BrockWI
Posts: 565
Joined: Fri Mar 28, 2014 6:28 am
Delivery Date: 28 Mar 2014
Leaf Number: 423875
Location: Green Bay, WI.
Contact: Website

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 12:16 pm

I am sorry for staying off topic, but I am still confused about this. Lets say for example you had two Leaf packs in the same Leaf. In one instance you ran one hour at speed to consume the C1 rate. Then the next day you run the exact same one hour at the same speed but with the two pack in parallel. Now each pack will see 1/2 of that load which will be 1/4 of the resistance and thus 1/4 the heat. But since each pack is heating 1/4 as much the total heat would technically be 1/2 that of the single pack?
3 kw solar pv - XW6048 - 8 L16's
4 ton GSHP
2003 VW TDI 170k miles - 52 mpg lifetime
evse level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013

camasleaf
Posts: 610
Joined: Sun Sep 26, 2010 5:20 am
Delivery Date: 17 Jun 2011
Location: Camas, WA

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 1:05 pm

BrockWI wrote:I am sorry for staying off topic, but I am still confused about this. Lets say for example you had two Leaf packs in the same Leaf. In one instance you ran one hour at speed to consume the C1 rate. Then the next day you run the exact same one hour at the same speed but with the two pack in parallel. Now each pack will see 1/2 of that load which will be 1/4 of the resistance and thus 1/4 the heat. But since each pack is heating 1/4 as much the total heat would technically be 1/2 that of the single pack?


Internal pack resistance does not depend on the load. It decreases as the pack heats up, and increases with age.
2011 SLe 06/17/11 Over 76000 miles 71%SOH 15.7kWh
2015 SV 09/02/14, Over 36000 miles soon to be returned for a 2018
5.7kW DC System

GetOffYourGas
Posts: 1648
Joined: Tue Dec 20, 2011 6:56 pm
Delivery Date: 09 Mar 2012
Location: Syracuse, NY

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 1:14 pm

BrockWI wrote:I am sorry for staying off topic, but I am still confused about this. Lets say for example you had two Leaf packs in the same Leaf. In one instance you ran one hour at speed to consume the C1 rate. Then the next day you run the exact same one hour at the same speed but with the two pack in parallel. Now each pack will see 1/2 of that load which will be 1/4 of the resistance and thus 1/4 the heat. But since each pack is heating 1/4 as much the total heat would technically be 1/2 that of the single pack?


A few things.

1) In your example, you are misusing the term "resistance". That is constant. It is 1/2 the current from each pack, which is 1/4 the heat to each pack.
2) This leads to perhaps a flawed assumption in my argument, in which I am considering the pack and not the cells. A pack is made from a combination of cells. In your example, the 2x pack is literally 2x as many cells. What's interesting is that each pack is producing 1/4 the waste heat, but you have two packs. So in the end, you have 1/2 the heat. But if you were to draw out the circuit showing the internal resistance, you would have 1/2 the internal resistance (resistors in parallel). So in your double pack, there is less internal resistance than in the single pack. Whereas my assumption was that the internal resistance of the 30kWh pack was the same as that of the 60kWh pack. Since I was talking about theoretical packs, it could be true, but is that a fair way to compare a 30kWh Leaf with a 60kWh Model S?
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier

BrockWI
Posts: 565
Joined: Fri Mar 28, 2014 6:28 am
Delivery Date: 28 Mar 2014
Leaf Number: 423875
Location: Green Bay, WI.
Contact: Website

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 1:24 pm

Ahhhhhhh (light goes on in my head) yes I had been thinking of it as doubling the pack size meant splitting the load to twice as many cells, but I get it now that is not likely to be the case, rather just larger capacity cells.
3 kw solar pv - XW6048 - 8 L16's
4 ton GSHP
2003 VW TDI 170k miles - 52 mpg lifetime
evse level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013

lorenfb
Posts: 1387
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 5:17 pm

Oils4AsphaultOnly wrote:
lorenfb wrote:
Oils4AsphaultOnly wrote:
2. That's great for you! I recently QC'd for 30 mins in 90F ambient and saw a 34F increase (18C) to 123F (9 bars)! Since ambient was still 87F by the time I had parked for the night, my pack temp was still at 118F. It took over 10hrs until the following morning before the pack temp had reduced to 98.6F (still 7 bars).

IF there was a TMS set to cool while charging, then my pack would've spent many HOURS less time at elevated temperatures.

Keep in mind that your 4C increase was above ambient (and most likely during cooler weather too). And it was only for 12-15mins. A higher ambient, means higher peak temps during charging and driving, exactly the times that a TMS would be most effective. We're not looking to keep the battery cooler than ambient. We're trying to limit how far above ambient that the pack temp rises to.


Actually, the ambient was about 90 F when mine was QCed for about 10 - 12 minutes and battery temp only increased by a small amount. Sorry your Leaf is abused, given your knowledge of one of the key factors for battery degradation,
extreme battery temps.


Care to explain what I should've done differently? I QC'd from 30% SOC to 81% SOC that night, because I had a bit more driving to do than you did. Should I have stopped at 60% (~15 mins) so that I end up at home at 2% SOC? Which would've been brilliant planning since I was driving through the mountains and all.

Edit: Frankly, your ambient temp claim leaves me with many questions, since my experience was detailed to the tee and completely different from yours.

Edit: Here's my screen captures for that night and the following morning: https://photos.app.goo.gl/H8O3fTTWVAgbXidB3

Yes I charged close to 100%, because Nissan took away the 80% charge limiter, so I sometimes forget to stop the charge at 7am versus 8am (even though the charge timer is set to stop at 10:40am - setting it at 7am would have the car reach 100% at around 4:30am ... because Nissan says there's NO ISSUE TO FIX).


New data:

Today I traveled east from basically LAX to Anaheim, approximately 30 miles. The battery temp was about
25 deg C
at start. Charged to 100% the previous night using home L2. On the return trip, needed to QC at the 605 & 91with
only 27.2 Ahrs remaining:

Start time - 2:02, Start battery temp - 28.4 deg C, ambient - 82 F
Stop time - 2:17, Stop battery temp - 32.7 deg C, 42.7 Ahrs

Battery remained at about 32 deg C during remaining trip home.

I avoid lengthy QC times and base my trips on that and that the min Ahrs will be always be greater than 17 - 18.
Luckily no tows have been required.

lorenfb
Posts: 1387
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 5:30 pm

SageBrush wrote:
camasleaf wrote:
SageBrush wrote:Reference ?


Heat is proportional to the square root of the current. Twice the current means four times the heat.
Yes, but keep in mind that the battery is arranged as 96s so you start at a very low current and work your way to charging ;-)


Why the confused discussion on 1C & 2C? The issue is about how the battery heats up at different driving speeds, right?
One speed discharges the battery at 1C (60 amps for a 24kWhr battery) rate and the other at C/2 (30 amps).

Confusion or did I miss something?

Oils4AsphaultOnly
Gold Member
Posts: 267
Joined: Sat Oct 10, 2015 4:09 pm
Delivery Date: 20 Nov 2016
Leaf Number: 313890
Location: Arcadia, CA

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 5:31 pm

lorenfb wrote:
Oils4AsphaultOnly wrote:
lorenfb wrote:New data:

Today I traveled east from basically LAX to Anaheim, approximately 30 miles. The battery temp was about
25 deg C
at start. Charged to 100% the previous night using home L2. On the return trip, needed to QC at the 605 & 91with
only 27.2 Ahrs remaining:

Start time - 2:02, Start battery temp - 28.4 deg C, ambient - 82 F
Stop time - 2:17, Stop battery temp - 32.7 deg C, 42.7 Ahrs

Battery remained at about 32 deg C during remaining trip home.

I avoid lengthy QC times and base my trips on that and that the min Ahrs will be always be greater than 17 - 18.
Luckily no tows have been required.


Thanks for the details. And again, great for you. The rest of us have to use our car in a manner that works for us. You still haven't told me how I could've NOT abused my leaf?

Indeed a TMS isn't going to help in your situation, since ambient was so low. But what if it was anything like 2 weeks ago, where it was 105 every day? Had I visited my friend and needed to QC (I make it a point to avoid this as much as possible) during one of those days, I would've been looking at 130+F (54+C) battery temp (~11bars) for the rest of the night. Not something I look forward to, and not something an average car owner should have to worry about either.
[2013 leaf traded for 2016 leaf S30:
build date: Sep '16 :: purchased: Nov '16
1 May 2017 - 7300 miles & 363 GIDs
6 Sep 2017 - 13k miles & 359 GIDs
26 Oct 2017 - 15.5k miles & 344 GIDs]

lorenfb
Posts: 1387
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 6:02 pm

GetOffYourGas wrote:
lorenfb wrote:
Using the relationships from the previous posts (1C & C/2):

Power = I^2 x R, where I is the motor current and R is the impedance of the battery (typically 60mohms @ 70 deg F)

Then at 1C I equals about 60 amps and battery Power = 216 watts.
Then at C/2 I equals about 30 amps and battery Power = 54 watts

The rise in battery temperature is a function of the thermal resistance from the battery to the chassis.
The actual battery temperature over time is a function of the chassis temperature which is a function of
ambient.


camasleaf wrote:Google battery 1c meaning

"Charge and discharge rates of abattery are governed by C-rates. The capacity of a battery is commonly rated at 1C, meaning that a fully charged battery rated at 1Ah should provide 1A for one hour. The samebattery discharging at 0.5C should provide 500mA for two hours, and at 2C it delivers 2A for 30 minutes."


So we are talking about two different things. Allow me to elaborate. Your numbers are looking at different C rates for the same battery. I was comparing the C rates for two different batteries. Like, for instance, a 30kWh Nissan battery and a 60kWh Tesla battery.

Let's assume both are 360V.

1C of a 30kWh battery (360V * 83.3Ah) = 83.3A
C/2 of a 60kWh battery (360V * 166.6Ah) = 83.3A

Both batteries output the same amount of current, despite having different C rates, due to the different capacities.

P = I^2 * R
Assuming again that both batteries have a 60mOhm internal resistance, they both have a power dissipation of 416W.


Consider a 60kWh battery as being two 30kWh batteries in parallel. The result also affects the effective output
impedance of the combined batteries (a 60kWh resulting battery). It's now 1/2 of the single 30kWh battery.
The combined battery can obvious supply 2X the current output of the original 30kWh.

So driving at the same speed for either a single or parallel 30Ahr (60Ahr) battery results in the same power consumption,
as would be expected. Also, the total heating effect of the 60Ahr battery will be less than the single 30Ahr battery,
i.e. the lower output impedance of the 60Ahr battery.

Example - 2 parallel 30kWh

P (for each) = (I/2)^2 x R
P (for combined (60kWh)) = 2 x (I/2)^2 x R) = I^2 /2 x R = I^2 x R/2

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

lorenfb
Posts: 1387
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 6:27 pm

Oils4AsphaultOnly wrote:
lorenfb wrote:
Oils4AsphaultOnly wrote:


Thanks for the details. And again, great for you. The rest of us have to use our car in a manner that works for us. You still haven't told me how I could've NOT abused my leaf?

Indeed a TMS isn't going to help in your situation, since ambient was so low. But what if it was anything like 2 weeks ago, where it was 105 every day? Had I visited my friend and needed to QC (I make it a point to avoid this as much as possible) during one of those days, I would've been looking at 130+F (54+C) battery temp (~11bars) for the rest of the night. Not something I look forward to, and not something an average car owner should have to worry about either.


Yes, I''m faced with the same issues when visiting my customers around SoCal. Last year I could make a round
trip to north Pasadena and back from LAX. Now I need to QC on the way back, but only need about 10 -15 minutes
of QC. Previously I could travel to Oxnard and L2 charge there for a return. Now my range not enough and there're
no QCs on PCH to Oxnard.

I wish I had simple answer for you. You just have to plan your drives based on the limitations
of the Leaf. You may just have to use a L2 if it's really hot and plan on the extra time if you don't
wish to further hinder your battery.

From the viewpoint of having had TMS which would operate when QCing, it questionable as to the capacity needed
from a TMS to offset the thermal rise, what the cost would be, and if it would easily fit in the Leaf.

lorenfb
Posts: 1387
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

Tue Sep 12, 2017 7:14 pm

Here's info as to one of the reasons (much higher battery temp losses than Leaf) for Tesla's use of TMS :

https://rennlist.com/forums/mission-e/984855-probable-base-price-2.html

It is a huge voltage drop and a huge power loss, with a correspondingly high cooling requirement. It's a fact of life for high performance EVs (which the Leaf is not by any definition). And why would they ever report that info publically? It's competitive advantage territory.

We tested various discharge rates and states of charge. The cells individually bottom out at about 42mOhm for really low discharge rate, 45mOhm+/-1mOhm for typical discharge rates and 20%-90% SOC, and go as high as 70mOhm at low states of charge.

There are cells with lower impedence, but they universally have lower energy as well, because there's a tradeoff between metal volume (low resistance, no energy) and jelly roll volume (high resistance, high energy).


The Tesla Model S pack resistance is around 0.064Ohms
Where did this number come from?

My Nissan with a 24kWh battery (~ 60 Ahr) has an output impedance of about 62 mohms
(.062 ohms) at 33 C now at about 50K miles. When it was new it had about 56 mohms
at the same temp.

The Model S with a 85kWh battery (Panasonic) should have less than 20 mohms. The Model S with
a 100 kWh battery should have less than about 15 mohms


Well, if your Tesla data are correct, Tesla's battery technology (Panasonic) compared to Nissan's
could use improvement:

Re - Nissan's effective overall battery impedance
Rs - Nissan's single cell battery impedance

Re = Rs X 96 / 20, where Re = 56 millohms (new @ 30 C)

Rs = Re / 4.8 = ~ 12 mohms

The Leaf's max motor current is about 225 - 250 amps which results in only about
only a 15 volt battery voltage drop compared to the Tesla's voltage drop at 1000 amps
of about 60 volts (poor efficiency).

If these data are accurate, it's time for Elon to use those SpaceX physicists on Tesla's battery technology.

Return to “LEAF Gen 2 & Infiniti EV”