Brake trailer module fault

[Snakebitten]

The hybrid system doesn’t start the truck or supply 12V power directly to the low voltage system. It just supplies a recharge current to the starter battery.

While I agree that the HV battery doesn't directly fire the traditional bendix/flywheel starter (coldstart/remote-start), nor the BISG starter for that matter, it IS supplying current to the low voltage bus which in turn is supplying current to the 12V batteries. The AGM battery IS likely providing the majority (if not, all) of the High Amperage current during the starting event.

The only thing that I have never been able to discover is whether that battery isolator ALSO isolates the AGM from the DC/DC converter? We do know that isolator isolates the modules/electronics from the AGM during its high amperage ICE starting event. I assume that also isolates the DC/DC converter from the AGM?

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[JEB]

While I agree that the HV battery doesn't directly fire the traditional bendix/flywheel starter (coldstart/remote-start), nor the BISG starter for that matter, it IS supplying current to the low voltage bus which in turn is supplying current to the 12V batteries. The AGM battery IS likely providing the majority (if not, all) of the High Amperage current during the starting event.

The only thing that I have never been able to discover is whether that battery isolator ALSO isolates the AGM from the DC/DC converter? We do know that isolator isolates the modules/electronics from the AGM during its high amperage ICE starting event. I assume that also isolates the DC/DC converter from the AGM?

I agree that the hybrid system is providing a charging current to the 12v battery when the truck is fully on—KOER. But I have never seen anything approaching a charging voltage on the 12v side in accessory mode—KOEO. Yes, the DCDC converter is alive. That’s easy enough to confirm in FDRS because it reports in during a network scan even in accessory mode. But little to no current is being delivered to the starter battery. Whether that’s because the isolator is preventing the current flow or instead the hybrid system isn’t fully operational downstream of the DCDC converter I don’t know, but I suspect it’s the latter for two reasons. We know for sure that the ProPower generator is not working in accessory mode. We also know that there is no need for the electric motor in accessory mode.

 

[Spiffy]

What I'm unsure of is what is starting the ice from a cold start. If the mechanical standard starter is doing it it's a very different sound. It feels like it's starting just like the transitional starts during normal ice/electric modes. I have experienced the mechanical starter sound only once.

Additionally I found out the hard way that the traction battery does not keep the 12v or whatever battery is using during accessories mode. I was involved in a fdrs programming of my ipma when the voltage dropped enough to mess up the programming thus causing a massive problem. I did have a Schumacher pro shop charger on it. Apparently it can supply 200amps it didn't keep the battery up.

 

[JEB]

What I'm unsure of is what is starting the ice from a cold start. If the mechanical standard starter is doing it it's a very different sound. It feels like it's starting just like the transitional starts during normal ice/electric modes. I have experienced the mechanical starter sound only once.

Additionally I found out the hard way that the traction battery does not keep the 12v or whatever battery is using during accessories mode. I was involved in a fdrs programming of my ipma when the voltage dropped enough to mess up the programming thus causing a massive problem. I did have a Schumacher pro shop charger on it. Apparently it can supply 200amps it didn't keep the battery up.

The starter battery is starting the ICE from a cold start. If the sound is throwing you off, disregard it. The Powerboost is just like any other truck as far as cold starts are concerned. During cranking the starter battery is isolated, which causes the auxiliary battery to kick in to keep the modules energized. Until the truck starts up the hybrid battery isn’t doing much of anything from what I can tell. That seems consistent with what you are observing. If the DCDC converter is providing some current prior to full start up (i.e., in accessory mode), it doesn’t seem to be much.

Another way to look at the starting system is to consider the starter battery itaself. It's an H7 capable of delivering 800 CCA. What in God's name would you need that many amps for if not to crank the ICE? If all you needed to do was energize the 12V side, just drop in a deep cycle and be done with it.

 

[Snakebitten]

Clearly in Accessory mode the HV battery is providing substantial current to the 12V side of the truck, as long as the SOC of the HV battery is high enough for the DC/DC converter to draw on it.

Here's the current at approach to the truck. (approach wakes the truck and, including OBD port)
The DC/DC converter is disabled, so the AGM is being taxed for 10amps.

Then Accessory mode is turned on.
Clearly the DC/DC converter is now enabled and is drawing 2.9A of 280V, converting it to 57Amps of 13V.
31 amps of that 57 are being used to "charge" the AGM/auxiliary

Then I "start" the truck.
DC/DC converter Voltage increases to 14.2V and 77amps are being made available to the low voltage bus. 45amps are being consumed by the truck, and 32 amps are "charging" the AGM/auxiliary.

Isn't the PIDs evidence enough of the DC/DC converter activity in all 3 states of the truck? (approach/accesory/ready)

 

[JEB]

Clearly in Accessory mode the HV battery is providing substantial current to the 12V side of the truck, as long as the SOC of the HV battery is high enough for the DC/DC converter to draw on it.

Here's the current at approach to the truck. (approach wakes the truck and, including OBD port)
The DC/DC converter is disabled, so the AGM is being taxed for 10amps.

Then Accessory mode is turned on.
Clearly the DC/DC converter is now enabled and is drawing 2.9A of 280V, converting it to 57Amps of 13V.
31 amps of that 57 are being used to "charge" the AGM/auxiliary

Then I "start" the truck.
DC/DC converter Voltage increases to 14.2V and 77amps are being made available to the low voltage bus. 45amps are being consumed by the truck, and 32 amps are "charging" the AGM/auxiliary.

Isn't the PIDs evidence enough of the DC/DC converter activity in all 3 states of the truck? (approach/accesory/ready)

Yes it is. I stand corrected.

 

[Spiffy]

I might be throwing me off. I have been a ford guy for 40 years. Every type of truck motor. 5 3.5 eco boosts. I know what a conventional starter sounds like when it engages. This PB is on cold start or any start is not it. I don't hear any engagement of a starter. If I press the start button after pressing the brake it starts up in electric. Every time. Then after about 2 min the ice starts. The sound when it starts is exactly like when it cycles on during normal driving conditions. I absolutely am sure that the electric motor is turning the ice to start.

Example is my 2016 3.5. Hit starter button, I hear starter engage. 2 or 3 revolutions and the ice starts.

With my PB when it starts its instant. Same at stop lights, enquired power after drive battery is depleted during normal driving.

I have heard the starter engage just once.

I think when I get my truck back tonight I might disconnect the starter and see.
It's really strange.

 

[Snakebitten]

Go to accessory mode and crank up the HVAC heater settings.
Then open your door and cold-start the truck. It should use the traditional bendix/flywheel starter for that start.

Or setup the truck for a remote start that will pre-heat the cabin. Then get down on the ground so you can hear the ICE start. Trigger a remote start.

Trouble is that these Powerboost 3.5 Ecoboost motors start so quickly that you aren't likely to get any cranking time. They are amazing. They just light up instantly and there's not much differentiation from a BISG start vs a Bendix start VS a traction motor clutch start.

 

[Spiffy]

So the traction motor does start the ice on occasion?

 

[JEB]

So the traction motor does start the ice on occasion?

Not from a cold start. The DCDC converter only puts out maximum of 260 amps under ideal conditions. That is not enough to cold-crank a 3.5L ICE.

 

[Snakebitten]

My wording might have been misplaced. The one instance that neither the Bendix starter or the BISG are necessary to fire up the ICE is when the traction motor is propelling the truck down the road and the crankshaft is "disconnected" from the transmission via a clutch and that traction motor/torque converter assembly.
So technically the clutch plays a roll in using the momentum of the traction motor and input shaft to start the ICE.
Very similar to push starting a standard transmission car?

 

[Spiffy]

So sitting at a light with ac running, lights on, lots of current draw. The ice cycles on and off. The starter motor is doing that?

 

[Spiffy]

Wait. How is the starter motor connected?
Is it like a gear and flywheel? Or is it also belt driven?

 

[Spiffy]

More problems. My heat exchanger is fixed but shop said no fix for the trailer brake module. The module is on national back order and no eta. What is up with ford?

Service manager said ford outsourced the module during the chip shortage and got subpar modules. They are trying to find a new supplier.
That module is causing other issues. Rear camera, battery drain. He said it can take months. I can't pull my trailer. No brakes or lights. God damit.
I need to find the part number, location and I will fix it myself.

 

[JEB]

The only thing that I have never been able to discover is whether that battery isolator ALSO isolates the AGM from the DC/DC converter? We do know that isolator isolates the modules/electronics from the AGM during its high amperage ICE starting event. I assume that also isolates the DC/DC converter from the AGM?

Revisiting your question, I could only find one thing in the shop manual that touched on whether the isolator isolates the AGM from the DCDC converter and it seems to suggest that it does, as you suspected. According to the shop manual, the auxiliary battery only kicks in to provide transient load support when the DCDC converter is maxed. So, it sounds like the DCDC converter is also providing transient load support during cranking and operating in tandem with the auxiliary, if I’m reading this correctly.

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