GAP tool and alternator measurements

greiswig

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Hi, all. I recently replaced both cigarette lighters in the center console with these little gems. I attached one to the secondary battery, which is now a LiFePo, and the other I'm just using with the stock cigarette lighter wiring.

I'm seeing some strange behavior of those voltmeters as I drive. If I am going downhill applying brakes or in the driveway idling, the voltage on both is around 14.5V. Which is also what I measure at idle with my Fluke multimeter.

But when I'm driving along at normal speed, the primary battery (or whatever supplies voltage to that cigarette lighter) is running about 12.2V, and the secondary battery is only at 13.4.

Since I have the GAP tool, I thought it would be helpful to check what the ECU sees the alternator doing. But trying to log any of the voltage/current options in the Body Control Module section of the GAP tool comes up with NA for all of them. Is there a trick to getting the GAP tool to monitor voltage that I can use? 2016 SCV6 LR4 HSE here for the complete alphabet soup.
 

djkaosone

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So, there's a few of us here that tried to figure out how the bms and pwm alternator works. Most don't have this issue or notice it.

From what I gathered, the charging system only charges when the battery is between 70-80%. After you battery reaches 80% it'll provide minimal voltage 12.xV, but the proper amperage to maintain all electrical needs. When the battery is 70% or low, it'll charge at full rate 14.xV. Anywhere in between 70-80%, it'll vary depending on what your battery "needs". The charging system is trying to "protect" your battery from overcharging and preemptively dying. However, this "smart" charging is THE dumbest thing ever adopted from Ford.

Within gap go to live values, body control, and select the following.

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greiswig

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This explains a lot, even without trying it. I didn’t realize it was doing PWM. I was worried that my alternator was dying because I was seeing such variable voltages. Now I would guess it is acting as designed, flawed as that may be.
 

djkaosone

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We've all tried disabling it. The best way to test your alternator is to unplug the bms connector from the negative battery post and it should default to 13.8V. You can leave it unplugged and ignore the warning lights without issues, but I couldn't deal with the light.
 

greiswig

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So is it a standard alternator, but the regulator is PWM? And presumably that's internal to the alternator, so...great idea for something that will wade in mud!
 

avslash

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I do remember hearing years ago that the armored version dispenses with the "smart" alternator functions.

I have no idea how to access those part numbers, but have wondered if those parts could be retrofitted to get rid of the mess the standard vehicles are equipped with.
 

bbyer

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Yes, they call it a Smart Alternator but it really is a Dumb Alternator.

Below is how the alternator system works on my LR3 but the LR4 is not much different.
I might also add that ambient air temperature also is a factor in the charge voltage. Colder means higher voltage and hotter, lower, again all to protect the sealed battery.

There is also a default charge voltage, 13.3 VDC that when something in the system quits, amps are still generated. What this means is that the engine will run, the lights will probably function OK but the battery will not charge or at least will not get enough volts to charge to to 80% state of charge that LR thinks is a full battery.

Load shedding also can set in - no heated seats, no radio amp etc, to keep the amp requirements down. Apparently this is all to achieve fuel economy numbers.

Yes, dumb!


Alternator Internal “Smart Regulator” design philosophy

The alternator, rather than having a “normal” internal regulator that looks at just the battery or the electrical buss and then decides what to do is instead what is called by LR a “smart regulator and takes instructions from the Engine Control Module (ECM).

It is almost like we are back to the external regulator designs of old, except that the ECM may decide instead of telling the alternator to make more power, to instead, load shed, and hence shut down the heated windscreen, seats or whatever else it decides to.

The "regulator" inside the alternator, (Transpo part # IN6349), is therefore really not a regulator in the old sense of the term but instead an instruction receiver from the ECM that translates Pulse Width Modulated (PWM) signals into a form that the alternator understands – digital like pulse signals from the ECM into current that the windings react to as one would normally expect.

On the jpg, the pin on the far left is called #1 in the diagrams and is Battery Voltage Sensing, (BVS, or AS); the middle pin, #2 ALT CON, receives a Pulse Width Modulated, (PWM) signal from the Engine Control Module, (ECM), and the right pin, #3, ALT MON, sends a PWM signal back to the ECM.

#1 is what used to be called the A, S, or Batt and now BATT SENSE, however in this case, #1 also provides excitation current to the rotor at startup. Transpo calls the pin up as AS, Alternator Sensing.

The #2 pin PWM signal overrides the #1 battery voltage signal once available.

#2 in Ford speak is called Generator Command/Control or GEN CON and

On Land Rover wiring diagrams, ALT CON; Transpo uses RC, Regulator Control.

#3 in Ford speak is often called Generator Monitoring or GEN MON and

on Land Rover wiring diagrams, ALT MON; Transpo uses LI, Load Indicator.

Land Rover calls this a Smart Regulator because it has to follow instructions from the ECU rather than dumbly reacting to the battery or electrical buss voltage.

The alternator is to be tested as a Ford PCM/RC type regulator / alternator.
 

Attachments

  • Regulator for Ford 6G PCM Controlled Alternators WAI Transpo.pdf
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callin

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Hi, all. I recently replaced both cigarette lighters in the center console with these little gems. I attached one to the secondary battery, which is now a LiFePo, and the other I'm just using with the stock cigarette lighter wiring.

I'm seeing some strange behavior of those voltmeters as I drive. If I am going downhill applying brakes or in the driveway idling, the voltage on both is around 14.5V. Which is also what I measure at idle with my Fluke multimeter.

But when I'm driving along at normal speed, the primary battery (or whatever supplies voltage to that cigarette lighter) is running about 12.2V, and the secondary battery is only at 13.4.

Since I have the GAP tool, I thought it would be helpful to check what the ECU sees the alternator doing. But trying to log any of the voltage/current options in the Body Control Module section of the GAP tool comes up with NA for all of them. Is there a trick to getting the GAP tool to monitor voltage that I can use? 2016 SCV6 LR4 HSE here for the complete alphabet soup.
I've never seen those things before, pretty cool. For the cigarette wiring, do they fit right into the lighter hole or do you have to drill it out?
 

greiswig

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I've never seen those things before, pretty cool. For the cigarette wiring, do they fit right into the lighter hole or do you have to drill it out?
The existing holes have a flat on one side to keep the lighter socket from rotating. I just used a dremel to put a flat on the plastic threads of these gizmos, too. They are the same diameter as the rest of the holes.
 

callin

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The existing holes have a flat on one side to keep the lighter socket from rotating. I just used a dremel to put a flat on the plastic threads of these gizmos, too. They are the same diameter as the rest of the holes.
cool, thanks. how hard is it to remove the lighter body and get to the wiring behind it?
 

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