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How does 12V battery get charged?

charging 12v battery

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16 replies to this topic

#1 OFFLINE   RickG

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Posted 26 September 2018 - 12:51 PM

Bought my Energi nearly 4 years ago, but I'm new to this forum.  Recently I had the low 12V battery problem others have reported, where everything just stops working.  After attaching a 12V battery charger to the 12V battery, it came up to 12.5 V and has stayed there for a few days now.

This got me wondering about how the 12V battery gets charged?  I read on this forum that there is a DC to DC converter that charges the 12V battery from the HV batttery.  But what if the HV battery is completing drained, as on a long driving trip for weeks without plugging in the vehicle?  I'm assuming the gas engine does not have an alternator, or does it?  Any information on the 12V charging system is appreciated!









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#2 OFFLINE   cr08

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Posted 26 September 2018 - 01:03 PM

First off the HVB will never be fully drained enough to be an issue. Once the plug-in charge is depleted the car drops to a hybrid mode where a small portion of the battery remains maintained by the engine as needed. You'll easily notice this when the battery gauge on the dash changes to the '2D' one without the miles listed. It'll regularly cycle up and down as you drive. Same as any other hybrid vehicle on the road. When the car is sitting and off, the HVB is completely disconnected from the rest of the car so there should be virtually zero drain there. On top of that, even at the lowest it will let you drain the HVB, there is enough actual capacity left in it to start the engine and not leave you completely stranded. In fact I don't think I've read of anyone so far being unlucky enough to have it drained far enough to be an issue.

 

As you read, the car does use a DC-DC converter in place of an alternator to convert juice from the HVB to the 12V battery. This is only active while the car is in 'ready to drive mode' or in some cases while plugged in and charging. If out and about and the car is off without being plugged in, the 12V battery is fending for itself without help from the HVB like any other conventional vehicle. While plugged in and charging however it will keep the 12V battery maintained as that is key to keeping all the modules including the HVB charging circuitry operational. It will even go so far as to top off the 12V battery after the HVB is completely charged. So leave it plugged in after it says it is done charging so it can do so.



#3 OFFLINE   dwdwone

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Posted 27 December 2018 - 10:04 AM

What does it mean when your HV battery (the 2D one on the dash) drops to a very low reading on the gauge? For example, I can either be driving on the freeway or idling. There has been no plug in charge for several hours. Over 10 or 15 minutes the 2D gauge drops all the way to the bottom and the idle becomes rough. When I restart the car, the engine light and the wrench light come on. After a day or so, so long as I plug the car in and charge it at night, those dash warning lights go away. First the wrench, then later the engine light.

Another symptom is that my bluetooth on the My Ford Touch keeps disconnecting from my phone while I am driving. At one point the audio also shut off and I was unable to turn it back on (Audio Off). A few days later it would not start and I had to get road service to jump it. After the jump, the audio was back on and everything worked fine, but only for about 5 days.

Ford has been no help in diagnosing the problem, but they have not forgotten to charge me diagnostic fees for a diagnoses they can't seem to agree on.

Any ideas?

P. It is a 2013 energi.


Edited by dwdwone, 27 December 2018 - 10:06 AM.


#4 OFFLINE   Tom_NC_1

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Posted 27 December 2018 - 10:54 AM

I have not seen the warning lights you observed but I have seen the depleted Hybrid battery indicator you described. What happened in my case was that while driving EV I got on the interstate highway and forget to cycle to EV Later. The EV capacity gets consumed.The car switches to Hybrid and consumes that capacity then the ICE comes on. Since the ICE now needs to warm up a bit the Hybrid capacity drops all the way to the bottom of the indicator before it recovers. Once the ICE has warmed up the Hybrid operation will cycle the battery between 1/3 to about 2/3 on the dash display. I can't help with the warning lights but there should be  codes that might give an indication on where to look.

 

I have also had problems with audio in the car going silent. This has occurred on several occasions usually within seconds after starting the car. I normally have the radio set to bluetooth as well. The radio goes to being non responsive to any command as well. The solution sometimes is to turn the car off and wait awhile and after turning the car on the radio starts working again. On at least one occasion cycling the car power off and on failed to correct the problem. It was then fixed by pulling/reseating  fuse 79 in the fuse panel under the glovebox. Pulling fuse 79 cause the SYNC 2 MFT to reset(Express negative Microsoft comment here).

 

Problems with the car not starting usually are related to the 12V battery and may indicate that it needs to be replaced. I have had a number problems with the 12V battery and am now on my third battery. The current one has lasted much longer than either of the first two and is still going strong. 

 

Tom



#5 OFFLINE   dwdwone

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Posted 27 December 2018 - 11:54 AM

Hopefully my attachment took.


#6 OFFLINE   dwdwone

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Posted 27 December 2018 - 11:59 AM

OK, that's better.

BTW I now have 200K miles on the car.

Attached Files



#7 OFFLINE   rbort

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Posted 27 December 2018 - 03:01 PM

That is showing a full hybrid battery.  Realisticly  speaking you should NOT drain the hybrid battery all the way down.  If you go on the highway and start the engine, you need to take it easy with the power for the first 2 miles at least until the engine has warmed up enough to take the load.  In the beginning the engine is pegged to a high idle at 1300 rpms and any additional power you require comes from the HVB.  If you switch to the engage screen try to feather the gas to keep the battery power no more than the engine power.  This will reduce the load and drain on the HVB until the engine warms up at which point you see the battery load go away completely.  Only and only then should you accelerate normally to your desired speed.  Before that you should stick to the right lane and drive like an old lady to protect the HVB from a deep discharge in the case of an empty traction battery and you just started the engine, or to prevent it from being drawn down too much and require the engine to recharge it all the way back up to the EV later set point in which case your MPG will suffer longer as you go through the discharge and recharge phase.  

 

It is best to always let the ICE warm up as slowly as possible until ready, and then once ready wait for the next downhill on the highway and accelerate up to 65mph then (or more if you want to speed).  I found 65mph to be very efficient on long trips, get your there quickly enough yet is good on gas mileage.  If you drive faster and because of that you need to make 1 stop for gas (which at 65 maybe you wouldn't have had to), then its actually slower.  In other words if you slow down and make it non stop its faster than going faster and having to make a stop to refuel because you're short on range to the destination.  That stop for fuel wastes all the gain in time you had for speeding.  Of course if you go faster and you don't have to stop then you get there quicker but just burn more gas.  65mpg will net MPGs in the mid to upper 40's in this car, 75mph is closer to upper 30's mpg.  Drag kills mpg and doubles when you go from 55 to 75mph.

 

-=>Raja.


Edited by rbort, 27 December 2018 - 03:04 PM.


#8 OFFLINE   dwdwone

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Posted 27 December 2018 - 03:18 PM

I'll give that a try. I usually go 65 and I keep the car in EV Later mode once I get on the freeway. However, unless I am in EV Auto mode, I rarely get over 38 mpg.



#9 OFFLINE   Billyk24

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Posted 27 December 2018 - 05:20 PM

There is something that rbot preaches, in that not to park and leave the car for a long time at or near 100% SOC.   Will plugging in your traction battery charger from 5am to 7am before leaving for work be sufficient for maintaining the 12V battery long term?   Maybe you have a second vehicle in the family and use the C-Max more infrequently during the winter months and want to maintain the 12V battery without keeping the traction battery at 100%SOC.   Then, it might benefit from have a trickle charger utilized when sitting unused.  



#10 OFFLINE   rbort

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Posted 27 December 2018 - 07:30 PM

Every time you drive the car Billy, it charges the 12v battery.  All you need to do is power up and that's it, the 12v is charging.  It can also charge while plugged in charging the traction battery.  But the 12v battery is not needed to crank the engine, so it doesn't need to provide alot of CCA to start the car, it just closes the contacts for the HVB and that battery takes over from there for everything.

 

If you are going to leave your Cmax for a long time unattended, you can just either a) plug in a trickle charger to the 12v battery, b) plug in a deep cycle battery to the cigarette lighter in the rear (always live), and that will allow you to leave the car rest for over a month for sure (I've done it), or c) disconnect the 12v battery and essentially put the car to sleep.  The car will automatically sleep if not accessed within a week to extend the life of the 12v battery, just FYI about that.

 

Hope this helps,

 

-=>Raja.



#11 OFFLINE   Billyk24

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Posted 28 December 2018 - 04:15 AM

Thanks for the reply.   Accessing the 12V battery is difficult so disconnecting will be a pain.   Easy to install the trickle charger and slide the cord thru the front grille opening so one doesn't have to open the hood to do so.   With reports on this site and elsewhere of the 12V battery durability issue, it seems as if the trickle charger routine is a no-brainer solution to a potential issue.    My 2005 Escape Hybrid has had a chronic 12V battery issue for a number of years that is "managed" with the use of trickle charger when sitting at home.



#12 OFFLINE   rbort

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Posted 28 December 2018 - 07:48 AM

If you needed to disconnect it you could reach it easily if you remove the funnel cover, you can see it through there.  Removing it completely is harder, but disconnecting is not that bad.

 

If you have a trickle charger you can do that no problem.  Either plug it into the cigarette lighter in the back (live one) or at the jump terminals under the hood.

 

-=>Raja.



#13 OFFLINE   komptonwhitey

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Posted 28 December 2018 - 11:09 AM

If you're having repeated 12v battery issues, I would make absolutely sure that you don't have problems related to either the modem being stuck on or water intrusion in connectors.  I bought a salvaged 2014 Energi for a great deal b/c it would die every time the HVB was charged.  The gentleman that rebuilt the body thought they were getting the car at a steal but couldn't figure out the wiring issues.  Being salvaged, all warranties are void.  Water had gotten inside and corroded the connectors for the ICE water pump and vacuum pump (both electric of course).  These both draw quite a bit of current and would run continuously whenever the vehicle was running or charging.  This would result in frequent dead 12v batteries and no-starts.  I was able to get the TSB from Ford for the water intrusion issue.  A helpful service rep also texted me pictures from the service manual that lists the affected connectors.  Sure enough, three of the listed connectors had bad corrosion.  After a new water pump and pigtail kit, and some new DIY connectors my battery drain issues are gone.  I also neutered my modem by pulling out the SIM card.  I don't have access to MFM but I can still edit my GO TIMES and value charging manually from inside the car and they work flawlessly.

 

There appear to be lots of things that can cause 12v battery issues on these rigs, these just happened to be mine.  Ford dealerships seem to be mostly ignorant of PHEV's and, at least in my neck of the woods, see very few of them.  In the end, after LOTS of research and time under the car, I got a steal at $8,200 for a car with 24,000 miles on it.  I'm sure we can figure out yours.

 

Attached is 2 service manual pics that detail locations of the affected connectors.

 

TSB 15-0089 ENERGI – DISCHARGED 12 VOLT BATTERY TSB-14-0155

Attached Files



#14 OFFLINE   dwdwone

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Posted 28 December 2018 - 11:32 AM

How do you unstick the modem?

I tried doing a diagnostic where the car sends a report through your cell phone, but the number is disconnected. Maybe I need to unstick something.



#15 OFFLINE   nikorasu

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Posted 30 December 2018 - 05:00 PM

As others have stated the HVB package has a DC/DC converter. The converter takes 281 volts and reduces it down to 14.5 volts. If you put a multimeter on the terminal you should get a 14.5 volt reading. If not you should check the 30 amp fuse in the junction block right next to the converter. The converter and the junction block are inside the black HVB package in the rear of the vehicle.

A breakdown of the battery components is at https://youtu.be/kmDpNr1PdMk?t=931. The battery is from a regular hybrid not a plug in but I would assume the hardware is the same.



#16 OFFLINE   ScottB

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Posted 08 January 2019 - 09:53 AM

great video on the battery charging system. Good thread on the 12 V battery. My 2017 battery went dead on a ski trip and I had to have Ford road side program send someone to jump start me. I could hear a relay clicking in the car before the jump. The 12V battery got drained somehow. I wonder if I was able to manually close the clicking relay, that the HVB would have charged back up my 12 V battery. I am not sure it is even needed to run the car, as long as the HVB has some juice left.

 

I will start a new post to detail what happened to me.



#17 OFFLINE   patbob

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Posted 12 January 2019 - 12:25 PM

If the relay was clicking, it was closing.

But you bring up a good question -- is there any way to manually turn on the DC-DC converter when the 12V battery is dead?








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