Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
61 20... AGM battery: Introduction
In September 2002 so-called VRLA batteries, better known as AGM batteries , were introduced.
(VRLA stands for Valve Regulated Lead Acid, i.e. lead acid battery with pressure relief valve; AGM stands for Absorbent Glass Mat, i.e. absorbent glass fibre fleece)
AGM batteries are fitted in models with electrical loads/consumers which have a high energy demand.
With the option SA 146 (2nd battery), the AGM battery (70 Ah) is fitted as the 2nd battery.
The constantly increasing energy demand of modern vehicle electrical systems calls for ever more powerful battery solutions.
Today, up to 100 servomotors, which have to be electrically powered, operate in a modern luxury-class motor vehicle. Added to these are safety, environmental and comfort and convenience elements which are increasingly becoming standard features, such as e.g. Anti-lock Brake System (ABS), Dynamic Stability Control (DSC), electric steering effort assistance (EPS), heated catalytic converter, electronic chassis and suspension control, air conditioning and navigation system.
The power consumption is considerable even when the vehicle is parked.
The somewhat higher price compared with a battery of similar size is fully balanced by the following benefits:
- Significantly longer service life
- Increased starting reliability at low temperatures
- Safe starting of engines with high starting current demands, e.g. high-performance diesel engines
- 100 % freedom from maintenance
- Low risk in event of an accident (reduced risk to the environment)
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.