I’m trying to charge my trailer batteries through the 7-pin connector. I will only be pulling 18a so I’m not looking at a separate cable from the truck battery to the trailer batteries.

I would like to understand the behavior of the Smart Alternator/ECM in regard to the charge wire (12v Battery Power wire) in the 7-pin trailer connector. I have a 2022 F150 Lariat.

1. At what state does the alternator provides power to the charging wire? It looks like it is not immediate after the truck starts. Is it after the truck battery reaches x% full?
2. The initial voltage measured is 13.5v. Is that correct?
3. When I place a load on the charge wire, the voltage drops to 9.8v. Does this sound correct? How low can it get?
4. When the truck turns off, is the connection to the charging wire dropped? I would like to avoid having the trailer drain the truck battery.

Thanks in advance for your help.

 

Does anyone know how the alternator works in our new Ford F150 truck?

 

I know this does not answer your specific question, but FWIW I installed a Renogy 20 amp charge controller in my trailer and couldn't be happier with how much better it charges. Should have done it on day 1. I did not change any wiring on truck.

 

On 4: you can check this with a voltmeter

The level of charging drops as the battery replenishes. That's normal. What you didn't test is battery voltage before the start, or say what level of load you had on the battery after starting. 13.5 suggests it's in a high state of charge therefore does need much more,

 

System operation: The PCM controlled Smart Charge charging system determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator.

The Smart Charge charging system is designed to set a DTC when a charging system fault is present. All of the DTC can set continuous faults, but not all DTCs set as on-demand faults. The smart regenerative charge system primary strategy is stored in the BCM. The BCM receives information relating to the battery condition from the battery monitoring sensor via a LIN. The BCM calculates and sends the set value needed for the generator charging voltage via the HS-CAN to the PCM. The PCM then adjusts the value received (if necessary) and sends it to the generator via a different LIN. The charging voltage is adjusted depending on various parameters, such as the current level of engine efficiency.

The smallest possible set value for the generator voltage is 12.2 volts, while the maximum charging voltage can be anywhere between 14.5 and 14.9 volts. However, when the battery is in a refresh phase, the voltage may occasionally reach up to 15.2 volts. These refresh phases are required when the battery charge status is 80% over long periods of time, which increases the risk of sulfation in the battery cells. The PCM simultaneously controls and monitors generator output. When the current consumption is high or the battery is discharged, the PCM raises engine speed as needed to increase generator output. The generator charges the battery and at the same time supplies power for all electrical loads.

The battery is more effectively charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM turns off the generator during cranking to reduce the generator load and improve cranking speed. Once the engine starts, the PCM slowly increases generator output to the desired voltage.

The PCM reports any charging system faults and sends a message through the HS-CAN to the BCM. The BCM then sends a message over the MS-CAN to the IPC, which controls the charging system warning indicator. The status of the PCM charging system warning indicator message can be confirmed by viewing the PCM Generator Fault Indicator Lamp (GENFIL) PID. Any charging system fault detected by the PCM results in 1 or more Diagnostic Trouble Codes (DTCs) being set and the GENFIL PID having a status of ON. If equipped with a charging system warning indicator, the IPC turns the indicator on or off. If equipped with a message center, the IPC displays the corresponding message to notify the driver of the condition.

Under certain circumstances, the charging system may have a concern but still keeps the battery charged while the vehicle is running. The LIN is normally used to initiate charging, but with a fault in this circuit the generator self-excites or begins charging on its own. The charging system warning indicator is illuminated and/or the corresponding message to notify the driver of the condition is displayed and the generator operates in a default mode (approximately 13.5 volts). This vehicle is equipped with an Electrical Energy Management system which manages battery charging and monitors the battery state of charge.

The Electrical Energy Management system also utilizes a load shed strategy to help control discharge of the battery and prevent, when possible, an excessively low battery state of charge. The BCM uses a battery monitoring sensor to monitor the battery state of charge.

The Generator current sensor and Battery current sensor serve as inputs to the Electrical Energy Management system software. If the sensors malfunction due to wiring issues or failure, a DTC will be set. In most cases the Electrical Energy Management system functions will be turned off until the sensor operation is restored. To maintain correct operation of the load shed system, any electrical devices or equipment must be grounded to the chassis ground and not the negative battery terminal. A connection to the negative battery terminal causes an inaccurate measurement of the battery state of charge and incorrect load shed system operation due to the current being used bypassing the battery monitoring sensor. Refer to the Battery Monitoring Sensor component description in this section.

Battery State of Charge: The battery monitoring system charges the battery current flow and voltage to determine the battery state of charge. During the drive cycle the battery monitorning system software monitors the charge and discharge current and increases the state of charge during charging, and decreasing it during discharge. During rest periods (key off with no electrical loads) when the vehicle enters sleep mode, the battery voltage is sampled to calibrate the state of charge.

The sensor automatically executes this calibration anytime the vehicle enters sleep mode and when the total vehicle current draw is below 400mA. It takes 4 to 6 hours in the sleep mode to calibrate the battery state of charge to high accuracy. If the system draw does not allow the battery state of charge calibration over the previous 7 to 10 days the state of charge quality factor changes to flag this and some battery monitoring system functions, which rely on the accuracy of the battery state of charge, may be temporarily turned off until a calibration takes place.
NOTE:Any devices left attached to the power socket that draw in excess of 200mA (or less depending on other battery loads), prevents a battery monitoring sensor from calibrating the battery state of charge.

 

Where did you mouint it? im looking at doing the same thing. Any advice I'd appreciate

 

My trailer batteries (sealed LiFePO4) are located in an inside compartment and there was room to locate the charge controller adjacent. You want to locate the charge controller as close to the batteries as possible. This particular controller also has an ignition trigger circuit which was not needed in this application and just I connected it to the incoming charge line so it turns on/off when trailer is connected to truck. FWIW I noticed that my F150 sends less current back than my older Explorer. In my Explorer I would get very close to 20 amps but with F150 it appears to be limited to about 15 amps. Still works so much better than just charge wire alone.

 

Sorry! can't delete

 

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Reading through the shop manual section seems not to address an external battery but only the on board battery.
Is there any other reference to a trailer battery?
We need to understand there is an Emg Trailer Brake Battery.
Charging inside a Trailer for utility use, is a different application that should require a separation between the truck battery and a remote battery where high currents are involved.
For example; if the truck battery is up to SOC and the remote needs a lot of current, how are the two handled?
One is charged the other needs charging so the truck battery is not overheated from being forced.
An AGM that is overcharge forced and overheats can blow it's cell seals from internal pressure build-up. This is very important in hot summer temps and camping/ towing times.
I would be very interested knowing how this is handled, if possible.
Up to this point, I would think the Utility Batteries need to be charged from a different source before the trip or at the destination from either commercial power of a Genset of some kind.
The trailer Brake Emg Battery also charged from another source so it does not require anything but float voltage applied that is almost no load on the truck system,
Thanks.

 

Same problem on a 2020 XLT. If I disconnect the current regulator on the ground post of the battery, will the battery be charged to full voltage?