What is a start and stop battery?


With the requirements of the national environmental protection policy, in order to reduce emissions, automatic start-stop technology came into being. All German cars such as Mercedes-Benz, BMW and Audi are equipped with start-stop technology and use AGM batteries (such as Exide, Germany, MOLL, Johnson Walta, and Banner, Austria) Japanese cars such as Mazda (Atez, Encore, cx4, cx5), Toyota (Highlander, Crown, Camry, Corolla dual engine, RAV4) equipped with automatic start-stop, all use EFB start-stop battery (Japanese cars start-stop mostly use GS unified Q85, S95 Start and stop the battery).

AGM/EFB batteries have gradually become familiar to everyone with the continuous update of automobile technology, but the use of AGM/EFB batteries has not been well-known by customers. AGM/EFB batteries are collectively referred to as start-stop batteries. AGM originated from Exeter, USA, and EFB originated from MOLL in Europe, Germany.

AGM batteries are mostly assembled on European brand vehicles, and EFB batteries are mostly assembled on Japanese brand vehicles. Each has its own strengths in use. Many battery friends will consult. Can cars without start-stop function be replaced with ordinary batteries? Most of those who inquire about this kind of problem encounter high-end cars such as Mercedes-Benz, BMW and Audi. Take Mercedes-Benz as an example. Many of the Mercedes-Benz S series have no start-stop function. Can ordinary batteries be used instead? The answer is “no”.

The new models of Mercedes-Benz S series, ML series, and GL series are basically all AGM batteries ranging from 70A to 95A. Although the S series does not have a start-stop function, it has on-board electrical appliances such as refrigerators, coffee heaters, and rear-seat DVD movies that require power supply. It is different to use ordinary batteries. Someone in the storage battery industry has tested using ordinary batteries instead of AGM batteries, and the results were failed in 3-6 months.

What is the start-stop system?

The start-stop system means that the engine starts and stops automatically when the vehicle stops temporarily (for example, waiting for a red light) while the vehicle is running. When it needs to move on, the system automatically restarts a set of engine systems.

Why use AGM/EFB to start and stop the battery?

Because when the engine is started, due to the need for ignition and the need to supply power to the starter motor, the on-board battery must be capable of high-current discharge performance; because the start-stop system frequently restarts the engine, the battery supports frequent high-current discharge; when the hybrid system provides power to the wheels The battery needs to provide energy support; it can meet the needs of electrical equipment such as audio and lighting in the car; when the on-board charger is charging the battery, the battery must have strong charging acceptance performance; AGM/EFB battery can meet the needs of start-stop function.

With the widespread use of start-stop technology, it is particularly important to be familiar with the use of vehicles and batteries with start-stop functions.

How to identify the original car battery (Note: mainly for vehicles equipped with AGM/FEB batteries)

1. Japanese cars

Most of the batteries used in Japanese cars with start-stop function are Yuasa EFB start-stop batteries.

2. European cars

European brand vehicles use AGM batteries the most, such as Mercedes-Benz, BMW, Audi, Porsche, Volkswagen, MG and other models, many of which are supplied by Exide and Germany’s MOLL

Let’s focus on whether the original cars are equipped with AGM batteries. We use Mercedes-Benz and BMW cars. The rich liquid battery and the lean liquid VRLA valve control/AGM battery are compared.

A. The original Mercedes-Benz battery, the normal flooded battery 100A starting current is 760, and the VRLA valve control/AGM battery 95A starting current is 850. (Note: The original Mercedes-Benz rich liquid battery does not have 95A, so use 100A for comparison)

B. The original BMW battery, the 90A starting current of the ordinary flooded battery is 720, and the 90A starting current of the VRLA valve control/AGM battery is 900.

The simplest identification method: Identification method: AGM (absorbent glass fiber board) or VRLA (valve-regulated sealed lead-acid battery) written on the label is an AGM battery. The labeling of AGM batteries is different due to different original car manufacturers and battery manufacturers. Some original car batteries are marked with AGM, and some are marked with VRLA.


AGM600 CCA600

AGM700 CCA700

AGM800 CCA800

AGM900 CCA900

AGM950 CCA850

AGM1050 CCA950 (Note: it is only for reference)

The characteristics and precautions of start-stop battery AGM and EFB battery:

The application of engine start/stop system is becoming more and more popular. It requires special batteries, which are more advanced than ordinary batteries and have a longer service life, but the price is definitely higher.

Cars equipped with a start-stop system cannot use ordinary standard batteries, even if the capacitance is large, they cannot withstand a current much greater than the normal current intensity during charging, and their service life is limited. According to a test conducted by the American company Exide , in the case of imitating urban driving, ordinary batteries can be charged 20,000 to 25,000 times, while the special batteries mentioned above can be charged 60,000 times.

For models with intelligent management of the alternator, ordinary batteries are even less competent, because charging is performed during deceleration and braking, and the current intensity of the battery is even greater. Two types of batteries are generally used on vehicles equipped with a start-stop system: EFB (Enhanched flooded battery, enhanced water-filled lead-acid battery) and AGM (Absorbed glass mat, glass fiber adsorption battery). Compared with ordinary batteries, the first type of battery has many improvements in details, and the second type is more advanced. Its plates are not immersed in electrolyte (diluted sulfuric acid), but most of the electrolyte is absorbed in Porous glass fiber separator. Additionally, the gas generated during the charging process will be attracted by chemical reactions, and the battery is also completely sealed, so the battery can be installed in the cab. However, AGM batteries also have shortcomings. They can not withstand high temperatures, so avoid installing them near the engine, otherwise they must maintain good ventilation, just as MINI does.

EFB battery is suitable for vehicles with start-stop system without intelligent charging management, such as Fiat 500 and Alpha. Romeo Giulietta, when equipped with alternator intelligent management system (such as BMW Efficient Dynamics), AGM battery should be used because of it The ability to withstand high-intensity charging current is mainly attributed to the special isolation equipment, the smaller thickness of the grid and the special mixture contained in the electrode plate, etc. to reduce the internal resistance. Additionally, unlike traditional batteries, the single substance constituting the AGM battery is compressed before entering the electrolytic cell, which makes it effective against shocks. Manufacturers have transplanted many of these technologies into EFB batteries, thereby increasing their charge and discharge times so that they can withstand high-intensity charging. It still does not reach the level of AGM batteries.

In short, batteries have regained the focus of designers’ attention, not only for electric vehicles and hybrid vehicles, but also for ordinary cars. Up to now we have been talking about lead-acid batteries ,but the situation with this battery is much more complicated than before. In the past, there was no problem with charging the battery, but now you must be vigilant to avoid failure.

What are the advantages and disadvantages of AGM and EFB?

AGM storage battery refers to a storage battery that uses ultra-fine glass  wool as the separator. Currently, the German department and the American department mainly promote AGM technology. Compared with ordinary batteries, the price is more expensive, but it has the following advantages:

(1) The cycle charging capacity is three times higher than that of lead-calcium batteries and has a longer service life.

(2)  Higher capacitance stability during the entire service life (about three years).

(3)  Low temperature starting is more reliable.

(4)  Reduce accident risk, no acid leakage and reduce environmental pollution.

Disadvantages: AGM batteries are not resistant to high temperatures and generally cannot be installed in the engine compartment

The EFB battery is a flooded enhanced start-stop battery, which is developed on the basis of the original ordinary lead-acid battery. It can withstand high temperatures and can be installed in the engine compartment. It can fully meet the requirements of the start-stop system and has an improved life performance three times than ordinary batteries. Higher performance, and more than twice as expensive as ordinary batteries. Currently, Japanese manufacturers mainly promote EFB technology.

Will EFB batteries self-discharge?

Even if the battery is not connected to the external circuit for discharge, it will slowly lose electrical energy. This phenomenon is called “self-discharge”. EFB batteries have more active materials than ordinary batteries and self-discharge faster.

How to maintain and maintain EFB battery

Regarding the inventory:

1. Regular replenishment (1 time each 3 months);

2. First in, first out

How to recharge the EFB battery?

When charging, there are usually two ways to recharge the battery.

1. Constant current charging (that is, constant current charging, recommended)

Remarks: Pay attention to control the recharge time to prevent the battery from overcharging.

2. Constant voltage charging (ie constant voltage and current limiting charging).

The exhaust type uses a constant voltage of 16.0V and a limited current of 2.5×normal charging current, charging for 16 hours.

Remarks: After using this method to recharge, the battery voltage may appear to be falsely high. Therefore, the measured voltage value will be more accurate after the battery is left standing for 4 hours after charging.

What are the precautions for loading EFB batteries?

1. Slow current charging for 15 minutes before loading;

2. Can start the vehicle;

3. It can start the start-stop system;

Can the starting battery and ordinary battery replace each other? How long is the life expectancy of replacing the start-stop battery with ordinary batteries?

The battery of the start-stop system vehicle cannot be replaced with an ordinary battery. Because the start-stop battery performance is higher in design than ordinary batteries, the service life will be reduced if ordinary batteries are used. It is inferred from the experimental data that the endurance life is generally only one-third of the start and stop. The battery of ordinary high-equipped vehicles can be replaced by start-stop batteries. At the same time, let’s reminding you that it is best not to power off when replacing the battery!

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