Many recent posts about installing the fastest charger and why this might not be the best approach?

[txaggies07]

While true, losing something like 25% or 28% (short of the warranty replacement) would be a serious disappointment. Thus part of why some want to try and minimize the degradation.

Or maximize....

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[DBC]

That doesn't make sense at all since the DC charging generates heat!

Sure it wasn't the charging that killed the battery but the heat (er from charging).

Right but the difference between Level-1 and Level-2 vs Level-2 and DCFC is huge.

This is not what Argonne/Idaho National Laboratories found. Here is the summary:

A study conducted by the Idaho National Laboratory (INL) concluded that while an electric car’s battery will deteriorate faster if it’s only power source is Level 3 charging (which is almost never the case) the difference isn’t particularly pronounced.

The INL tested two pairs of Nissan Leaf EVs from the 2012 model year that were driven and charged twice daily. Two were replenished from 240-volt "Level 2" chargers like those used in one's garage, with the other two taken to Level 3 stations. They were each were driven on public reads in the Phoenix, Ariz. area over the course of a year. They were tested under the same conditions, with their climate control systems set at 72 degrees and the same set of drivers piloting all four cars. The vehicles’ battery capacity was tested at 10,000-mile intervals.

After all four test cars had been driven for 50,000 miles, the Level 2 cars had lost around 23 percent of their original battery capacity, while the Level 3 cars were down by around 27 percent. The 2012 Leaf had an average range of 73 miles, which means these numbers represent a difference of around just three miles on a charge.

Even with daily DC fast charging the difference in degradation was 4%. Not a big deal. Given this low number, it would hardly seem to matter if your MME is DC charged as frequently as once a week. No doubt the difference in AC charge rates will be even less.

The bigger issue was the Nissan cells, not even the lack of a thermal management system, though that aggravated the problem.

 

[Rhynri]

One other reason to have an installed L2 power source of some kind is that it's simply more efficient than L1. Here's an IEEE document on the subject.

 

[Woeo]

The bigger issue was the Nissan cells, not even the lack of a thermal management system, though that aggravated the problem.

So you’re saying you don’t have any data about the effect L3 vs L2 charging would have on new cells with thermal management? ?

 

[horsevxi]

For a battery, power in and power out are the same amount of stress.
Driving at 12kW is equal to less than 60 mph.
L2 charging is doing less damage than using that charge.

Do the math a how much stress you put on the battery doing 0-60 in less than 5 seconds.

This is not true. Power in and power out are two completely different chemical reactions in a lithium ion battery. Discharging power is an exothermic chemical reaction that the cell materials and other barriers are naturally designed to perform. Charging power is an endothermic reaction with a high reverse voltage potential required to perform the basic charging reaction while overcoming parasitic processes and oxidation. Lithium Ion batteries are usually rated for 10X lower charge current capability than discharge current capability, and the charging temperature range is also usually more narrow than the discharging temperature range to manage the stresses of the charging chemical reaction.

Hybrid electric vehicles can charge and discharge the battery as much as the engineers want to maximize life and performance. Hybrids are calibrated to try to maintain the high voltage battery between 40% and 60% at all times because that is truly the best range for the health of the battery. I have a daily commute of 45 miles total, so I plan to charge my MME to 65% each night and run it down to 45% during the day, then charge back up to 65%. I'll only charge more than 65% when I anticipate actually needing the range or during the winter.

 

[JamieGeek]

This is not what Argonne/Idaho National Laboratories found. Here is the summary:

A study conducted by the Idaho National Laboratory (INL) concluded that while an electric car’s battery will deteriorate faster if it’s only power source is Level 3 charging (which is almost never the case) the difference isn’t particularly pronounced.

The INL tested two pairs of Nissan Leaf EVs from the 2012 model year that were driven and charged twice daily. Two were replenished from 240-volt "Level 2" chargers like those used in one's garage, with the other two taken to Level 3 stations. They were each were driven on public reads in the Phoenix, Ariz. area over the course of a year. They were tested under the same conditions, with their climate control systems set at 72 degrees and the same set of drivers piloting all four cars. The vehicles’ battery capacity was tested at 10,000-mile intervals.

After all four test cars had been driven for 50,000 miles, the Level 2 cars had lost around 23 percent of their original battery capacity, while the Level 3 cars were down by around 27 percent. The 2012 Leaf had an average range of 73 miles, which means these numbers represent a difference of around just three miles on a charge.

Even with daily DC fast charging the difference in degradation was 4%. Not a big deal. Given this low number, it would hardly seem to matter if your MME is DC charged as frequently as once a week. No doubt the difference in AC charge rates will be even less.

The bigger issue was the Nissan cells, not even the lack of a thermal management system, though that aggravated the problem.

You don't see the flaw in that study?

The fact that they tested Leaf's without active cooling? In Arizona!

You can see they were trying to find a worst case scenario, which they likely did but they didn't prove temperature had nothing to do with it at all.

They simply found that Level-2 and DCFC on a Leaf had little difference on the overall degredation of the batteries (which was quite significant!).

On a 2012 Leaf with its bad batteries (mentioned at the end). Nissan eventually recalled those batteries.

 

[dbsb3233]

You don't see the flaw in that study?

The fact that they tested Leaf's without active cooling? In Arizona!

You can see they were trying to find a worst case scenario, which they likely did but they didn't prove temperature had nothing to do with it at all.

They simply found that Level-2 and DCFC on a Leaf had little difference on the overall degredation of the batteries (which was quite significant!).

On a 2012 Leaf with its bad batteries (mentioned at the end). Nissan eventually recalled those batteries.

Yep. It's also a small battery (24 kWh). Charging at a low DCFC rate.

A 99 kWh battery charging at rates as high as 150 kW is gonna have a lot more potential for degradation if not managed well. The BMS does most of that, of course, but it still allows for a fair amount of latitude by the user to impact the degradation via charging patterns.

 

[Matthewmohan]

I apologize for highlighting something that was brought up previously, but I HIGHLY suggest people look into whether their local utilities offer a discount or rebate on any connected EVSE. Many do and I used the program my local utility is offering to buy an EnelX Juicebox 40. I believe when I bought it, I was able to get it on sale for $550. Right off the bat, that is significantly cheaper than the Ford option without a significant drop in performance. I submitted my receipt to my utility (PSE&G) and they covered $500 of the cost in the form of a credit on my account. But here’s the best part, yesterday I received a check for $50 from PSE&G. I have never even used this thing and it has already cost me nothing for the unit. And I get back 30% of the installation costs in my taxes. And my utility will pay me $50 a year “in perpetuity”. Not a bad deal.

 

[dbsb3233]

I apologize for highlighting something that was brought up previously, but I HIGHLY suggest people look into whether their local utilities offer a discount or rebate on any connected EVSE. Many do and I used the program my local utility is offering to buy an EnelX Juicebox 40. I believe when I bought it, I was able to get it on sale for $550. Right off the bat, that is significantly cheaper than the Ford option without a significant drop in performance. I submitted my receipt to my utility (PSE&G) and they covered $500 of the cost in the form of a credit on my account. But here’s the best part, yesterday I received a check for $50 from PSE&G. I have never even used this thing and it has already cost me nothing for the unit. And I get back 30% of the installation costs in my taxes. And my utility will pay me $50 a year “in perpetuity”. Not a bad deal.

That's a great deal. Well, for those that can take advantage of it. Not so much for the other rate-payers that are paying for it.

 

[Matthewmohan]

That's a great deal. Well, for those that can take advantage of it. Not so much for the other rate-payers that are paying for it.

Yeah-But that’s their problem...

 

[DBC]

So you’re saying you don’t have any data about the effect L3 vs L2 charging would have on new cells with thermal management? ?

You don't see the flaw in that study?

The fact that they tested Leaf's without active cooling? In Arizona!

First off, you are making assertions, so the obvious question is: What studies can you share that shows DC charging accelerates battery degradation in actual BEVs? My guess is there won't be one because the engineers have structured how the pack handles DC charging so it doesn't happen. You can show an effect on cells in the lab but that's an entirely different situation than when you have a pack in a vehicle.

With respect to the lack of a thermal management system in the Leaf, you have it backwards. If the claim is that DC charging cooks the cells and degrades them, then cells which are actively cooled during charging would experience less degradation in comparison to cells charged at a lower rate. So not having an active thermal management system makes for a better test. It's not a flaw it's a feature. ?

 

[DBC]

That's a great deal. Well, for those that can take advantage of it. Not so much for the other rate-payers that are paying for it.

More electric vehicles means lower rates for all rate payers so long as the electric vehicle is paying anything above the marginal cost of generation. This will invariably happen since most of the cost of delivering electricity is in the high embedded fixed costs of transmission and distribution.

To give an example, where I am a kWh might cost $.27. Of that amount $.05 is the cost of generation. So long as electric vehicle owners are paying more than this amount they are contributing to a reduction in the bills of other ratepayers.

In a time of demand destruction for electricity, electric vehicles are about all electrical utilities have going for them. In this regard the big problem for ratepayers is not discounts for electric vehicle charging, that's a positive, it's bypass by large companies.

 

[DBC]

Yep. It's also a small battery (24 kWh). Charging at a low DCFC rate.

Exactly. Charge rates for batteries are usually designated in "C" rates, with 1C being a full charge in one hour. A 24 kWh pack charged at 50 kW would be 2C and a 100 kWh pack charged at 150 kW would be 1.5C.

It would depend on the taper of course, but 30 kW charging for a 24 kWh pack would be similar to 150 kW charging for a 100 kWh pack.

 

[JamieGeek]

First off, you are making assertions, so the obvious question is: What studies can you share that shows DC charging accelerates battery degradation in actual BEVs? My guess is there won't be one because the engineers have structured how the pack handles DC charging so it doesn't happen. You can show an effect on cells in the lab but that's an entirely different situation than when you have a pack in a vehicle.

With respect to the lack of a thermal management system in the Leaf, you have it backwards. If the claim is that DC charging cooks the cells and degrades them, then cells which are actively cooled during charging would experience less degradation in comparison to cells charged at a lower rate. So not having an active thermal management system makes for a better test. It's not a flaw it's a feature. ?

Here is a study, it looks a lot like the study you cite (same lab) and here is a quote from it:

The higher rate of capacity fade in both packs when compared to the cells can, in part, be attributed to higher pack temperature.

Top of page 11.

and

The temperature distribution of the DCFC pack was much wider than that of the AC Level 2 pack and extended up to 45°C, which likely contributed to the additional capacity fade observed in the DCFC pack.

Seems to me they found some temperature dependencies.

If temperature wasn't such an issue why do OEM's (including Tesla) go to such great lengths to control it?

 

[EV Lab]

Even a higher current Level 2 home EVSE will not be able to supply enough current to the pack to cause any kind of degradation. A 40A Level 2 charger will supply the following current to the pack:

For the extended range pack:
(240V x 40A x 0.94) / (3.7V x 94 x 4) = 6.486A

For the standard range pack:
(240V x 40A x 0.94) / (3.7V x 96 x 3) = 8.468A

where:
0.94 = the vehicle OBC (on-board charger) efficiency - assumed
3.7V = nominal cell voltage
94 or 96 = number of series cells (ER and SR respectively)
4 or 3 = number of parallel cells (ER and SR respectively)

The cells are ~72Ah each (they have to be based on the pack architecture and stated capacities), and the latest LG chemistries typically support a minimum of from a 1C continuous charge rates (C is a multiplier to the Ah to denote current). The rating of these cells are likely higher and could be as high as 2C, but we'll need to wait for a datasheet to leak somewhere... So LG rates the cells at being able to handle 72A of continuous charge current. The current calculated above sourced from the OBC is nothing to a 72Ah cell.


To go a little further, calculating for DCFC charge rates... Ford states that the pack can charge from 10% to 80% in 45 minutes. Applying these numbers

For the extended range pack:
(88000 x 0.7) / (3.7V x 94 x 4) = 44.28A nominal

For the standard range pack:
(68000 x 0.7) / (3.7V x 96 x 3) = 44.67A nominal

where:
88000 or 68000 = usable kWh of pack (ER and SR respectively)
0.7 = 70% (10 - 80% of pack)

These are at nominal voltage, so using the lowest cell charge (assuming 3V is the discharge voltage cutoff, 10% might be ~3.12V, and 80% ~3.96V) which would be calculated like below:

For the extended range pack:
(88000 x 0.7) / (3.12V x 94 x 4) = 52.51A max (at 10% SoC)

For the standard range pack:
(68000 x 0.7) / (3.12V x 96 x 3) = 52.97A max (at 10% SoC)

As you can see, even the charge rates Ford is stating for the charge curve they have programmed into the vehicle, they are still being pretty conservative.

Just as an additional sanity check, I calculated the battery current the Tesla Model Y (sourced here) is seeing. Not sure the exact specs of the Tesla MY cells, but I think they are ~4.8Ah, so likely able to support 4.8A continuous discharge current.

(75000 x 0.8) / (3.7V x 96 x 46) = 3.67A nominal
(75000 x 0.8) / (3.12V x 96 x 46) = 4.35A max (at 10% SoC)

where:
75000 = kWh of model Y pack
0.8 = 80% (10 - 90% of pack)
46 = number of parallel cells

It would appear that Tesla is pushing the discharge current a little more closer to the max discharge current rating than Ford is in the Mach-e...

Note: There are some assumptions used in these calculations, but the values used are based on data from other very similar cells that are known and well understood. These calculations can be refined when more specific Mach-e data is known/leaks.

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