Best Practice for battery preservation

[ChasingCoral]

So this is probably a question for everyone as well as you, so I’m going to do some tagging @LYTMCQ @dbsb3233 @ChasingCoral @JamieGeek @hybrid2bev - So I remember hearing from a vlogger who was reading back info from Ford on the MME, and he was saying that the available batteries on the MME are 70kw & 90khw, but the sizes are actually 75kwh & 98kwh... does that mean the extra 5kwh & 8kwh are the buffer? If so, would this mean we can charge to 100%, as we’d only be at 90khw on the battery?

Or, more likely, the blogger was just shortening 75 and 98 to 70 and 90 as shorthand.

Sponsored

 

[SJ_Okay]

Or, more likely, the blogger was just shortening 75 and 98 to 70 and 90 as shorthand.

So just to be clear, he was saying you’ve got 70kwh of useable battery on the 75kwh size and 90kwh on the 98kwh. Here is the video. He says it right up front, and appears to be reading it from a notebook, which makes me think he’s just been given that info by Ford.

 

[dbsb3233]

First time I've seen that video. The 70 and 90 seem to be coming completely out of left field, as I don't think we've ever heard that anywhere else. It would really surprise me if he were given that info and that we'd never heard it confirmed anywhere else. Especially since that video was from 2 months ago.

I think I'd take it with a grain of salt. But they are probably ballpark. I've been estimating 90 usable for the ER battery anyway. Not based on anything specific, but seems like something roughly around 10% buffer is common for BEVs.

 

[SJ_Okay]

First time I've seen that video. The 70 and 90 seem to be coming completely out of left field, as I don't think we've ever heard that anywhere else. It would really surprise me if he were given that info and that we'd never heard it confirmed anywhere else. Especially since that video was from 2 months ago.

I think I'd take it with a grain of salt. But they are probably ballpark. I've been estimating 90 usable for the ER battery anyway. Not based on anything specific, but seems like something roughly around 10% buffer is common for BEVs.

I’m just going to ask him where he got that info. Will let you know what he says.

 

[hybrid2bev]

So this is probably a question for everyone as well as you, so I’m going to do some tagging @LYTMCQ @dbsb3233 @ChasingCoral @JamieGeek @hybrid2bev - So I remember hearing from a vlogger who was reading back info from Ford on the MME, and he was saying that the available batteries on the MME are 70kw & 90khw, but the sizes are actually 75kwh & 98kwh... does that mean the extra 5kwh & 8kwh are the buffer? If so, would this mean we can charge to 100%, as we’d only be at 90khw on the battery?

I think to the point of your question, no don't charge to 100% daily.

I think for the purpose of long term battery preservation we would ignore the buffer capacity when considering how far to daily charge. You only want to keep the charge between 80% and 20% of the USABLE capacity. So, daily charge up to what DISPLAYS as 80% on the vehicle screen, not the technical capacity. I think the buffer is there to keep you from destroying the battery by over/under charging, not maintaining it's health in the long run.

 

[JamieGeek]

Keep in mind that I believe Ford has said that you can set the charge to level.

So if you set that to something like 80% you can plug in daily and not charge to full.

Battery degredation isn't really as big of a deal as everyone makes it out to be. On my Focus Electric I had to charge to full daily and after 3 years it showed no degredation (in addition I had posted a link to the Focus Electric forums where someone posted that they had 100,000 miles on their Focus Electric with a minimal amount of degredation over that time).

 

[ChasingCoral]

I’m just going to ask him where he got that info. Will let you know what he says.

Yes, it's clear he's reading from notes. It will be good to hear where he got that. I don't recall seeing it anywhere else. It certainly isn't mentioned by the MME engineer in the Jalopnik video:

He cites them as over 75 and a over 98. That's consistent with the Tech Specs in US and EU of 75.7 and 98.8. I think any time a vlogger or other non-Ford source comes out with a unique bit of information we need to take it with a grain of salt until it's confirmed by another source.

 

[engnrng]

Hopefully Ford will have a clear manual on charging. My Hyundai Kona has a lifetime warranty on the 64 kWh battery. The manual says the following:
Charging Time Information CHARGING INFORMATION
Level 2 AC Charging Takes approx. 9 hours 35 minutes at room temperature when charged to 100%.
DC Fast Charging 100 kW charger Takes about 54 minutes at room temperature when charged to 80%. Can be charged to 100%.
50 kW charger Takes about 75 minutes at room temperature when charged to 80%. Can be charged to 100%.
Level 1 AC Charging Takes approx. 59 hours at room temperature when charged to 100% (voltage at 120V).

Note that prolonged and continuous use of DC fast charging may reduce the long term life of the EV battery. Usage of a DC fast charger should be minimized when possible in order to help prolong the life of the EV battery.

DC fast charging (also known as Level 3 charging) provides high power DC current directly to the EV battery. DC charging stations are capable of charging the EV battery to 80% in less than 75 minutes under normal conditions. While DC charging is very fast compared to AC charging, prolonged and continuous use of DC fast charging may reduce the long term life of the EV battery.

 

[dbsb3233]

While DC charging is very fast compared to AC charging, prolonged and continuous use of DC fast charging may reduce the long term life of the EV battery.

That's another reason that I wouldn't consider buying a BEV if I didn't have secure, dedicated L2 charging for it (typically a house with a garage).

 

[timbop]

In general the usable battery should be computable just with the numbers that the EPA publishes. Logically if we take the published EPA numbers for total range in miles and multiply that by the published average kwh/mile rating we should end up with the total kwh capacity of the battery. This is based on the assumption that the range and kwh/100mi values are based off the same data. Simple, right?

Except that the numbers that the EPA publishes appear to be inconsistent with the known battery sizes, at least with the examples I have found. For example, the generally accepted battery sizes for the Chevy Bolt are 66 kwh for the 2020 model, and 60 kwh for the 2017-2019 version. The 2020 kona electric is reported to have a 64kwh battery. The EPA numbers for the below calculations can be found here. Using the numbers from EPA (converting published kwh/100 mi to kwh/mi):

• 2020 Bolt (should be 66): 259 mi * .29 kwh/mi = 75
• 2017-2019 bolt (60): 238 mi * .28 kwh/mi = 66
• 2020 kona (64): 258 mi * .27 kwh/mi = 70

Even if the EPA range is computed on best-case city driving, using the values for MPGe and 33.7 kwh/gal of gas the results are still higher than they should be:

• 2020 Bolt (should be 66): 259 * .265 = 68
• 2018-2019 bolt (60): 238 * .263 = 62
• 2020 kona (64): 258 * .255 = 66

Clearly there is a discrepancy, and it seems like the EPA numbers are where the inconsistency lies. Paying close attention, the battery capacity based on EPA range is off by on the order of 10% (9.4% to 13.6%) - some of which is due to the rounding of the reported EPA kwh/100 mi ratings. Completely speculating here, but I wonder if the range number for the EPA range is in fact based on the total battery size including buffer, and the reported battery sizes are in fact the usable values? Or is the EPA computing total range and kwh/mi off of different metrics?

What am I missing?

 

[dbsb3233]

In general the usable battery should be computable just with the numbers that the EPA publishes. Logically if we take the published EPA numbers for total range in miles and multiply that by the published average kwh/mile rating we should end up with the total kwh capacity of the battery. This is based on the assumption that the range and kwh/100mi values are based off the same data. Simple, right?

Except that the numbers that the EPA publishes appear to be inconsistent with the known battery sizes, at least with the examples I have found. For example, the generally accepted battery sizes for the Chevy Bolt are 66 kwh for the 2020 model, and 60 kwh for the 2017-2019 version. The 2020 kona electric is reported to have a 64kwh battery. The EPA numbers for the below calculations can be found here. Using the numbers from EPA (converting published kwh/100 mi to kwh/mi):

• 2020 Bolt (should be 66): 259 mi * .29 kwh/mi = 75
• 2017-2019 bolt (60): 238 mi * .28 kwh/mi = 66
• 2020 kona (64): 258 mi * .27 kwh/mi = 70

Even if the EPA range is computed on best-case city driving, using the values for MPGe and 33.7 kwh/gal of gas the results are still higher than they should be:

• 2020 Bolt (should be 66): 259 * .265 = 68
• 2018-2019 bolt (60): 238 * .263 = 62
• 2020 kona (64): 258 * .255 = 66

Clearly there is a discrepancy, and it seems like the EPA numbers are where the inconsistency lies. Paying close attention, the battery capacity based on EPA range is off by on the order of 10% (9.4% to 13.6%) - some of which is due to the rounding of the reported EPA kwh/100 mi ratings. Completely speculating here, but I wonder if the range number for the EPA range is in fact based on the total battery size including buffer, and the reported battery sizes are in fact the usable values? Or is the EPA computing total range and kwh/mi off of different metrics?

What am I missing?

I've wondered the same thing. In theory, we should just be able to back-calculate it, and the difference should be how much of the battery is held as safety reserve. But it doesn't seem to work out that way. I've just written it off as just one more "fuzzy number" when it comes determining the efficiency and range of BEVs. It all varies so dramatically based on driving speeds and conditions anyway that I find the ratings just a few notches short of worthless. I don't really trust it until I see some people posting real-world YouTube videos showing what they're really getting for miles/kWh at specific speeds.

(As an aside, I can't tell you how much I hate that it's getting flipped it into "kWh per 100 miles". That's like saying "Gallons per mile" to me. Just seems totally upside down.)

 

[eager2own]

(As an aside, I can't tell you how much I hate that it's getting flipped it into "kWh per 100 miles". That's like saying "Gallons per mile" to me. Just seems totally upside down.)

Most of the world focuses on gallons per mile (or liters per 100 kms) rather than miles per gallon as we do in the US. And their system is the better one.
Here's a good summary explaining why focusing on gallons per mile leads to better decisions:

https://www.popularmechanics.com/cars/a12367/4324986/

Maybe the BEV transition will facilitate our adopting the better metric also.

Sponsored