So don't replace the battery just because the start-stop doesn't work all the time, it may still be a perfectly working batteryThe system may not shut down the engine under certain conditions, for example:
- To maintain the interior climate.
- Low battery voltage.
- The outside temperature is too low or too high.
- The driver door has been opened.
- Low engine operating temperature.
- Low brake system vacuum.
- If a road speed of 3 mph (5 km/h) has not been exceeded.
- The driver safety belt has not been fastened
So it's not working as often as you like- is the fuel saving your concern? A new battery is going to cost a lot of money and you're supposed to get the Battery Monitoring System reset when the battery is replaced. If you aren't keen on disassmbling some of the vehicle you'll have to pay to get the battery fitted and if you haven't got an OBD2 interface (and software like ForScan) you're going to need to pay Ford to reset the BMS. So factor that into your battery cost.I’m aware of all that, but the only time I get the start stop to function is if I unplug dash cam, switch off radio, switch off heater, switch off lights, ensure not got indicator flashing, drive car for half an hour, outside temp is up near 10c, not sure what else i can switch off, even doing all of the above it only works occasionally