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Low Battery warning on dash


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28 replies to this topic

#21 PURPLE_2L_LX

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Posted 13 March 2020 - 10:09 AM

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.


MK4.5 TDCI 140 Business Estate.

 

MK3 FUSE INFO CLICK HERE ... FORD WIKI CLICK HERE .... FORD ETIS CLICK HERE

Adding your location may find someone local who could offer assistance.

F-Super, Bluetooth OBDII (ELM) and a MS509 scanners (test subjects required).

ForDiag now available to victims.


#22 Steammachine

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Posted 13 March 2020 - 05:22 PM

The voltage sensor box is actually on the negative battery terminal. That was the one i tried to jinx with my little black box.



#23 PURPLE_2L_LX

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Posted 14 March 2020 - 10:00 PM

Have to get a spare one, is it just a shunt or is there circuitry to it?


MK4.5 TDCI 140 Business Estate.

 

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#24 Speedlimit

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Posted 15 March 2020 - 08:08 AM

*
POPULAR

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).


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#25 PURPLE_2L_LX

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Posted 15 March 2020 - 02:19 PM

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.


MK4.5 TDCI 140 Business Estate.

 

MK3 FUSE INFO CLICK HERE ... FORD WIKI CLICK HERE .... FORD ETIS CLICK HERE

Adding your location may find someone local who could offer assistance.

F-Super, Bluetooth OBDII (ELM) and a MS509 scanners (test subjects required).

ForDiag now available to victims.


#26 Speedlimit

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Posted 17 March 2020 - 07:05 AM

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



 

Attached Thumbnails

  • bms.jpeg

Edited by Speedlimit, 17 March 2020 - 07:07 AM.


#27 Automatic1

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Posted 19 March 2020 - 03:38 PM

There is an option to adjust the capacity of the battery in the files, i changed my setting to a bigger battery for example 74Ah.

But, for that you need to read the file and OBD-USB or do it wirelessly. 



#28 mondiest

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Posted 21 March 2020 - 08:32 PM

Mine did this. But if I press the ignition button to turn everything off, then press the on / off button on the radio just to use the unit on its own, then the message didn't appear

#29 PURPLE_2L_LX

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Posted 21 March 2020 - 11:47 PM

No start button on mine, old school ignition key. Key no in theg ignition and mine still pops

up saying low battery. How long depends and seems fairly random.

 

Car unused for over a week and a short journey, it may work for a couple of minutes or 20

minutes. Car used daily with decent runs then a journey of several hundred miles and it could

be as little as a couple of minutes also.

 

Not managed to track mine down to any pattern yet.


MK4.5 TDCI 140 Business Estate.

 

MK3 FUSE INFO CLICK HERE ... FORD WIKI CLICK HERE .... FORD ETIS CLICK HERE

Adding your location may find someone local who could offer assistance.

F-Super, Bluetooth OBDII (ELM) and a MS509 scanners (test subjects required).

ForDiag now available to victims.





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