Battery capacity loss of 6.6 kW charger versus 3.3-kW

[roperld]

I searched but could not find a thread on whether the 6.6-kW charger causes the battery to lose capacity faster than the 3.3-kW charger.

 

[ebill3]

I searched but could not find a thread on whether the 6.6-kW charger causes the battery to lose capacity faster than the 3.3-kW charger.

There is no experience to help answer your query, but I'll suggest that even with the 6 kW charger, the charging rate is still quite low considering the battery capacity. For my money, it will not make a bit of difference in the rate of battery derogation.

 

[TonyWilliams]

I searched but could not find a thread on whether the 6.6-kW charger causes the battery to lose capacity faster than the 3.3-kW charger.

There is no experience to help answer your query, but I'll suggest that even with the 6 kW charger, the charging rate is still quite low considering the battery capacity. For my money, it will not make a bit of difference in the rate of battery derogation.

I agree.

 

[surfingslovak]

I searched but could not find a thread on whether the 6.6-kW charger causes the battery to lose capacity faster than the 3.3-kW charger.

There were similar discussions about trickle vs 3 kW charging. You might want to review one of the older threads. The upshot was that batteries might prefer C/2 charge rates, in the long run anyway. In the light of this, even 6 kW is pretty slow, since it corresponds to C/4.



Click to open

 

[GaslessInSeattle]

from what we've seen, it appears that ambient temps will far outweigh the influence of charging speeds. OTOH, I would avoid charging any battery while it's still hot, like 8 or 9 bars (unless of course you are in a climate where that is normal ~)

 

[Yogi62]

FYI, for 2013 on the 6.6kw charger, it starts to taper the charge starting at about 93%.

These are the draw readings at a chargepoint, with the car already charged overnight to 80%.
Exactly how much was going into the battery is hard to say, but there is definitely a taper at the end and we know that it stops at 97% SOC from other readings.

That old chart that appears to indicate some very small advantage of C/2 over C/4 is not testing the Leaf battery or charging protocol (did it charge to 100%? What level of discharge?) so I wouldn't put too much weight on it.

Minutes Draw    Estimated Dash reading
0       0.00    80.00%
5       5.89    81.54%
10      5.89    83.08%
15      5.89    84.62%
20      5.89    86.17%
25      5.89    87.71%
30      5.89    89.25%
35      5.89    90.79%
40      5.89    92.33%
45      5.89    93.87%
50      4.38    95.02%
55      3.69    95.98%
60      2.77    96.71%
65      2.33    97.32%
70      2.15    97.88%
75      1.22    98.20%
80      1.36    98.56%
85      1.00    98.82%
90      0.87    99.04%
95      0.68    99.22%
100     0.69    99.40%
105     0.30    99.48%
110     0.00    99.48%
115     0.51    99.62%
120     1.11    99.91%
125     0.00    99.91%
130     0.32    99.99%
135     0.00    99.99%
140     0.04    100.00%
145     0.00    100.00%

 

[EVDRIVER]

Many charge points are on 208V so the output is lower. When my pack is at in the higher 70s and I charge on 3kw the increase is minimal, when I charge over 6kw the temp seem to go up much more and I am tapering faster than the Nissan 6kw charger would. When I charge at home I set my EVSE to about 3kw and use that setting simply because I dont' need it, at public stations I charge faster. I need to look at this closer and log some of the differences but I seem to be able to keep my pack cooler on the 3kw setting. When my pack is cold it is really irrelevant.

 

[surfingslovak]

That old chart that appears to indicate some very small advantage of C/2 over C/4 is not testing the Leaf battery or charging protocol (did it charge to 100%? What level of discharge?) so I wouldn't put too much weight on it.

Yea, the table I quoted above was for illustrative purposes only. The numbers and results do not apply to the LEAF. That said, the results of that study illustrate that the difference in degradation based on various charge rates could be quite small, perhaps even negligible. While we cannot be sure what the numbers might look like for the LEAF, the study does show that the concerns about the speed of charging could be overblown, which is relevant to the question the OP has asked.

I could share more details about the study, which should be linked above as well, if this was of interest. Personally, I believe that the thermal properties and the temperatures reached during and after the charging process will be more relevant than the charging protocol. The cells used LMO chemistry, but were of consumer-grade quality. They were charged to 100% true SOC and not 95% like the cells in the LEAF.

Given the uncertainty and the need for consumer education, it would be beneficial if Nissan and other OEMs published their own numbers or found a way to communicate this type of information more effectively. Vague and generic statements can sometimes prove to be counter-productive and create more questions than answers.

 

[smkettner]

In practical use it would appear heat is a far bigger issue than even L3 charging.
The only question to me is how much more temperature rise is there during 6kW charging vs 3.3kW charging.

 

[Yogi62]

In practical use it would appear heat is a far bigger issue than even L3 charging.
The only question to me is how much more temperature rise is there during 6kW charging vs 3.3kW charging.

I'll try gathering some temps before during and after a charge.

Test 1:
Start: 68 degrees air temp, 60.5% SOC (59% on the dash) pack temp average 68.5
45 minutes later...
finish: 68 degrees air temp, 79.1% SOC (79% on the dash) pack temp average 70.0

 

[TomT]

Barely enough to even measure, let alone worry about.

The only question to me is how much more temperature rise is there during 6kW charging vs 3.3kW charging.

 

[smkettner]

Then that is the answer IMO.

 

[DaveEV]

FYI, for 2013 on the 6.6kw charger, it starts to taper the charge starting at about 93%.

These are the draw readings at a chargepoint, with the car already charged overnight to 80%.

Pretty interesting that it spent an hour around 1 kW topping off the pack and took over 2 hours to charge from 80-100%, though it was pretty much done after an hour.

On my '11 it might taper for 15-30 minutes before stopping and a 80-100% charge has never taken more than 90 minutes (has ranged from 60-90 minutes) despite only charging the first hour at 3.3kW. It looks like the '13 works a lot harder to keep the pack balanced before stopping on a 100% charge.

Looks like you got around 5.5 kWh from the wall on that charge 0.5 kWh more than I've even recorded on mine.

Barely enough to even measure, let alone worry about.

I don't know - I know for sure that charging on my '11 results in the battery pack sensors reading higher. A 2 hour charge can get the pack a few degrees warmer - the heating isn't even, either. I think some think that the charger coolant lines may be partially responsible, in which case the '13s have it good since the charger and coolant remains under the hood.

 

[TomT]

The 6.0Kw charger (which is what its output is, versus the 3.3 Kw) is a very low C rate. Not worth worrying about...

I don't know - I know for sure that charging on my '11 results in the battery pack sensors reading higher. A 2 hour charge can get the pack a few degrees warmer

 

[Yogi62]

I'd like to try a drive 40 mph steady speed taking the battery from 80% to LBW and then immediately charge it back to 80% and then repeat. From my calculations that is optimal speed for cross country travel when you can recharge at 6KW/h. I'd like to see if there is any heat gain from that duty cycle on a 60, 70 and 80 degree days.

 

[TonyWilliams]

I'd like to try a drive 40 mph steady speed taking the battery from 80% to LBW and then immediately charge it back to 80% and then repeat. From my calculations that is optimal speed for cross country travel when you can recharge at 6KW/h.

No, optimum cross country speed for no charging is 12mph, and for charging at 27.5 amps and 240 volts (6.6kW from the wall) is about 5.8kW usable from the battery.

65mph = 4kWh per mile consumed * 21 kWh usable** = 84 miles traveled in 1.29 hours

Refueling at 6.6kW from the wall (5.8kW usable) * 4 = 23.2 miles per hour divided into 84 miles takes 3.62 hours***

So, perfectly positioned charge stations take 4.91 hours to travel 65 miles, or 13.23 miles per hour overall travel

At 23.2mph traveling, I drive at about 8 miles per kWh, so I can travel 168 miles in 7.24 hours and 3.62 hours to refuel equals 10.86 hours, or 15.46 miles per hour overall travel

At 40mph, at 5.9 miles per kWh = 123.9 miles traveled in 3.1 hours + 3.62 charging hours = 6.72 total hours, or 18.4 miles traveled overall per hour.


** (my perfect, brand new condition, warm battery)

*** (not accounting for any inefficiencies for cold batteries, or tapering down of charge at top of charge, or increased internal resistance from degradation)

 

[Yogi62]

I'd like to try a drive 40 mph steady speed taking the battery from 80% to LBW and then immediately charge it back to 80% and then repeat. From my calculations that is optimal speed for cross country travel when you can recharge at 6KW/h.

No, optimum cross country speed for no charging is 12mph, and for charging at 27.5 amps and 240 volts (6.6kW from the wall) is about 5.8kW usable from the battery.

65mph = 4kWh per mile consumed * 21 kWh usable** = 84 miles traveled in 1.29 hours

Refueling at 6.6kW from the wall (5.8kW usable) * 4 = 23.2 miles per hour divided into 84 miles takes 3.62 hours***

So, perfectly positioned charge stations take 4.91 hours to travel 65 miles, or 13.23 miles per hour overall travel

At 23.2mph traveling, I drive at about 8 miles per kWh, so I can travel 168 miles in 7.24 hours and 3.62 hours to refuel equals 10.86 hours, or 15.46 miles per hour overall travel

At 40mph, at 5.9 miles per kWh = 123.9 miles traveled in 3.1 hours + 3.62 charging hours = 6.72 total hours, or 18.4 miles traveled overall per hour.


** (my perfect, brand new condition, warm battery)

*** (not accounting for any inefficiencies for cold batteries, or tapering down of charge at top of charge, or increased internal resistance from degradation)

I think we are agreeing.

I was thinking about very long distance trips 500 miles+ or track competitions. Assuming you want to be at the same state of charge at the end of the journey, the fastest you can travel with repeated charge ups is 18.4 MPH, and while driving move at 40 MPH. The math is a little more complex if you can charge to 100% at the start and be at LBW at the end, and charge up overnight again.

Here are my initial estimates for 3, 6 and 24 KW average charging using 70% DOD (15% to 85%) cycle:

70.00%  DOD
20.00   Battery Capacity                                                
14.00   KW used                                         
3.00    Charge rate kw/h                                                
5       minutes to start/finish charge                                          
                                                        
KW/draw Speed   m/kw    Miles   Dr/min  Ch/min Tot/Min Travel Speed
1.00    5       5.00    70.00   840.00  285.00  1125.0  3.73    
1.43    10      7.00    98.00   588.00  285.00  873.00  6.74
1.85    15      8.10    113.40  453.60  285.00  738.60  9.21
2.56    20      7.80    109.20  327.60  285.00  612.60  10.70
3.42    25      7.30    102.20  245.28  285.00  530.28  11.56
4.41    30      6.80    95.20   190.40  285.00  475.40  12.02
5.56    35      6.30    88.20   151.20  285.00  436.20  12.13
6.78    40      5.90    82.60   123.90  285.00  408.90  12.12
8.65    45      5.20    72.80   97.07   285.00  382.07  11.43
10.87   50      4.60    64.40   77.28   285.00  362.28  10.67
12.79   55      4.30    60.20   65.67   285.00  350.67  10.30
15.38   60      3.90    54.60   54.60   285.00  339.60  9.65
18.06   65      3.60    50.40   46.52   285.00  331.52  9.12
21.21   70      3.30    46.20   39.60   285.00  324.60  8.54
25.00   75      3.00    42.00   33.60   285.00  318.60  7.91
29.63   80      2.70    37.80   28.35   285.00  313.35  7.24
35.42   85      2.40    33.60   23.72   285.00  308.72  6.53
42.86   90      2.10    29.40   19.60   285.00  304.60  5.79

70.00%  DOD
20.00   Battery Capacity                                                
14.00   KW used                                         
6.00    Charge rate kw/h                                                
5       minutes to start/finish charge                                          
                                                        
KW/draw Speed   m/kw    Miles   Dr/min  Ch/min Tot/Min Travel Speed
1.00    5       5.00    70.00   840.00  145.00  985.00  4.26
1.43    10      7.00    98.00   588.00  145.00  733.00  8.02
1.85    15      8.10    113.40  453.60  145.00  598.60  11.37
2.56    20      7.80    109.20  327.60  145.00  472.60  13.86
3.42    25      7.30    102.20  245.28  145.00  390.28  15.71
4.41    30      6.80    95.20   190.40  145.00  335.40  17.03
5.56    35      6.30    88.20   151.20  145.00  296.20  17.87
6.78    40      5.90    82.60   123.90  145.00  268.90  18.43
8.65    45      5.20    72.80   97.07   145.00  242.07  18.04
10.87   50      4.60    64.40   77.28   145.00  222.28  17.38
12.79   55      4.30    60.20   65.67   145.00  210.67  17.15
15.38   60      3.90    54.60   54.60   145.00  199.60  16.41
18.06   65      3.60    50.40   46.52   145.00  191.52  15.79
21.21   70      3.30    46.20   39.60   145.00  184.60  15.02
25.00   75      3.00    42.00   33.60   145.00  178.60  14.11
29.63   80      2.70    37.80   28.35   145.00  173.35  13.08
35.42   85      2.40    33.60   23.72   145.00  168.72  11.95
42.86   90      2.10    29.40   19.60   145.00  164.60  10.72

70.00%  DOD
20.00   Battery Capacity                                                
14.00   KW used                                         
24.00    Charge rate kw/h                                                
5       minutes to start/finish charge

KW/draw Speed   m/kw    Miles   Dr/min  Ch/min Tot/Min Travel Speed
1.00    5       5.00    70.00   840.00  40.00   880.00  4.77
1.43    10      7.00    98.00   588.00  40.00   628.00  9.36
1.85    15      8.10    113.40  453.60  40.00   493.60  13.78
2.56    20      7.80    109.20  327.60  40.00   367.60  17.82
3.42    25      7.30    102.20  245.28  40.00   285.28  21.49
4.41    30      6.80    95.20   190.40  40.00   230.40  24.79
5.56    35      6.30    88.20   151.20  40.00   191.20  27.68
6.78    40      5.90    82.60   123.90  40.00   163.90  30.24
8.65    45      5.20    72.80   97.07   40.00   137.07  31.87
10.87   50      4.60    64.40   77.28   40.00   117.28  32.95
12.79   55      4.30    60.20   65.67   40.00   105.67  34.18
15.38   60      3.90    54.60   54.60   40.00   94.60   34.63
18.06   65      3.60    50.40   46.52   40.00   86.52   34.95
21.21   70      3.30    46.20   39.60   40.00   79.60   34.82
25.00   75      3.00    42.00   33.60   40.00   73.60   34.24
29.63   80      2.70    37.80   28.35   40.00   68.35   33.18
35.42   85      2.40    33.60   23.72   40.00   63.72   31.64
42.86   90      2.10    29.40   19.60   40.00   59.60   29.60

Notes and observations:
1. The miles/KW are estimates, especially at the low and high end. YMMV.
2. The exact charge rate over the entire charge include some taper for the QC. YCRMV.
3. The amount of DOD is only a factor because of the time it takes to stop and
start a charge as long as the average charge is not lowered because of taper.
4. The optimal drive speed increases with the charge rate, 35, 40 and 65 mph
respectively, but can you drive at 65 and then QC repeatedly?
5. Assuming heat isn't an issue, you could cover 12.13, 18.43 and 34.95 miles per hour.

 

[TonyWilliams]

but can you drive at 65 and then QC repeatedly?

That is some solid work !!!

Yes, I did do that last summer with up to 10 QC's per day. That, of course, doesn't mean the battery won't get smoking hot, as mine did in 65-ish F ambient temps in the middle of rainy Oregon in June (battery temp about 130F).

I'm confident that we will have folks doing it starting June 29, 2013 for BC2BC-2013, the All Electric Vehicle Rally, 1500 miles from Canada to Mexico.

So, now we (do you like how I included me in this?) need to make a spreadsheet to type in all the variables to get uber accurate date.

Like the QC rate... it's going to be 48kW (394v @ 120 amps) until 50% SOC, then it will taper down. But, not all QC are 48kW, like the EVoasis Fuji (ChargePoint network) 25kW unit in San Juan Capistrano, California. Then, there is only 394v @ 60 amps until much higher than 50% SOC, which is why it doesn't take twice as long to charge the car.

 

[Yogi62]

Momentarily back to the original topic:
2 hours and 15 minutes of 6KW charge (from 24.1% SOC to 79.1% SOC) and temp went from 69.9 to 73.4. Yes it warms it up, but not much.

I'd love to get scientific and test my theoretical predictions so I might drive the 495 ring around boston and stop at the level 2 chargers installed by the power company at a restaurant chain, but that is far as the charging network extends out in Boston.

The nearest QC is 1000 miles away in Chicago, so I'll have to leave that part to you (yes, Tony, it is all about you!). Besides, with no QC's out here, I didn't get that option. This time.

 

[surfingslovak]

Momentarily back to the original topic:
2 hours and 15 minutes of 6KW charge (from 24.1% SOC to 79.1% SOC) and temp went from 69.9 to 73.4. Yes it warms it up, but not much.

Nice! Any chance that you could find a 16 amp or 3 kW EVSE and get the same type of data to compare? A rise of 3.5 Fahrenheit is nothing to be concerned about, but given that the pack will stay at an elevated temperature for several hours after a charge, this will likely impact battery longevity, even though it will be a small contribution.