Hi All,

I'm trying to charge the battery in my MK4 ST as I keep getting alerts of low battery on the FordPass App.

 

I have connected the Positive to the Postive Terminal and the Negative to what I presume is a grounding point.

 

However the battery doesn't seem to be charging. I connected to the car using Forscan and the battery voltage dropped from 12v to 11.7v even with the charger connected. 

 

Am I doing something wrong? Im using a NOCO Genius 10 battery charger. On the Charger it is showing as full charged and is just flashing the last green light.

 

Thanks,

At the moment, i can't see anything wrong with your set up (unless there's no connection between your negative lead and the battery or the likely fitted monitoring device has completely failed but that would stop the car from starting?) but, to me, if the battery voltage isn't affected by connecting the charger then that may be faulty?
What does a voltmeter say across the charger (I don't know the logic of this likely intelligent charger as it may have some protection or other parameters built in to it)?
Bring back a simple always on dumb device that you can test?

There's only RTFM of course as multiple modes seem to need Press and Hold (I know you say the fully charged light is on but it may need a reset):
https://no.co/media/wysiwyg/downloads/User_Guides/Genius/genius10na_user_guide_4.9.2024a.pdf

Have you checked the in line fuse on the charger positive supply ?

I think the quickest option here is just to try the charger on another car if you have friends/relatives/neighbours nearby.

I can't see anything wrong with the location of the clips although they don't look to be making the best possible contact patch from those images.  That wouldn't stop the charging from charging though.  So unless you can post an image of the charger itself I'm not sure why it won't charge like that.

5 minutes ago, TomsFocus said:

I think the quickest option here is just to try the charger on another car if you have friends/relatives/neighbours nearby.

I can't see anything wrong with the location of the clips although they don't look to be making the best possible contact patch from those images.  That wouldn't stop the charging from charging though.  So unless you can post an image of the charger itself I'm not sure why it won't charge like that.

The charger just has the last light slowly flashing green. I couldn't get the greatest connection on the Negative lead as it kept popping off originally. Think the nut is a but small for the clamps

28 minutes ago, PLB said:

Have you checked the in line fuse on the charger positive supply ?

Is that the little black box on the Positive lead?

3 minutes ago, TENCHI125 said:

The charger just has the last light slowly flashing green. I couldn't get the greatest connection on the Negative lead as it kept popping off originally. Think the nut is a but small for the clamps

I'd put the clamp on the flatter metal part of the connector behind the nut if you can.  Poor connections can cause strange issues.

Flashing green is the maintenance charge so you are right that it thinks the battery is full for some reason.  I don't know why that's happening in this case though.  I'd have to go back to the previous suggestion of trying it on another car.

11 minutes ago, TomsFocus said:

I'd put the clamp on the flatter metal part of the connector behind the nut if you can.  Poor connections can cause strange issues.

Flashing green is the maintenance charge so you are right that it thinks the battery is full for some reason.  I don't know why that's happening in this case though.  I'd have to go back to the previous suggestion of trying it on another car.

It is a strange one, I'll try adjusting the Negative Clamp to be on the flatter part. I'll also try it on my partners car when they get home see if it behaves any different. Thanks,

58 minutes ago, TENCHI125 said:

Is that the little black box on the Positive lead?

Difficult to tell from the angle in the photograph. Does that black box contain a spade type fuse or is it just an in line connector for the crock clip ? An inexpensive multimeter would be useful to investigate further.

............ this looks like a job for 'Maypole' 🎉

Disconnect the battery first and then try to charge it again.

I have seen many times before that the Battery Monitoring System prevents a battery charger from charging the battery properly.


An alternative for disconnecting the battery is locking the car with the bonnet open, wait 30 minutes and connect the battery charger once the vehicle has fully entered sleep mode. 
 

On 12/21/2025 at 7:53 AM, JW1982 said:

Disconnect the battery first and then try to charge it again.

I have seen many times before that the Battery Monitoring System prevents a battery charger from charging the battery properly.


An alternative for disconnecting the battery is locking the car with the bonnet open, wait 30 minutes and connect the battery charger once the vehicle has fully entered sleep mode. 
 

Absolutely.

Charge it with the negative cable disconnected and both charger connectors on the battery poles.

 

On 12/21/2025 at 7:53 AM, JW1982 said:

I have seen many times before that the Battery Monitoring System prevents a battery charger from charging the battery properly

Any idea on how it manages to do this and does it only apply to "intelligent" chargers?

I'd have thought the only way it could do it is by somehow increasing the voltage drop across the current shunt in the device to fool the charger into "thinking" the battery is fully charged. If that's the case it could easily be defeated by simply connecting the charger negative cable directly to the battery post.

4 hours ago, mjt said:

Any idea on how it manages to do this and does it only apply to "intelligent" chargers?

I'd have thought the only way it could do it is by somehow increasing the voltage drop across the current shunt in the device to fool the charger into "thinking" the battery is fully charged. If that's the case it could easily be defeated by simply connecting the charger negative cable directly to the battery post.

A smart battery charger usually measures voltage, current, and the more high end chargers do often also measure temperature. Based on the voltage and current measurement the charger calculates the internal resistance and type/capacity of the battery and determines the optimal charge strategy based on this data.

With the battery connected, and the CANbus network being active the charger does not only measure the battery itself but also all circuitry connected to the battery. This can cause the smart charger to detect the complete wrong type of battery or capacity. I have seen many times before that a smart charger does not charge the battery properly when the CANbus network is still active. The smart charger being connected can also prevent the CANbus network from entering sleep mode.

You can directly connect the negative clamp of the charger to the negative pole of the battery (before the BMS sensor). This however results in the BMS not detecting the battery being charged. Not a major problem as long as the BMS is reset after the battery has been charged. The same applies when the battery is fully disconnected while being charged.
 

I may be missing the point but if you reset the BMS does it not start from day 1 of a new battery, fine if it's almost new but if it is old then the car charging regime will be wrong (as I understand it of course)?