Vw Polo

There can be many reasons why a battery has gone flat - here are the most common causes:

• Undercharging - This is the most common cause of a flat battery. Modern vehicle charging systems are designed to reduce CO₂ emissions and improve fuel economy by increasing battery usage, while at the same time not providing sufficient charge to fully recharge the battery. A flat battery may also be a result of a fault in the vehicle's charging system.
• Human Error - None of us are perfect. Leaving the headlights or interior lights on, or not closing the boot properly can all potentially flatten a vehicle's battery overnight.
• Parasitic drain - This is caused by components in the vehicle which continue to operate after the engine has been turned off. The most common offenders are dashcams, alarm systems, or electronic rust prevention systems. These items can gradually wear a battery down over time.
• Driving habits - If a vehicle is driven on a lot of small trips, the battery may not receive enough charge to recover the energy lost cranking the engine at the start of the journey. Lead-acid batteries also lose power gradually over time when not in use, so batteries in vehicles which are rarely driven will eventually end up going flat.
• Old battery - Old batteries are simply not as good at holding their charge - so if a vehicle consistently won't start it is possible that the battery has reached the end of it's life. Lead-acid batteries last 42 months on average, so if a battery is beyond this age it is on borrowed time.

If you've recently experienced a flat battery, it is important to have an expert investigate whether any problems exist with the vehicle's charging system before a new battery is fitted.

Simply going for a drive will not provide enough charge to recharge a flat battery. Vehicle charging systems are designed to provide a 'surface charge' which is sufficient to maintain a healthy battery, but nowhere near enough to bring a flat battery back from the dead.

The only way to recharge a flat battery is to use a proper multi-stage battery charger, with an amp rating high enough to restore the battery to peak performance. We recommend selecting a charger which is rated at 10% of the battery's Ah rating.

For example, a Century 68 MF has an Ah rating of 64. 10% of 64 = 6.4amps = Use a 6amp charger.

Almost all batteries have a natural tendency to go flat over time, especially when they're not in use. If you've got an old mobile phone stored in a draw at home, you'll notice it'll probably be flat the next time to try to turn it on - and it's the same story with the battery in your vehicle.

Lead-acid batteries lose charge over time, and this problem is often made worse by the parasitic drain of electrical devices within the vehicle which continue to operate even whilst parked. For vehicles which are rarely driven, a battery maintainer or trickle charger should be used to prevent the battery from self-discharging and going flat.

Most of today's vehicles have 'smart charging' profiles which automatically disengage the charging system and stop charging the battery when it is near full capacity. Therefore, a vehicle fitted with a heavily discharged battery will place more load on the engine as the alternator remains engaged to recharge the battery. This will typically result in increased fuel usage.

Batteries are typically rated using CCA - which is a test of how much current a fully charged battery can deliver for 30 seconds at a temperature of -18°C. Generally, the electrical system in your vehicle is designed to pull a fixed amount of current for each of the tasks it needs to perform - so batteries with a higher CCA will not start your vehicle faster or make it perform better.

The CCA rating of a battery will gradually reduce with time, so batteries with higher CCA ratings do have the potential to last longer. However, other factors come into play here - including how well the battery has been built, the strength and thicknesses of the internal lead plates, and how much electrolyte it contains.

Lead-acid batteries last 42 months on average - however this figure may be reduced or extended depending on a number of factors, including:

• Whether the battery has been installed correctly.
• If the battery chosen is suitable for the vehicle and driving application.
• The climate in which the vehicle is driven.
• The voltage which the battery is usually kept at.
• Whether the vehicle has high or low parasitic drain when not in use.
• How often the vehicle is used, and the length of the journeys.
• Whether the battery and the vehicle itself have both been well maintained.

Based on these factors, batteries fitted to vehicles which are used in hot climates, driven on short journeys, and rarely maintained would be expected to have a shorter life. Conversely, vehicles which are used in milder climates, driven further, and receive regular maintenance would typically have a longer life.

There are a few easy things you can do to get the absolute maximum amount of life out of your battery. As a rule, the following items should be checked on a monthly or bi-monthly basis:

• Ensure the top of the battery is clean, and that the terminals are free of corrosion.
• Check the voltage with a voltmeter. 12.7 to 12.8v is considered to be fully charged.
• If your battery is below 12.5 volts, recharge immediately using a suitable smart battery charger.
• For maintainable batteries, remove the plugs and ensure that the electrolyte is covering the battery plates. Top up with distilled water if required. For maintenance free types, check the water indicator.
• We recommend charging batteries with an appropriate battery charger every 3 months to maintain peak performance.

Maintenance free batteries are designed to satisfy the 'fit and forget' mentality of today's motorists - providing reliable starting power without the need to keep an eye on electrolyte levels. However, this doesn't mean that maintenance free batteries won't benefit from regular servicing.

Following the maintenance advice listed in the question above is a great way to extend the life of your maintenance free battery.

No. While tap water might be easy to source, adding it to your maintainable battery is not a great idea unless you are in an emergency situation. Tap water contains minerals which will accelerate corrosion - reducing the performance and life of the battery.

Always use distilled or demineralised water to top up maintainable batteries.

The simple answer is no. Car batteries are designed to provide short, sharp bursts of power to start an engine, followed by a full recharge via the vehicle's charging system. Draining a car battery with a load from an external piece of equipment (such as a portable fridge) could potentially damage the battery, and will reduce the overall life of the battery over time.

Driving a vehicle fitted with an unsecured battery is not recommended. Unsecured batteries can be damaged by impacting on other parts of the engine, and you also run the risk of it 'shorting out' on the underside of the bonnet - potentially starting a fire or causing the battery to explode. 

Unsecured batteries also tend to have a reduced lifespan - due to increased vibration damage.

This is not recommended. Most vehicles with Stop-Start technology have active energy management systems which require the replacement battery to be correctly configured to the vehicle following installation.

Without proper configuration, the vehicle may begin charging the new battery using parameters determined by years of use on the old battery. This could result in:

• Undercharging or overcharging of the battery resulting in premature failure
• Potential damage to the vehicles electrical system
• Loss of Idle Stop Start system functionality
• Increased CO₂ emissions & fuel consumption
• Possible loss of non-critical vehicle functions