Hi all,

Just wondering if anyone else has run into persistent battery issues on a Ford Focus ST Edition.

Mine keeps throwing “Low Battery” warnings and “Driver Aid Not Available” messages. Took it to Ford they tested the battery twice and told me it was fine, no faults found, just gave it a charge and sent me on my way.

Went away on holiday for 5 days and the exact same issue happened again. Took it back, kicked up a bit of a fuss because it’s a fairly new car and should absolutely be holding charge, especially with daily motorway runs to and from work. They eventually replaced the battery.

A few months later, the voltage is dropping back into the 60s again. The car is used daily and does plenty of long runs, so it shouldn’t be struggling.

Dealership are now allowing me to take it to a third-party specialist for full diagnostics, but any repair still has to be done by them to keep the warranty.

Has anyone experienced similar drain issues on the Focus ST? Any known quirks or modules that cause parasitic drain on these cars? Would appreciate any advice before I take it in again. P.s it has randomly flashed the headlights on an off, by itself when been off parked and locked for hours. Any advice would be appreciated.

Edited May 7May 7 by Alker67
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Hi Amy,

Quite a few issues on this and the Focus ST owners site, with Focus Mk 4/4.5 (all versions).

https://www.focusstoc.com/threads/battery-issue-after-10-months.585319/

https://www.focusstoc.com/threads/mk4-4-5-battery.584534/

https://www.fordownersclub.com/forums/topic/144919-focus-mk4mk45-battery-issue-petition/

https://www.fordownersclub.com/forums/topic/148905-focus-mk-45-mhev-battery-issues/

Similar story with Fiesta Mk 8/8.5 and Puma - many of us have found a smart battery charger is a good investment!

2 hours ago, Alker67 said:

it’s a fairly new car and should absolutely be holding charge, especially with daily motorway runs to and from work.

This has been covered frequently on this forum but to save you searching I'll briefly repeat it:

The charging system on these modern cars has been designed to not charge the battery when the engine is under load. This is primarily to reduce emissions. It will only charge when the engine is on overrun or when it's running lightly loaded at small throttle openings or idling so won't be charging much, if at all, at motorway speeds. The system is also set to never charge the battery to more than 80% of it's maximum capacity.

The result is that it's often the case the system simply doesn't put back the charge that's being used. Members have found that increasing the maximum charge to 95% and fitting a higher capacity Yuasa battery in place of the standard Ford one, which is widely recognised as being of very poor quality, helps considerably but it may only increase the time intervals before an external charger is required.

I personally find it totally unacceptable that owners should have to regularly use a charger which is one reason I still run an old model that doesn't suffer from this nonsense.

I think this is not confined to Ford but as a matter of interest I don't find these problems on my 2019 Vitara.

Yes, it seems counterintuitive, but the old advice (which dealers still come out with) to "take it for a long run" at steady speed is of little use.

By no means confined to modern Fords - similar topic on the Toyota owners forum is now up to 6,500+ posts.

As another example of an older car without all the environmental stuff and other bells and whistles our 2014 SEAT is still on its original battery.

Thanks guys! Appreciate you getting back. At least I know I'm not going crazy! I am honeslty in two minds at the moment if to keep or return, my last ST 72 plate was perfectly fine. New car is only 12 months old, and shouldn’t be annoying me as much as it is.

Thanks again 😊

I ran into the exact same issue with my 2018 Fiesta ST2 MK8 last year. After doing some research, I decided to upgrade the battery to a Yuasa YBX7027 (12V 65Ah 600CCA EFB).

Crucially, I also used FORScan to adjust the battery target state of charge from the factory 80% up to 95%. While I can’t confirm this will definitely solve your specific problem, I haven't had a single issue since making those two changes. It might be worth looking into as a more robust setup!

Thank you!