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.
6120... AGM battery: Introduction
In September 2002, the first so-called VRLA batteries, better known as AGM batteries came into use. (VRLA means V alve R egulated L ead A cid, i.e. lead acid battery with pressure relief valve; AGM stands for A bsorbent G lass M at, 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. A modern luxury-class vehicle has some 100 actuator motors that have to be fed with electrical current. 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. Current consumption is considerable even when the vehicle is not in use.
The somewhat higher price compared with a battery of similar size is fully balanced by the following benefits:
- greatly longer service life
- improved starting reliability at low temperatures
- reliable starting of engines with high starting current requirements, e.g. high-performance diesel engines
- 100 % freedom from maintenance
- low risk in the event of an accident (reduced environmental risk)
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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.
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