I'm struggling with my battery behavior here.

Yes, I've read about the battery problems previously reported and the cases of unwanted power consumption when the car should be idle. I can only agree that this is an issue, and for that matter, whoever found it a good idea to put a 60 Ah battery in a full option car packed with electronics that draws 20A with ignition on...?

But that is besides the point. What I'm struggling with is despite the electronic usage, my battery still drained too fast over time so I connected it to FORScan and recorded battery and charging behavior during some drives. I did the same with my friend's '22 Fiesta that has about the same Ecoboost engine but without MHEV, and is a little lighter on the options.

 

My friend's Fiesta gave me a beautiful power current graph that makes total sense to me. First we have -12A with ignition on, then we get a major dip of -127A when I started the car, next the current jumps up to as much as +60A, dropping to a stable +30A within a few minutes. After a couple minutes driving around, the current keeps dropping to +5A and another 10 minutes later to +2A. All of this makes total sense because at the end, the SOC was at 95% of its set target.

 

Now... moving on to my Focus, first we have a -20A with ignition on (headlights, climate control, and radio completely off) which is a lot... but I guess still makes sense for a car with the amount of options and electronics it has. We see no dip when I start the engine, and I suppose this is where things get a little different for a MHEV vehicle. I'm not sure how it all works but I can only assume the hybrid power pack and electric motor may play a part in starting the regular engine rather than the conventional method. Please correct me if I'm wrong.

However after this, things do not make much sense to me. First 2 minutes of engine running, the current keeps fluctuating between -9A and -6A, which is still consuming more than regenerating. Next, it goes up a little and keeps fluctuating between +3A and +7A with occasional dips below 0. After 10-15 minutes, it drops to fluctuating between +1A and +5A, again with occasional dips.

 

All this being said, the Fiesta charged well beyond what it used in less than a half hour drive.

The Focus on the other hand, I drove for almost an hour and it charged barely +2% to +3% on a battery with 45% SOC when I began, of which half was lost from opening my door when leaving the vehicle.

 

I don't knnow much about how these MHEV battery systems work, but I do know there's still a lead battery and that's the one I'm obviously talking about. Is there anyone with a MHEV who can confirm, deny, or even explain this behavior? The low charging current seems nowhere near okay, and the heavy fluctuations don't give me a lot of confidence either.

I tried taking this discussion with my Ford dealer more than once, but they just keep telling me to buy a battery charger and say this is normal on modern cars packed with electronics. Well I'm not buying that excuse. But obviously I'm a little bit careful showing them proof generated using a tool that's capable of changing their software on a car that's under warranty...

Hello Jesse,

An interesting read and comparison of vehicles.

Firstly I have to tell you that you do need to buy a smart charger and 'top up' your battery every 5 or 6 weeks. Sadly that is the case for most modern vehicles not just Ford. Having said that, I see that you say the SOC was only 45% and the vehicle alternator was only charging it between 1 and 5 Amps. The only way that any battery can be made to accept a charge is if the charging voltage is higher than the batteries standing voltage. So typically if the battery voltage is 12.6V and the charging voltage is 13.8V then you would expect to see a charge current of around 1 to 2 Amps.

So back to your battery with a SOC of 45% and it only accepting a charge current of a couple of Amps. It would suggest to me that the batteries internal resistance is high and in order to get it to accept a higher charge current the voltage would need to be 17.5 to 18V The problem with that is if the alternator increased it's output to those sort of values then it would destroy much of the cars 12V equipment.

• How old is the battery ?
• Are the earth leads between the battery and the chassis and also the engine in good condition ?

If I gotta go with the Battery age parameter, it should be less than a year, from October 2022. Which on its own is pretty odd considering the car was first used in February that same year. I bought the car in December, being second owner after it was used internally by the dealer. But yeah, that means within the first year they already replaced it... or reset the BMS for whatever reason.

The battery is or should be original, at least it's Ford branded.

The voltage during the low current charge was 13,2V (thankfully included that in my recordings).

The earth leads appeared fine on first sight. Actually they have been preventively replaced today by the dealer for another problem they couldn't find the source of. Being last week a number of various errors starting to appear on my dashboard.

 

46 minutes ago, JesseNight said:

The battery is or should be original, at least it's Ford branded.

The Ford branded batteries are in most cases made by Varta. There has been a lot of these batteries failing to hold a charge, even when less than 2 years old. Many UK Ford dealers have been forced to replace batteries, some only 4 or 5 months old.

It is indeed a Varta:

 

I honestly don't know if holding the charge is the problem here. I mean I have no idea how much telemetry features and modern electronics all use when the car is (supposed to be) sitting still.

But I do know when I make a long drive of an hour or more (effectively driving), I expect it to get a decent charge out of it. If I wanted to have it on the charger all the time, I could have bought a PHEV. Sadly this is not very practical where I live.

Hi Jesse,

Check out the last 8 or 10 posts on the below thread.

Ford Focus ST '22 Battery Drain

mines an mhev too, and I list some of my experiences from today.

ST owners have been fitting a larger 75ah battery. I am considering the same 

On 9/1/2023 at 11:26 PM, JesseNight said:

If I gotta go with the Battery age parameter, it should be less than a year, from October 2022. Which on its own is pretty odd considering the car was first used in February that same year. I bought the car in December, being second owner after it was used internally by the dealer.

 

I wonder what the usage pattern was by the dealer.  Lots of short test drives or similar on a low battery might mean the battery is knackered and unable to hold a charge properly any more.  Just a thought.  Normally I’d say try another battery but not even that looks to be the simple task it once was these days!  If you do buy a bigger battery go for the largest capacity one that you can afford and fits.

On 12/15/2023 at 12:17 PM, Plimp92 said:

ST owners have been fitting a larger 75ah battery. I am considering the same 

Fit the Yuasa 75Ah YBX7096

On 12/15/2023 at 12:03 PM, unofix said:

Yes that will be the reason that the Stop/Start still works. Kind of ironic that it should work, thus further preventing the alternator from being able to get some charge back in to the regular 12V vehicle battery. Once again a classic case of poorly thought out software and systems working against each other.

I think it's time to replace the 12V battery with something decent like the Yuasa YBX7096

 

I've had a few busy months but it's time to give a final update on this matter.

The charging behavior (or lack thereof) was definitely not normal. This aside, the car had a few serious electronic problems, up to the point where nothing but just driving worked anymore and the error messages piled up on my dashboard monitor. Errors considering ESC, adaptive headlights, pre-collision assist, hill start assist, air conditioning...

 

To keep the story somewhat short, something was very wrong on the electronics or software level. It took them a week to get it fixed but in the end they did. And much to my surprise, the battery behavior problem has been gone ever since!

Of course is still goes into deep sleep after 48h not driving (as intended according to the user manual), but after a drive it comes out immediately and the battery charges normally. Right now I haven't driven for almost 3 weeks and it's still fine!

 

As for what had been done about the car, the garage was a bit vague and wouldn't give me a paper with the exact description. A lot was reset (modules and BMS too), things were updated, and a few parts were replaced among which the main ground cable (possibly BMS too?). The battery itself was checked and not replaced because it was still fine.

I am a bit sad that I didn't get any clear answers, but at the same time happy the problem seems to be fixed. I can only say to anyone experiencing this... keep trying, because apparently it is possible without the need of bigger batteries or custom tweaks.