Interesting conversation with a Ford techie

[Jus-A-CMax]

Went back to my Ford dealer and they happen to run a training class on the C-Max Energi. As my salesman was in this class, I kinda stepped in and listened to some discussions. 

 

One interesting tid-bit that effected my wife and I, was to learn of a safety feature in our C-Max. If you open the rear passenger door, you will see an hole (about an inch in diameter) in the plastic. On the door is a pin that goes into that hole. From just listening, that pin is connected to a side bar and anchored into the chasis and in the event of a side collission, by anchoring into the chasis, it prevents provides additional bracing to the door and prevents it from crumpling inward into the passenger. 

 

Why did this effect me, my wife was recently tboned driverside by some numnutz, which is the reason I got a CMax as a replacement vehicle. Luckily it was a low speed collision but her Jaguar saved her life with the side bar on the driver door. It still shook and hurt her though and she's undergoing chiro and therapy because of the force of the impact on her body.

 

It's nice to know Ford builds these safety niceties.

 

Also, I had a chance to talk to the techie as to why Ford decided to cut the EV off at 62mph, given most of us drive at 65+ on the highway and he stated it was predominantly the battery. The Energi has a way, way bigger battery than the regular CMax so it can sustain the higher EV speeds. 

 

Just passing this tid bits on...

 

[AgentCMAX]

Thanks for the info.  I was wondering why they cut it off so early.  I see full EV comes on higher than 62mph occasionally, depending on the charge level of the battery.  And your info sort of confirms that.

[MikeB]

I'll second that: thanks for the info.

 

 

Some background, for those who are interested: Battery behavior generally depends heavily on what's known as the C rate, or (dis)charge rate. If you draw power from the battery at a rate that will discharge it in 1 hour, that's 1C. If you draw power twice as fast, you'll empty the battery in half an hour, so that's 2C. A 3C rate discharges fully in 20 min, etc. EV designers always look at the C rate when engineering a system, most lithium batteries should never exceed a C rate of 3 (though some chemistries are good up to 20). This is also why fast charging is an issue, if you want to fully charge in 20 minutes, you're at a C rate of 3, which might be near your upper limit.

 

When you look at translating the C rate into actual watts, it's a direct function of size. So pulling 1C from a 1.4kWh battery gives you 1.4kW, but you can get 7.6kW from a 7.6kWh battery. (Yea, metric units for electricity are really that simple).

 

So if the 62mph electric speed rate was limited because they didn't want to exceed a certain C rate on the battery, the Energi would clearly have a higher limit. Of course, ever component in an electric drivetrain has it's own limits, and they are all generally chosen with a similar power level, but you always end up with one item being the weakest link.

 

As I think about the numbers, something else comes to mind: the peak C rate in the Hybrid looks pretty high to me, but it's always used in short bursts. The C rate in the Energi is much lower since the battery is larger, but it also has to sustain that C rate for a much longer period of time.

Edited December 10, 2012 by MikeB

[RachelnLa]

Safety features also impressed us from knee bags to side bar to air bags, parental controls. I am not sure of the correct name but the car has sensors that will slow you down if taking the curve too fast. It's one awesome vehicle. I cannot wait to have mine.

[Fits2at]

Is the side bar the same for the C-Max hybrid vs. the C-Max Energi?  Sorry...don't have my owners manual yet. :-)

[AgentCMAX]

I'll second that: thanks for the info.

 

 

Some background, for those who are interested: Battery behavior generally depends heavily on what's known as the C rate, or (dis)charge rate. If you draw power from the battery at a rate that will discharge it in 1 hour, that's 1C. If you draw power twice as fast, you'll empty the battery in half an hour, so that's 2C. A 3C rate discharges fully in 20 min, etc. EV designers always look at the C rate when engineering a system, most lithium batteries should never exceed a C rate of 3 (though some chemistries are good up to 20). This is also why fast charging is an issue, if you want to fully charge in 20 minutes, you're at a C rate of 3, which might be near your upper limit.

 

When you look at translating the C rate into actual watts, it's a direct function of size. So pulling 1C from a 1.4kWh battery gives you 1.4kW, but you can get 7.6kW from a 7.6kWh battery. (Yea, metric units for electricity are really that simple).

 

So if the 62mph electric speed rate was limited because they didn't want to exceed a certain C rate on the battery, the Energi would clearly have a higher limit. Of course, ever component in an electric drivetrain has it's own limits, and they are all generally chosen with a similar power level, but you always end up with one item being the weakest link.

 

As I think about the numbers, something else comes to mind: the peak C rate in the Hybrid looks pretty high to me, but it's always used in short bursts. The C rate in the Energi is much lower since the battery is larger, but it also has to sustain that C rate for a much longer period of time.

 

Wow, I'm always learning something new on this forum!  Thanks, Mike!

[darrelld]

I'll second that: thanks for the info.

 

 

Some background, for those who are interested: Battery behavior generally depends heavily on what's known as the C rate, or (dis)charge rate. If you draw power from the battery at a rate that will discharge it in 1 hour, that's 1C. If you draw power twice as fast, you'll empty the battery in half an hour, so that's 2C. A 3C rate discharges fully in 20 min, etc. EV designers always look at the C rate when engineering a system, most lithium batteries should never exceed a C rate of 3 (though some chemistries are good up to 20). This is also why fast charging is an issue, if you want to fully charge in 20 minutes, you're at a C rate of 3, which might be near your upper limit.

 

When you look at translating the C rate into actual watts, it's a direct function of size. So pulling 1C from a 1.4kWh battery gives you 1.4kW, but you can get 7.6kW from a 7.6kWh battery. (Yea, metric units for electricity are really that simple).

 

So if the 62mph electric speed rate was limited because they didn't want to exceed a certain C rate on the battery, the Energi would clearly have a higher limit. Of course, ever component in an electric drivetrain has it's own limits, and they are all generally chosen with a similar power level, but you always end up with one item being the weakest link.

 

As I think about the numbers, something else comes to mind: the peak C rate in the Hybrid looks pretty high to me, but it's always used in short bursts. The C rate in the Energi is much lower since the battery is larger, but it also has to sustain that C rate for a much longer period of time.

 

Since the traction motors are AC Synchronous does the Energi have a different Variable Frequency drive converting the DC from the traction battery to AC?

[zhackwyatt]

Is the side bar the same for the C-Max hybrid vs. the C-Max Energi?  Sorry...don't have my owners manual yet. :-)

You can find the manual online at http://www.motorcraftservice.com/ (use the Owner Guides link on the left).

[zhackwyatt]

Safety features also impressed us from knee bags to side bar to air bags, parental controls. I am not sure of the correct name but the car has sensors that will slow you down if taking the curve too fast. It's one awesome vehicle. I cannot wait to have mine.

When are they just going to fill the whole car up with foam like in Demolition Man?

[kechair]

Thanks for the explanation, Mike - very interesting. So if the battery size & C rate dictates EV threshold, I would LOVE to know the cargo space tradeoff of a bigger battery allowing for higher speeds in EV! For example, I would be willing to sacrifice some incremental cargo space to get at 70mph which would boost my MPG. I do know that the cargo space give-up on the Plug-in CMax is too great a sacrifice for my needs, though.

[Jus-A-CMax]

You can find the manual online at http://www.motorcraftservice.com/ (use the Owner Guides link on the left).

 

This has GOT to go into an FAQ for this website!!!! Cool, thanks for the link!