How to fit a car battery

  1. Park on a flat, level surface in a safe place, put on the hand brake and take the keys out of the ignition (some vehicles may activate the central locking when replacing the battery, so keep the keys somewhere safe). Don’t forget to wear protective goggles and gloves, as car batteries contain acid which is highly corrosive.
  2. Before replacing the battery make sure you’ve got all the PIN codes and settings for your electronic equipment such as radios and satellite navigation etc. Some modern vehicles have systems that need to be reset after the battery has gone flat or been disconnected. Check the owner’s handbook or an expert if you are unsure.
  3. Open the bonnet and use the bonnet stay to keep bonnet open (Some vehicle’s bonnets may stay up on their own)
  4. Locate the battery. They are normally under the bonnet, but they can also be in the boot or even under the seat. Again, check the owner’s handbook for more information.
  5. Remove any plastic trims / covers from the battery
  6. Label the battery cables so that they don't get mixed up. It’s important that you disconnect the negative connection before the positive, or you may cause damage to the vehicle’s electrical system.
  7. Loosen and disconnect the negative cable clamp (normally marked with “ –“ (minus) ) and move the clamp away from the battery post.
  8. Loosen and disconnect the positive cable clamp and move away from the battery post.
  9. Remove any screws, clamps or bars holding the battery in place. Disconnect any vents that are attached and carefully lift the battery out of the vehicle. Remember that a car battery is quite heavy so you may need a helping hand.
  10. Fit the new battery making sure the positive and negative posts are on the correct sides. Connect any vent pipes, screws, clamps or bars that hold the battery in place.
  11. Remove any covers from the new batteries terminals.
  12. Reconnect and secure the positive cable clamp (make sure the connection is as far down on the battery post as possible).
  13. Reconnect and secure the negative cable clamp (make sure the connection is as far down on the battery post as possible).
  14. You are now ready to start the vehicle.

If you’ve ever suffered the let-down of a flat car battery, you'll know what a drain it is. If it does go flat for no obvious reason it may be time to replace your battery. Just like the ones in your TV remote control, car batteries need to be replaced at some point. Here are 10 car battery facts that may indicate you need a new battery – and, if so, why you should replace it.

  1. Causes are varied but fall into two broad categories – either something electrical (such as the lights) were left on, or the battery has become unserviceable and needs replacing.
  2. Modern vehicles are equipped with a number of on-board computers that control and monitor various systems. These often place a constant small drain on batteries even when the vehicle is parked up. It can mean that when the vehicle is left standing for a long period, when left in an airport car park for example, the battery can slowly discharge.
  3. The battery is a vital component of all cars. A good battery can last for over five years with proper care. However, battery failure can occur in as little as three years, depending on the usage, maintenance and seasonal temperatures.
  4. Premature battery failures can be caused by defective charging systems that cause the battery to be over, or under-charged; or other electrical faults.
  5. Ensure you get the correct battery for your vehicle’s specification. Depending on the level of equipment fitted, the battery specification can vary. It may help to make a note of the numbers on the existing battery. However, be aware that if it’s not the original battery, it might not even be the correct battery type for the car – so check the owners’ manual or call an expert if in any doubt.
  6. Your vehicle’s on-board computers may require particular procedures to be carried out when the battery has been replaced. Check your owners’ manual or consult an expert if you're not sure.
  7. More and more vehicles now come with “Stop-Start” technology. This significantly helps drive down fuel consumption, saving you money on fuel and lowering the impact of driving on the environment. “Stop-Start” technology places greater demands on car batteries, so you should expect to pay a little more for these more sophisticated batteries.
  8. Don't forget battery disposal. This must be done in an environmentally responsible way.
  9. Call in the experts if you're in any doubt.
  10. Just because the battery is under the bonnet it doesn’t always mean it’s easy to replace. The location of the battery differs depending on the make and model. Batteries are fitted in various locations such as the foot well, in the boot or even under the seats.

After long periods of storage (12 months or more) the battery will need to be recharged when the terminal voltage falls below the required voltage. When recharging, please keep yourself and your colleagues safe by following all the relevant safety recommendations (such as wearing protective glasses).

To charge an automotive battery, refer to your car owners’ manual and your battery charger manual for instructions. Review the safety instructions that came with your charger and battery. Remember that batteries contain sulphuric acid that can cause severe burns, and hydrogen-oxygen gases that can be explosive. Read the complete safety section on this website.

NEVER ATTEMPT TO CHARGE A BATTERY WITHOUT FIRST REVIEWING THE INSTRUCTIONS FOR THE CHARGER BEING USED.  In addition to the charger manufacturer’s instructions, these general precautions should be followed:

1      Always wear proper eye, face and hand protection.

2      Always charge batteries in a well-ventilated area.

3      Keep vents tight and level.

4      Turn the charger and timer “OFF” before connecting the leads to the battery to avoid dangerous sparks.

5      Never try to charge a visibly damaged or frozen battery.

6      Connect the charger leads to the battery; red positive (+) lead to the positive (+) terminal and black negative (-) lead to the negative (-) terminal. If the battery is still in the vehicle, connect the negative lead to the engine block to serve as a ground. Be sure the ignition and all electrical accessories are turned off. (If the vehicle has a positive ground, connect the positive lead to the engine block.)

7      Make sure that the charger leads to the battery are not broken, frayed or loose.

8      Set the timer, turn the charger on and slowly increase the charging rate until the desired ampere value is reached.

9      If the battery becomes hot, or if violent gassing or spewing of electrolyte occurs, reduce the charging rate or turn off the charger temporarily.

10    Always turn the charger “OFF” before removing charger leads from the battery to avoid dangerous sparks.


These instructions are designed to minimize the explosion hazard. Keep sparks, flames and cigarettes away from batteries at all times. 

Both batteries should be of the same voltage (6, 12, etc.)

1      When jump starting, always wear proper eye protection and never lean over the battery.

2      Do not jump start a damaged battery; inspect both batteries before connecting booster cables.

3      Be sure vent caps are tight and level.

4      Be sure that the vehicles are not touching and that both ignition switches are in the “OFF” position.

5      Turn off all electrical equipment (radio, defroster, windshield wipers, lights, etc.)

The following steps should be followed exactly.

  1. Connect positive (+) booster cable to positive (+) terminal of discharged battery.
  2. Connect other end of positive (+) cable to positive (+) terminal of assisting battery.
  3. Connect negative (-) cable to negative (-) terminal of assisting battery.
  5. Be sure that cables are clear of fan blades, belts and other moving parts of both engines.
  6. Start vehicle and remove cables in REVERSE order of connections.

Handling and the proper use of Lead Acid Batteries are not hazardous providing sensible precautions are observed, appropriate facilities are available and personnel have been given adequate training.

In accordance with the Consumer Protection Act 1987, the purpose of this guide is to :-

1. Indicate the main hazards which may arise

2. Outline the precautions to be taken to minimise such hazards

3. Indicate the emergency actions to be taken in the event of the occurrence of a hazard


The Hazard

Batteries contain Sulphuric Acid which may leak for various reasons. Also acid may be given off as droplets and/or spray/mist during recharge.

Sulphuric Acid is a corrosive and poisonous liquid which will cause burns and irritation to the skin and eyes and could severely damage clothing.

Refer to Health & Safety Executive Guidance Note EH40 for the latest occupational exposure limits for acid mist in air.


  1. Always handle batteries with care
  2. Never overfill with acid
  3. Always store upright
  4. Never allow children access to a battery
  5. Always charge in a well ventilated area
  6. Never allow battery vents to become blocked
  7. Always wear eye protection
  8. Always wear protective clothing

Accident or Emergency Action and Treatment

Skin contact –

Immediately soak the affected area with copious amounts of clean water, remove any contaminated clothing and seek medical attention if irritation persists.

Eye contact –

Immediately irrigate eyes for at least 10 minutes with clean water, seek medical attention.

Ingestion –

Immediately drink as much water as possible – do NOT induce vomiting, seek urgent medical attention.

Spillages –

For small spillages wash away with large quantities of water. For larger volumes dispose of in suitable acid resistant containers, clearly labelled.

The Hazard

Accidental short circuit of battery terminals by a conductive object, such as a metal tool or item of jewellery etc. may generate sufficient heat to cause severe burns, create arcing or cause any metal to melt and splash.
Severe electrical shocks may be received from faulty mains electrical charging equipment and during the recharge of high voltage battery systems or the recharge of a number of batteries connected in series i.e. 5 or more 12V batteries in series = 60V nominal.


Always remove metal objects from hands, wrists & neck e.g. rings, bracelets, watches & necklaces.

Always, when working on vehicle electrical systems, disconnect the battery,

but before disconnection :-

• Switch off all electrical loads

• Refer to vehicle manufacturer’s handbook

• Make the first disconnection and the last reconnection the earth point as far from the battery as    possible

Always take great care to avoid shorting the live terminal to earth.

Never place tools or metal objects near to or on top of a battery.

Accident or Emergency Action and Treatment


Apply a dry sterile dressing and seek medical treatment.

Electric shock

Approach person with care. If the individual is clear of the conductor then, with caution, switch off equipment or break the current. If the individual is still attached to the conductor do not touch with bare hands. If possible use a suitable insulating material e.g. wood, rubber, plastic or rolled paper, to detach the conductor from the victim. If necessary, summon assistance then give artificial respiration until it arrives.

The Hazard

Hydrogen gas emitted during charging is explosive at concentration levels above 4%. Hydrogen & oxygen gases are both evolved during battery recharging. These gases may also be emitted at other times, for example, if the battery is moved or shaken.


1 Always charge in a well ventilated area

2 Always ensure the charging leads are correctly fitted before switching on the mains

3 Always ensure the mains is switched off before disconnecting the charging leads

3 Always use eye protection and protective clothing

4 Always wait at least 5 minutes after ceasing recharge before disconnection

5 Always take care to ensure that cables and connections are handled in a way that avoids    accidental sparking

Never smoke near a battery

Never allow naked flames near a battery

Never create sparks near a battery

Accident or Emergency Action and Treatment

Seek medical advice as appropriate to injury.

In an explosion acid will have been sprayed and ejected and plastic & metal parts may have caused severe lacerations.

The Hazard

Batteries are awkward and heavy to handle resulting in possible strains to the human body as well as potential for dropping the battery, with resultant acid spillage, injury etc.


Always use correct lifting procedures to minimise strain to the human body.

Always use lifting handle or lifting ledges if available on the battery.

Accident or Emergency Action and Treatment

Seek medical advice as appropriate to the injury. Remember that acid may have been spilled.

No attempt should ever be made to renovate or repair a ?damaged battery.

This work involves all of the hazards detailed in sections A to F above and should only be carried out by suitably trained personnel with appropriate facilities and in accordance with the manufacturer’s instructions.

All spent batteries and waste arising from spillages and fires must be disposed of in conformance with the Environmental Protection Act, the Special Waste Regulations 1996 and the Environmental Protection (Duty of Care) Regulations 1991.

Since batteries contain combustible materials, the local Fire Authority should be consulted where a quantity of batteries are stored together.

The following symbols are being used on all batteries and mean the following: