How to change a car battery

Car batteries do not last forever, and it is most likely that you will need to replace a battery on a car you own at some time.

Where is my car battery ?

Here is a typical layout, highlighting the car battery and battery clamp along with the red and black battery terminals.

Sometimes the car battery will have a cover over it so you cannot see the red and black terminals.
Most car batteries are clamped securely into place within the engine bay.  These clamps will need to be removed in order the get the battery out.

Here are some examples ;

Bar runs across top of battery, with a nut at each end (probably 10mm).
Removing the bolts will allow the car battery to be lifted out.

All batteries have a lip around the base, the one above has one front and back.
The clamp holds on to this lip and is bolted to the battery tray shown underneath.  Which battery do I need ?
You can walk into most shops and tell them the make, model and year of your car and they will be able to provide you with the correct battery.
You can do the same when you buy online, choose a reputable website and enter your car details and then you should get a price back.
Make sure that the online store is offering a guarantee on the battery.
Most car batteries have stickers on them normally stating the 'Amps'  and
the 'Ampare Hours' ratings.  You can always get this info off your old battery and cross check it against your new purchase.
Also, the 'owners manual' for your car or a Haynis Manuals should tell you what battery you need for your car.

IMPORTANT - never fit a smaller battery than was originally fitted by the manufacturer, it will not last and you will be asking for trouble.
For example, diesel engines normally need more current from the battery to start the engine than petrol engine cars.

 WARNING - BATTERIES ARE HEAVY !! and you will also be bending over, so if you have back trouble, be more careful and perhaps get someone to help you with the lifting.  TIPS

You can use normal vaseline on your battery terminals to prevent corrosion instead of lithium grease. Vaseline works just as well and will keep your terminals dirt and corrosion free meaning better conduction.

Always buy your battery from a reputable outlet that offers a guarantee, normally lasting for 1 to 2 years.  This means that if the battery fails within that time, you can it back with your receipt and get a replacement (free).  I strongly recommend a guarantee as I have had a new battery fail on me and took it back to the shop for an exchange.