Auto Electrical Service
Battery Diagnostics
Precision load testing, replacement, and parasitic drain diagnosis.
Not every flat battery needs to be replaced. And not every replacement battery will solve the problem if the real fault is elsewhere. Mobile Auto Elec provides comprehensive battery testing before making any recommendations — so you only pay for what you actually need.
What We Test
- Resting voltage and state of charge
- Cold cranking amps (CCA) load test
- Internal resistance measurement
- Alternator output and charging voltage
- Parasitic drain test (for batteries that go flat overnight)
Battery Types Available
We carry AGM (Absorbent Glass Mat), EFB (Enhanced Flooded Battery), and standard lead-acid batteries for most popular vehicles. AGM batteries are required for vehicles with start-stop systems — fitting a standard battery in these vehicles will cause premature failure and module faults.
Frequently Asked Questions
There are three common causes: the battery itself has failed (internal cell breakdown), the alternator is undercharging, or there is a parasitic drain — something drawing current when the car is switched off. We test for all three before recommending a solution.
A parasitic drain is a current draw that continues after the ignition is switched off. It could be a faulty relay, an aftermarket accessory (alarm, tracker, dashcam), or a module that fails to go to sleep properly. We diagnose it by measuring current draw with a clamp meter while systematically eliminating circuits.
Yes. Start-stop vehicles require AGM or EFB batteries specifically designed to handle the repeated charge and discharge cycles. Fitting a standard battery will cause premature failure and may trigger warning lights. Always specify your vehicle's requirements.
Typically 2–4 years in Johannesburg's heat, compared to 4–6 years in cooler climates. Regular maintenance and keeping the battery charged extend its life.