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Low Battery warning on dash

27K views 38 replies 18 participants last post by  Eli_100 
#1 ·
Hi if I listen to radio without engine running after about 2 minutes I get a low battery warning appear on dash with a symbol similar to a book it's not the key battery low warning any ideas why this might, not been using car much in this weather used motorbike for work but yesterday while I was cleaning it I had radio on and noticed this low battery warning
 
#2 ·
Car battery maybe a bit low if it's been sat for quite a while. Try putting it on charge or taking it for a good drive to get some juice back in it.
 
#4 ·
I had this warning coming on also. I went to halfords today and had a new battery fitted. I got home turned off the ignition. When I came out 10mins later and turned ignition on . The low battery warning came on again. The fitter at halfords did check to see if reset was needed and it said no. Can anyone help with this problem?
 
#6 ·
Had this problem with mine Here is the cure. (2 THROUGH TO 4 MUST BE DONE WITHIN 10 SECONDS)

1 Turn headlight switch so headlights will come on when you do step 2

2 Turn ignition to position 2 (headlights will come on)

3 Switch REAR fog light on and off 5 times

4 Switch HAZARD lights on and off 3 times ( battery light should flash 3 times within next 15 seconds and may then go off altogether for a few seconds)

5 Problem should be solved
 
#32 ·
Had this problem with mine Here is the cure. (2 THROUGH TO 4 MUST BE DONE WITHIN 10 SECONDS) 1 Turn headlight switch so headlights will come on when you do step 2 2 Turn ignition to position 2 (headlights will come on) 3 Switch REAR fog light on and off 5 times 4 Switch HAZARD lights on and off 3 times ( battery light should flash 3 times within next 15 seconds and may then go off altogether for a few seconds) 5 Problem should be solved
This message is very helpful my car was doing this battery low follow this and then sorted 😊 thank you 👍
 
#7 ·
I had this warning coming on also. I went to halfords today and had a new battery fitted. I got home turned off the ignition. When I came out 10mins later and turned ignition on . The low battery warning came on again. The fitter at halfords did check to see if reset was needed and it said no. Can anyone help with this problem?
It's not much use to you now, but my car does this since I bought it at 8 months old. It's now over 11 years old and still on the original battery.
I think it's something Ford decided to build into it for no reason at all.

Sent from my F8331 using Tapatalk
 
#8 ·
I had this warning coming on also. I went to halfords today and had a new battery fitted. I got home turned off the ignition. When I came out 10mins later and turned ignition on . The low battery warning came on again. The fitter at halfords did check to see if reset was needed and it said no. Can anyone help with this problem?
It's not much use to you now, but my car does this since I bought it at 8 months old. It's now over 11 years old and still on the original battery.
I think it's something Ford decided to build into it for no reason at all.

Sent from my F8331 using Tapatalk
agreed. more pointless stupid electronics just for the sake of it.
 
#9 ·
Mine has its moments, it will be fine for weeks then show low battery and the radio

only works for a few minutes before it shuts down. Battery at 12.8v

I did 300 miles to Cornwall stopping about halfway, at the destination i parked up and it

popped up low battery as everyone got out the car and unloaded the boot.
 
#10 ·
Mine has its moments, it will be fine for weeks then show low battery and the radio

only works for a few minutes before it shuts down. Battery at 12.8v

I did 300 miles to Cornwall stopping about halfway, at the destination i parked up and it

popped up low battery as everyone got out the car and unloaded the boot.
mine does the same. if i could 'delete' the warning permanently, i would! much like many of the other bleeps and warnings they put on cars now just for the sake of it, it seems
 
#11 ·
Its ok, i also get this message since my aftermarket unit, has a sleep mode to wake up in about 1 sec when i turn on the car.

My car audio digital capacitors and my multimeter shows a solid 12.5V after engine shut down and 14.5-14.8 solid when the car is running depending on the RPM.

It is just a stupid warning with no real benefits to it.

My guess is that who ever got this message, have something that is using car battery power after shut off and the system detects it- for sure.

Never ever i had this message when i didn't had an aftermarket headunit, just when i was playing music and the car is off.

Could be a dash camera in the wrong fuse, OBD device left in the port (it works for hours) Etc.

One cool feature though is that one where once in a 2-3 years it will tell you to replace key fob battery, well that's cool.
 
#12 ·
I have had this problem for years. It is caused by the fact that the Ford charging system will not let the battery fully charge so that when you are coasting or going down hill the Alternator can go up to full ,power and act as engine braking without cooking the battery. When it first happened I was parked up listening to the radio, up came the warning and the whole car then switched off. I thought that the battery must have died so I bought a new one. The warning still kept coming up and I then got the story that the car had to have a Ford battery as the Computer could only read those. So I bought a Ford battery at vast cost but the problem still persisted. I then got the story that a Ford dealer has to reset the Computer when a new battery is fitted so I went to a dealer. The first dealer said that they could not access the computer but still charged me then I went to another Dealer who charged me and said they had reset the Computer but the problem still carried on. I then bought a second hand Battery Computer monitoring unit from a car breaker in Austria which fixed the problem for about two years. Now I have the problem back again. It is an absolutely pig of a problem and if you look on the internet there are 1,500,000 posts about it but nobody has really found a fix.
 
#13 ·
I have had this problem for years. It is caused by the fact that the Ford charging system will not let the battery fully charge so that when you are coasting or going down hill the Alternator can go up to full ,power and act as engine braking without cooking the battery. When it first happened I was parked up listening to the radio, up came the warning and the whole car then switched off. I thought that the battery must have died so I bought a new one. The warning still kept coming up and I then got the story that the car had to have a Ford battery as the Computer could only read those. So I bought a Ford battery at vast cost but the problem still persisted. I then got the story that a Ford dealer has to reset the Computer when a new battery is fitted so I went to a dealer. The first dealer said that they could not access the computer but still charged me then I went to another Dealer who charged me and said they had reset the Computer but the problem still carried on. I then bought a second hand Battery Computer monitoring unit from a car breaker in Austria which fixed the problem for about two years. Now I have the problem back again. It is an absolutely pig of a problem and if you look on the internet there are 1,500,000 posts about it but nobody has really found a fix.
i found a fix. i just ignore the stupid warning!

no big deal if the radio shuts off, i dont plan on being parked long enough anyhow. as long as the car starts, im fine with seeing the warning. after all, ive been driving long enough (and worked with cars long enough) to know how a car sounds when the battery gets sluggish! why would i need to rely on a computer to tell me something that clearly i can tell just as well, or better on my own?

i get the point of the warning if theres a danger of the car not starting again, but such a slight variation is insane! although now its been mentioned about resetting after changing a battery, i wonder if that includes removing the battery and reconnecting it later? if so can the reset be done on Forscan? ive had my battery disconnected a few times now for various reasons!
 
#14 ·
Tried the reset procedure on mine and it made zero difference. I have the larger 110 size

Bosch S5 on my car. Bought new when I got the car due to the battery warning and having

a 5 year old battery. Made zero difference.

The stereo shutoff is a pain though.
 
#15 ·
Some of the expensive Diagnostic Code reading tools have the facility to reset the Computer unit which gives this low battery signal. The trouble is that my Mondeo model is the one model that cannot be reset not even it seems by Ford dealers. The theory also is that if you disconnect the battery for over three hours the Computer resets itself, that doesn't work either.

The annoying thing is that Ford have taken a Patent out to protect this Charging System from being copied but the question is, who the hell would want to copy it as it is a total pain in the neck.
 
#17 ·
No idea. I did it the method described on here somewhere. But i think that was

for cars with stop start?
 
#18 ·
I tried to get clever to solve this problem. I made up a little black box with some electronics inside so that when the engine was running the computer sensor on the battery was always sent a lower voltage than the battery really had. I hoped that this would fool the system into thinking that the battery voltage was lower so that the charge rate would be turned up and then the battery would be fully charged. That idea didn't work either.
 
#19 ·
The cars ECU is too clever for us mere mortals :)

I remember someone on the MK3 threads raising the idel speed by adjusting the throttle

position. Didnt take long for the ECU to compensate for that and lower the idle again.

Need to find where the voltage sensor is and increase the voltage on that feed.
 
#21 ·
Its not an issue with the state of charge. My battery is fully charged and the

stupid low voltage warning still pops up.

Thought it was funny after a 300 mile drive on a sunny day, battery voltage showing

over 13volts still as the car was unloaded yet the stereo decided it was still too low

and the warning popped up.
 
#23 ·
Have to get a spare one, is it just a shunt or is there circuitry to it?
 
#24 ·
On my Mondeo the battery management sensor communicates with the BCM module via one wire carrying a digital signal (LIN bus - local area interconnect), so no it isn't a simple shunt. It must contain an IC and maybe a Hall effect sensor. The alternator also contains an IC which listens to instructions from the BCM.

The battery management system is not a single component, is it a system: smart sensor on the battery, smart algorithm in the BCM and a smart alternator. The BCM listens to the sensor (via single wire LIN bus) and tells the alternator what it has decided (via single wire LIN bus).
 
#25 ·
I know everything else is working as it should. If its left parked for a while and the

voltage drops the charge rate increases to around 15volt for a little while, then drops

back to 14.4volt.
 
#26 · (Edited by Moderator)
Gleaned from Ford literature:

The PCM receives information directly from the alternator. Not the BCM as I previousy said.

Some of this information is used for example to help stabilise idle speed depending on the load.

The BCM receives information on battery temperature, voltage, current, battery age in days from the sensor on the battery via LIN.

The requested alternator charge voltage is adjusted by the PCM and BMS working together.
True.

The BCM calculates a required charge voltage using battery temperature and state of charge and maybe others. This is sent to the PCM via HS-CAN. The PCM then adjusts the value according to the smart regenerative charging algorithm before sending it to the alternator via LIN.

From what I'm reading here it seems the battery monitoring sensor estimates losses in battery capacity over time. Maybe that's why spurious low battery warnings are set. If BMS reset is not done the BCM thinks there's less capacity available than there is?

1 is PCM, 2 is BCM
 

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