FFE Battery Size

[Fluke]

The specifications for the FFE indicate that the battery capacity is 23 kW-h. I have also seen reports that the car can actually use about 85% of the battery capacity in order to not cause damage (for comparison, Nissan Leaf is reported to use 87.5%).

Does anyone know if the 23 kW-h figure equates to the 85% usable capacity or is it the total battery capacity? Has anyone measured the electricity required to recharge a completely discharged battery (since this would be measured before the EVSE, it would include 10-15% losses if similar to a Chevy Volt)?

[georgek]

The specifications for the FFE indicate that the battery capacity is 23 kW-h. I have also seen reports that the car can actually use about 85% of the battery capacity in order to not cause damage (for comparison, Nissan Leaf is reported to use 87.5%).

Does anyone know if the 23 kW-h figure equates to the 85% usable capacity or is it the total battery capacity? Has anyone measured the electricity required to recharge a completely discharged battery (since this would be measured before the EVSE, it would include 10-15% losses if similar to a Chevy Volt)?

Fluke,
The FFE total battery is 23 kwh. The Leaf's is 24 kwh.

"Designed with enough range to cover the daily-driving habits of most Americans, the 2012 Ford Focus Electric is powered by a permanent-magnet electric motor making 123 hp (92 kW) and 181 pound-feet of torque. Packaged just under the back seats is a 23-kWh LG Chem (and Holland, Michigan-assembled) battery pack that's actively liquid-heated and cooled, to help maximize battery life and range."

http://www.greencarreports.com/news/105 ... led-at-ces

[Fluke]

I've also been following the recent Nissan Leaf battery degradation issues in hot climates and note that the Leaf's Owner Manual recommends charging the battery to not more than 80% to maximize battery life (this recommendation is independent of climate).

I read through the Focus Electric Owner Manual and found no similar recommendation from Ford on charging. I've been charging mine to 100% - what are other owners doing?

[slyastro]

I've also been following the recent Nissan Leaf battery degradation issues in hot climates and note that the Leaf's Owner Manual recommends charging the battery to not more than 80% to maximize battery life (this recommendation is independent of climate).

I read through the Focus Electric Owner Manual and found no similar recommendation from Ford on charging. I've been charging mine to 100% - what are other owners doing?

I'm also charging at 100% ... I also found nothing about that in the owner manuel saying the contrary other than plugging the FFE as often as possible.

Anyway, is the any settings in the FFE or the MyFordMobile App where you can set a maximum charge limit other than 100%?

I estimate that we can use between 20.2 to 20.4 KwH from full charge to empty. I asked Ford Canada for the exact amount of KwH usable out of the 23 KwH battery.

Sly

[felkster]

I've been watching this as well, and it's frustrating to see the number of people playing engineers on forums on a system that they didn't design and don't intimately understand. I can't speak for Ford, Nissan, etc, but I do have a decade history of working on electric vehicles, robotics, and currently battery-powered consumer electronics, so I'm somewhat familiar with a variety of battery charging systems & techniques.

In almost all cases, the battery charging systems are very smart - they will make sure you don't overcharge or undercharge the battery. For larger battery systems, they have heating/cooling systems to quickly and efficiency charge and discharge batteries.

It's hard to imagine that cars with so much testing and so many sophisticated systems onboard would allow us, as drivers, to cause damage to our batteries. Again, I'm only guessing here, but I would imagine that Ford (and Nissan, Tesla, etc) have mechanisms in place to protect the batteries from the user's abusive driving & charging behaviors, to ensure the best range for the longest possible time. I know for a fact on that previous hybrids from Ford, they've been very clear that a full charge on a hybrid was not 100% of battery capacity, and that "running out of battery" was not actually 0%. They floated the Escape Hybrid between 40% and 60% of the capacity (so to the driver, 40% was "empty" and 60% was "fully charged").

Only a Ford or Nissan engineer would truly know the values behind the scenes, but I very much doubt that when we are at 100% charge on a Focus Electric, that you are using the full 24kWh battery pack at 100%. I would also bet that Ford put in some overhead to account for degradation (for example, call 18kWh as 100% so that as the battery pack degrades, your computed range does not for several years).

[Fluke]

Thanks for the replies. I agree that the car's control systems should be designed to take care of the battery under all conditions. I was surprised to see such a recommendation from Nissan in the Leaf's manual. I take it as a good sign that such wording does not show up in the Focus manual.

I also have a Chevy Volt, and GM definitely recommends keeping the battery fully charged. Also, there is an experienced GM engineer who actively participates in the discussions at GM-Volt.com who is extremely helpful. I wish that Ford would make someone with technical expertise available to the Focus Electric community. This is a major difference I have noticed between Ford and GM in their first electric offerings - GM has been much more informative and actively communicates with owners.

[Charged Up]

I had the opportunity to speak with an engineer on the FFE, and asked what portion of the battery is being used and the answer was "we are using between 19 and 20 kWh."

So 85% seems like a pretty good number to use.

Somewhere on fordfocuselectric.com there is a post from that conversation.

[klaus]

Speaking of which - Charged Up, you did a lot of posting on FordFocusElectric.com. It looks to me like that forum is dying?

[igh]

It is because of their broken registration system. I tried to register twice couple of months back. I am still waiting for the moderator to activate my account. If you do not allow the forum to expand, it dies a slow death.

[slyastro]

I had the opportunity to speak with an engineer on the FFE, and asked what portion of the battery is being used and the answer was "we are using between 19 and 20 kWh."

So 85% seems like a pretty good number to use.

Somewhere on fordfocuselectric.com there is a post from that conversation.

Charged Up: That makes a lot of sense. My initial estimate of 20.2-20.4 was too high. I you look at my last trip (almost 130 Miles on one charge!):

http://www.myfocuselectric.com/forum/vi ... f=14&t=663

We can see that I used 18.8 KwH, and with the 10 KM of range left, that would mean a total usable between 19.5 and 19.7 KwH.

That's right in the 85% of battery total capacity !