Battery Capacity (mAh or Ah)

Capacity represents specific energy in ampere-hours (Ah). Ah is the discharge current a battery can deliver over time. You can install a battery with higher Ah than specified and get a longer runtime; you can also use a slightly smaller pack and expect a shorter runtime.

However, if you’ve discovered more acronyms about your next potential Willard battery, let’s help you break down the stats.

Using Willard’s battery finder tool and selecting a typical car (like a 2014 Volkswagen Polo), you will see that a 646 is suggested as the perfect replacement battery. It is a sealed and maintenance-free (SMF) unit and uses enhanced flooded technology (EFB), which means it can be used in vehicles with start/stop technology.

However, eagle-eyed readers will see a lot of acronyms, which means the following:

 

20 Hr Capacity Ah: 70

This means the battery can give 3.5 amps continuously for 20 hours (3.5 x 20 = 70).
If you draw a small amount of power, the battery will last around 20 hours.

 

Reserve Capacity Minutes: 110

RC reflects the discharge time in minutes at a 25A discharge.

Specifically, it can supply 25 amps for 110 minutes before the voltage drops too low.

 

Cold Cranking Amps (CCA)

Depending on where in the world you live, you will have different Cold Cranking Amp (CCA) ratings.

Starter batteries, also known as SLI (starter light ignition) are marked with CCA. The number indicates the current in ampere that the battery can deliver at -18°C (0°F). American and European norms differ slightly.

• EN CCA Amps: 560.5 – European standard
• DIN CCA Amps: 340 – German standard
• SAE CCA Amps: 590 – American standard
• IEC CCA Amps: 564 – International standard

Now that we understand what’s on the box and battery, what exactly does voltage mean?

 

Voltage (V) – Power Potential

Batteries are marked with nominal voltage eg. 12V for a modern automotive lead acid battery. However the open circuit voltage (OCV) on a fully charged battery is higher at 12.8V

For those checking their older batteries with a voltmeter, you will be checking whether:

• Fully charged at 12.8V,
• About halfway charged at 12.2V,
• And if it is 12V or less, it needs to be recharged.

You can wire multiple batteries in series to increase voltage, which can void your battery’s warranty.

 

Cycle Life

Your car’s battery will constantly be discharged and recharged throughout its life.

Each discharge/charge event constitutes one cycle.

The number of complete charge-discharge cycles a battery can go through before it fails, is determined by the battery design and influenced by the depth of discharge and temperature.

 

Battery Type – Standard/Conventional Flooded, EFB, AGM

While lead-acid batteries have been around for over 150 years, they are still being perfected and improved.

 

Standard/Conventional flooded batteries

Since its development over a century ago, the conventional flooded lead-acid battery has been continually further developed and is still in use. It continues to offer a very good compromise between reliability, usability, robustness, availability and price

Conventional flooded batteries are the most common and economical lead-acid chemistry and are suitable for conventional vehicles. They are, however, being slowly superseded by EFB’s.

Some conventional batteries may also be classified as SMF (Sealed Maintenance Free), where no maintenance of the electrolyte levels(Inspecting and topping up of electrolyte) is required. In many cases access to the individual battery cells is restricted by using a sealed top cover design. Tampering with the sealed top cover can void product warranty provisions.

Conventional batteries experience a substantial reduction in life if they are frequently discharged to anything more than a moderate depth-of- discharge.

 

EFB Batteries

Enhanced Flooded Batteries are referred to as EFB’s and are designed for Start-Stop applications.

They are different to Conventional Batteries in that:

• They cycle better.
• They accept charge better.
• They have a wider operating range of temperatures.

EFB’s must only be used in vehicles whose electrical systems are designed for EFB’s or Conventional Batteries.

EFB’s are increasingly used as replacements for conventional batteries.

 

AGM Batteries

AGM’s are different in construction to Flooded Batteries in that:

• The electrolyte is absorbed into a glass mat separator.
• They are equipped with a pressure release valve.
• The cases are made from thicker plastics.
• Their plates operate under high compression.

 

AGM’s perform better than Conventional Batteries due to:

• Special paste formulations.
• Oxygen recombination cycles (eliminates water loss and balances active material ratio).

AGM’s are LESS robust than Flooded Batteries due to extreme sensitivity to over-charging and high temperatures.

 

AGM’s offer better performance than Conventional Batteries in that:

• They cycle better.
• They accept charge better.
• They have no water loss.

AGM’s must only be used in vehicles whose electrical system was designed for these batteries.

 

Self-Discharge Rate

Lead acid batteries naturally lose time even when not in use. This is called self-discharge.

The self-discharge rate can vary from 5-15% per month for flooded lead acid batteries and 3-5% per month for AGM batteries. Higher temperatures can significantly increase the self-discharge rate.

Self-discharge is caused by internal chemical reactions and impurities in the electrolyte. Older or poorly maintained batteries may self-discharge faster.

In order to minimise self-discharge

• Store batteries is a cool dry place.
• Keep batteries fully charged during storage.
• Use a smart charger to keep them topped up.
• Avoid storing for long periods without charging.

 

However, if you’re still unsure what features to look out for with your next battery purchase, you can always ask one of the battery specialists at Willard battery stockists.