuration with diagnostic software after the battery is replaced.

    specific connection points and manufacturers procedures should be used if boost starting.Waste Battery Disposal

    Waste Batteries classify as Hazardous Waste

    Dispose of your disused vehicle battery correctly. If you are located in Shropshire, Car batteries can be taken for disposal at local authority waste sites or disposed of through your battery supplier.

    Battery Manufacturer & Waste Disposal Links: Yuasa Bosch Varta G & P Batteries ; disposal & recycling

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