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About this tool
Predict when your car battery needs replacing from its age, battery type, climate, usage pattern and warning signs.
The Car Battery Replacement Planner estimates how much service life is left in a starter battery by taking its typical life for the construction fitted — flooded, maintenance-free, EFB or AGM — adjusting it for heat and charging pattern, then subtracting a penalty for the failure symptoms you are already seeing. It is for drivers deciding whether to replace a battery now or wait, especially before a long trip or a cold season. The two adjustments that matter most are sustained under-bonnet heat and habitual short trips, because both leave a lead-acid battery permanently undercharged.
Open Car Battery Replacement Planner on AltFTool — it loads instantly in your browser.
Add your input to the workspace.
Adjust the options until the result looks right.
Copy or download the output and put it to work.
Uses a separate typical life for flooded, MF, EFB and AGM instead of one generic number.
Jump starts, slow cranking and warning lights reduce the estimate, not just the calendar.
Returns a clear verdict plus the specific habit changes that would extend the battery's life.
Typically 3 to 5 years, varying by construction: around 36 months for a conventional flooded battery, 48 months for a sealed maintenance-free one, and 54 to 60 months for EFB and AGM batteries fitted to start-stop cars. Sustained heat is the biggest single reducer — lead-acid life roughly halves for every 10 to 15 °C of extra sustained temperature.
The clearest sign is slow cranking that is worst first thing in the morning, followed by needing a jump start, headlights dimming at idle, the battery warning light appearing, and the clock or radio presets resetting. A swollen or bulging case is different — that battery is gassing internally and should be replaced immediately, whatever its age.
Starting the engine takes a large slug of charge, and a drive of under 15 minutes does not give the alternator enough time to put it back. Repeating that daily leaves the battery permanently at a partial state of charge, which sulphates the plates and permanently reduces capacity. One 30-minute continuous run a week, or a monthly session on a smart charger, largely prevents it.
It will physically work but will fail early, often within half the normal life. Start-stop systems cycle the battery constantly at a partial state of charge, which is exactly what EFB and AGM constructions are designed for and what a plain flooded battery is not. Many cars also need the new battery registered to the energy-management system, so have it fitted by someone with the right tool.