AGM vs EFB vs standard battery: which one suits my car?

The three battery technologies: AGM, EFB and standard in detail

Before we compare suppliers, it is worth taking a close look at the heart of the matter: the battery technology itself. After all, only those who understand what happens under the casing can make a well-founded purchasing decision.

Standard flooded battery (SLI – Starter, Lighting, Ignition)

The conventional lead-acid battery is the original among starter batteries. Inside it are lead plates bathed in liquid sulphuric acid (electrolyte). During the starting process it delivers high currents for a short time and is recharged by the alternator while driving. It is robust, inexpensive to manufacture and proven millions of times over. However, it has clear limits: it copes poorly with deep discharges, its cycle resistance is limited, and it is not designed for modern start-stop systems. Anyone driving an older vehicle without start-stop automatic and with a manageable electrical load is still well served by a high-quality standard battery. Look for solid workmanship and sufficient cold starting performance (CCA value).

EFB battery (Enhanced Flooded Battery)

The EFB battery is a further development of the classic flooded battery – you could say it is the more robust, more cycle-resistant sister. The electrolyte is still liquid, but the lead plates are made significantly more resistant to the material fatigue caused by frequent charge and discharge cycles thanks to special alloys, thicker grid structures and polyester fleece reinforcements. EFB batteries were developed specifically for vehicles with simple start-stop systems and brake energy recuperation. They cope with roughly twice as many charge cycles as a standard battery and are the economical choice for many compact and mid-range vehicles with a start-stop function. In terms of price they sit between standard and AGM technology and offer excellent value for money for urban stop-and-go traffic.

AGM battery (Absorbent Glass Mat)

The AGM battery is the premium class among starter batteries. Here the electrolyte is no longer liquid but fully bound in a glass fibre fleece (Absorbent Glass Mat). This principle brings several decisive advantages: the battery is leak-proof, extremely vibration-resistant and has a significantly lower internal resistance. As a result it can deliver and absorb higher currents more quickly – ideal for the recuperation technology of modern vehicles. AGM batteries achieve three to four times the cycle life of a standard battery and are the obligatory choice for vehicles with advanced start-stop systems, lane keeping assistants, adaptive suspension or hybrid support. They are also first choice for motorhomes, boats or emergency vehicles with high on-board power requirements. In terms of price they are the most expensive option, although the higher purchase price is put into perspective by the significantly longer service life and the operational reliability they offer.

Rule of thumb for a quick overview: Do you drive a vehicle without start-stop? A good standard battery is sufficient. Do you have a simple start-stop system (mostly vehicles before 2017)? The EFB is your economical choice. Do you own a modern vehicle with extensive on-board electronics, strong start-stop or do you travel through Europe in a motorhome? Then there is no way around AGM technology.