Smart alternator output

[miller75]

Can anyone confirm the alternator output voltage I should be seeing on my 2013 1.6 TDCI? The battery went flat at the weekend, I managed to get it going and checked the outputs, the battery was at 11.97v and the alternator was putting out 14.4v.

I have replaced the battery today and I am now seeing 13.5v from the alternator at idle, is this what I should be expecting as its a new battery that is at 100% and the smart charging system charges to about 80%

Thanks

[unofix]

To charge a 12 Volt battery you need at least 13.6 Volt (so 13.5V is just below normal limit).

After you fitted your new battery did you reset the BMS ? otherwise the alternator is not going to know that the car has a new battery.

[StephenFord]

6 hours ago, unofix said:

 

After you fitted your new battery did you reset the BMS ?

Now, where's that nice video you posted before on how to do this procedure? 😁

[miller75]

Thanks for the reply’s, I have reset the BMS but it was after I tested the output. I will check the output again today

[miller75]

Just tested it and it’s putting out 12.5 at idle, turning air con and lights it goes up to 13.3

[unofix]

You have a charging fault !! you need to get the alternator load tested but I'm afraid your smart alternator looks likes its gone dumb.

[miller75]

I have put it into test mode and monitoring the battery while driving, it’s ranging between 12.5 and 14.2. Does that not suggest it’s actually working and putting charge in when needed?
I have read that the BMS keeps it at 80% but surely that can’t be correct because it would be keeping at 10v?

[mjt]

56 minutes ago, miller75 said:

I have read that the BMS keeps it at 80% but surely that can’t be correct because it would be keeping at 10v

It's not 80% of the voltage, it's 80% of the full capacity (Ampere-hours).

[unofix]

There is little more I can add other than repeat:

21 hours ago, unofix said:

To charge a 12 Volt battery you need at least 13.6 Volt (so 13.5V is just below normal limit).

At any voltage less than 13.6V your alternator is not charging the battery, it is simply running the electrics of the car. Over a few days (possibly a week) your battery will eventually reach a level of discharge such that it will not have enough capacity to start the car.

[JW1982]

There is no way to tell whether a Ford smart alternator is working or not just by the charging voltage. 

The smart alternator is fully controlled by the PCM using a PWM (Pulse Width Modulation) signal. This basically means that the PCM decides when and how much the battery is being charged. The system is primarily designed to improve fuel economy. It is basically a compromise between fuel economy and battery health. Below just some characteristics of the system:

* During acceleration the alternator is not charging at all to improve performance.
* During deceleration the alternator is fully charging (regenerative charging).
* If the SoC (State of Charge) is near the treshold value the battery will not be charged at all unless there is a big electrical power demand.

In my opinion the only dependable way to determine whether a Ford smart alternator is working correctly or not is by comparing the charge request of the PCM (either by diagnostics or by analyzing the PWM signal) with the actual output of the alternator.

[miller75]

Quote

There is no way to tell whether a Ford smart alternator is working or not just by the charging voltage. 

The smart alternator is fully controlled by the PCM using a PWM (Pulse Width Modulation) signal. This basically means that the PCM decides when and how much the battery is being charged. The system is primarily designed to improve fuel economy. It is basically a compromise between fuel economy and battery health. Below just some characteristics of the system:

* During acceleration the alternator is not charging at all to improve performance.
* During deceleration the alternator is fully charging (regenerative charging).
* If the SoC (State of Charge) is near the treshold value the battery will not be charged at all unless there is a big electrical power demand.

In my opinion the only dependable way to determine whether a Ford smart alternator is working correctly or not is by comparing the charge request of the PCM (either by diagnostics or by analyzing the PWM signal) with the actual output of the alternator.

Thanks for that it confirms what I have been thinking, its logical when you think about it.

I have done about 100 miles since changing the battery with air con on full, auto stop start is still working fine and no other issues