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How to Check & Change your Car Battery

Flat Battery

In the breakdown top 10 the number one problem is problems with batteries. A flat battery or a battery that has not been used for a long time will usually mean that the car won't start. This problem is especially prevalent with classic cars that can be unused for long periods of time especially over the winter months.

If your car won't start then the only option is to get a jump start either using jump leads or from a portable power pack which is essentially another battery in a box with jump leads attached. These can be very useful if you do not have access to another car and leads to do the jump start.

Top Tips to avoid a flat battery

1. Have your battery tested regularly (most tyre and exhaust centers will do this for free) or you can buy your own battery tester.
2. Check the level of the electrolyte level in the battery, the plates must be covered with liquid or this will cause damage
3.If you have a breakdown and have access to a breakdown service then call them as they are experts in restarting cars. If you are going to try and restart the car yourself remember you cannot bump/push start a car with a catalytic converter (I know this is a classic car web site but some do have cats). Also damage can be done to car electronics especially fuel injection models.
4. Only use thick copper core cables (especially for large or diesel engines) as the small cheap thin cables cannot carry the current required to start the car and will get hot.
5. Take care when connecting the cables that you do not get the polarity wrong, it can be sometimes quite difficult to see the + or - on the batteries especially in the dark or in a garage. Connect the positive cable first then the negative, to remove them take off the negative first.
6. The assisting car should be run on fast idle and ideally have the heated rear window on and the heater blower before you disconnect the starter cables to prevent damage to the electronics.

Not used for a long time

By standing still for a long time even a new battery will slowly discharge, again this situation is common to classic cars and their winter hibernation. If you do get the car started then you must go for a drive to recharge the battery from the alternator.

Top Tips to avoid a flat battery (not used for a long time)

1. If the car is going to be standing for a long time then disconnect the negative cable from the battery in case there is a small leakage, also clocks etc all draw current so will discharge the battery if left long enough.
2. If the car is going to be standing for more than a month then occasionally charge the battery, alternatively if you have electricity in your garage you can use a battery charger/conditioner which you can leave connected all the time and will keep the battery in top condition and ready to start the car when you need it.
3. Not battery related but if the car has not been used for more than 6 months change the oil as it will have oxidized and not offer full protection.
4. When the car starts after a long lay up run the engine slowly so that the oil can be pumped round the engine again.

On the MGB the battery is located behind the seats which is a real pain when it comes to removing batteries, jump starting or charging as half the interior has to come out to get to it.