Ford ´smart charge´ undercharging battery

[Pumalhd]

We have a 2018 Ford C-Max ecoboost with a ´smart charge´ system that is supposed to maintain the battery at about 80% charge, which would be about 12.5V. However, it only charges to 12.1V, corresponding to about 40%. The voltage increases to 13.4V when there is more load (like headlights) and to 14.7V coasting downhill, so the alternator isn´t faulty. I had to replace the original battery at 3 years; the batteries in my older cars are all at least 10. The car is not used for short journeys, and the stop/start is generally turned off. I tried to increase the target state-of-charge using Forscan, but this option doesn´t seem to be available for this vehicle. I see this issue has been raised on other forums, but without a solution. So two questions: (a) could it be a faulty sensor, and (b) would disabling the ´smart charge´ shorten the alternator life?

[JONATHAN_11_80]

Hi,

Don't mess with it unless you are getting problems ie flat batteries Smart charging helps save fuel so it will only charge when needed. In my experience the battery charges on overrun ie when you are off the throttle. You can disconnect a wire on the alternator to disable this but it will cause wear on your alternator and battery.

[Pumalhd]

Thanks for your reply. After 3 years the original battery wouldn't start the car. I'm currently charging the new battery after each trip with a Ctek in the hope of extending its life. The 'smart charge' system seems a false economy as the fuel saving is greatly outweighed by the cost of replacing the battery so frequently, both in cash and carbon terms. For comparison I changed the battery in my Puma at 11 years as a precaution before a long trip (and put it in an old diesel van as it was fine), and the replacement is still going strong after another 11 years. I guess this is just 'progress'!

[budgie smuggler]

Sorry I can't help but just to add a +1 here, I had the exact same problem with an 18 plate focus.
Ford main dealer garage told me to change the battery, i did and the same problem came up with 6 months. It's honestly such a st system.

Same as you I 'fixed' it in the end by charging up once or twice a month with a mains smart charger (Maypole MP7428).

Edited by budgie smuggler on Wednesday 26th October 09:40

[Pumalhd]

Thanks, it seems to be a 'feature' not a 'fault'. To make matters worse, the air filter housing has to come out to access the battery, then the battery management system has to be told about the replacement via Forscan, so it's not a 5 minute job any more.

[budgie smuggler]

Pumalhd said:

Thanks, it seems to be a 'feature' not a 'fault'. To make matters worse, the air filter housing has to come out to access the battery, then the battery management system has to be told about the replacement via Forscan, so it's not a 5 minute job any more.

Yes mate bugger me, I actually did that job myself. Total PITFA. A couple of tight/easy to snap clips as well, not an ideal job on the driveway in cold weather.

I'd kind of blanked how bad this technology was out of my memory until reading your post.

About a year after replacing the battery (Bosch £300) I drove all the way from Essex to Bude (approx 300 miles) and when I got there i noticed stop/start still wasn't working. Checked the battery SOC with Torque app and it was still sitting at below the threshold for enabling it. How on a 300 mile journey can the battery still not be fully charged?!

And on my journey to work I can often coast approx 1 mile if traffic conditions are okay. So you'd think that would fully charge the fker. Yet I'd often get a message from the ford app saying the car was entering "Deep sleep" mode because the battery was low.

[C-J]

I've only just seen this post - and it seems to mirror my own experiences (mk4.5 mondeo 1.6 diesel), except I just changed as a precaution at 5.5 years when despite only using for long journeys there would occasionally be a 'low battery' message.

Having tried various tests and recharges on both the original and then replacement battery (latter now 3 years old), and having bought a plug in voltage display, I've concluded that the 'smart' charging system works consistently - just not how I'd like it to!

I've resigned myself to having bought a Halfords branded (made by Yuasa?) battery with a 5 year guarantee, (chosing Halfords rather than Tayna to make it easier to get a health check and return) - keeping an eye on the charging pattern - and hoping that I can get to near 5 years from the battery, falling back on the warranty if needed.

Jump leads stay in this car just in case needed - and in colder weather I sometimes pop the headlights on for the return leg back home just to force the charging up to 13.7 volts for a while, in the hope that some of it is retained.

If a replacement battery was just £40 ish then I'd be less annoyed - however at £125 for an EFB it stung (my average annual spend on battery will be more than the £20 RFL!!!) - especially when on other cars decent (especially Bosch) batteries have lasted 13-16 years.

It's not what I call progress - especially as the rare occasions that I'm in heavy traffic I am quite capable of turning the engine off/on myself! I rarely idle for long therefore s/s isn't saving me anything. Thus I turning off for every journey since the day I got it, as I believe the previous family member owner did too. That might of course be bad for this type of battery if it doesn't exercise it enough? However it has to be better for unnecessary engine load, otherwise it would sometimes be restarting just seconds later.

Or maybe I'm applying old logic - and 12.3v being only 50% or whatever charged is 'old school' and not applicable to EFB batteries?

I think I posted my experiences elsewhere on PH at the time - if anyone finds any solutions, then please do share.

Edited by C-J on Sunday 7th May 09:22

Edited by C-J on Sunday 7th May 09:29