Protecting Ourselves Against Discharged 12v Battery

[HPRifleman]

I have been looking forward to the C-Max ever since it has been announced. Now that they are showing up at local dealers I am ready to buy. But the reports of discharged 12v batteries are concerning. I rely on my car to start and operate on demand. I don't have the luxury of waiting around for someone to power up the 12v electrics if the car won't start.

 

The long term solution is certainly Ford's responsibility but I am looking for possible actions that can either monitor the battery voltage or keep it from over discharging. In other words, is there anything I can do to head off being stranded when I go out to my car in the morning to go to work?

 

For example, should I be monitoring the battery voltage every time I park? If so, what is the acceptable low-end for being able to start the electrical system? Does anyone know how quickly the battery goes from fully charged to that low-end state? Should I charge the battery from an external source periodically?

 

I would appreciate any comments from those of you who have tinkered with this problem.

[PWBarrett]

I too would like numbers from someone who has monitored the battery voltage all the way down to where it won't power up.  I may be mistaken but I think all we have are reports from after it gets in that state, of seeing something like 5-6V.

In lieu of that, I just make sure the car is shut down with the doors locked when I leave it, and keep one of these http://www.amazon.com/gp/product/B007KDFXNO/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1 in the back.

I haven't had to use it yet, but it sounds like just plugging it into the 12V port in the back for a few seconds would get things going again.

 

I also don't think that you get a representative sample of C-Max owners on a forum like this.  I suspect that the actual frequency of this problem is rather lower than it seems by reading here.

[Max Power]

If you have a battery drain with other accompanying symptoms, like a stuck clock or radio acting funny, the solution is to give the car back.

 

 

If you are in the other boat like I think I am, the solution is to monitor voltage.  I have a battery monitor that I plug in to an open 12V port. If I get around 12.0 then I put it on the charger.  A lead acid battery that reads 12.0V with no load and surface charge depleted, is fairly dead

A battery should read 12.6 and I get to maybe 12.3 by Friday after several short commutes, but a longer trip usually completely charges the battery.  If I didn't take a weekend trip, I'd put it back on the charger.

 

The device that PWB linked to should work perfectly if your battery is totally discharged.  You can only use it on the port in the cargo area.  The hatch won't open with a dead 12V, but you can still get to it through the back.  I'm not sure the back-seat door will open either, so I hope you are an acrobat.  If I was using that type, I would consider leaving the adapter plugged in without the battery part and route it somewhere over the back seat that you could easily snag it from the driver's seat.

Edited March 18, 2013 by Max Power

[ArizonaEnergi]

I put a voltmeter in the 12v outlet today and it read 12.0v.  I haven't had any problem in the month we have had it with the battery.  So I put my charger on it and it confirmed it was 12.0v and 75% charged, so I set it to charge at 8amp and in less than 10 minutes it said it was charged 100%.  The battery read 12.6v at that point.

 

We made a short trip after that, I charged the big battery, and now, six hours later, it reads 12.0v again.

 

First, does that short charging time make sense?  And second, am I on the road to a dead, really dead, battery?

[BobJustBob]

 

...And second, am I on the road to a dead, really dead, battery?

 

I can't answer that--I do not know the threshold voltage below which the C-Max won't start.  I have decided to add a weekly ritual to my routine and charge my battery every Friday night until Ford comes up with an effective solution to the battery problem.

[ArizonaEnergi]

I think I'm going to measure battery voltage every morning and post the results and see if others can post theirs too.  As a preview, I measured 12.0v this morning, and then started it with the voltage jumping to 14.3 for a few seconds then dropping to 13.8v while the engine ran.  After a minute I shut if off and it read 12.2v, but that may have just been temporary.  I also checked the final reading at the jumpstart connection with another voltmeter and it was the same.

 

A weekly charge may be a very good idea, especially as a test to see if the battery will hold it overnight!

Edited March 29, 2013 by ArizonaEnergi

[JAZ]

As I reported earlier, I've seen voltages from 12.7 to 12.1 several hours after shutdown.  If I open any doors or do anything inside the vehicle the voltage will drop further immediately after, but eventually creeps back up to about 12.3 or 12.4.   Also seems to gradually decline if the engine isn't operated for a few days.  No conclusion yet, but the dead battery problems seem to stem from some sort of parasitic drain.  Glad so many are posting their info also.

[Max Power]

If you are testing your battery, don't make the mistake that I did.(thanks Sparky)  You need to run off the surface charge before you make a measurement. After parking and turning the car off, turn your headlights on for 10 seconds and then turn them off.  Take a reading until it stabilizes.(Various power draws in the car will turn off in the first minute)

 

After fully topping off my battery a few weeks ago, I really don't notice that much parasitic drain.  At least not anything that shouldn't be replaced by the charge applied while driving.

 

IMO, the converter isn't letting enough charge out and the battery is just too small to be a buffer between the times you have high energy draws and when you don't.   I'm not sure this can be fixed with software.

[C-MAXER]

For accuracy, you need to take voltage reading at the battery not from a 12V line source which will contain line losses.   Scroll down to the yellow chart at this link for SOC (state of charge) readings (again taken at the battery):

 

http://www.emarineinc.com/pages/Batteries-101.html

 

IIRC, one of the choices in "My View" is voltage but you can't, of course, read it with the car off.

Edited March 30, 2013 by C-MAXER

[Sparky]

For accuracy, you need to take voltage reading at the battery not from a 12V line source which will contain line losses. 

The only way for a voltage test to be accurate is with the battery disconnected and after the surface charge is dissipated.  If you are testing with the car door open, the interior lights will cause a voltage drop.  If you test at the jumper cable connection points under the hood, after the car has been unused for several hours, you will get a fairly accurate state of charge. The cables extending from the jumper points to the battery are so large that voltage drop is insignificant.   Warning: Disconnecting the battery will cause loss of programming!

 

The most accurate method to determine the state of charge is by measuring the specific gravity of the electrolyte. This is done by removing a cell cap and withdrawing some solution with a hydrometer.  http://www.amazon.co...ds=E-Z Red S101

Edited March 30, 2013 by Sparky

[ArizonaEnergi]

Ran another set of voltage tests today.  Opening the door and measuring from the 12v outlet is not the optimum method because the various lights and electronics puts a fluctuating impact on the voltage.  Mine started out at 11.9 then went to 12.2 after 10 seconds, and the 11.9 when I opened the door again, finally stabilizing at 12.4v.

 

Measuring from the jump points under the hood is easier, and the calculation of any voltage drop to the battery at the rear of the car shows a 12.0 reading at the battery might be 11.98v under the hood, assuming 10AWG wire.  Close enough for the convenence. http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=12&phase=dc&noofconductor=1&distance=10&distanceunit=feet&amperes=1&x=62&y=13

 

I ran the car EV for 5 minutes and it showed a 14.5v charging voltage, so that seems to be working.  I then let it sit for an hour and the voltage returned to 12.4v.  So I put a battery charger on it which showed 12.5v and 75% charged.  After 10 minutes a 8amps it was fully charged according to the charger, but measuring it after 3 hours shows the voltage back down to 12.4.

 

So, while the battery has enough power to run the HV relay and start the car, it clearly is not maintaining a full charge.  When I take the car in next week for the NAV service bulletin fix, I will bring this up and have them check the battery and see about getting a new one.

Edited March 30, 2013 by ArizonaEnergi