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Battery Configuration

cmax batteries

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11 replies to this topic

#1 OFFLINE   dwdwone

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Posted 27 December 2018 - 09:51 AM

I'm trying to wrap my head around how this works because I am having some battery problems.

My understanding is that there are three batteries. One is the 12V which operates like most non hybrid batteries operate and is located under the hood.

Then there is a sort of 2 in 1 battery in the back known as the HVB. This battery consists of the hybrid battery which charges the car, and an attached set of cells that holds the plug in charge.

Am I understanding this correctly?

Thanks!
Dan









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#2 OFFLINE   Tom_NC_1

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Posted 27 December 2018 - 10:21 AM

The 12V battery main function is to close the relays that enable to HVB to be used. This is why a full HVB is useless if the 12V battery was also dead. The 12V battery is a bit smaller that normal car batteries since there is no starter in the car and no need to draw heavy amounts of current from the 12V battery. Once the HVB is connected the DC to DC converter is used to both run the low voltage systems and charge the 12V battery.

 

The HVB is a battery pack with 84 cells connected in serial to output a maximum of about 342 volts. The computer in the car controls how the available kWh's are used. Normally about a maximum of 5.5kWh are used for EV driving. An additional <1.5kWh is reserved for hybrid operation. Typically the hybrid capacity will rarely deplete completely. When driving EV Later the Hybrid portion will deplete and recharge and every opportunity and the ICE will run as needed. There is a low end reserve capacity that is controlled by the computer and is not allowed to be used. This is to prevent the HVB from becoming completely discharged to prevent any damage to the HVB.

 

If a HVB has been damaged so that overall capacity has diminished the Hybrid portion will function the same as a new HVB. Any lost capacity will show up as decreased capacity in the EV portion of the HVB. This is why a number of owners have reported fewer EV miles available over time. In my own case I have lost 1 kWh of capacity most likely due to overheating of the HVB at a time when I did not know better. The lost capacity means fewer EV miles for me.

 

Hope that helps you understand the batteries. If you are having specific battery problems, post details. Could be that someone else has had the issue and might be able to help. 

 

Tom


Edited by Tom_NC_1, 27 December 2018 - 10:23 AM.


#3 OFFLINE   dwdwone

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Posted 27 December 2018 - 11:29 AM

Thank you Tom.

This explains a lot. My HVB overheated a number of times this summer while driving to San Antonio. The "leaves screen" on the MFT told me the battery was overheating. This happened whenever the outside temperature went over 100 degrees. It got up to 115 degrees outside that day.

 

Ford replaced my HVB about 8 months before that and I noticed my EV charge improved (# of miles available) but not for very long.


Edited by dwdwone, 27 December 2018 - 11:48 AM.


#4 OFFLINE   dwdwone

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Posted 27 December 2018 - 11:57 AM

Here's a shot of the leaves screen.

 

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#5 OFFLINE   rbort

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Posted 27 December 2018 - 02:49 PM

Tom explained it very well.  If you can help it, stop cooking the battery in the heat, that's just a sure fire way to degrade it quickly.  If might mean that you don't drive on the battery during the hot weather, or only go out at night.  I know its tough, if its 115 degrees outside there isn't a whole lot you can do to avoid overheating the battery.

 

Tom will tell you that cooler is better for the HVB, less than 100F would be the best.  It is the same battery for hybrid as well as plug in miles, so I would tend to think if you degrade your cells to the point where they crash sooner and give less range, that this would also affect the hybrid operation in the manner where you won't be able to stay in hybrid mode for say 2 miles.  No-one will notice hyrbid mode operation normally, as the engine and on and off all the time, but if you stick to just battery to see how far you can go on the hybrid battery by babying the gas pedal to stay in EV mode, I'm quite sure it won't go as far.

 

Sad to say, this car is not suited for very hot climates, up here in the Northeast its perfect, down in Texas its a whole different story.   Tom is 1/2 way there in NC and it gets quite hot there during the summer.

 

-=>Raja.



#6 OFFLINE   dwdwone

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Posted 27 December 2018 - 03:27 PM

Typically I'm able to get about 10 miles off an EV charge. However, since many here have recommended not to run it all the way down I rarely use the full EV charge. Once it is down around 20% or so, I take it off of auto and move it in to Later mode. If I let the EV charge run all the way down, then I get the very low battery indicator (as I did today, see attached). The engine then goes in to a high idle and I get the engine light and the wrench icon.

 

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#7 OFFLINE   rbort

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Posted 27 December 2018 - 04:04 PM

Well the hybrid battery is not supposed to be run all the way down.  Might be why the system is giving you the wrench icon.  Technically speaking you should not be in AUTO mode until the battery runs down and then switch to EV later.  The idea is as follows:

 

If you can make it 100% EV, then use EV all the way in Auto mode.

 

If you can't make it 100% EV all the way and need to use the ICE, then use it battery where its good for the battery and use the ICE where it excels.

In other words, don't drive on the highway on the battery until its drained all the way and then switch to EV later.

Another example is don't climb long hills with the battery either.  But you must warm up the engine to take the load, remember that, always, before you can use it back and forth quickly.

 

If the engine is warm already and you see an upcoming hill, 500 feet before the hill tap tap on the EV button to go into EV later and climb the hill on the engine.  Then once cresting the top let off on the gas to stop the engine, tap once on the EV button, and then back on the gas to continue in EV power.

 

Try to use the engine for hills and high loads, and the battery easy loads.  If on a long trip stretch the battery by using it on the easiest of tasks so it lasts longer and you get the best range out of it.

 

Hope this makes sense.

 

-=>Raja.



#8 OFFLINE   Tom_NC_1

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Posted 28 December 2018 - 06:04 AM

I actively monitor the HVB temperature using a ScanGauge. This direct feedback allows extra control over managing the HVB temp. As a general rule anytime the HVB exceeds 90ºF I do not charge the pack. Anytime the HVB exceeds 100ºF drive only in EV Later mode. In hot summer climates like here in NC there are times during the summer that the overnight lows are so high the HVB does't cool down much. During these time do not charge the HVB and drive EV later all the time.

 

Raja got to the heart of the issue in that this car is not really suited for hot climates. Do what you can to minimize overheating. What this car has taught me is that air cooled HVB packs are a pour cooling method. My next EV will have to have a much more effective cooling system.

 

Tom



#9 OFFLINE   rbort

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Posted 28 December 2018 - 08:05 AM

Tom,

 

One thing that I do in the summer after driving around is charge the pack while its hotter to bring the battery temp down some.  This is usually late at night when the temps have cooled down some, and what I do is open all the windows and sometimes even the tailgate and charge the pack slowly on 120v for 45 minutes to bring the battery from hybrid mode back up to around 10%.  During the charging, and, if you leave the car on when you come home before plugging in, the HVB cooling fan will be running and will continue to run.  Plug it in then turn the car off (keeps the HVB fan running) If the temps outside are cool enough, I've found that you can drop the battery pack temp maybe 4 degrees before unplugging to go to bed.  Sometimes more depending on its temp and the outside temp.  Slow charging is this case is better than 240v charging, as it takes longer to recharge and runs the HVB fan longer to effectively drop the temp of the HVB.  Less charge amps helps also not raise the temp while charging, 240v would charge at around 9 amps like a constant regen, while 120 around 3 amps.

 

After I charge it a little bit then I unplug it, pull it into the garage, and let it sit.  Many times I have to charge it outside before pulling it, as the temps outside are cooler than the garage inside when I get home, and I leave the garage door open to let some of that hot air out before going to bed.

 

Something to consider I suppose.  I prefer not to leave the battery dead in hybrid mode and found that slow charging as late as night as possible 1 hour before bed is best to drop the temp a few degrees.  Try it next time Tom before bed, see if it helps.  The car's battery likes to be at least 28.2% SOC, if you do value charging that's where it wants itself to be before waiting to charge.  I don't like leaving it below 20% SOC, it can drop further when the battery cools and I've had mine drop to 9% SOC while eating dinner in Boston with a dead HVB (hybrid only) pulled in to park at 17.8% when I came out and turned the car on the engine started immediately with 9% SOC!!  Mistake on my part I should have not drained it so deeply if I didn't have a charger to plug it in right away and prevent the deep discharge drop.

 

-=>Raja.


Edited by rbort, 28 December 2018 - 08:09 AM.


#10 OFFLINE   Tom_NC_1

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Posted 28 December 2018 - 09:29 AM

Raja,

I am way to lazy to think that hard about managing charging. It the HVB is hot I will wait until late evening to charge or I will just not charge the car at all that night. can't open windows since the car lives outside and must remain locked when parked at home.  I use a level II charger so slow charging is not my preference. As long as I control for HVB Temperature charging to full has had no detrimental effects on the HVB. You are gentle and careful and I am the bull in the china shop when it comes to charging. So the bottom line here is that charging method is much less important that making sure to keep the HVB from overheating. My goal is to not exceed 102ºf for the HVB at any time. 

 

Tom



#11 OFFLINE   cr08

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Posted 28 December 2018 - 12:25 PM

Exactly why Value Charging is a key tool to use. I know many seem to have their odd issues with MFM. Personally mine has been flaw-free since I have had this car. I simply set it to begin charging at midnight and plug it in the moment I get home in the afternoon. Does what it is supposed to and as a benefit will run the fans straight away to cool the battery without any extra rigmarole. Just plug it in and forget about it. And if the plug-in charge is depleted or is below 10% (per Sync/MFM, not OBD read SOC) it'll immediately begin charging up to that level and leave the remainder for the set VC schedule.



#12 OFFLINE   rbort

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Posted 28 December 2018 - 02:51 PM

Sure Tom (bull in china shop that's funny!), but all damage to the HVB is additive, some are worth less that others (damage), so overheating is worth the most (i.e. causes the most damage), but leaving it full all the time ALSO cause damage, but not as significant.  To minimize the degrading it would be best to do all possible things to reduce degrading, not just address the biggest hitter.   But, being the bull if you have to only do one then watching the temperature certainly the most worthwhile.

 

When I come home and the battery is hot, by using the 120v charger and dropping the temp 4 degrees for example, I see that as a PLUS as the battery spends less time sitting hotter over its whole life.  I try my best to avoid raising its temperature while driving, and that means not climbing a long hill with it, it also means rolling down all the windows and driving home with cold air in the summer while dressed in shorts (60's at night and the battery is still in the 80's for example).  If I leave all the windows up and I'm nice and comfortable inside with 70-75 internal temp, then the battery does not DROP in temp on the hour drive home.  But roll down all the windows and feel the cold driving back, and it could drop from 86 to 82 coming home.  Then charge it for 45 minutes with windows down tailgate open and I could drop to 78 for example.  On the other hand, drive with all the windows shut, get home with 86F assuming it didn't go up any further, and leaving it sit at 86 is different over the long haul than going to bed with it at 78 instead of 86.  The little things we do add up, but they don't go away by themselves if you skip them.

 

Value charging has its place Cr08, but I don't use it all the time.  This is because I don't want to go to bed plugged in, and wake up with the car full.  This is because I may not need it tomorrow.  Also, value charging can be deceiving.  The fan that runs is the charging circuit fan, not the HVB fan that you hear inside the car.  The HVB fan is very hard to hear, very quiet.  You cannot hear it over the charging fan.  If the charging fan is not on (very short period after you plug in) and the HVB fan is running you can barely hear it if you go to the rear to listen carefully.  Anyway leaving the car plugged in all the time with value charging will consume (if you care) 60w to run the charging circuit fan while not charging.  If you get home in the afternoon and plug it in to recharge to 10% normally (charge now), and unplug it, then later plug it in before you go to bed (value charge), perhaps you won't pay for 60 watts for 8 hours worth.  That 8 hours doesn't do anything for the HVB fan.  NOTE THAT the HVB fan will NOT run if the car is not charging.  The minute you go to value charge and the car is "waiting to charge" then the HVB is shut off if running.  So you're not benefiting from anything there.  Just running the charging circuit fan which really isn't required but runs because the OAT is warm.  Just FYI.

 

With all that being said, when I'm on the road travelling I use value charging all the time.  That is because tomorrow morning I need 100% charge, and, I set value charging to start charging at 4am.   Usually the car is ready somewhere between 8 and 9:30 depending on charge level.

 

-=>Raja.


Edited by rbort, 28 December 2018 - 02:56 PM.









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