AGM vs EFB vs Conventional Flooded Battery Technologies

It all starts with the battery ...

More than 70 percent of all new cars are equipped with a start-stop function. The start-stop technology saves fuel at every traffic stop and is good for the environment.

As a rule of thumb, if your car has start-stop technology it most likely came with an AGM or EFB battery out of the factory. When the time comes to replace the battery, it is important to use an equivalent or better battery technology.

The conventional wisdom is:
- replace an EFB with an EFB or an AGM.
- replace an AGM with an equivalent AGM only.
- replace a conventional flooded battery with the same or an EFB.

EFB and AGM batteries are used across a growing range of Start-Stop function vehicles. The manufacturer will choose the type that best balances the vehicle's lifetime electrical load requirements. An EFB is the bare minimum requirement for the Start-Stop car.

There's more to the story than just Start-Stop.

If we look at conventional cars from 20 years ago, most came with fewer than 20 electrified devices. Today's modern cars are packed with over 150 electrified components. Features like power doors and windows, heated seat, power tailgate, passive boost and start-stop systems are common in middle and high range vehicles.

These growing energy and high cranking demands can only be met by the more robust and consistent peformance of AGM and EFB batteries.

Cars are fast becoming computers on wheels.

Recognising this trend, car manufacturers increasingly turn to AGM batteries to reliably power the growing list of electronic wizardry that consumers come to expect in their modern vehicles.

AGM stands for Absorbent Glass Mat. Built for demanding applications.

AGM batteries are manufactured with a special glass fibre fleece separator which absorbs the electrolyte. This makes it virtually impossible for the battery acid to leak. AGM technology has been around for a number of decades with a proven track record in high demand and exacting applications for industries ranging from aviation to telecommunication. The plates within AGM batteries are installed under controlled compression which maintains the efficacy of the active material and makes the battery especially robust. The AGM battery can withstand cyclic loads up to three times higher than conventional batteries.

The humble car battery has never been more important; with new technology that keeps us safe and comfortable piled into the latest cars. City traffic driving and short journeys add new demands on the vehicle's electrical system which can consume more power than the alternator can supply. The AGM battery becomes the go-to energy source for all vehicles with brake energy regeneration, Start-Stop function and/or auxiliary heater.

EFB stands for Enhanced Flooded Battery.

The EFB is a variation of the conventional wet (flooded) battery. The term appropriately highlights the improved nature of the battery technology which enables their application in many modern cars. For example, the popular Mazda CX-5 SUV with Start-Stop technology (i-stop) have been rolling off the factory floor, ever since the first model, with an EFB battery (Battery Codes: Q85 or T110).

The EFB Battery should not be confused with a Standard Flooded Battery as it carries a number of advatanges:

- greater charge acceptance - "charge acceptance" is the ability of a battery to accept and store energy under given external parameters like time, temperature, state-of-charge, charging voltage or battery history (https://www.sciencedirect.com/topics/engineering/charge-acceptance);

- and greater cyclic durability when operating in a reduced state of charge. Critical in Stop-Start Vehicles.

Therefore, it is critical that the correct battery is paired with your car.

Why it is so important to use the right battery for the vehicle?

The answer is, simply: longevity, performance capacity and reliability under high demand. Cars have become more reliable because of advancements in automotive technology which has benefited tremendously from recent innovations in computing power. In the process, manufacturers select the best battery technology for the job. After all, if the car won't start, there's a good chance it begins with the starter battery.

Standard/Traditional/Conventional Flooded (Wet) Lead-Acid Battery.
These batteries are most common in older (10+ years) and non stop-start vehicles.

The greatest advantage of the standard flooded battery is: lower cost. It provides reliable starting power and gives basic charge acceptance.

The main disadvantages are:

- It is limited by its ability to power large accessory loads.
- Due to the physical make-up of the battery, it has reduced cycling capability compared to EFB or AGM batteries.
- Whilst in some cases, it may appear to last as many years as a higher cycling battery, it actually provides less life per cycle.