CHAdeMO power tapering question

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madscientist

Member
Joined
Oct 21, 2015
Messages
8
Does anyone have a handle on the Nissan Leaf DC charge cycle,


what is the max allowable constant current phase power allowable, i.e. what proportion of C is Nissan allowing

do they actually taper the power in the CC phase for safety ?

what cell voltage do they transition from CC full power to CV tapering power


thanks
 
The Leaf can do the full 125A from standard CHAdeMo.. The Nissan chargers I think only put out 105A. (?)
Power only drops when the the highest cell gets to about 4.10-4.12V (around 394V on the pack.. same as a normal charge). The lizard packs might charge to a slightly higher voltage.

For me that's around 40% SOC :cry:
(due to my lower capacity and increased impedance)

This will be a big bonus for the 30kWh packs... I would imagine you could scoop up a lot more juice in 30 minutes.
 
At Nissan HQ, the most I've seen (with mine and others) is 105 amps max or (400V x 105A) or 42kW I think? Once the charge hits over the 60% mark, it has a steady, slow decline down to around 45 amps (18kW) when nearing 80% SOC. As the previous posted said, it can probably do more, so it might be a limitation of the Nissan charger or max input power at that location.
 
GregH said:
This will be a big bonus for the 30kWh packs... I would imagine you could scoop up a lot more juice in 30 minutes.
The Daily Kanban article on the 2nd gen LEAF has a slide that says this:

24 kWh LEAF - 100 km in < 30 min (50 kW CHAdeMO)
30 kWh LEAF - 100 km in ~15 min (50 kW CHAdeMO)
60 kWh LEAF - 100 km in ~8 min (100 kW CHAdeMO)

My LEAF on the other hand is like yours - due to increased impedance the charge rate really slows down above 50% SOC. Limiting cell voltage to 4.10V unlike the 2013+ LEAF which is limited to 4.12-4.13V makes a significant difference in charge rate.

 
drees said:
24 kWh LEAF - 100 km in < 30 min (50 kW CHAdeMO)
30 kWh LEAF - 100 km in ~15 min (50 kW CHAdeMO)
60 kWh LEAF - 100 km in ~8 min (100 kW CHAdeMO)

My LEAF on the other hand is like yours - due to increased impedance the charge rate really slows down above 50% SOC. Limiting cell voltage to 4.10V unlike the 2013+ LEAF which is limited to 4.12-4.13V makes a significant difference in charge rate.

Nice chart, I wonder why they leave such a large gap of "less than 30 minutes" for the 24kWh Leaf? I've brought my Leaf into a QC station at 3% SOC to see how long it takes to go from near empty to 80% SOC and getting enough power for 100 km (62 miles) took less than 13 minutes, it is the other top end (70%, 80%, etc.) that takes nearly another 10 minutes to reach when the power ramps down so much. If the chart was set for miles, then I could see it taking 30 minutes to hit a near 100% SOC on the 24kWh Leaf.
 
Are people saying that Nissan will allow the chademo to put in whatever max it can , are Nissan allowing 4-5 C. Charging ? I find that hard to believe
 
4-5C? I've got a 50Ah pack now and can charge at 125A..
Nissan allows full speed as long as the cells remain below 4.1V.
Not sure how much it would allow on a 100kW CHAdeMO.. (do they even exist yet?)
 
madscientist said:
Are people saying that Nissan will allow the chademo to put in whatever max it can , are Nissan allowing 4-5 C. Charging ?
The car CANNOT allow the quick charger free reign since the charger has NO WAY to know if it is overcharging any of the cells in the pack. Only the BMS can tell that since it is what measures the voltage of each cell.

GregH's description is the best one, and note that the cell with the HIGHEST voltage is the one which causes the BMS to limit the current. If you would put in 96 times 4.1V instead, you would get a MUCH higher current because all the other cells have lower resistance than this one. That would cause the AVERAGE voltage to be 4.1V, but would cause this one cell to have a much higher voltage.
madscientist said:
I find that hard to believe
You should, since that is NOT what happens.
 
The Nissan / Sumitomo chargers are 115 amps max. Most other stations are 120 amps. All the Fuji chargers are 63 amps. BTC chargers are 48 amps. Some Eaton units are restricted with 20 amp increments; either 120, 100 or 80 amps is typical. Blink units are generally 125 amps. Some ABB units are 125, also.

Next year, ABB will likely have a 200 amp charger.

Here's a taper profile with the 45kWh battery in the 2012-2014 Toyota RAV4 EV. The battery voltage is very similar to the LEAF (395 volt for LEAF, 382 volt for RAV4).

Because the CHAdeMO protocol is limited to 200 amps, any "100kW" stations would require a 500 volt battery (which no modern EV has). Therefore, even those future stations will be practically limited to 200a * 400v = 80kW maximum. The nominal charge rate rate would be closer to 200a * 350v = 70kW.

kW is simply volts multiplied by amps:


Rav4chargeGraphic.jpg
 
its still not clear, what I mean is that if you could find a bigger DC charger for the leaf, surely the BMS limits the max charge current to a value that Nissan have decided in the maximum.

I design with Lithiums, no one allowed uncontrolled mac power charging of Lithiums, unlike lead acid, they have a huge charge acceptance ability and can damage themselves .
 
Most likely there is no real C-limit on Leaf (what do 8 bar Leaf owners see when QC-ing?)
Leaf1 just doesn't ask above 125Amps. Maybe the wiring is not made for more.
What we do know that maximum voltage for any cell is 4,13V and that is the main
limitation above 1/3 charge state.
Even at really low SOC and ideal temperatures it is hard to get over
125A on 24kWh pack. That voltage limit is reached really fast especially if
temperature of the pack is not ideal. And this is why all EV-s taper while QC-ing.

24-30kWh pack on 50kW 125A charger is pretty much maxed out.
Teslas 70-90kWh packs on 135kW 330A are pretty much maxed out.
We can expect Leaf2 and Tesla3 both suck 100kW from chargers as MAX speed.
Even if Superchargers are able to give more - battery will not be able to take that.


*
Kia Soul EV with 30kWh pack did charge few minutes faster on 100kW ChaDeMo.
Is it worth it? 2x power to lose 5 minutes on 0-80% time :lol:
100kW charger does make sense only for packs above 50kWh.
This is not Nissan specific.
 
This thread clarifies that charge tapering is driven by the max cell voltage. On my 2014 Leaf I am seeing the tapering start at quite low rates and wondering if that is normal when the pack temperature is around 20 deg C (68 deg F). Some key sample points with CHAdeMO charger input and max cell voltage:
Time Gids kW In Max CP mV Pack T1 C
00:00:00 124 40.1 4044 20.5
00:02:05 140 32.3 4084 20.5
00:04:03 154 29.4 4103 20.9
00:06:04 166 27.8 4114 21.2
00:08:04 178 26.5 4123 21.7
00:10:01 188 23.6 4125 22.1
00:12:04 197 20.0 4126 22.6
00:14:03 206 18.3 4124 23.1
00:16:04 213 14.6 4122 23.5
00:18:01 219 13.3 4121 23.9
00:20:03 224 11.9 4126 24.3

Is it normal to taper from such an early stage? This charge started at 43% as indicated by dash. I can understand starting to taper by 4.12V but curious why is starts to taper before 124 GIDs. I have discussed with the charging provider and they assure me it is the Leaf solely in control and I watched the subsequent session with a Hyundai Ioniq and that was getting over 40 kW growing as pack voltage rose (limited to 125A).

We are doing a nationwide trip of New Zealand promoting EVs http://www.leadingthecharge.org.nz/ and interesting to compare the different vehicle charging results.
 
That looks like a fairly normal CHAdeMO taper for a '14 LEAF.

The BMS will not let cell voltages rise over 4.1V, so it has to taper the charge rate.

If you watched cell voltages for the Ioniq you'd probably find that the pack reaches 4.1V/cell at higher SOC / charge rates. The Ioniq has the benefit of a slightly larger pack (a larger pack all-else being equal will be capable of higher charge rates), but it also appears that the Ioniq's battery pack has exceptionally low internal resistance and is able to accept very fast charge rates.
 
drees said:
That looks like a fairly normal CHAdeMO taper for a '14 LEAF.

The BMS will not let cell voltages rise over 4.1V, so it has to taper the charge rate.

If you watched cell voltages for the Ioniq you'd probably find that the pack reaches 4.1V/cell at higher SOC / charge rates. The Ioniq has the benefit of a slightly larger pack (a larger pack all-else being equal will be capable of higher charge rates), but it also appears that the Ioniq's battery pack has exceptionally low internal resistance and is able to accept very fast charge rates.
Thanks for the confirmation. A related question is as temperature changes how much does it move the tapering point. After a few DCFC where battery was about 35 deg C the taper didn't start until about 65%. Conversely if the pack is cold could it start even earlier?

We pay here by both the minute and kWh (good fair system) and as our winter approaches could we expect even lower start of the taper.
 
Internal resistance of the battery goes up as temperature decreases so charge tapering will start sooner in cold weather. The battery in my 2015 has much lower internal resistance than the 2011 so it charges much faster and reaches a higher SOC before tapering.
 
The 2017 LEAF battery charges REALLY FAST !!! Taper doesn't start until over 80%. Full charge in about 30 minutes... FULL charge... not 80% full in 30 minutes.

Obviously, the older batteries have higher internal impedance, and cold affects all batteries, The older those cells get, the more degradation / more resistance / lower SOC% prior to taper.
 
GetOffYourGas said:
Full charge in 30 minutes? Wow! What is the starting SoC for that? Near 0? Or does it need to be 20%?

I didn't start at zero (and I used a 115 amp charger instead of a 125 amp charger). Staring at about 15%, I think.
 
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