8 min readPublished 20 January 2024
There are only three passenger-vehicle battery technologies that matter today: standard flooded (wet lead-acid), Enhanced Flooded Battery (Start/Stop, and shortens battery and alternator life.
Use the matrix below to match the technology to your vehicle’s energy demands, then confirm the original equipment specification before ordering a replacement.
Quick Answer
Conventional cars without Start/Stop can use standard flooded batteries, basic Start/Stop cars need EFB}}, and advanced Start/Stop or high electrical load vehicles require {{AGM.
Common causes
- -Downgrading to save money after the original AGM fails
- -Installing an EFB in a vehicle with regenerative braking
- -Ignoring battery registration so the BMS overcharges the new unit
Typical fixes
- -Match the OE spec printed on the battery or owner’s manual
- -Use online battery lookup tools tied to the number plate or VIN
- -If upgrading tech (EFB → AGM), recode or inform the BMS
Technology Snapshot
Budget commuter without Start/Stop
Likely cause: Only needs standard flooded battery
Next step: Choose a quality flooded battery, focus on CCA and capacity
Basic Start/Stop with modest electrics
Likely cause: Designed for EFB
Next step: Replace like-for-like or upgrade to AGM for extra headroom
Luxury car with regenerative braking
Likely cause: Requires AGM
Next step: Use AGM and register it so the BMS learns the new capacity
Start/Stop disabled after cheap battery install
Likely cause: Downgraded to standard flooded
Next step: Reinstall correct tech; see Start/Stop compatibility section
What is an AGM battery?
An AGM battery (Absorbent Glass Mat) uses glass fibre mats to hold the electrolyte instead of liquid acid. This design gives excellent vibration resistance, high cold-cranking power, faster charging, and a longer lifespan. AGM batteries are ideal for start-stop vehicles and cars with heavy electrical loads.
What is an EFB battery?
An EFB battery (Enhanced Flooded Battery) is an upgraded version of a standard wet battery. It offers better charge acceptance, improved durability, and is suitable for basic start-stop systems. EFBs sit between standard and AGM batteries in performance, lifespan, and cost.
AGM vs EFB vs Standard Batteries: Comparison Table
This comparison table helps you understand the key differences between AGM, EFB, and standard flooded batteries across important characteristics.
| Feature | Standard | EFB | AGM |
|---|---|---|---|
| ---------- | ----- | ----- | |
| 3–5 years | 4–6 years | 5–8 years | |
| Low | Medium | High | |
| No | Basic | Full | |
| Low | Medium | Very High | |
| £ | ££ | £££ |
Why Battery Technology Matters
Modern vehicles draw power long after the engine stops: infotainment, telematics, security, and Start/Stop systems keep consuming energy. Each technology handles these demands differently, so fitting the wrong one shortens lifespan and may even brick Start/Stop systems.
AGM and EFB batteries tolerate deeper discharge cycles, recharge faster, and deliver higher cranking amps per size. Standard flooded batteries cannot keep up with repeated Stop/Start events, so they sulfate rapidly if misapplied.
See also: Troubleshoot a weak battery
Standard Flooded (Wet Lead-Acid)
These are the traditional batteries found in older vehicles. Plates are immersed in liquid electrolyte, which makes them affordable and tolerant of minor overcharging, but also susceptible to vibration and deep discharge damage.
They suit drivers who rarely run heavy electrical loads and only need a dependable starter battery.
- Ideal for petrol cars without Start/Stop
- Requires occasional topping-up on non-sealed designs
- Shorter lifespan if frequently discharged below 80% state of charge
Enhanced Flooded Battery (EFB)
EFB batteries beef up the standard flooded design with thicker plates, scrim material, and improved separators. They handle roughly twice the number of charge cycles and recover faster after a Start/Stop event.
Manufacturers fit EFBs to vehicles with entry-level Start/Stop systems or light commercial vehicles that suffer repeated short journeys.
- Supports partial state-of-charge operation
- Costs roughly 20-30% more than standard flooded
- Can be upgraded to AGM if the Battery Management System (BMS) is coded accordingly
Absorbent Glass Mat (AGM)
AGM batteries hold electrolyte in fiberglass mats pressed tightly against the plates. This design resists vibration, allows extremely high discharge and recharge rates, and is sealed for life.
They are mandatory for premium Start/Stop vehicles, cars with regenerative braking, and anything running heavy electrical accessories (winches, premium audio, heated everything).
- Delivers up to 3x the cycle life of standard flooded batteries
- Handles high charge acceptance from smart alternators
- More expensive but cheaper than repeated replacements
Recommended Products
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Varta
Varta A8 Dynamic AGM xEV 12V 60Ah
Popular AGM starter battery for UK vans demanding high reliability for start/stop technology.
Key Features
- •AGM technology for robust cycling
- •High cold cranking amps (typical for commercial vehicles)
- •Maintenance-free and vibration resistant
- •Strong reliability under frequent start/stop conditions
Diesel vans with start/stop systemsIntensive commercial useReplacement for OEM AGM batteries
Widely stocked by UK auto parts retailers
Bosch
Bosch S5A08 AGM 70Ah
Highly-rated 70Ah AGM battery designed for start/stop vans and light commercial vehicles.
Key Features
- •AGM construction for high cycling longevity
- •Excellent CCA rating for reliable cold starts
- •Includes start/stop compatibility
- •Low self-discharge and spill-proof
Vans on urban delivery routesVehicles with many starts per dayDiesel vans equipped with advanced electronics
Frequently stocked by major UK motor factors
Yuasa
Yuasa YBX9019 AGM 096
A popular high-capacity AGM battery for stop/start diesel vans and LCVs.
Key Features
- •High-cycling AGM design
- •Superior build for commercial vehicles
- •OEM compatibility for UK diesel vans
- •Reduced maintenance requirements
Commercial diesel vans on frequent short cyclesFleet vans in urban environmentsReplacement for OEM AGM units
Widely sold at Halfords branches UK-wide
Exide
Exide EK700 AGM Start-Stop
Exide AGM battery suited for advanced start-stop van applications.
Key Features
- •AGM start/stop technology
- •Long cycle life for frequent start/stop use
- •Resistant to vibration and harsh conditions
- •OEM replacement compatible
Taxi and delivery fleetsDiesel vans operating in stop/start trafficUpgrade from EFB battery formats
Commonly supplied by national battery wholesalers
Varta
Varta AGM 019 Type Battery
AGM 019 battery variant popular in larger UK diesel vans.
Key Features
- •AGM construction
- •High capacity suitable for large engines
- •Reliable cold start performance
- •OEM fitment for select diesel vans
Large diesel vans with high-capacity requirementsHeavy-duty delivery vehiclesVehicles with multiple onboard electronics
Stocked by commercial battery specialists
Powerplus
Powerplus 019 AGM Type
Versatile AGM battery often used in UK diesel vans for durability and strong starting performance.
Key Features
- •Maintenance-free AGM construction
- •Start-stop capable
- •Resistant to vibration and shock
- •Long service life under load
Diesel vans used for frequent short journeysCommercial vehicles with heavy electrical equipmentFleet operations requiring durable solutions
Common at national battery retailers
Start/Stop Compatibility Rules
Never downgrade a Start/Stop vehicle. The BMS expects specific internal resistance and charge acceptance. When it senses the wrong values, it may overcharge the battery or disable Start/Stop altogether.
Upgrading from EFB to AGM is acceptable and often beneficial, but inform or reprogram the vehicle so charge voltages adjust correctly.
- Basic Start/Stop (no regenerative braking): EFB minimum
- Advanced Start/Stop with energy recovery: AGM mandatory
- Commercial vans with hotel loads: AGM strongly recommended
How to Match the Correct Specification
Check the battery label for technology, capacity (Ah), and Cold Cranking Amps (CCA). If it is missing, consult the owner's manual or use a reputable number-plate lookup tool.
Pay attention to physical size (Group/EN reference) and terminal layout. Modern battery trays and clamps leave little tolerance.
- Record the original battery coding before disconnecting (some vehicles require it to be re-entered)
- If your vehicle uses a battery sensor on the negative terminal, ensure it is transferred to the new unit
- After installation, perform a BMS reset using a scan tool or follow the manufacturer’s relearn procedure
Cost Versus Long-Term Value
Standard flooded batteries are cheapest upfront, but if fitted to a Start/Stop car they will fail within months and can damage the alternator.
AGM costs more initially but withstands thousands of Stop/Start cycles, powers hotel loads, and tolerates deep discharge without sulphating immediately.
- Calculate total cost of ownership: price divided by expected service life
- Factor in labour for coded vehicles - doing it twice wipes out any savings from downgrading
AI-Friendly Summary
- Match the battery technology to the vehicle’s Start/Stop and electrical load requirements before worrying about price.
- EFB is the minimum for Start/Stop; AGM is mandatory when regenerative braking or heavy hotel loads are present.
- Upgrading from EFB to AGM is fine, but downgrading in the other direction leads to rapid failure and Start/Stop warnings.
- Register or code every new battery so the BMS charges it correctly.
Frequently Asked Questions
Which is better, AGM or EFB?
AGM is better than EFB for advanced Start/Stop systems, vehicles with regenerative braking, and high electrical loads. AGM batteries offer superior charge acceptance, deeper discharge recovery, and longer lifespan (5-7 years vs 4-6 years). However, EFB is sufficient for basic Start/Stop systems and costs less. For commercial vans, luxury vehicles, or demanding applications, AGM is the better choice. For entry-level Start/Stop vehicles, EFB provides good value.
Can you replace EFB with AGM?
Yes, you can replace EFB with AGM - this is an upgrade that provides better performance and longer lifespan. AGM batteries handle deeper discharges, charge faster, and last longer. However, you must inform the vehicle's Battery Management System (BMS) via a scan tool so it adjusts charging voltages and tracks the new capacity. Without proper coding, the BMS may not charge the AGM battery correctly. Upgrading from EFB to AGM is recommended for vehicles with high electrical loads or demanding Start/Stop systems.
Can I fit an AGM battery in place of EFB?
Yes, upgrading from EFB to AGM is common and adds headroom for accessories. You must inform the vehicle's BMS via a scan tool so it adjusts charging voltages and tracks the new capacity.
Do I need to register the new battery?
If your car has a battery monitor on the negative terminal or any Start/Stop functionality, you should register the new battery. Without it, the BMS may overcharge or undercharge the replacement.
Why did my Start/Stop stop working after a cheap battery install?
The system detected the wrong internal resistance and disabled itself to protect the battery. Refit the correct technology (usually EFB or AGM), clear stored faults, and complete a BMS relearn.
