Battery drain
My 2014 Ford Fiesta Ecoboost 1.0 three-cylinder turbo petrol with 17,000 miles keeps flattening the battery. It is a Titanium model with start/ stop technology. I have to recharge the battery every two weeks after it drops to 11.9 volts. It has been doing this for the last two years and has been to two Ford garages, but they were no help.
The car is fitted and coded with a proper new Ford battery. When I disconnect the battery earth from the chassis, after switching off the ignition, there is a substantial spark. When I connect a digital ammeter, it reads 3.25 amps, which drops to around 0.25 amps after two minutes and then stays there for some time. If I switch on the ignition and then off again, it goes back to 3.25 amps, followed by slow drop to 0.25 amps. Despite this, there are never any starting problems, even after being laid up for two weeks. I would expect a fully-charged battery to read about 12.7 volts and stay there and my battery reads 14.4 volts with the engine running, so there is no problem there. Sandy Mackie
When you say that the vehicle needs charging after two weeks, I am assuming that this is two weeks of not being driven. Modern vehicles contain complex computer systems that need to be kept running even when the car is off the road. The vehicle alarm system needs to be running constantly, which would account for the minimum drain you have. Unlike older vehicles, complete shutdown is not possible without disconnecting the battery. Some more complex vehicles cannot be left to stand for more than two weeks without being connected to a trickle charger, while others such as the larger Mercedes-benz models use separate batteries to supply the starting current and the computer control.
The state of your battery will also depend on the driving cycle. If the vehicle constantly covers short trips which are insufficient to replenish the charge, then the battery’s charge state will drop. Also, as your vehicle has a smart-charging system, I would check the charge rate after the vehicle has been running, to ensure that the initial charge rate of 14.4 volts is being delivered constantly. You may also find that the standing voltage will be different with the battery disconnected, as the systems on the vehicle are putting a load on the battery even when stationary.
The initial high draw of 3.25 amps is normal and this should reduce as the systems are put into ‘sleep’ mode. This is happening on yours, as shown by the drop to 0.25 amps, only raising again when being awoken by turning on the ignition. From the data I have, your Fiesta should be fitted with a 65Ah battery. Given the 0.25 amp drain if the battery is in a fullycharged state, it should take around 46 days (equivalent to 1119 hours) to reduce the charge and leave it in the condition you are finding it.
As the vehicle does not have a problem starting, it may be the case that the 11.9 volts you are reading is due to the drain from the vehicle systems. With this in mind, it may be worth checking the readings with the battery disconnected, remembering that the vehicle systems, radio and window operation will all need to be reset. Sandy Mackie then said The two weeks I refer to is with daily use (ie, starting the engine five or six times daily). If started once daily or not at all, it only needs charging every three or four weeks. I know when it is getting really flat as the start/stop technology stops working. The car never sounds as if it has a flat battery when winding over with the starter motor, which surprises me as that wasn’t the case with cars 20 years ago. That being the case, I suspect the issue is due to the smart-charging system rather than current drain. I would check the charge rate once the battery has stabilised from the initial start-up. This may reveal something being overlooked.