triangles
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Re: Which plug to use 240 or 120

Fri Sep 15, 2017 10:56 am

Pearl wrote:Faster is not really better with charging. Faster charging means more current, means more heat, means more harmful to the battery.
While this generalization is true, L2 charging the FFE at 6.6kW is still a "slow charge" relative to the battery size and capabilities. Considering the 23kWh pack, 6.6kW charging is only putting 20.7A into the 75Ah rated battery. That's only charging at 0.28C which is still slow charging. I"m not familiar enough with the Lithium NMC battery chemistry to know what it's upper charging limits are but I'm I would think charging at 1C (23kW) would not not harm the battery although you'd probably want to slow the charge rate as you approach a full battery.

Out of curiosity I measured the amps going back into the battery under heavy regen and IIRC it topped out at a little north of 130A which is just less than 2C. Granted that regen is just short pulses into the battery and I don't know what charge rate would be considered bad for the battery chemistry, I mentioned it here for illustration that regen rates are many times what you normally charge at.
2014 Blue Candy FFE
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amped
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Joined: Thu Aug 11, 2016 3:31 pm

Re: Which plug to use 240 or 120

Fri Sep 15, 2017 9:13 pm

Carbuff wrote:If I have the option of using a 240v plug or a 120v plug to charge my ffe overnight. Which uses less electricity? They will both fully charge my car overnight and my power company charges the same rate at all hours, is one more efficient than the other? Any other factors to consider?
As others have pointed out out L2 (240v) will be a bit more efficient. Under "other factors" I would say:

1) Having L2 charging available might be handy in an emergency if you need to top up quickly.

2) It looks like you're in NY? The cabin heater is a real energy hog. Cabin pre-heating from grid electricity will not work well at L1.

3) Along the same lines as #2, the FFE has a thermal management system for the battery that can draw a lot of power to maintain battery temp if the car is charging in a very cold environment. At level 1, this might dramatically lower the effective rate of charging.

WattsUp
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Re: Which plug to use 240 or 120

Fri Sep 15, 2017 11:11 pm

Pearl wrote:
WattsUp wrote: So, with gas too, faster is better.
Faster is not really better with charging. Faster charging means more current, means more heat, means more harmful to the battery.
Excess heat, yes. But, generally speaking, being warmer is more optimal... warmer batteries perform better.

And some battery chemistries, like Li-ion and NiMH, actually get cooler when charging (endothermic), hotter when discharging (exothermic).

Excess heat involved in charging is usually not from the battery itself, but from resistance to current flowing through the charging electronics and wiring located near the battery.

Managing this excess heat is what a cooling system is for and, if it is sufficient to transfer the excess heat away, no harm should come to the battery itself from fast charging.
2013 FFE, Platinum White, Delivered January 2013
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jmueller065
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Re: Which plug to use 240 or 120

Sat Sep 16, 2017 7:43 am

The difference in speed is close to 4x. With a Level 2 EVSE I was able to charge up enough over dinner to be able to go out again in the evening with the car--wasn't able to do that when I was using Level 1.
2018 Cajun Red Chevy Bolt
2016 Magnetic C-Max Energi (lease returned)
2014 Sunset Escape
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2013 Focus Electric (lease returned Jan 2016 for the C-Max above)
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spirilis
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Location: Maryland

Re: Which plug to use 240 or 120

Sat Sep 30, 2017 4:04 am

Fwiw, point of data coming from FORScan Lite...
Sitting in the driveway with a fully charged 2017, running the heater:

Charger input: 26A at 241VAC
Charger output: 16A at 349VDC
Roughly 89% efficiency if my math is right.

My BECM kwh to empty is 28.05kwh so I guess that's where we are with that. Battery coolant input temp was 79F so despite it being 53F outside I assume the battery isn't "cold" right now.
2017 Ford Focus Electric (Magnetic)
2017 Ford C-Max Energi SE (Kona Blue)

WattsUp
Posts: 2113
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Location: SF Bay Area, CA

Re: Which plug to use 240 or 120

Sun Oct 01, 2017 10:13 am

spirilis wrote:Charger input: 26A at 241VAC
Charger output: 16A at 349VDC
Roughly 89% efficiency if my math is right..
Note that the process of charging the battery itself is also around 90% efficient. What you have measured is basically the efficiency of the charger in 1) converting voltage and 2) converting from AC to DC.

So, when taking both this electrical conversion efficiency (roughly 10%, as corroborated by your numbers) and the battery charging efficiency, the overall efficiency for charging the FFE is about 80%. (The numbers hold for pretty much any EV, and most kinds of Li-ion charging scenarios.)

In other words, for every 1 kWh you pay your utility for, about 800 Wh will be stored in your car's battery for you to actually use to drive around. The rest (about 20%) is wasted mainly as heat.
2013 FFE, Platinum White, Delivered January 2013
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