A few months ago, I found myself with  a flat battery. After a start by the RAC who condemned the battery, I booked the car into the local Ford dealership. I was told that there was nothing wrong with the battery and it went flat due to my low mileage. Although I wasn't especially happy with the response, I reluctantly accepted it after some complaining. As "insurance", I had a brand new Ford battery fitted by an independent garage (at my own expense).

A few days ago, I bought a little battery voltage monitor that plugs into the 12v Auxiliary socket and the voltage seemed very low (12.1v).  I wasn't sure if the socket had a stabilized 12v supply (which I doubted) but decided to check the voltage at the battery terminals.

The video in this link shows what I found:

 https://www.youtube.com/watch?v=7K2aROHcW7c&feature=youtu.be

Before I go back to the main dealership and start demanding they fix it, I'd be grateful if someone could confirm that this charging/alternator behaviour does indicate a fault and isn't some fancy battery management system..

Thanks,

John.

It could be a fault but fiestas have a "smart charge" system. it tries to not charge the battery where it would cause an increase in fuel consumption unless the battery is below threshold values in that case it charges continuously until threshold charge is achieved. What should happen under normal conditions is the battery should recharge when slowing down in gear. Try lifting off early for traffic lights junctions etc instead of using the brake so it has more chance to charge. Driving like this you should also notice improved fuel consumption. Also check for power drains when switched off as this could cause a flat battery.

I have smart charge system fitted to my mk7.5 and on a average I do 20 1.1 mile and 2 3.5mile journeys per week with a longer journey a couple of times a month and a dash cam running in parking mode and never had. A flat battery. 

 

3 minutes ago, cjay1 said:

It could be a fault but fiestas have a "smart charge" system. it tries to not charge the battery where it would cause an increase in fuel consumption unless the battery is below threshold values in that case it charges continuously until threshold charge is achieved. What should happen under normal conditions is the battery should recharge when slowing down in gear. Try lifting off early for traffic lights junctions etc instead of using the brake so it has more chance to charge. Driving like this you should also notice improved fuel consumption. Also check for power drains when switched off as this could cause a flat battery.

I have smart charge system fitted to my mk7.5 and on a average I do 20 1.1 mile and 2 3.5mile journeys per week with a longer journey a couple of times a month and a dash cam running in parking mode and never had. A flat battery. 

 

Thanks for the reply.   Last time I checked, there was a 35mA constant discharge - after an initial 1 or 2 amps - which I think is acceptable for the alarm and remote locking receiver.

As it is at the moment, I'd have thought that 12.4 volts is well below the battery's charging threshold although I haven't (yet) noticed the "System off the save battery" warning that I started to get with the original battery. 

Yes, I thought the main dealer's excuse of low mileage causing the flat battery to be just that, an excuse. I did take it to their CEO but he obviously sided with his technicians at the end of the day and, as they have a virtual monopoly in the area, there's not much I can do while it's still under warranty. 

I had it on charge overnight and it was at about 13.5 volts this morning but, as soon as I started the engine, it was dragged down to 12.5v even with the engine running. I guess I'll just have to keep an eye on it for now -- I somehow suspect that their "technicians" will have no more of  a clue than I have.

It looks as though the 12.4 volts I measured initially isn't just a random figure. 

According to this website: https://www.optimabatteries.com/en-us/experience/2010/09/124-magic-number-batteries  it's the "magic number" below which sulfation begins.  I turned on the headlights and, lo and behold, the alternator voltage wound up to 13.7v and began charging the battery.  So, in effect, the battery could spend its entire life working at its least efficient point. No wonder they only last two or three years. My 17-year old Corsa only had one replacement in its entire life.  It's like asking someone to breath through a drinking straw all their lives!

So, thanks cjay1  it looks like you're right.

John.