Intermittent Battery Drain

[Cobraracer79]

I have been having intermittent dead battery issue. I have no after market accessories, there is about 6500 miles on it. Checked a lot of the threads but did not see anything kit this.

My car does sit for long periods and has gone in to deep sleep mode before, but I was still able to start it even after some time had past.
Recently it had sat a couple days since I had it out and was dead when I went to start it. Placed it on the charger in the morning. When I got home it was charged and the battery had 13.4 volts. I then drove 100 miles stopped for a few hours and then parked it about 8:00 PM. The next morning it was dead and I had a deep sleep activation notice about 4:15 AM. Out of town so I replaced the battery and went to my event the next morning it started, went to my event and then drove home. The next morning it was dead again and I had a deep sleep notice. Charged it up again and left for work, got home in the evening and the battery voltage was 13 volts, the next morning deep sleep alert and battery voltage was 7.2, when I got home from work it was down to 2 volts. Charged it up again and now 24 hours later it is 12.8 volts and no low battery alerts.
Testing was done with a voltmeter, not using the car gauge.

Something in the car seems to be cycling on and off, nothing plugged in to the 12 volt outlets. Even checked the trunk light to make sure it went off.

Taking it in to Ford, but still trying to figure out what it could be????? Looking for ideas.

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[GT Pony]

The battery has been fully discharged enough times to probably damage it to some degree. Might want to get a new battery after trouble-shooting to make sure the system is OK. Only way you could tell what's going on would be to monitor the current draw over a long period of time to see if it goes up/down over time for some reason. It shouldn't go up once the car has went into "sleep mode".

 

[khsonic03]

I have been having intermittent dead battery issue. I have no after market accessories, there is about 6500 miles on it. Checked a lot of the threads but did not see anything kit this.

My car does sit for long periods and has gone in to deep sleep mode before, but I was still able to start it even after some time had past.
Recently it had sat a couple days since I had it out and was dead when I went to start it. Placed it on the charger in the morning. When I got home it was charged and the battery had 13.4 volts. I then drove 100 miles stopped for a few hours and then parked it about 8:00 PM. The next morning it was dead and I had a deep sleep activation notice about 4:15 AM. Out of town so I replaced the battery and went to my event the next morning it started, went to my event and then drove home. The next morning it was dead again and I had a deep sleep notice. Charged it up again and left for work, got home in the evening and the battery voltage was 13 volts, the next morning deep sleep alert and battery voltage was 7.2, when I got home from work it was down to 2 volts. Charged it up again and now 24 hours later it is 12.8 volts and no low battery alerts.
Testing was done with a voltmeter, not using the car gauge.

Something in the car seems to be cycling on and off, nothing plugged in to the 12 volt outlets. Even checked the trunk light to make sure it went off.

Taking it in to Ford, but still trying to figure out what it could be????? Looking for ideas.

I had a similar issue with my 2017 GT that I bought earlier this year with 100 miles. Obviously, it hadn't been driven or probably even started much for the first 2 years of its life. Once I got it and was driving it a couple times a week, I would occasionally come out to a dead battery. No rhyme or reason and it was all stock.

Brought it to the dealer and they couldn't find anything wrong with it. They replaced the battery on a whim and it has been fine since then (about a month). Not holding my breath, but it was definitely strange. I figure maybe I had a bad cell in the battery or some sulfation from not being driven enough.

I researched a lot and the closest thing I could find was people who had the enhanced security package seemed to be the ones who had similar issues. Do you have that package?

 

[Zinc03svt]

Take a look at the Battery Management System thread. I actually unplugged mine because it was varying the voltage from 12.1-14 all the time. Now it just sits @ 14.1-14.4. Fyi.

 

[GT Pony]

Take a look at the Battery Management System thread. I actually unplugged mine because it was varying the voltage from 12.1-14 all the time. Now it just sits @ 14.1-14.4. Fyi.

The voltage varying is how the system is supposed to behave. It cuts voltage down when the battery is fully charged, just like a "smart charger" does. Charging it constantly at 14.1-14.4 volts will most likely be over charging.

 

[Zinc03svt]

The voltage varying is how the system is supposed to behave. It cuts voltage down when the battery is fully charged, just like a "smart charger" does. Charging it constantly at 14.1-14.4 volts will most likely be over charging.

I do not seem to be having any issues with over charging. Thank you though.

 

[GT Pony]

I do not seem to be having any issues with over charging. Thank you though.

Give it time.

 

[Zinc03svt]

Give it time.

I have actually 3 different times after driving the car hooked it up on my 8amp charger/tender. Every time it took a charge for 30-1 hour before switching over to maintenance mode.

 

[GT Pony]

I have actually 3 different times after driving the car hooked it up on my 8amp charger/tender. Every time it took a charge for 30-1 hour before switching over to maintenance mode.

If it took 30~31 hours to get the battery charged and into maintenance mode, then there's something wrong with the battery or the charger.

I've put a Battery Tender (only puts out 1.25 amps) on my battery after the car sits for 2 weeks and it only takes 11~12 hours to hit fully charged maintenance mode.

 

[Zinc03svt]

If it took 30~31 hours to get the battery charged and into maintenance mode, then there's something wrong with the battery or the charger.

I've put a Battery Tender (only puts out 1.25 amps) on my battery after the car sits for 2 weeks and it only takes 11~12 hours to hit fully charged maintenance mode.

30 minutes to 1 hour tops. Reread.

 

[GT Pony]

30 minutes to 1 hour tops. Reread.

Maybe re-word would be better.

 

[Zinc03svt]

Maybe re-word would be better.

I re-plugged it back in (BMS) and took a drive with multiple stops to run a few errands. The voltage was still reading the same between 14.1 to 14.6. I’m not going to sweat it. ;).

 

[GT Pony]

I re-plugged it back in (BMS) and took a drive with multiple stops. The voltage was still reading the same between 14.1 to 14.6. I’m not going to sweat it. ;).

From what I've seen on my GT, the charge voltage will stay high until the car is driven for quite awhile. I've seen the voltage readout on the dash drop down to as low as 12.7 volts at idle. Then if I revved the engine to 2000 RPM in neutral the voltage would rise to 13.2 volts, then back to 12.7 at idle. I've also seen the voltage remain at around 14 volts at idle after some drives. The "smart charging" system seems pretty complicated, and may be using sensor data to control charge voltage.

I also think that if the battery is going bad (higher internal resistance) that the charge voltage will always stay high (14+ volts) to try and keep a weak battery fully charged.

 

[Zinc03svt]

From what I've seen on my GT, the charge voltage will stay high until the car is driven for quite awhile. I've seen the voltage readout on the dash drop down to as low as 12.7 volts at idle. Then if I revved the engine to 2000 RPM in neutral the voltage would rise to 13.2 volts, then back to 12.7 at idle. I've also seen the voltage remain at around 14 volts at idle after some drives. The "smart charging" system seems pretty complicated, and may be using sensor data to control charge voltage.

I also think that if the battery is going bad (higher internal resistance) that the charge voltage will always stay high (14+ volts) to try and keep a weak battery fully charged.

Well, when I was in for warranty work late May for idle issues I had them check the battery. It was all over the place on voltage 12.1-14.9. They said it was good? After I unplugged the bms the voltage immediately started staying up. Maybe the battery is going bad? Car was built in May last year.

 

[ugstang17]

Looks like OP took it to Ford and had it resolved.

For a car battery to be fully discharged from a complete charge in 24 hours it would need to see a minimum of 2.08A current draw for that period of time to be completely flat. It would likely not be able to turn over the engine to start at that rate within 16 hours. This is based on the battery being on the high side of an average car battery which is 50 aH. Most car batteries are 45-50aH storage capacity. Not to be confused with CCA or CA which is an instantaneous rating. A 50 aH battery can produce 50 amps at rated voltage for 1 hour. That means that the battery fully charged could produce 650 amps (CA) for up to 4 minutes before being fully discharged. However the internals and posts need to be capable of handling that current level as well...which most car batteries can but not for 4 continuous minutes.

Current draw will determine if the battery is seeing parasitic loss at a high enough level to drain the battery in that period of time or if the alternator is actually failing and not keeping up with the system. Current draw up to 10A can be measured by most multimeters. Beyond that you need a DC amp clamp or a shunt to put in line that will allow a voltage measurement to be made across it to then calculate current draw.

Don't be fooled by the size of a car battery. A 50aH battery at 12vdc can weld. At 650 amps of current over a 4 minute duration at 12vdc it can generate continuously 7800 watts of power (E*I=P(watts) ). Think how quickly a 60 watt bulb can burn your fingers after being on for just 30 seconds. Then multiply that by 130 times.

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