Best place to connect negative to chasis when charging battery?

[xFiestaLoverx]

Hi guys, quick one, as the title says. This is for a 19 plate focus 1.5 ecoboost. 

Thank you for your help. 

Actually would anyone happen to know what type of battery our cars use? Is it AGM etc etc? 

 

Thanks again 

[Comares2001]

Normally fitted with EFB .

[williamweb]

19 hours ago, xFiestaLoverx said:

Hi guys, quick one, as the title says. This is for a 19 plate focus 1.5 ecoboost. 

Thank you for your help. 

Actually would anyone happen to know what type of battery our cars use? Is it AGM etc etc? 

 

Thanks again 

Never had a problem connecting charger to the battery terminal posts. Sorry my Mk 1 has a smart charge rather than a BMS system so this post doesn’t help you👍

Edited February 28, 2021 by williamweb
Edit

[JW1982]

On a vehicle with the Ford battery Montitoring System (BMS) a battery charger must never be connected directly to the negative battery terminal.

When the charger is connected directly to the negative battery terminal the BMS will not detect that the battery is being charged. As a result of this State of Charge (SoC) of the battery will be completely different from what the BMS expects. This can (and will) result in overcharging the battery which seriously affects the life expectancy of the battery.

A battery charger must be connected after the BMS sensor (which is usually integrated into the negative battery terminal).

 

[Comares2001]

40 minutes ago, JW1982 said:

On a vehicle with the Ford Battery Montitoring System (BMS) a battery charger must never be connected directly to the negative battery terminal.

When the charger is connected directly to the negative battery terminal the BMS will not detect that the battery is being charged. As a result of this State of Charge (SoC) of the battery will be completely different from what the BMS expects. This can (and will) result in overcharging the battery which seriously affects the life expectancy of the battery.

A battery charger must be connected after the BMS sensor (which is usually integrated into the negative battery terminal).

 

You didn't read the op's post just the header

[mjt]

8 hours ago, JW1982 said:

On a vehicle with the Ford Battery Montitoring System (BMS) a battery charger must never be connected directly to the negative battery terminal.

When the charger is connected directly to the negative battery terminal the BMS will not detect that the battery is being charged. As a result of this State of Charge (SoC) of the battery will be completely different from what the BMS expects. This can (and will) result in overcharging the battery which seriously affects the life expectancy of the battery.

A battery charger must be connected after the BMS sensor (which is usually integrated into the negative battery terminal).

 

@JW1982 are you suggesting that the BMS is active even when the ignition is off? I find it strange that the BMS would be monitoring the charge of an external charger.

On my Mk3 the negative cable goes straight from the battery post to the chassis earth point. The BMS appears to be contained in a power distribution component that connects to the positive post (as shown below).

[iantt]

BMS is always active. 

The battery Monitoring Sensor continuously monitors the condition of the battery.

 

The sensor is equipped to vehicles which have Smart Regenerative Charging or Start-Stop. These systems require knowledge of the battery state of charge. The Battery Monitoring Sensor is the sensor used to provide this information.

 

Battery Monitoring Sensor connection

 

The Battery Monitoring Sensor is clamped directly to the negative terminal of the battery and grounds to the vehicle at the chassis ground connection point by means of a thick (25 to 35mm²) cable and eyelet. External customer loads must only be connected to the vehicle at the customer battery connection point. If the external customer load is connected at the negative battery post, the Battery Monitoring Sensor accuracy cannot be guaranteed.

 

It is recommended that the Battery Monitoring Sensor pole clamp is not removed unless a battery replacement is required. Should the battery need to be isolated, this should be done by disconnecting the ground eyelet at the chassis ground.

[JW1982]

Below a picture of the Focus MK3 BMS sensor:

The sensor is fully integrated into the negative battery terminal. The sensor measures the battery voltage, current and temperature.

Note that not all Focus MK3 cars do have the battery Monitoring System. There were also Focus MK3 versions that still had the older Smart Charge system combined with a Silver Calcium battery.

 

[xFiestaLoverx]

Thanks everyone. 

Could you let me know a good place to clamp the negative though? 😂

Thanks 

[JW1982]

You basically have 2 possibilities:

1. Connect the negative clamp of the battery charger to a suitable earth point (Ground).

The most commonly used earth point is where the negative battery cable is connected to the bodywork.

2. Disconnect the battery and charge the battery while disconnected. In this case the Battery Monitoring System must be reset if the battery is fully charged and reconnected.

[mjt]

9 hours ago, JW1982 said:

Below a picture of the Focus MK3 BMS sensor:

The sensor is fully integrated into the negative battery terminal. The sensor measures the battery voltage, current and temperature.

Note that not all Focus MK3 cars do have the Battery Monitoring System. There were also Focus MK3 versions that still had the older Smart Charge system combined with a Silver Calcium battery.

 

I stand corrected. Mine does indeed have this unit. Fortunately when I charge the battery I always use the chassis ground point of the cable.

[xFiestaLoverx]

Excellent, thanks guys