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How Start-Stop Affects Batteries
A start-stop system can restart your engine 100+ times per day in urban driving. Each restart is a deep discharge event. A conventional starter battery is rated for up to about 30,000 engine starts over its life. An EFB is rated for up to around 270,000 and an AGM for up to around 360,000 — roughly nine and twelve times as many. Manufacturers express deep-cycle capability separately, as a multiplier: Bosch quotes up to three times a conventional battery for EFB and up to four times for AGM.
EFB vs AGM for Start-Stop
| Feature | EFB | AGM |
|---|---|---|
| Engine starts (manufacturer-rated) | Up to ~270,000 | Up to ~360,000 |
| Recharge Speed | Fast | Very fast |
| Deep Discharge Recovery | Good | Excellent |
| Vibration Resistance | Good | Excellent |
| Spill Proof | No | Yes |
| Suitable for Mild Hybrid | Yes | Yes |
| Price | £70–110 | £100–180 |
Recommended Batteries for Start-Stop
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Sources: engine-start ratings from GS Yuasa’s YBX3000, YBX7000 and YBX9000 range data (VARTA and Banner publish the same 270,000 / 360,000 figures); deep-cycle multipliers from Bosch; mild-hybrid guidance from Exide’s hybrid and electric vehicle application data. Prices are indicative UK retail. Last verified August 2026.
Battery Registration
When you replace the battery on a start-stop vehicle, the Battery Management System (BMS) must be told that a new battery has been fitted. This process is called ‘battery registration’ or ‘battery coding’. Without it:
- The BMS continues charging based on the old battery’s wear profile
- The new battery will be undercharged or overcharged
- Start-stop may stop working
- The new battery will fail prematurely (sometimes within months)
Frequently Asked Questions
Can I fit a standard battery to my start-stop car?
No — it will fail within weeks to months. Start-stop systems require EFB at minimum, AGM for premium systems. Always match or exceed the original type.
Does start-stop really save fuel?
Yes — studies show 5-10% fuel savings in urban driving. The battery cost increase is offset by fuel savings over 3-4 years.
Why is my start-stop not working?
Common causes: battery charge too low, cabin temperature not reached, defrost running, battery not registered after replacement, or battery degradation. Have the battery tested.
The same AGM and EFB replacement rules apply to electric cars — see EV consumables for what an EV still needs.
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How we check fitment for this guide
We cross-reference fitment figures against manufacturer specifications and OE-supplier catalogue data where available, and matched to the standard codes that actually govern fit — battery type/group sizes, wiper lengths and fitting types, bulb fitment codes, tyre size markings, and oil specifications. We work by make, model, year, engine, and build date, because a single model can take different parts across its life. Where the right part depends on your exact vehicle, we tell you to confirm by registration or VIN. More on our method →