An online Ford Focus Electric Forum discussion group

It is currently Tue Sep 26, 2017 8:16 am

All times are UTC - 8 hours




Post new topic Reply to topic  [ 17 posts ]  Go to page Previous  1, 2
Author Message
PostPosted: Sat Jun 20, 2015 5:36 pm 
Offline

Joined: Mon Apr 07, 2014 12:46 pm
Posts: 1456
Location: Minneapolis
The Fusion Energi shows the DCDC converter low voltage setpoint as 14.6 or 14.7 volts. The Focus Electric usually is 13.0-13.6 volts. The Fusion Energi used to use a lower voltage but a software update increased the voltage because of low 12V battery concerns. I wonder if the Focus Electric update to address low 12V battery concerns will increase the DCDC converter low voltage setpoint. The Fusion also keeps a fixed voltage from the DCDC converter. The Focus Electric will vary the DCDC voltage. If you turn on the headlights the DCDC converter low voltage setpoint will increase. If you turn on the HVAC system it will increase.

_________________
2013 Ford Focus Electric - Ice Storm - leased through 8/15/16
Replaced by a 2016 Tesla Model S 60D


Top
 Profile  
 
PostPosted: Sun Jun 21, 2015 4:45 am 
Offline

Joined: Mon Apr 07, 2014 12:46 pm
Posts: 1456
Location: Minneapolis
The car is plugged in and charging now. The DCDC low voltage setpoint is 12.3 V only. The car is not really trying to charge the 12V battery, sending only 0.12 amps of current to it. It currently shows an SOC of 69.

_________________
2013 Ford Focus Electric - Ice Storm - leased through 8/15/16
Replaced by a 2016 Tesla Model S 60D


Top
 Profile  
 
PostPosted: Sun Jun 21, 2015 5:23 am 
Offline

Joined: Tue Feb 12, 2013 4:36 am
Posts: 2196
Location: Southeastern MI
Could just be trickle charging it.

_________________
2016 Magnetic C-Max Energi
2014 Sunset Escape
2014 Thor Axis (V-10)
2013 Focus Electric (lease returned Jan 2016 for the C-Max above)
https://spareelectrons.wordpress.com/


Top
 Profile  
 
PostPosted: Sun Jun 21, 2015 12:45 pm 
Offline

Joined: Mon Apr 07, 2014 12:46 pm
Posts: 1456
Location: Minneapolis
After charging for 1 hr 36 mins the HVB temp had risen to 99 F. At this point I had to leave so I unplugged the car & left. The car had charged from about 40% useable SOC to about 75% useable SOC. I drove a ~6 mile trip and the HVB temp stayed at 99 F. The TMS was not cooling the HVB while charging or while driving. Coming home a few hours later the HVB temp had dropped to 95 F. After arriving home I plugged in the Focus Electric and it is waiting to charge. The car is not cooling the HVB while waiting to charge.

I expected the TMS to kick in when the HVB temp was 99 F, but it didn't.

_________________
2013 Ford Focus Electric - Ice Storm - leased through 8/15/16
Replaced by a 2016 Tesla Model S 60D


Top
 Profile  
 
PostPosted: Tue Sep 12, 2017 7:26 am 
Offline

Joined: Tue Aug 16, 2011 11:40 am
Posts: 559
Location: Toledo, Ohio
Resurrecting this 2+ year old thread to provide some more information on how the car handles the 12V system. Correct me if I am wrong but I'm pretty sure the DC-DC converter just puts out a constant voltage and the battery draws whatever current it wants. The DC-DC converter is also supplying power for all the other low voltage electrical systems too. So if the 12v battery is drawing low current when turned on, it's not that the car isn't charging it enough it's that the battery is already nearly full so it won't draw much more current. I have observed a jump started FFE pumping 47A into a 7v dead 12V battery. Supposedly the DC-DC converter is capable of putting out 150A. I know they did a software update in 2015 that was supposed to fix most of the 12V problems. I'm not sure what it changed but when the car is on the DC-DC converter puts out about 14.5ish volts. I have measured when the car is charging the HVB the DC-DC is putting out 13.5V which I assume is to less aggressively charge the 12V and to supply power for the battery TMS. I did not track the whole charging cycle so I do not know at what point the DC-DC converter turns off.

_________________
2014 Blue Candy FFE
http://www.fuelly.com/car/ford/focus/2014/triangles/303811 (since this forum doesn't allow BBcode in sigs)


Top
 Profile  
 
PostPosted: Tue Sep 12, 2017 11:06 am 
Offline

Joined: Tue Aug 06, 2013 9:10 pm
Posts: 800
Location: Chicago Area
Triangles - I don't know this for sure, but I would suspect all the 12V devices draw from the battery, and the DC-DC converter only charges the battery. If that converter drove all the 12V devices, there wouldn't be a need for a 12V battery ever.

I think the logic is that ICE components all run off the 12V battery (none run directly off the alternator), and they are using all kinds of off the shelf parts for electric cars. Like why, reinvent the windshield wiper if you can just use the same one from an ICE Focus?

_________________
2014 Platinum White FFE (Turning in mid Dec. 2016 25,000 miles)
2013 Ingot Silver FFE
2012 Titanium ICE Focus
2014 Tesla Model S 85


Top
 Profile  
 
PostPosted: Tue Sep 12, 2017 1:35 pm 
Offline

Joined: Mon Jan 21, 2013 8:58 pm
Posts: 376
Location: So Cal
Using Forscan and the OBDII reader, there is a value for a set voltage for charging the 12V battery. I've seen it at different values, but I don't know what the intent would be to change it. I think that the DC-DC is there to charge the 12V battery; however, it will supply current for the 12V devices as well. For instance, if you charge your cell-phone while using it, the current needed to run the phone will come from the charger while the phone battery continues to charge.

The amount of current that the DC-DC needs to provide is proportional to the difference between the set voltage of the DC-DC charger and the state of the 12V battery. If the 12V battery is already close to the DC-DC set-voltage, the current will be small. If the 12V battery is low, then higher current will need to be provided. There are limitations to what the DC-DC can provide, so if the current needed to charge is too great, then the voltage at the DC-DC will drop.

If say the charger is set to 14V and the battery is at 12V, and the resistance in the wiring between them is 0.1 Ohm, then the voltage drop will be 2V and the current will be 20A. As the battery recovers back to 13V, the drop is now only 1V, the resistance is the same, and the current provided is 10A. This is just an example, and there are other resistances at play...like internal resistance in the battery and in the DC-DC circuit itself.

But since the current to charge the battery is going into the battery at the same point that current coming out of the battery to run the car, you can say that the DC-DC converter is the current supply for the on-board electrical equipment.

Although the High Voltage battery could power the whole car without a 12V battery, no one is going to do that yet. You hear all those clicks when you plug the FFE in or before you start the car? That's the car controlling the isolation of the high voltage battery. When sitting idle and not charging, the high voltage battery is isolated for safety...so someone doesn't get electricuted. The 12V system runs the car until the car is started and the DC-DC can provide the current the power the car accessories and motor controller after that...so the 12V is essential to run the car's system when the car isn't running. In addition to that, the battery helps regulate the 12V power from the DC-DC. Not sure how essential that is in this application, but it does at least help some.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 17 posts ]  Go to page Previous  1, 2

All times are UTC - 8 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
© Ford Focus Electric Forum - part of the MyElectricCarForums.com Group