Why Does 11.7V seem to be magic number?

[Bob The Builder]

I have noticed that 11.7V seems to be a trend for low voltage cutoff. Most OBD2 dash cam power supplies use 11.7 as their cutoff and Ford uses it, in my experience, for the battery saver mode in my Maverick. Readings base on a 12V power port volt/usb dongle.

Very confusing to me as back in my day a battery reading 11.7V is most likely on its way out and doubtful it will start the vehicle, yet here we are and my truck starts just fine even down to -24F this winter.

I guess I am a bit confused why Ford would allow the battery to drop this low while the truck sits not used for a few weeks.

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[sajohnson]

11.7 volts is very low:

 

[wavok]

In small scale solar applications using AGM storage batteries we were told (by the battery mfg) that 11.7/11.8 VDC is the low voltage cutoff. this was hard coded into off the shelf solar charge controllers. maybe your knowledge is based around old lead acid batteries?
I haven't had to think about this in over 15yrs FWIW.

 

[HeyBales]

Usually it's 12.1V when battery saver starts kicking in.

But who would notice lights normally on for what - 75 sec, going to 60 sec?
Not until you get around the 20 sec dropping to 15 during the dark winter might it be noticed, because you aren't settled upon entry.

11.7 is rather low - I'm living at 11.8 usually.

Have you measured voltage at powerport to see if the USB adapter is accurate?
I know - doesn't change much - it's too low.
And on your EB at that!

 

[Bob The Builder]

So, even solar charge controllers are hard coded at 11.7V. Interesting. This is something that has been bugging me since I got my Mav over two years ago why ford allows these batteries to drop so low. In the old days, a 20% charged battery at -24F spelled certain doom. Now? The Mav spins over like it's July 16, not Jan. 16.

 

[sajohnson]

The rule of thumb with FLA and AGM batteries is to not discharge them below 50% SOC.

It's not as if 48% SOC will kill a battery, but the greater the depth of discharge, the fewer cycles the battery will provide. This is just an example:

11.7V is 80% DoD.

 

[Darryl]

I was reading the battery saver strategy yesterday. I don't remember the particular numbers. But they have cutoffs for a running vehicle as well as for a sitting vehicle. And it's on a graduated scale. At certain voltage levels certain components go offline. And at the lowest level it goes into deep sleep mode where everything other than what's critical to the running or starting of the vehicle goes offline. Again, I don't remember the exact numbers. But at the lowest cutoff, the vehicle will usually still start unless the battery is simply toast. I've had several vehicle start that had dropped to 11.3- 11.5 volts (as measured by the vehicles computer) in my service bay .. I think the PCM and other modules critical to the running of the engine actually need only just above 10v to function.

 

[Cherokee]

My AGM was at 12.43 VDC.
I put my Genius on and charged at one amp for 18 hours, it peaked to green.
VDC was then rechecked.
It was now 12.23

One year old now, 13,000 miles, Ecoboost. Starts every time like it has a fully charged battery. Never seen a low volt mode.
Often sits two or three days. Sat two weeks when new. No sign of VDC dropping at all.
I think my BMS is retarded. I’m not gonna reset anything.

Go figure.

 

[Darryl]

My AGM was at 12.43 VDC.
I put my Genius on and charged at one amp for 18 hours, it peaked to green.
VDC was then rechecked.
It was now 12.23

One year old now, 13,000 miles, Ecoboost. Starts every time like it has a fully charged battery. Never seen a low volt mode.
Often sits two or three days. Sat two weeks when new. No sign of VDC dropping at all.
I think my BMS is retarded. I’m not gonna reset anything.

Go figure.

My general practice is if no warning notifications come on, all is well. No need to reset anything unless a battery is replaced. If a battery is replaced, reset it. Sometimes nothing unusual will happen if you don't. But sometimes it will. So just reset it if the battery is replaced. Also, If you receive a warning and you believe you have a good battery, then that's when I recommend doing a BMS reset. It's fixed Numerous issues where the vehicle gives a low battery warning. Is the BMS retarded? Maybe. But if resetting it fixes an issue, do it. If nothing is wrong, don't worry about it.

 

[Bob The Builder]

The rule of thumb with FLA and AGM batteries is to not discharge them below 50% SOC.

It's not as if 48% SOC will kill a battery, but the greater the depth of discharge, the fewer cycles the battery will provide. This is just an example:

11.7V is 80% DoD.

Very good info. Yet here I am, a battery replaced under warranty two years ago due to the fact the A.S.S. was not working (not that I liked it, but perceived it as a barometer that something was not right.) When signing out at the dealership they tell me I need to drive the truck more. They told me the vehicle was not being driven enough to charge the system. I told them I had never heard of such a thing and never needed to do it before on any of my vehicles. In other words, what a crock of shit.

Anyhoo, I perceive this as a lost cause issue basically. It's obvious there is something not right in all this, yet the truck starts every time even in adverse conditions. So.....I will continue to carry a jump starter with me that fortunately I have not needed except to help someone else.

 

[sajohnson]

I was reading the battery saver strategy yesterday. I don't remember the particular numbers. But they have cutoffs for a running vehicle as well as for a sitting vehicle. And it's on a graduated scale. At certain voltage levels certain components go offline. And at the lowest level it goes into deep sleep mode where everything other than what's critical to the running or starting of the vehicle goes offline. Again, I don't remember the exact numbers. But at the lowest cutoff, the vehicle will usually still start unless the battery is simply toast. I've had several vehicle start that had dropped to 11.3- 11.5 volts (as measured by the vehicles computer) in my service bay .. I think the PCM and other modules critical to the running of the engine actually need only just above 10v to function.

I'm surprised that a battery at 11.3 > 11.5V could start an engine. That's basically dead -- 0% SOC. Maybe the measurement was off, or perhaps the battery was under load when the measurement was taken?

Regardless, deep discharges will severely limit the number of cycles the battery is capable of.

Ideally there would be no load on the battery when the ignition is off. That used to be the case. I realize that is no longer possible, but Ford (and other mfrs) have designed their vehicles such that the load is much greater than it needs to be -- only shutting some of them down after the battery is significantly discharged.

I wonder how the design would differ if the battery was covered under the a long term mfr warranty?

I continue to put a Battery Tender (BT) on ours.

 

[Darryl]

I'm surprised that a battery at 11.3 > 11.5V could start an engine. That's basically dead -- 0% SOC. Maybe the measurement was off, or perhaps the battery was under load when the measurement was taken?

Regardless, deep discharges will severely limit the number of cycles the battery is capable of.

Ideally there would be no load on the battery when the ignition is off. That used to be the case. I realize that is no longer possible, but Ford (and other mfrs) have designed their vehicles such that the load is much greater than it needs to be -- only shutting some of them down after the battery is significantly discharged.

I wonder how the design would differ if the battery was covered under the a long term mfr warranty?

I continue to put a Battery Tender (BT) on ours.

Did you have the SSM done where they update the Air compressor control module? (ACCM) , the combination of reprogramming that module, putting a full charge on the battery (especially if it's been discharged repeatedly, and resetting the BLM. This combination has corrected the battery drain issue on most vehicles. By the way, the acceptable parasitic draw is very low. It's. 50 milliamps . At that rate it will take a fully charged battery over a month to discharge. At minimum it will take 2 weeks before anything goes into protection mode. And even though the acceptable standard is 50 mA, it's typically closer to 30mA. So these modules are not pulling a large draw. And every low voltage reading is not equal sometimes there is sufficient current to start a vehicle if the battery is otherwise good.

 

[sajohnson]

Did you have the SSM done where they update the Air compressor control module? (ACCM) , the combination of reprogramming that module, putting a full charge on the battery (especially if it's been discharged repeatedly, and resetting the BLM. This combination has corrected the battery drain issue on most vehicles. By the way, the acceptable parasitic draw is very low. It's. 50 milliamps . At that rate it will take a fully charged battery over a month to discharge. At minimum it will take 2 weeks before anything goes into protection mode. And even though the acceptable standard is 50 mA, it's typically closer to 30mA. So these modules are not pulling a large draw. And every low voltage reading is not equal sometimes there is sufficient current to start a vehicle if the battery is otherwise good.

First I should point out that we have a 2022 BS Badlands. In addition to the BS forum I belong to the Maverick forum since some issues are the same or similar.

50 mA is reasonable. The question is, why do many Maverick and Bronco Sport owners report that the system goes into 'battery saver' and 'deep sleep' mode so frequently?

Is the initial draw, prior to 'battery saver' greater than 50 mA?

We've had zero problems, I'm just curious.

 

[Darryl]

First I should point out that we have a 2022 BS Badlands. In addition to the BS forum I belong to the Maverick forum since some issues are the same or similar.

50 mA is reasonable. The question is, why do many Maverick and Bronco Sport owners report that the system goes into 'battery saver' and 'deep sleep' mode so frequently?

Is the initial draw, prior to 'battery saver' greater than 50 mA?

We've had zero problems, I'm just curious.

In the case of the Maverick hybrid in particular, there was and is a problem where some have an excessive drain. Ford is aware and still working on it although they had an update that fixes the problem for most of them. As for the bronco Sport, many were initially equipped with weak batteries that allowed the battery life monitor to get out of whack. In some cases the battery was replaced WITHOUT resetting the battery monitor. In either case, performing a battery monitor reset has taken care of the problem for the vast. Vast majority of them.
By the way. The drain should settle down to 50mA within a few minutes of shutting off the vehicle. Ford tells us to give it 90 minutes. But in reality it usually only takes about 15 minutes. I've noticed that upon shutoff, it may pull several amps until all interior and exterior lights shut off. The next phase may be around 1 amp for a couple of minutes. Then maybe 100 mA before gradually dropping to the 5mA level

 

[sajohnson]

What caught my eye initially was that the OP, Butch, wrote:

"I have noticed that 11.7V seems to be a trend for low voltage cutoff. Most OBD2 dash cam power supplies use 11.7 as their cutoff and Ford uses it, in my experience, for the battery saver mode in my Maverick. Readings base on a 12V power port volt/usb dongle."

His readings may be off some, but even cheap 12V power port plug-in meters are fairly accurate (maybe +/- 0.2V).

Batteries should be kept at 12.4V or higher to avoid sulfation:
https://www.power-sonic.com/what-is-a-sulfated-battery-and-how-do-you-prevent-it/

The further below 12.4V, the greater the risk of sulfation. So levels like 11.7V are concerning.

I'm gonna keep using the Battery Tender (BT) rather than rely on 'battery saver mode.'.

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