Battery voltage above 15V?

[JohnnyBronco]

I‘m not sure that a 12V 100Ah LiFePO4 battery — popular for off-grid solar power systems and often used as a drop-in replacement for 12V lead acid batteries — is the correct baseline to use when talking about the Bronco’s OEM lead acid battery. According to that link, the LiFePO4 battery is fully charged at 14.6V (or 13.6V resting).

The Bronco’s OEM lead acid battery is a typical, “12V” car battery, but each cell is actually 2.1V, so a “12V” battery is actually fully charged at 12.6V.

The full operating range when the vehicle and charging system are both active is anywhere from 12.6V to just a little over 15.0V (i.e., the green range shown on the chart below).

This chart is listed on the BatteriesPlus Blog at the link below, which provides lots of useful information.

Source: How Do I Find The Voltage of My Car Battery

Good clarity added. What drivers need to understand is that the onboard voltmeter measures the instantaneous voltage of the entire system, not isolated terminal voltage. This of course includes the charging input. When engine is stopped at a light the voltage will drop since there is no charging, but when engine restarts voltage will increase to the alternator output level (minus any resistance voltage losses)

With the internal diode bypassed a vehicle alternator can put out over 100 volts and we have done so on farm tractors for years to run household tools in the field without an inverter. But 100 volts directly to a 12 volt battery would in short order boil off the electrolyte or otherwise fry the insides. That's why a practical limit of charging systems is somewhere around 15-16 only

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[Tonka Bronka]

Charging System

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 DTC's 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. 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 13.8 volts).

Hi Phil and Happy New Year! This is what's up. I have a 21 Badlands 2.3 MT that I am getting ready to pull an off grid overland trailer with. The RV dealer tells me that my trailer will require a 30 Amp charging feed from the Bronco battery to properly charge the two 100 Amp trailer batteries while towing, or parked if needed, because the 12v charge feed from the 7 pin plug is not adequate. He also tells me that it can be an issue if the vehicle is equipped with a smart alternator, but there is a work around part available if it does. I put a multi meter across the battery terminals and had 15.03v at startup, and an immediate drop to 14.94v, which is where it stayed for a 30 minute idle. It doesn't seem like it's doing anything that would limit trailer charging but from what I've read, it sounds like I do have a smart alternator. Can you shed any light on this or can anyone who reads this? Thanks!

 

[thesocalexplorer]

Hi Phil and Happy New Year! This is what's up. I have a 21 Badlands 2.3 MT that I am getting ready to pull an off grid overland trailer with. The RV dealer tells me that my trailer will require a 30 Amp charging feed from the Bronco battery to properly charge the two 100 Amp trailer batteries while towing, or parked if needed, because the 12v charge feed from the 7 pin plug is not adequate. He also tells me that it can be an issue if the vehicle is equipped with a smart alternator, but there is a work around part available if it does. I put a multi meter across the battery terminals and had 15.03v at startup, and an immediate drop to 14.94v, which is where it stayed for a 30 minute idle. It doesn't seem like it's doing anything that would limit trailer charging but from what I've read, it sounds like I do have a smart alternator. Can you shed any light on this or can anyone who reads this? Thanks!

From what I've read from the folks on the Ranger5g forums (link), if you unplug the BMS module from the negative battery terminal connector, the charging system would revert back to "old school" style charging. I was going crazy watching my battery voltage fluctuate until I learned more about the smart charging system as a whole.

 

[Tonka Bronka]

From what I've read from the folks on the Ranger5g forums (link), if you unplug the BMS module from the negative battery terminal connector, the charging system would revert back to "old school" style charging. I was going crazy watching my battery voltage fluctuate until I learned more about the smart charging system as a whole.

Interesting, thanks.

 

[Area51BS]

It bothered me at first until I realized they over complicated the charging system like everything else on new cars. Seeing these higher voltages change rapidly is normal now.

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