Been suffering from a strange charging issue since a month and I have not been able to identify the issue.

On most days the alternator seems perfectly fine and charges between 13.5V and 14.8V.
However, on some days, totally random, the alternator gives out only 12.2V - 12.4V. The alternator puts out 13V-14.8V only when I leave the accelerator and voltage drops back to 12.2V while driving. Seems like the regenerative charging kicking in.

It all started a month back when the dreaded "Charging system fault" came up on the dash. Items changed out were the BMS sensor at the negative terminal and its fusible link and finally the alternator for the error to disappear.

Two weeks back, my battery died again and on checking, found that the alternator was bad, (or I thought so) as it was only charging at 12.2V-12.4V. I replaced the alternator again and everything was fine for two weeks. Then again, last week the charging stopped again one evening on way back from work and I was about to condemn the alternator again when everything got back to normal the the next morning on the way to work and for a week there was no issue.

Again today morning, the issue has cropped up on the way to work and I am lost on how to identify the issue, if it is one to be worried about.

I never got stranded yet, but I am worried when i see the voltage going below 12.2V. I started using a bluetooth battery monitor and that is how I have been keeping an eye on the charging system since the initial issue.

Any Idea what i should look for? This is 2013 with the ford 2L ecoboost engine and the pcm controlled alternator. I read somewhere that the PCM only charges the battery when required. Can anyone confirm how this system works?

All cables and negative terminal points look fine, no parasitic drains, voltage at alternator matches the voltage at the battery.

 

Yes, newer engines eco-tuned engines such as the ecoboost will attempt to manage the battery charge for efficiency reasons.

On most battery systems, that means the charger adjusts voltage to the battery. But in the case of vehicles, the battery is hard-wired to the alternator so the only way to do that is reduce the entire system voltage.

I've heard of problems with that on the ecoboost (don't own one). Also heard there's an associated sensor which can be disconnected which will disable the battery management system and make the alternator run at 14v+ like a normal alternator.

 

Hmm. The only time I had problems with charging and the battery dying was when my starter went south.

 

How old is the battery? Have you tested it using a battery tester (CCA, internal resistance)?

All modern vehicles have a parasitic draw for the electronics stuff that remains active. What is your measured draw in milliamps?

 

The battery is a year old and tested fine. I also checked the parasitic draw and is around 17-22mA. Since I added the bluetooth battery monitor (the drain increased by another 1-4mA.)
I see from the monitor logs that the voltage decreases by only 0.2V overnight. This is why i wanted to know if it is normal for the alternator to stop charging once in a while as a smart charge process in these vehicles. The charging was perfect on the way back home yesterday and was in the range of 12.6V to 14.7V and this morning as well.

I noticed today that there seems to be a pattern in this over the last month that this issue happens every 8th day and resolves itself the next drive cycle after a few hours. From the charging history i saw that the issue happened on 8th, 14th and 21st of this month and only once. I usually see this either driving to work or on the return journey. Attached images. Appreciate if anyone with the same model verify if their voltage cycles in anyway like this, then I can assume this is normal and not worry. I had already changed out two alternators and now think it may have been a mistake? The voltage would remain low for a few hours irrespective of how many times you restart. Now i realize it has a pattern and happens every 7th or 8th day. On this day, the battery also never goes below 60% while driving. Or I am going crazy and i got Shrodinger's battery monitor without which i would never have noticed.


14th Day, on the way to work was normal and on the way back from work, voltage was 12.2 while driving and above only when coasting.

21st Day, yestarday on way to work, voltage was 12.2 while driving and above only when coasting. Way back from work was normal.

Today, on way to work normal as any other day.

 

Interesting issue OP.
Have you checked all of your grounds to major components? I have a 2008, so an entirely different engine and most likely charging system. You charging data looks normal sans the dip.
@merlinj79 has posted a 'hard battery reset' procedure likely a few times on this forum which should fully reset all control modules and remove any corrupted data. It's worth a shot.

 

Yes, when i changed the alternator and the BMS sensor, I charged the battery externally overnight and reset the Battery Monitoring system data. I read later that this should be only only when battery is replaced with a new one as per the service manual. My battery was a year old and still under warranty. I took it to the shop and they returned it back next day with a note that there is nothing wrong with it.
I forgot to mention that i did not replace with a brand new alternator, they cost an arm and a leg. Got an OEM one from salvage, which was from a car that ran around 25k miles. I did not want to take a risk with reman or Chinese ones.
Also, I wanted to share my observations with other owners and also to make sure I understand how this charging system works, and if i should be worried. I will keep checking if the pattern holds as the battery state of charge shown on the monitor never went below 60% during the issue, although voltage was 12.2V.

 

Yes, this “adaptive” battery charging system seems to work on the periodic schedule you mention.
And yes, the output from the alternator does accordingly vary with “need”.

It is interesting though that this complex system seems to work no better than the classic constant output charging a wet lead-acid battery…. but perhaps we are gaining .00001 mpg.

Forgive me, but have you missed one test. Putting the vehicle into high electrical load and monitoring the alternator. In this situation (fans, stereo, seat warmers, steering wheel warmer, front and rear defogger… running) my alternator does output at full capacity.

Cheers All.

 

Thanks, Yes you are right, the voltage does go up to around 13.3V-14V under load, but only when I put my AC blower in the full setting. This will now be my backup plan incase the voltage drops below 12.1V if ever this will happen. I think it happens after every nth startup, and I am trying to figure out and make some sense of the pattern.

Luckily this happened today on the way back from work and I was able to test. The issue only happens once in a while, after around 15-20 trips or 6-7 days whichever comes first, I don't know. When this happens, the voltage drops to around 12.2V (60% charge) and remains there while driving. When I added the load this time the voltage went up, but dropped back down to 12.2V as I removed the load. You will notice that the battery is not charging at this time and shows around 62%.

Below is a screenshot of the test I did to give you an idea. All the spikes in voltage you see are when I put the blower in full blast. The smaller spikes up to 12.5V is during coasting and the alternator has a regenerative braking effect.

All other normal days, the voltage is perfect and between 12.6V and 14.8V. I am not worried any more as this seems to be a normal process which was always there and perhaps I started noticing only now only after adding the battery monitor.
Perhaps this is how the BMS system works and the ECM cycles the battery once in a while to extend life.

 

Conclusion - All seems ok. Lesson learned - How the LR charging system behaves and never to panic.

The last six days the voltage was normal between 13V and 14.8V depending on the load.
As expected, today morning, the 6th day after the last incident and the 14th trip, the alternator output was around 12.2V (62%), goes down sometimes to 12.1V (56%) at traffic lights in drive. This intermittent drop pattern holds so far for the last three weeks and I am getting used to it.

Climate control was in auto mode and blower was in minimum. Voltage goes up to 13.5V when coasting or going downhill, but drops back down to 12.2V while driving and whenever my foot is on the accelerator.
Voltage never went below 12.1V ever, even though i was prepared to put the blower at full power incase of emergency, but never needed to.

Hope this gives an insight to other owners of the 13-15 LR2. I did change the alternator, but am now really unsure if I should have when I noticed the low voltage and the local shop said the alternator was not working. Never do that. Recommend getting a bluetooth battery monitor, as I did after the issue kept coming back and really helped me investigate and understand the trend.

Wish you all a very happy new year and a wonderful 2022 !!