DaveinOlyWA
Posts: 14810
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Nov 2019
Leaf Number: 319862
Location: Olympia, WA
Contact: Website

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sat Apr 07, 2018 4:56 pm

This was from the log of yesterday's trip. One thing also noticed is the length of time for the batteries to cool off. They lose heat fairly well when very hot but are slow to return to ambient temps. My S30 would return to ambient or near it in less than 12 hours. Yesterday, I started out nearly 19 hours after the previous QC still 16º above ambient temps. In my garage, the Winter ambient temps (due to leakage from furnace I think) does not vary very much running from low to upper 50's over a HUGE range of outside temps. Yesterday's ambient was 57º on a slightly warmer than normal day.

But today, I did see first EVER significant drop in HX dropping from 115.87% to 115.48 %
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 10,081 mi, 95.03% SOH
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sat Apr 07, 2018 5:37 pm

lorenfb wrote: Using your charging data (I assume), the 2018 40 kWh Leaf battery has about the same battery resistance (55 mohms) as the 24 kWh battery.
Given that adding more cells in parallel (effectively) for more energy when using the same chemistry should have resulted in about .60 (24/40)
the battery resistance (on average) of the 24 kWh battery resistance, so one can possibly conclude a change in battery chemistry (worse).
Additionally, since the 2018 battery is running hotter with the approximate same battery resistance, i.e. same internal heat generation,
one would assume that its thermal resistance to ambient has increased. Reg/LeftieBiker have noted/implied this up-thread.
Am I reading this right -- about 1-2% of power is lost to heat ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

lorenfb
Posts: 2426
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sat Apr 07, 2018 7:54 pm

SageBrush wrote:
lorenfb wrote: Using your charging data (I assume), the 2018 40 kWh Leaf battery has about the same battery resistance (55 mohms) as the 24 kWh battery.
Given that adding more cells in parallel (effectively) for more energy when using the same chemistry should have resulted in about .60 (24/40)
the battery resistance (on average) of the 24 kWh battery resistance, so one can possibly conclude a change in battery chemistry (worse).
Additionally, since the 2018 battery is running hotter with the approximate same battery resistance, i.e. same internal heat generation,
one would assume that its thermal resistance to ambient has increased. Reg/LeftieBiker have noted/implied this up-thread.
Am I reading this right -- about 1-2% of power is lost to heat ?
You're correct. At about 56 mohms and 100 amps QC charging, that's only .56 kW instantaneous power
loss when supplying about 35 kW actual charging power. Although the relative power loss seems small,
it becomes problematic if not dissipated (TMS) or avoided (charging tapering).
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 10.3K miles, SOH 109Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sun Apr 08, 2018 2:22 am

lorenfb wrote:
SageBrush wrote:
lorenfb wrote: Using your charging data (I assume), the 2018 40 kWh Leaf battery has about the same battery resistance (55 mohms) as the 24 kWh battery.
Given that adding more cells in parallel (effectively) for more energy when using the same chemistry should have resulted in about .60 (24/40)
the battery resistance (on average) of the 24 kWh battery resistance, so one can possibly conclude a change in battery chemistry (worse).
Additionally, since the 2018 battery is running hotter with the approximate same battery resistance, i.e. same internal heat generation,
one would assume that its thermal resistance to ambient has increased. Reg/LeftieBiker have noted/implied this up-thread.
Am I reading this right -- about 1-2% of power is lost to heat ?
You're correct. At about 56 mohms and 100 amps QC charging, that's only .56 kW instantaneous power
loss when supplying about 35 kW actual charging power. Although the relative power loss seems small,
it becomes problematic if not dissipated (TMS) or avoided (charging tapering).
Indeed, it does seem like a small amount.
I imagine a 200 Kg pot of water being heated by a 560 watt element.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

iPlug
Posts: 443
Joined: Thu Apr 28, 2016 6:47 pm
Delivery Date: 25 Apr 2016
Location: Rocklin, CA

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sun Apr 08, 2018 8:22 am

SageBrush wrote:I imagine a 200 Kg pot of water being heated by a 560 watt element.
I do as well, but that's because those specs fairly accurately describe the water capacity and maximum power usage for a typically sized heat pump water heater operating in heat pump only mode.

Sorry, now back to topic. :D
'19 Model 3 SR+ (own), '19 Leaf SV (leased), '12 Plug-in Prius (sold 3/19), '16 Leaf SV (prior lease), 11.43kW Solar PV (16MWh/yr real production), 20.5 SEER/13.0 HSPF ducted air-source heat pump, 3.70 UEF heat pump water heater, Induction Cooktop

Joe6pack
Posts: 163
Joined: Tue Oct 09, 2012 4:57 pm
Delivery Date: 07 Oct 2012
Leaf Number: 025854

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sun Apr 08, 2018 8:41 am

SageBrush wrote:Nissan screwed the pooch on QCFC, although it remains to be seen (or figured out) whether even one charging session at 45 kW will be available in warm/hot weather.

The no less important question is how hot the battery gets throughout the summer. I asked Joe "the mechanical engineer" in another thread how much heat dissipation drops on a 95F day compared to 35F based on a simple model of conduction but no answer was forthcoming so I'll provide it here: 75%

Ignoring just for a moment other variables in play like specific heat, better ventilation during driving and time, we are starting the game from the sqrt(0.25) = 50%, or about 11 kW based on the reports of 22 kW throttling when the battery reaches 115F. I am not saying that the LEAF will be throttled to 11 kW in the summer or that the battery will live at 115F for months on end. I am saying that the LEAF battery in the 40 kWh model appears to be even more vulnerable in warm climates than prior models and more information is absolutely required to be an informed buyer.

Caveat Emptor. Or just plop down $30k based on "confidence" from Nissan Corporate and a battery warranty that will keep the car running at something over 60% of new range for 8 yrs/ 100k miles.
I ignored it because it's not relevant. It's obvious that ambient temperature has very little to do with the LEAF's battery temperature rise during quick charging. Your 75% delta, if it's even correct, is only looking at the cooling of the outside of the case which is dependent on ambient temps and the design of the case. However, the issue is that the LEAF's battery cells (and maybe all battery cells) have high thermal capacitance and low thermal conductance. It's analogous to a block of steel which has high thermal capacitance and low thermal conductance. An equivalent block of aluminum, copper or silver would have lower thermal capacitance and higher thermal conductance. This is why steel is never used as a heat sink while aluminum is very common. Any heat generated in the cells tends to stay in the cells and is slow to be conducted away to the outside and that's why battery temps can remain high many hours later. The solution is to cool smaller groups of cells by putting space between the cells and circulating a fluid (air or liquid) thereby reducing the temperature gradient across the cells. Of course the fluid would have to be cooled using a separate radiator or the car's A/C system. This adds cost, increases size, increases weight and decreases efficiency - but it does reduce cell temperatures. It would also have to work while sitting still since we are talking about quick charging thereby increasing charging times - so pick your poison. Nissan looked at "their" markets and "their" customer's use cases and determined this was not necessary. They chose to approach it from the other direction and to limit the amount of heat that is generated in the first place. So there you go.
2012 Leaf SL leased October 4th, 2012
Braselton, GA

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sun Apr 08, 2018 8:47 am

Joe6pack wrote:
SageBrush wrote:Nissan screwed the pooch on QCFC, although it remains to be seen (or figured out) whether even one charging session at 45 kW will be available in warm/hot weather.

The no less important question is how hot the battery gets throughout the summer. I asked Joe "the mechanical engineer" in another thread how much heat dissipation drops on a 95F day compared to 35F based on a simple model of conduction but no answer was forthcoming so I'll provide it here: 75%
I ignored it because it's not relevant.
You mean you cannot see the relevance.

Wait until warmer weather, then even you will wise up. Maybe
Your 75% delta, if it's even correct
I'm having a hard time believing that you are an engineer, even though I know that competency spans a large range.
Last edited by SageBrush on Sun Apr 08, 2018 10:15 am, edited 2 times in total.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sun Apr 08, 2018 8:49 am

iPlug wrote:
SageBrush wrote:I imagine a 200 Kg pot of water being heated by a 560 watt element.
I do as well, but that's because those specs fairly accurately describe the water capacity and maximum power usage for a typically sized heat pump water heater operating in heat pump only mode.

Sorry, now back to topic. :D
Electric tea kettle, not a heat pump ;-)
Resistance heat with a COP of 1.0
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

LeftieBiker
Moderator
Posts: 14874
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
Location: Upstate New York, US

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Sun Apr 08, 2018 1:38 pm

Has anyone looked yet to see if the little cabin air exhaust flap in the passenger compartment floor is still there, by the emergency power cutoff?
Last edited by LeftieBiker on Wed Apr 11, 2018 10:25 pm, edited 1 time in total.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

borugee
Posts: 50
Joined: Fri Sep 15, 2017 8:06 pm
Delivery Date: 18 Mar 2018
Location: Dallas TX

Re: Possible Widespread 2018 Traction Battery Quick Charge Problems

Wed Apr 11, 2018 9:58 pm

SageBrush wrote: Perhaps we need a new acronym: DCSC "DC slow charging."
:D :lol: :lol:
Borugee
2018 SL ; 03/18 Delivery ; Dallas TX ; @10k Mile ; SOH=94.83,AHr=109.47,Hx=109.12

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