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TonyWilliams
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Re: CHAdeMO power tapering question

Thu Oct 29, 2015 10:48 am

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madscientist
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Re: CHAdeMO power tapering question

Sat Feb 20, 2016 2:47 pm

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 .

arnis
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Re: CHAdeMO power tapering question

Sat Feb 20, 2016 4:37 pm

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.
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

dwl
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Re: CHAdeMO power tapering question

Tue May 02, 2017 10:24 pm

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.
2014 S - 6000 km Jan 2016; 23000 km Sept 2016; 45000 km May 2017; 95% SOH

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drees
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Re: CHAdeMO power tapering question

Tue May 02, 2017 11:42 pm

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.
'11 LEAF SL Powered By 3.24 kW Enphase Solar PV

dwl
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Re: CHAdeMO power tapering question

Wed May 03, 2017 1:51 pm

drees wrote: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.
2014 S - 6000 km Jan 2016; 23000 km Sept 2016; 45000 km May 2017; 95% SOH

GerryAZ
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Re: CHAdeMO power tapering question

Wed May 03, 2017 7:40 pm

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.
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015

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TonyWilliams
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Re: CHAdeMO power tapering question

Wed May 03, 2017 9:23 pm

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
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Re: CHAdeMO power tapering question

Thu May 04, 2017 7:26 am

Full charge in 30 minutes? Wow! What is the starting SoC for that? Near 0? Or does it need to be 20%?
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV
2015 C-Max Energi (302A package)

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TonyWilliams
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Re: CHAdeMO power tapering question

Thu May 04, 2017 8:47 am

GetOffYourGas wrote: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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