Guide Category

Start/Stop Systems & Batteries

Future-proof your Start/Stop vehicle with in-depth explainers on AGM and EFB technology, BMS resets, and cold-weather readiness. Why it matters: incorrect batteries fail within months.

Start/Stop
Start/Stop

Why Start/Stop Systems Need AGM or EFB (Not Standard Flooded)

Understand why vehicles with Start/Stop technology require AGM or EFB batteries, not standard flooded batteries. Learn what happens if you fit the wrong type, how Start/Stop systems work, and why the correct battery technology matters.

9 min read

Published: 25/01/2025

Why Start/Stop Needs Special Care

  • Systems monitor internal resistance and disable themselves if the wrong battery is fitted.
  • Charging profiles differ—AGM can accept higher voltages, so coding is critical.
  • Diagnostic trouble codes often appear after battery swaps; always perform a relearn.
  • Never fit a standard flooded battery to a Start/Stop car—it will fail prematurely.

Common Questions

Can I replace an AGM battery with a standard lead-acid one?

No. Standard batteries cannot handle the rapid cycling and high charge rates of Start/Stop systems. Doing so will lead to battery failure in 3-6 months and may damage your car's electrical system.

Do I really need to code a new battery to my car?

Yes, for most modern cars (BMW, Audi, VW, etc.). The Battery Management System (BMS) adjusts charging rates as the battery ages. If you don't reset it, the alternator may overcharge the new battery, shortening its life.

What is the difference between AGM and EFB?

AGM (Absorbent Glass Mat) is designed for high-load, energy-intensive vehicles with regenerative braking. EFB (Enhanced Flooded Battery) is an entry-level Start/Stop battery for smaller cars. You can upgrade from EFB to AGM, but never downgrade from AGM to EFB.