Charging Voltage Question

[DonImbimbo]

Regarding 2021 Badlands

I'm about to replace the second AGM battery on Wife's Badlands. The battery monitor I use shows the charging voltage between 14.95 and 15.01. This seems a bit high to me. I see the same numbers using my DVM.

In addition, the cranking voltage is usually below 9.5, yesterday it was 8.5 but still started.

The AGM specifications I have found say the upper limit for charging should be 14.8.

Do you think the charging voltage may be damaging the battery?

Current battery will be 2 years old next month.

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[alank2]

I would think an AGM would definitely last more than 2 years. I know there is a battery management system (BMS) forscan setting that controls or limits the state of charge, but I'm not sure if it actually adjusts the charging voltage or not or if it limits the current instead.

 

[DWG]

I don't think those numbers sound right for the AGM battery. Too high for charging voltage, especially in the summer and too low for cold start cranking. and the battery should last more than 2 years. Some more information:

Was your Badlands delivered with an EFB or AGM battery?
If originally an EFB battery was the BMS reset for the AGM battery?
Who installed the AGM battery? If you got the battery at the Ford Dealer, they should have reset the BMS for an AGM battery. it comes with a 3 year 36,000 mile warranty.
Did you have Ford recall 24S24 done which updated the BMS and PCM software?

If you set your dashboard messages to show auto start/stop status does it constantly show not working because vehicle is charging? Might be something wrong with the charging system. With my 24 badlands which is driven every day, the auto start/stop engages almost immediately when driving from a cold start in warm weather.
How many miles on your badlands?
If you have a meter that shows the State of Charge what does it say? Otherwise if you stop in to your Ford Dealer, the service writer can look up your Badlands in their computer and let you know what the current State of Charge is. From my own experience with my 20 Escape, the State of Charge needs to be at least 70% for the auto start/stop to engage. I would expect the Bronco Sport to be similar.

My Badlands was delivered with an EFB battery and needed to go back to the dealer when in the warm weather the auto start/stop was not engaging. Turned out the battery SOC was in the low 60's. The dealer replaced the battery with an AGM battery and have not had a battery issue since. Shortly after replacing the EFB battery there was a recall for some vehicles with EFB batteries to be replaced with the AGM battery because the EFB batteries were defective. When the dealer replaced the battery they reset the BSM for the AGM battery.

 

[DonImbimbo]

The Badlands was delivered with an AGM. I installed the replacement AGM two years ago, just as the recall was issued. The battery I installed is a Diehard AGM from Advanced Auto. The battery has a 4 year warranty so I assume there will be some discount if I buy another from Advanced. Not sure I will do that. I did the battery reset procedure when I changed it.

We have not had the 24S24 or the 25S26 done.

Auto Start/Stop seems to be disabled as we have not experienced the engine stopping at a stop light in years.

The Bronco has about 16,000 miles on it. Yep, Wife really piles on the miles, 3,000 per year.

The battery tester shows (after charging yesterday morning):

• 84% SOH (state of health)
• 100% SOC
• 4.4 mohm

I don't know if I can set the dash display for Auto Start/Stop or SOC. I'll have to look.

Wife does allot of short trips and every couple of weeks a long trip. But usually every few weeks I have to put the battery on a trickle charger or She will get dash message to turn ignition off or start the car to conserve battery.

 

[DWG]

I do not recall the exact path to get the auto start/stop status to display but I think it is my view menu. I think the fact that the auto start/stop has not worked in years and you have not disabled it indicates there might be something wrong with the BMS or charging system. Interesting that you show the SOC to be 100%. I thought the battery management system is supposed to not let the battery SOC go higher than 80%. Maybe that is because you did not have the recall done. I do not know what the max SOC was before the recall but the google search below indicates it was still 80%

I would be curious to know what the dealer shows for your SOC? Also I think you should have the BMS and auto start/stop systems checked by the dealer, something sounds off

From Google:
Before recall 24S24, the Body Control Module (BCM) software in affected Ford vehicles (such as the Bronco Sport and Maverick) was observed and discussed by owners in technical forums to target a maximum 12-volt battery state of charge (SOC) parameter around 80% (roughly 12.5V for AGM/EFB types) as part of its charging profile strategy, rather than pushing a full 100% continuous charge.

Recall 24S24 Overview

• • The Issue: The BCM and Powertrain Control Module (PCM) failed to detect or compensate for sudden 12-volt battery degradation.
  • The Symptoms: Low-speed engine stalling, failure to restart after auto start-stop events, and loss of 12-volt accessories like hazard lights.
  • The Fix: Ford issued a software recalibration via the Ford Owner Support portal or dealerships to improve SOC detection during drive cycles and adjust alternator thresholds

 

[DonImbimbo]

To add a couple of details,

Battery tester is a Motopower MP0515A. I don't know how it determines SOC. It might be purely based on current voltage. I think SOH is based on internal resistance.

Battery Monitor is a Ancel BM300 with Bluetooth support.

Yea, I think it is time to head to Ford., at least to check the charging voltage.

 

[DWG]

Don't forget to ask the Ford Dealer what the SOC is through their computer system. I would bet the number comes from the BS's BMS. I was not even aware of the fact that the car is constantly talking to Ford and a lot of items can be seen by the technician in their computer until recently. In the mean time I would still try and find the auto start/stop message screen. It will give you information like why it is not engaging like the vehicle is charging. If auto start/stop was operating normally and you do drive enough to charge the battery than if you are actually moving the message would say something like operating normally and once you stop it would say it was on. If it wasn't engaging while stopped it could give you a few different messages like system charging, outside temperature to hot or cold or operating temperature not reached yet if starting out from a cold start. I am paraphrasing so the messages will not read exactly as I am writing them here.

This is from page 103 in the 2021 owners manual.

PERSONALIZED SETTINGS
Select one of these options to display on your main screen.
Note: Some options could appear slightly different or not at all if the items are optional.
Select Screens

Calm Screen
Fuel Economy
Trip 1
Trip 2
Tire Pressure
Intelligent 4WD
Off Road
Trailer Light Check
Seatbelts
Auto StartStop
Now Playing

After making your selection:

1. Select a setting and press the OK button. This offers more information on the feature.

2. Select fuel economy, trip 1 or trip 2 to reset. Press and hold the OK button for a few seconds.

Fuel Economy
An Instant Fuel Economy gauge is provided along with average fuel economy. Average fuel economy is continuously averaged since the last reset.

 

[DonImbimbo]

Dave - Thanks for the extra info. I'll head out to the Sport this evening and poke around.

Don

 

[DonImbimbo]

Follow-up

Wife went on a longer distance shopping spree yesterday. This should have topped off the battery.

This morning I went out to the Sport to personalize the display for Auto Start/Stop. This took only a few minutes. Car was ib Accessory mode while doing this. The Auto Start/Stop displays in the upper left of the dash display.

I popped the hood to check battery voltage and also downloaded the voltage history from the monitor. Here's the interesting results.

At 9:15 AM the battery voltage was 12.55. Before I got into the Sport.
At 9:20 AM the voltage was 10.5 !!! after the display change and popping the hood.

Before the Wife went shopping yesterday I checked the charging voltage and it was well over 14 volts.

So my conclusion is the 2 year old Diehard AGM is really DEAD.

What else would explain this?

Additional info:
Put a 6 amp charger on the battery and in only 20 minutes the charge current is down to 2.5 amps and the battery voltage is at 14.5.

Sounds like one cell is dead.

 

[alank2]

Are you really digging the voltmeter probes into the posts? Sometimes oxidation can really affect the voltage, especially if you are seeing inconsistent readings. Also, how is the connection between the posts and the connectors on them?

 

[DonImbimbo]

The readings I just posted are from a battery monitor that is firmly attached to the battery terminals. This is the Ancel BM300. It records the battery voltage and you can download the history to their app on your phone. And I have cross checked their voltage readings with my DVM.

 

[DWG]

So are actually connecting to the negative terminal directly? It is my understanding the you should never connect to the negative battery terminal directly because the BMS sensor is there.

This from Google:

You should not connect a battery monitor or external charger directly to the negative terminal of a Ford Bronco Sport because it bypasses the vehicle's Battery Management System (BMS) sensor.

Why Bypassing the BMS Causes Issues

• • Inaccurate State of Charge: The Bronco Sport Owner's Manual specifies that the negative cable contains a sensor that tracks current flowing in and out of the battery. Connecting directly to the post hides charging or draining activity from the sensor.
  • Charging Errors: If the BMS cannot detect that the battery is being charged, the powertrain computer may assume the battery is still low. This can cause the alternator to overcharge the battery or constantly trigger battery-saver modes.
  • Start-Stop Malfunctions: The Auto Start-Stop system relies entirely on accurate data from the BMS sensor; incorrect readings will disable or glitch the feature.

Proper Connection Method

• • Connect the positive monitor/charger lead to the positive battery post.
  • Connect the negative lead to a designated chassis or engine ground point located past the BMS sensor (on the vehicle body or shock tower)

and this (not BS specific)

You should not connect external loads, chargers, or monitors directly to the negative battery terminal of a modern vehicle because it bypasses the factory Battery Current Sensor. [1, 2]

Why Bypassing the Sensor Causes Problems

• • Confuses the Computer: Modern vehicles use a Battery Management System (BMS) attached to the negative cable to track power usage and state of charge.
  • Misses Current Flow: Any accessory or charger wired straight to the battery post bypasses the sensor, meaning the car's computer cannot detect that power is being drawn or replenished.
  • Triggers Overcharging: The alternator relies on accurate data from this sensor; if it cannot read the discharge, it may assume the battery is always low and overcharge it, shortening its lifespan.
  • Breaks Start-Stop Systems: An unmonitored or damaged sensor disables the vehicle's automatic start-stop feature.
  • Risks Power Surges: Direct connections during high-current operations (like jump-starting or fast charging) can send a voltage surge that fries the delicate monitoring electronics

Could may be why your auto start/stop system stopped working and you are getting readings saying that your battery is charged 100% when the BMS will only let the battery charge to 80%?

 

[DonImbimbo]

I always connect the charger to the fender stud, which does not bypass the battery sensor.

 

[DWG]

Sorry, If I misunderstood what you ment when you said that your monitor was firmly attached to the battery terminals. Based on what I have read the monitor should not be attached directly to the negative terminal either.

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