Hi everyone, just looking for some advice on a matter. Will try and keep it not too long.

Last December 2022 my Fiesta ST Line X (26500) miles was having trouble starting and so I called out the AA. They determined that a new battery was needed, however they didn't have the right one and as I was staying over at in-laws they came back the next day.

Fast forward to July/August this year and I was getting a sat nav reset keep happening, and then 2 non starts. AA called again, said they can find nothing wrong with alternator or battery and there best advice would be to take it to a Ford dealership.

Booked car in with Ford dealership whom I purchased car from 3 years ago. Got a call back few hours later to say that the AA had fitted a wrong size battery, they had fitted a 70amph and it should have been a 60amph. They also said in the AA in fitting the wrong size have removed part of my battery tray to fit this new one in. Ford had to refit this part to put the new battery in. 

I spoke to the mechanic who worked on my car at Ford and he said that the AA have caused this problem. That stop start technology is very specific to having the right battery fitted. He said that the AA battery was the wrong size physically and voltage wise and that is why I started experiencing start up problems and resets on my sat nav, as he said the battery and the car were having trouble working together.

I put all this in writing to the AA, along with the invoice and small report Ford gave explaining what damage the AA have done. 

They deny any such liability, they argue that the battery fitted was suitable for my vehicle.

It seems Ford recommend and fit a 60 amp battery, the AA argue the car can handle 70.

I'm at a loss here, moreso out of pocket! 

Any advice would be much appreciated.

It might be the wrong size phyiscally, but a larger battery as long as it is still EFB is completely fine electrically.

You can program the car so that it better understands the capacity when you fit a larger battery, but at best it makes a few percent difference to the calculated SoC for the Stop/Start.

The voltage is exactly the same regardless of capacity.

The AA shouldn't fit a battery that doesn't physically fit, but just in terms of capacity, that will cause no issues.

Thankyou for your reply

Don't know the tech side of voltages etc but the fact that the AA as you said removed part of the battery tray to make battery fit doesn't sound right. Did the removed part of the battery tray get replaced.

Sounds like "ah lets drill  hole in the side of the engine block so we can bolt on another part".

Battery tray size was made that size by Ford for a reason, to fit proper sized battery, not to be modified by third party. Just a thought, when you take on car insurance one of questions asked is has the vehicle been modified in any way.