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12 v battery charging


Jack Schmidling
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  • 2 months later...

Per page 121 of the 2014 CMAX Hybrid manual, the 12V power points stay powered and will discharge the battery if the engine is not running. There is no mention of power shutoff after a number of minutes. That's why I'm looking to hardwire my dashcam to a switched fuse on the fusebox.

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Per page 121 of the 2014 CMAX Hybrid manual, the 12V power points stay powered and will discharge the battery if the engine is not running. There is no mention of power shutoff after a number of minutes. That's why I'm looking to hardwire my dashcam to a switched fuse on the fusebox.

The cigar lighter Power Points (center console and center storage compartment) are controlled by the interior light relay on the BCM.  The 12V power outlet in the rear luggage area is hot all the time.

 

I've never tried this but supposedly the BCM has a timer (battery saver feature) for the demand lamps that is set for 30 minutes.  So, the cigar lighters should go off after 30 minutes.  See Service Manual excerpts below.

 

"The demand lamps subsystem consists of:

  • Interior lamps (map lamps)
  • Vanity mirror lamps
  • Luggage compartment lamp
  • BCM

The demand lamps provide illumination to specific areas within the vehicle when needed.

 

The BCM energizes the interior light relay to supply voltage to the demand lamps when the battery saver feature is not active. ...

 

When 10 minutes (30 minutes for demand lamps) have elapsed, the BCM automatically shuts off voltage to the lamps. The timer restarts (voltage is restored if the BCM is in battery saver mode) if:

  • the ignition transitions out of OFF.
  • any door or liftgate/luggage compartment lid becomes ajar.
  • the UNLOCK button of the RKE transmitter is pressed.
  • a door is unlocked using a key.
  • the door lock switch is pressed."  - Service Manual 
Edited by Plus 3 Golfer
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  • 1 year later...

I just want to take a moment to acknowledge this forum... particularly this thread... and say that this is a perfect example of what makes these kinds of discussion groups so valuable. Serious props to all who posted on this topic... I learned a tremendous amount about our newly acquired 2016 C-MaxE... which had the dead battery issue right after leaving the dealer floor... classic.  Popped a charger on the terminals (after suspecting the FOB batteries were the fault) and away we went back to the dealer.  Not necessarily "happy" about it... but knowledge is everything... and you all provided a TON of it... thanks!

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  • 3 weeks later...

Rather than starting a nw thread I am going to post my issue here since it obviously related.

 

I have not had an issue with my cmax starting. What happened was that I was looking at the battery for other reasons and I noticed some corrosion/sulfide on the negative battery terminal. Since the battery is exposed to the cabin I didn't like the idea of breathing in sulfide. So I measured the battery with a multimeter and it read slightly less than 12V. So I then used Forscan to check the battery. The charging voltage was reading 14.5V but the SOC was only 20%. I also notice a few fault codes saying that some of the modules had experienced a low voltage condition.

 

So I decided to keep an eye on it. A few weeks later I noticed that the SOC charge was reading zero but the car was still starting. Odd. Given that Forscan is reporting the life of battery at 61 months I decided to take it to the dealer and stick in a new battery. However, the battery test at the dealer came back with a low battery (12V) but that battery health was good. So I had them charge the battery back up an hour and their equipment showed a battery with 13.3 volts. I then went back to the car and before driving off looked at the data in Forscan. Weirdly, Forscan is still showing the 12V battery SOC as zero.

 

So I am not sure what to think now. Forscan's readings do not jibe in any way with independent dealer testing, making me wonder about the reliability of that software. Also, I don't understand why the battery accepted a full charge from the dealer's equipment but the cmax itself is unable to recharge the battery to full health even with the proper charging voltage.    

 

Does anyone have any thoughts, insight, theories as to what might be going on here?

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The 61 months is the HVB age. The 12 V battery age is in days. A fully charged battery will not read 13.3 V. 100% SOC will yield around 12.6 - 12.7 volts open circuit after the battery sets for an hour or so. The dealer did not (cannot ) fully charge the battery in one hour.  Also, if the 12 V BXT67R battery is 61 months old (assume the original battery and virtually the same age as the HVB), I would expect a 5+ year old battery to have lost a significant portion of its new rating of 43 Ah. Actual SOC is measured based on the 43 Ah new battery rating. 

Also, I believe by definition 10.5 V = 0% SOC (although I don't know what Ford uses) even though there is likely sufficient charge at 10.5 V to start the C-Max because there is no starter as in a conventional car. All that needs powered up are the control modules. Look at this discharge curve link. When you measure you battery voltage there is current drain on the battery. Opening the door will cause a spike in the current as modules become active. So, when reading the curve, I'd look at the C/100 to C/20 curve. Your voltage reading of a little less than 12 V between those curves would likely correspond to a SOC between around 10-20%.

 

With respect to the low battery voltage trouble codes, 10.5 V is the general trigger to set a DTC for low battery voltage in a module even though modules can and do operate below 10.5 V.  

The 12 V Battery Monitoring System uses a BMS sensor to measure current into and out of the 12 V battery and the algorithm integrates the current (coulomb counting) over time for several operating states. Basically the accumulated difference in Ah into and Ah out of the battery is an estimate of the loss es of the 12 V battery capacity. So the BMS (nothing to do with ForScan), has accumulated battery losses based on the original new battery and the aged battery of over 1800 days.

Did the dealer remove the battery to test and charge? My guess is yes as the procedure is to inspect the battery terminals, wiring and so forth before charging and running the discharge test requires disconnecting the battery cables from the battery terminals to determine battery health.   If so, the BMS algorithm did not record the charging current or Ah of charge the dealer put in. I believe that most BMS periodically, gradually adjusts the SOC estimation from the coulomb counting based on voltage checks to account for estimation drift. So, the adjustment will likely be in small increments over a longer period of time.

Thus, as I've said many times, the PCM then use these losses in establishing the charging regime. Hence, unless you drive for hours at a time, the SOC will continue to fall from the 20% reading after the external charging. I've documented exactly what your are seeing. I have never seen the PCM provide an initial set point charging voltage above 14.8 V. The PCM will then continually lower the set point voltage as the SOC increases to what the PCM estimates is the current maximum Ah capacity. So, because the internal resistance of an aged battery is higher than a new battery, there will be less charging current at these voltages. Also, one does not want to subject a lead acid battery to continual overcharging by applying higher voltages say 15.5V to "force" more current into the battery to increase SOC faster.

Bottom line: there is nothing wrong with what you are experiencing. It is normal as the battery ages. What is important though is that when a new battery is put in that the BMS be reset. ForScan can reset the BMS which zeros out the battery age and the accumulated losses. So, the PCM now assumes the Ah capacity of the 12 V battery is at 43 Ah.

Edited by Plus 3 Golfer
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Double post, sorry about that, but I'd like a response ASAP.

 

2013 Cmax, 100k miles. 3rd OEM 12V battery replacement in Sept...6 weeks ago...(battery #4)

 

College student car, max length drive time 1 hour, probably twice a week, otherwise very few short trips.

 

Entertainment system fail (again). Decided to put the battery on a BatteryTenderPlus, 1.25amp.

 

18 hours of charging, battery STILL not charged to 80%.

 

We're losing faith in this car, which has otherwise been flawless. We're keeping a lithium battery charger in the car, haven't needed to use it yet.

 

What can my son do differently to keep this battery charged???

Edited by pianewman
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A new C-Max BXT67R battery is rated at 43 Ah.

 

18 h * 1.25 A = 22.5 Ah input from tender at battery terminals.

 

Assume 50 mA normal battery drain. Ah drain = 18 h * 0.05 = 0.9 Ah

 

Assume Battery efficiency = 85%. Ah battery charge capacity increase = 85% * (22.5 - 0.9) = 18.4 Ah .

 

SOC increase = 18.4/43 = 42%

 

So, by putting the battery on the 1.25 A tender for 18 hours, the SOC should have increased by around 42%. What if your battery drain is 10 times the 50 mA drain or 0.5 A. The SOC increase will be significantly less. The tender would only be putting 0.75 A into the battery and the SOC would only increase by 27%.

 

My guess is that you’ve got a large battery drain in the APIM or other modules associated with the entertainment system. Perhaps have your son pull the fuses associated with the system when he shuts the car off. There are probably several that could pulled including Fuse 79 under the glove box.

Edited by Plus 3 Golfer
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  • 2 months later...

It seems that lots of folks have dead 12 volt battery issues that occur after something unusual happens with the radio, particularly with the radio not shutting off when you open the door.  We have found that this happens most often in cold weather.  Hmmm.  Could there be a connection between cold weather, opening the door, and dead 12 volt batteries???

Well, I think so.  As it turns out there is a push-switch located under the door latch inside the door.  Check this video out https://www.youtube.com/watch?v=HyTFsi809Hs

It shows the switch and describes what happens when the switch sticks.

I checked with Ford and unfortunately they do not sell just the switch.  You get to buy an entire door latch just to get the switch so the cost of the switch (without considering the labor to install it) is ~ $140. 

Some folks apparently have had success by spraying WD-40 in the lock to free up the switch.  That's what we are trying.

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On 1/20/2020 at 9:26 AM, TwoFeetDown said:

It seems that lots of folks have dead 12 volt battery issues that occur after something unusual happens with the radio, particularly with the radio not shutting off when you open the door.  We have found that this happens most often in cold weather.  Hmmm.  Could there be a connection between cold weather, opening the door, and dead 12 volt batteries???

Well, I think so.  As it turns out there is a push-switch located under the door latch inside the door.  Check this video out https://www.youtube.com/watch?v=HyTFsi809Hs

It shows the switch and describes what happens when the switch sticks.

I checked with Ford and unfortunately they do not sell just the switch.  You get to buy an entire door latch just to get the switch so the cost of the switch (without considering the labor to install it) is ~ $140. 

Some folks apparently have had success by spraying WD-40 in the lock to free up the switch.  That's what we are trying.

I don't believe the switch is involved in the radio not shutting off.  The BCM shuts down the radio after no more than 10 minutes (assuming it was left on) after car is turned off whether the door is opened or not.  A bad switch could keep the BCM (and perhaps other modules from going into "sleep" mode.  With a weak battery, it's possible that one could get a dead battery from the drain of modules not going to sleep after a few days or so. 

 

But, if switch is stuck open, the door will show ajar on the display when starting up.  If switch is stuck closed when entering vehicles, dash and lights should not come on. Thus, an owner should know something is amiss and the problem is easily diagnosed.  AFAIK, there has not been a TSB on the this issue (stuck door ajar switch) for the C-Max.  So, I highly doubt this is the cause of the many 12 V dead battery issue that some owners have had . If it were, Ford would have issued a TSB.

Edited by Plus 3 Golfer
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There are various 12v battery drain issues on the C-max.  I also had problems and had a heck of a time getting info on the issues.  Most dealerships and techs are not familiar with these cars and rarely if ever have tried to tackle these problems.  There can be chafed wires near the trunk and a couple of other areas that can cause the battery drain.  Mine happened to be the 12v water pump and 12v vacuum pump connectors.  They would get water in them and, since there is a constant 12v supply at the pumps, cause them to run when the HVB was charging.  After replacing the water pump, connector pigtail and re-splicing the vacuum pump wires, I have had no problems.  Let me know if you're interested in info on checking some of these items.

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51 minutes ago, JackSprat said:

There are various 12v battery drain issues on the C-max.  I also had problems and had a heck of a time getting info on the issues.  Most dealerships and techs are not familiar with these cars and rarely if ever have tried to tackle these problems.  There can be chafed wires near the trunk and a couple of other areas that can cause the battery drain.  Mine happened to be the 12v water pump and 12v vacuum pump connectors.  They would get water in them and, since there is a constant 12v supply at the pumps, cause them to run when the HVB was charging.  After replacing the water pump, connector pigtail and re-splicing the vacuum pump wires, I have had no problems.  Let me know if you're interested in info on checking some of these items.

Below is a thread and my post on connector water issue.  Ford techs should have know about this issue in 2013.  IRRC, there was a TSB / SSM on water in connectors.

 

 

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This has been interesting. I drove my 2013 CMax yesterday (in the rain) and this afternoon I had to jump start it - for the first time ever.  It still has the original battery, so I will replace that (I think I've gotten my money's worth on that).  Haven't been on this site in maybe 3 years. Glad to know I can still find answers to questions I never knew I had!

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jack up and support front.  get the bottom covers off.  Water pump is easy to find as it’s just a 12v electric pump bolted to bottom of engine.  Find it’s connector and check it inside for corrosion.  Also where same water pump and the 12v vacuum pump have a 4-way shared connector further up the harness.

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  • 8 months later...
On 1/6/2018 at 11:10 AM, Jack Schmidling said:

I have had a 2014 Cmax for about two week and yesterday the battery was dead and had it jumped and then got into this battery mess.

 

  We typically use the car only to go shopping once a week with an occasional run in between.  Was buying this car a bad idea?

 

My real question is based on the words of the guy who came out to jump it.  Something like, let it run for 45 minutes before driving or turning it off.  Sounded reasonable.

 

After about 15 minutes I went out to find nothing running but blowers for the heater it seems obvious that this is no way to charge a battery.

 

Which one of us is wrong?

 

He also said  not to connect a 12 v charger to terminals under the hood but to go directly to the battery in the trunk.  This seems grossly inconvenient and his reason didn't make much sense because he didn't do a very good job of explaining why.

 

It also occurred to me that I might charge it through the 12 v lighter jack in the cab.but I measured 0 volts when I went out to check it with a DVM.

 

Nuff for now.  Any help?

 

js

 

 

 

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