changing a start stop car battery

I have a 2016 Ford Fiesta 1l ecoboost car with start stop technology. The battery needs changing and I would like to do this myself as I do most of my car maintenance. Reading up on this and looking at U-tube the changing of the battery is quite straightforward but some sources say the new battery has to be registered with the onboard electronic management system. I have no way of doing this and wonder if this is really required or will the system just reset itself automatically over time.

Has anyone experience of this and can advise. Halfords (in UK ) offer a fitting service at £27, which I would like to avoid, but will reluctantly pay if I really must. I have also read that some Halfords stores won't do a fitting since they don't have properly trained staff (that does not fill one with confidence ). Any thoughts welcome.

Doug

The system will re-set over time. Absence of power will temporarily upset the module in the battery earth lead which informs the ecu of battery condition. You could avoid this by keeping a 12v supply to the car, perhaps using a battery charger, but you will of course have to take care to avoid shorting ( which should be within your capability) - this will also maintain other learned settings of the car.

I had the same problem on my Honda Jazz about a year ago, it has stop/start technology so required the much more expensive battery for the technology. I just changed the battery over, there was no instructions in the car handbook that it required any special fitting procedures, my battery change was just straightforward and everything worked as it should do, maybe your Fiesta would be the same. Dave W

I wondered if the battery was 'smart', as making them so is a trend. Putting intelligence inside a battery allows it to regulate itself more accurately than an external unit. The downside is fitting a new battery may require it to be told stuff so it matches properly with the load and charger.

However, the instructions on this site suggest to me that the necessary control is in the Fiesta. It says the reset procedure is:

To completely reset the start-stop feature on a Ford Fiesta, start by turning the ignition on and waiting 10 seconds. Then, press the foglight switch five times in succession. Next, depress the car’s hazard light three times.

Once you do this, you should see the battery LED light flash on your dashboard. This will indicate that the battery monitor (and thus the engine start-stop feature) has been reset. You can now shut the ignition and hazard lights off and restart your car.

This sort of hoop jumping is typical of a reset control sequence, as used by computer systems to do a full reboot, more than an ordinary on/off does. As such it's likely to do whatever is needed to configure the battery, either an old one that's lost it's marbles, or a new one.

Dave

Hi, Do NOT use a battery charger to power your car while changing the battery. Output from charger can be upto 17volt, which will do a lot of damage.

I would just change old for new or get proffessional advice.

Maurice

Edited By Maurice Taylor on 01/03/2023 15:20:50

Thanks for the replies. That site you highlighted Dave is very interesting and seems to be a way of resetting the management system. For the past few years my start stop system has not worked, possibly due to the state of the battery, and to be honest I prefer it not working since it can be a pain at times. When I have a new battery fitted it will probably start working again and I will have to get used to disabling it each time I use the car since it resets to an "on " state each time the car starts. £150 for the right type of battery is another pain in the wallet!

Doug

One way to keep power on the system whilst changing a battery is to use a cig lighter plug connected to another battery of 12v. Polarity is important and remember that your leads to your car battery will remain live. Noel.

The RAC changed the stop start battery in my Skoda recently and did indeed teach the vehicle electronics about the new battery including type and serial number. I was told that the charge regime was modified over time and that there was danger of overcharging the new battery if the parameters were not updated. Also might impact warranty if not done. Given that I was stuck I paid willingly as it was a minor cost compared to the cost of the battery!

Went with a friend to Kwik-Fit to get a new battery fitted to his 2015 Fiesta - basically followed in my car with jump-leads at the ready just in case, having used them at his home to start the car. Nothing special was done by them apart from taking the leads off the old one, swapping the batteries over and re-connecting the leads to the new one - I was watching the whole process.

I'm not saying this is the best or approved method, but it's all they did and it seemed to work fine afterwards. His old battery had deteriorated to the point where the stop-start system had disabled itself some months before, but that started working again immediately after the new battery was fitted.

Rob

On my wifes Suzuki which has stop start,I changed the battery and used another battery and some light gauge wire to maintain a current to the car, Last year I used the Halfords service to replace the battery at home ok it cost but the battery on Dicovery 4 is very heavy and at rear of the engine bay under the windscreen so difficult to lift and fit when one gets ancient, the Halfords fitter just disconnected the battery lifted it out and put the new battery ,no jump leads or resetting, I asked how about the possibly lost settings he replied that on most vehicles there is now a time limit in the vehicle system so as long the change over is done quickly no resetting is required. I then asked the fitter if he had a battery tester to see if a cell or the whole old battery was duff (it was 7 years old) his reply "sorry we dont carry battery testers on the van" !!! about 2 years ago the Suzukis battery had run down due to low use,when I went to charge it I found out that with these stop start batteries a special function on the battery charger is required,lucky my newish small hi tech charger has this function.

For cars with stop-start (and even some with "smart" alternators) you need to follow the maunfacturers instructions when changing the battery. These systems monitor battery usage and condition and make adjustments to usage accordingly. Just changing the battery may be OK, it may appear work but not meet full perfomance or it might even be damaged. Typically there is a "sensor" on one of the battery terminals. Often these have a quick release so you can disconnect the cable without taking the sensor off the battery because even that can cause issues. For a "simple plastic blob" these sensors can have a complete dats system with microprocessor and non volatile memory tha records data.
You have to "tell" the system that a new battery has been fitted but how you do that depands n the model, hence my fist statement. Unfortunatly sometimes even the main dealers don't know how to do this (and similar tasks) properly.
Read the car handbook first.

Robert.

I'm beginning to suspect the stories about damaging the battery through overcharging if a proper reset is not done are mainly a way of persuading people to fork out for a "professional " fitter. I also suspect that a lot of those "professional " fitters don't bother to do a proper reset themselves. I am also wary of the competence of the staff at Halfords to do a good job.

Doug

I recently had to renew my 15 Passat battery, the battery service man hooked the ccar up to an auxilary power unit and then swapped the battery, then had to negotiate with a hand held device to connect to the cars electronics.

battery and set up £179.

Had this on a Porsche Boxster, which is not stop-start, but allegedly does require the new battery to be initialised with the car's ECU.

This is apparently because the charging system no longer just applies 13.8 Volts when the engine is running, but allows for the battery age, amongst other parameters, and modulates the charging voltage up to 16 V or so. (I initially thought the charging system had gone wrong when I saw these high voltages).

You can simply swap batteries over - as we all used to, (making sure to check things such as radio codes and car ECU procedures first), but then the charging voltage and duty cycle might be incorrect for the precise model, age and chemical construction of the new battery, meaning the new battery might not charge properly or last very long.

All a bit of a PITA really - I am no technophobe at all, but in my book there is something wrong when a simple battery swap requires a £1,000 scan tool or 30% on top of the cost of the battery itself just to make it work. Why must garages, (and everyone else, apart from Wetherspoons), rip us all off? The amount they charge for using their scan tool would buy them a brand new one every few months.

A bit like plumbers these days - you would not believe the trouble I am having trying to fix a simple electronic control board. Nobody will give out any information, apart from "call a plumber to put in a new board" - yeah sure, that's a nice cheap, option.......NOT !

Edited By John Doe 2 on 06/03/2023 09:33:04

I am still pondering my next move. Buying a top brand battery from one of the online suppliers is so much cheaper than getting the exact same battery from a local supplier so I am tempted to do that. Resetting the battery monitoring system would appear to be just a matter of pressing the fog light switch 5 times followed by pressing the hazard warning switch 3 times . Needless to say the car handbook gives absolutely no information about changing the battery.

Doug

John you have missed the point ! We no longer make anything it's mostly imported ! so we have to charge for our services - if we tell you how to do the job, WE have no job ! It is only folks like us who have the brains and gear to fix things who realise we are being HAD ! eg Small EV speed sensor on trans axel, about £130 ! in truth a bit of plastic with a hall effect device in it at £1.64. John Deere tried VERY hard to find out how I fixed it with out buying a new one from them ! HE HE ! As for JD see the fun in the states in court as farmers DEMAND the right to the info to fix their tractors Noel.

Sometimes when buying a part off the internet the seller will give instructions haw to reset and use them. Hope abounds. Just ask.

I have also had a similar issue with my diesel Ford SMAX.

As part of the emissions regulations modern cars are expected to act like hybrids, cutting the alternator on acceleration and charging heavily under deceleration. So the battery needs some space to put that energy and the computer needs to know if its there. Stop-start is an extension of this.

The AA installed a battery for me, I paid a small fortune to have the car checked and the car "programmed" for the new battery. The battery then randomly flattened itself over the next four years. Sometimes I had to call the AA out who never recognised it was their batteries fault.

Just after the end of the warranty, delayed by covid, I bought a new one, fitted, from Halfords. No problems since, including all winter. I am a little disappointed in the AA.

But that does not give people a valid reason to rip us off. On top of large call-out fees, spare parts have an enormous mark-up. If costs were far more reasonable, people would be happy to go to a main dealer, but as it is, the costs are so high that many folk either fix things themselves or don't have regular maintenance done. Either way, this potentially leads to a worse place for everyone. I have read that manufacturers will be "licensing" extra features, and owners will need to pay a regular licence fee to continue using those extras.

More power to the farmers' against John Deere !

See Front Seat Heating | BMW UK for an example!! £15/month, £150/year, £250/2 years or £350 unlimited(?). And all the functionality is already there in the car you just paid for.

Reminds me of the old (1970's) days when a £1M upgrade to an IBM mainframe was done by an engineer who came out and snipped a wire on the backplane. In those days it was mainly businesses that got ripped of, now its all of us.