Mobile battery replacement · Alternator or battery?
Alternator Or Battery? On-Site Testing in Selly Oak
Battery light on, or a car that dies after a jump in Selly Oak? That points to charging, not storage. On-site diagnosis and Battery Replacement.
The two faults feel identical from the driver's seat and cost very different amounts to fix. The distinguishing test takes about ninety seconds with the engine running, which is why nobody should be guessing.
Mobile battery replacement across Selly Oak and the B29 area, with the correct AGM, EFB or standard flooded chemistry fitted the first time — not whatever's on the shelf.
A properly registered AGM battery in a BMW, Audi or VW will last 6–8 years. A flooded battery dropped in without coding, in the same car, will fail in under 2.
The readings that separate them
- Ripple voltage is checked for failed diodes in the rectifier pack, which can charge adequately but destroy a battery over months.
- Engine-running voltage should sit roughly between 13.8V and 14.7V — below 13.2V under load is a charging fault regardless of how new the battery is.
- OBD battery registration for BMW, Audi, VW, Mercedes, Ford, Vauxhall, Peugeot, Citroen — included in the fit price
- Battery Replacement work here is judged against the vehicle's own specification rather than a generic pass mark.
How the two faults present
Around Selly Oak this comes up most with higher-mileage vehicles and with cars that have been repeatedly jumped by well-meaning neighbours.
Locally that means the streets between Selly Oak and Birmingham, with access via A38 Bristol Road and a practical radius reaching Birmingham (~3 mi) and Smethwick (~3 mi).
Who needs this test
Drivers with a battery warning light that comes and goes.
Domestically, student HMOs and Victorian terraces dominate around here, which shapes how these jobs are accessed and worked.
Charging faults found nearby
Recent job nearby: a vehicle in Selly Oak jumped four times in a week. Charging voltage 12.7V at 2,000rpm with lights on — alternator, not battery, and the owner stopped throwing money at parts.
Recent job nearby: a car near Birmingham with an intermittent battery light. Ripple test showed a failed diode; the battery itself tested perfectly.
Local reference data — Selly Oak
- Page focus
- Alternator or battery?
- Postcode districts
- B29
- County
- West Midlands
- Area type
- Neighbourhood
- Nearest major town
- Birmingham (~3 miles)
- Reference point
- University-of-Birmingham student district on the Bristol Road corridor.
Alternator vs battery questions
Q.How do I know my battery needs replacing rather than jumpstarting?
If it's over 4 years old and going flat repeatedly, or the CCA on a load tester reads under 60% of rated, it's replacement time. Jumpstarting will only get you a day or two.
Q.What's the difference between AGM and EFB?
AGM is a fully sealed absorbed-glass-mat battery for premium and stop-start; EFB is an enhanced flooded battery for entry-level stop-start. Fitting the wrong one is a warranty-void job.
Q.The car started on jump leads and then died. What does that mean?
Classic charging fault. The engine ran on borrowed energy and stopped when the battery could no longer supply the ignition system.
Q.Can a bad alternator ruin a new battery?
Yes, in both directions. Undercharging sulphates the plates; overcharging boils off electrolyte. Both shorten life dramatically.
Q.Do you replace alternators too?
We diagnose them on-site and can replace batteries on the spot. Alternator replacement is a workshop job, and we will tell you exactly what needs doing so you are not paying for diagnosis twice.
Q.Do you cover Selly Oak and the B29 area for this?
Yes. Selly Oak is inside our routine coverage from Oldbury via A38 Bristol Road, roughly 3 miles from Birmingham. We cover it alongside Birmingham and the surrounding streets.
How the visit runs
- 1
Vehicle lookup
By reg on the phone — we confirm the exact OEM battery spec before quoting.
- 2
Fixed all-in price
Battery, fitting, coding, recycling, warranty — one number on the phone.
- 3
The readings that separate them
Engine-off resting voltage establishes the battery's state of charge before anything else is judged.
- 4
Driveway fit
Memory saver in, old battery out, new one in and terminals torqued to spec.
Areas we test in
Selly Oak sits about 3 miles from Birmingham, and the same van covers Birmingham (~3 mi), Smethwick (~3 mi) and Sutton Coldfield (~7 mi) on the same run.
Jumped and died again?
That is a charging symptom. We test the alternator under real electrical load before anyone mentions a new battery. Tell us the vehicle and the symptom and you will get a firm price before anyone sets off.
Related pages
- Fleet & Business Jumpstart — alternator or battery? in Selly Oak
- 24/7 Emergency Jumpstart — alternator or battery? in Selly Oak
- Taxi and private hire — battery replacement in Selly Oak
- Stranded in a car park — battery replacement in Selly Oak
- Trade van, first job of the day — battery replacement in Selly Oak
- Alternator or battery? in Birmingham (~3 mi)
- Alternator or battery? in Smethwick (~3 mi)
- Alternator or battery? in Sutton Coldfield (~7 mi)
- Alternator or battery? across Birmingham
- Battery Replacement in Selly Oak — main page
- All jumpstart services in Selly Oak
The short version
Storage fault or supply fault — the tests are different, the costs are different, and guessing is expensive. Every visit here includes the charging check. If you would rather plan it than react to it, a battery replacement can be booked for a time that suits.
Stranded with a flat battery?
Call now or send a WhatsApp — we'll confirm your quote and dispatch the nearest engineer.