12 volt battery losing charge

[vonoretn]

At 85000 miles now, the car sat in our garage 4 days and wouldn't start.  The 12 volt battery read 8.5 volts.  I charged the 12 volt battery, my charger has voltage and % charged readings.  It took a hour to charge it to 100%  Vehicle started, drove it, restarted twice, once after gasing it and once after 30 minute in grocery.  I located the battery in the back of the car and gave it my 100 amp voltage drop test.  It dropped to 10.3 volts.  That would be my lower limit for a normal car, but this battery doesn't have to do much,  like start the car, since that's done by the high voltage battery.  Anyway, it keeps losing % charge and the voltage drops from like 12.8 to 12.1 just sitting there.  And the percent charge drops to 50% just sitting there.  Yes it could be the battery, but how do I know there is not something draining it, like an improper load of some type?   No engine warning lights. 

 

My 2010 Ford Fusion hybrid made it to 112K miles before I had to get a new 12 volt battery. 

Edited February 24, 2021 by vonoretn
added info

[fbov]

With 12v batteries, it's time, not mileage. Hotter climates kill lead-acid batteries sooner. I live near Lake Ontario, and my 10/2012-built C-Max made it to trade-in last January with no odd problems beyond the radio/fuse thing. Conversely, the procedures for BDCM reset are on the forum, so it's an easy replacement. 

[vonoretn]

Good job Fbov, 8 years on your 12 volt battery.  I took the car to the dealer today, and they gave it all their tests, and said it was fine.  Well of course it was fine, it had just been charged for 25 minutes driving to the dealer, and the C-max charge voltage is 14.5 volts.  I don't think they did an engine off battery drain test however, because it would probably only take 100 ma or so, to drain the voltage down to 8.5 volts over 4 days.  But the dealer cost for a new battery is $144, so I decided to just keep an eye on it, if the voltage goes under 12, I will charge it ahead of time before going anywhere.  The dealer in Sweetwater Tn. charged me nothing for their battery test. 

[plus 3 golfer]

So what size charger do you have? If your battery has 0% SOC <= 10.5 V by definition (8.5V) and if you charged for one hour and SOC = 100% as you say, then the charger had to put out 43 A for one hour.  100% SOC = 43 Ah for the BXT67R Motorcraft battery.  Because your battery is around 5 years old (2015 MY?), it’s maximum capacity will be less than 43 Ah.  You got 12.1 V after allowing surface charge to drain which is a maximum SOC of around 30% +- maybe 10% depending on load on battery when you checked voltage.  This would mean that if you charged for one hour you likely added between 8 - 16 Ah of capacity (8-16 A charger) to your battery.  IMO, this is normal for a 5 year old battery. See attached discharge curve.  C = 43 Ah, so the C /20 discharge curve is likely the one to use when measuring battery voltage.  Just opening doors activates modules and puts load on battery.

 

Driving the C-Max adds little to the SOC of the battery.  In 25 minutes of driving you will likely add less than 2 Ah and more than likely around 1 Ah. So, best case is you might have increased SOC around 5%.  Normal car off battery drain should be less than 50 mA.  So if car is off for four days,  normal max. drain would be around (96 h x 0.050 A) = 4.8 Ah (should be less unless there is a parasitic drain).  I believe around 30 mA would be typical.  Thus, the four day Ah drain would be around 3 Ah.  This 3Ah drain is still greater than the charge put back in 25 minutes of driving.

Edited February 27, 2021 by plus 3 golfer

[13max]

Hey Plus.

 

I am still having similar problems with my Battery draining. In Forscan, How can one check the SOC of the battery?

I was wondering if you could send me the link where you explained how to reset the battery age perameter in my 2013 Cmax Energi. I am considering replacing my batter but your explanation in your previous post makes me think I should try charging the battery up before getting a new one. Current battery is 3 years old.

 

Thanks!

 

[plus 3 golfer]

10 hours ago, 13max said:

Hey Plus.

 

I am still having similar problems with my Battery draining. In Forscan, How can one check the SOC of the battery?

I was wondering if you could send me the link where you explained how to reset the battery age perameter in my 2013 Cmax Energi. I am considering replacing my batter but your explanation in your previous post makes me think I should try charging the battery up before getting a new one. Current battery is 3 years old.

 

Thanks!

 

There is a PID (parameter identification code) for virtually all stored data in the car.  With the FORScan App and an appropriate OBDII adapter one selects the 12 V Battery State of Charge PID and then initiates FORScan to scan all selected PIDs in FORScan.  Your Energi has a separate converter (not the main DCDC converter) which should charge the 12 V battery when you are plugged in and charging your Energi. 

 

[13max]

Ok, Again, thank you for your input as always. Very much appreciated by me and others!

[13max]

On 2/28/2021 at 6:35 AM, plus 3 golfer said:

There is a PID (parameter identification code) for virtually all stored data in the car.  With the FORScan App and an appropriate OBDII adapter one selects the 12 V Battery State of Charge PID and then initiates FORScan to scan all selected PIDs in FORScan.  Your Energi has a separate converter (not the main DCDC converter) which should charge the 12 V battery when you are plugged in and charging your Energi. 

 

Ok So I have been tracking a parasitic Drain for the past 2 months or so. What I found is that when I park the car, turn ignition off and set lock the doors, I will leave it for 2-3 hours and then I would get a 12v Battery is low notification from the app. After numerous times of the battery draining and having to jump the car to get it going agian I have tried something that has eliminated the drain so I am hoping to get some feedback from the crowd here on potential problems....

 

I have replaced the coolant pump as the first place I looked and the water in the connector was an issue so I replaced both.

 

If I pull fuse 71 (10amp) (Heating control head (manual air conditioner), Climate control module) in the fuse panel below the glove box the battery is stable and lasts overnight at 12.0. (I am pretty sure the battery has sulfated after many drains down to 8.0)

When I put the fuse back in and leave it, the drain comes back. Is it a module or is it the climate control panel? I see in Forscan that there is an option to reset modules? Anyone think this would help?

 

Thanks,

Corby

[vonoretn]

On 2/27/2021 at 9:21 AM, plus 3 golfer said:

So what size charger do you have? If your battery has 0% SOC <= 10.5 V by definition (8.5V) and if you charged for one hour and SOC = 100% as you say, then the charger had to put out 43 A for one hour.  100% SOC = 43 Ah for the BXT67R Motorcraft battery.  Because your battery is around 5 years old (2015 MY?), it’s maximum capacity will be less than 43 Ah.  You got 12.1 V after allowing surface charge to drain which is a maximum SOC of around 30% +- maybe 10% depending on load on battery when you checked voltage.  This would mean that if you charged for one hour you likely added between 8 - 16 Ah of capacity (8-16 A charger) to your battery.  IMO, this is normal for a 5 year old battery. See attached discharge curve.  C = 43 Ah, so the C /20 discharge curve is likely the one to use when measuring battery voltage.  Just opening doors activates modules and puts load on battery.

 

Driving the C-Max adds little to the SOC of the battery.  In 25 minutes of driving you will likely add less than 2 Ah and more than likely around 1 Ah. So, best case is you might have increased SOC around 5%.  Normal car off battery drain should be less than 50 mA.  So if car is off for four days,  normal max. drain would be around (96 h x 0.050 A) = 4.8 Ah (should be less unless there is a parasitic drain).  I believe around 30 mA would be typical.  Thus, the four day Ah drain would be around 3 Ah.  This 3Ah drain is still greater than the charge put back in 25 minutes of driving.

My charger is a Schumacher SC-8020A, which means 80 amp start but only 20 amp max quick charge.  More data, after 3 days of not driving the battery reads 11.7 volts. According to my charger, the % charge was 38%.   After 1.5 hours of charging it read 100% .  The voltage level reads 13.3.   Do you know at what voltage the car won't start?  We know it won't at 8.5, but I'm guessing it will down into the 10s.   I have heard that the computer, injectors, and ignition need at least 8 volts to operate.  Of course once started, no problem.   I don't think I would ever need the 80 amp start mode, because as soon as I hook up my charger the battery voltage is into the 13's and it will start.  The battery is the original battery so I assume it is the BXT67R.

[vonoretn]

And more data:

Immediately after driving for 3 hours on the highway yesterday, I checked the 12 volt battery voltage.  It read 12.01 volts, with everything off on the car..   I hooked up my charger, and it read 12.1 volts, with a % charge level of 54%.  While charging, the battery level was at 13.2.  After 20 minutes it was reading 74% charge, but if I disconnected the charger then reconnected it, it read 100%.   The voltage level at this point disconnected read 12.9.  

 

I am calculating that my initial new battery amp hour rating was 54, (cold cranking amps/7.25)  which is not exact but a rough estimate since there is no mathematical relationship between CCA and Amp Hours.  But I think now, it's amp hour rating may be only 10, or some low number. But since it never has the  burden of starting the engine, it can function at that lower amp hour rating for some time, as long it doesn't drain to below about 10.5 volts (a guess).  A week ago I did check the fluid level in the battery, and none of the plates were exposed.  I added a few ounces of distilled water to bring the level up to the bottom of the black tubes at each cell.  I know better than to overfill a battery.