Keeps saying battery in saver mode, has anybody else had this, and what does it mean?

It means the main car battery has a low state of charge.  The car turns off non-essential items to prevent draining the battery any further.

Ideally you need to use a mains powered battery charger to fully recharge the battery.  Though that takes several hours to do and access can be difficult if you can't park right next to your property.

1 hour ago, Shaza said:

has anybody else had this, 

Virtually everyone (or so it seems from posts on here) with a Mk 4 Focus or Mk 8 Fiesta!😀

Lots of threads on this if you search around, but basically it's a general issue with modern charging systems, especially if you don't drive the car regularly, or only do short trips.

Many of us do exactly as Tom suggests - give the battery a regular top up.

NB is your profile (Puma) still correct?

 

Maybe you should qualify that with 'modern Ford charging systems'. I don't think it's necessarily applicable to all makes.

1 hour ago, mjt said:

I don't think it's necessarily applicable to all makes.

Possibly not, however quite a few threads like this around the various forums:

https://www.toyotaownersclub.com/forums/topic/217673-12v-battery-maintenance-issues-etc/

As said, it's a low battery, happens to everyone. I just ignored it for months, and even after a 400-mile trip it's still low.

If it gets REALLY low (like mine did) you may also get warning about hill start assist or auto brake holding not working.

The advice from my ford dealer is like other have said, use a mains charger. They also said to charge it properly, you must disconnect at least one lead from the battery.

Once fully charged and reconnected, do a BMS reset,

Ignition on (don't start the engine), flash headlights 5 times, press brake 3 times and WAIT at least 20 seconds until the dashboard battery icon flashes 3 times.

 

Just did mine overnight, Stop Start now working after 3 years, all 4 doors working with touch lock unlock, it's back to showroom functioning.

6 hours ago, Mark-UK said:

They also said to charge it properly, you must disconnect at least one lead from the battery.

Once fully charged and reconnected, do a BMS reset

I think @unofix would disagree with that. The battery should be charged in situ with the negative charger lead connected to a chassis earth point. This ensures the BMS sensor on the battery negative terminal monitors the state of charge. The BMS should only be reset when a new battery is installed because it maintains data about the age of the battery and likely adjusts the charging profile accordingly.