lorenfb
Posts: 1245
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?

Wed Sep 13, 2017 7:24 am

GetOffYourGas wrote:
lorenfb wrote:
GetOffYourGas wrote:


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.


Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.


Did you overlook this?

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


A 60kWh battery is a 2X a 30kWh battery and would dissipate 1/2 the original power of the single 30kWh
by itself supplying all the power, right?

The equations above also indicate that if you actually did combine (not practical) two 30kWh batteries to
make a 60kWh battery, each would dissipate 1/4 (as noted by Reg & indicated above) each's original power.
Remember, all the 'new' powers need to sum correctlly whether you actually did use two 30kWh batteries
or a single 60kWh battery.

GetOffYourGas
Posts: 1607
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?

Wed Sep 13, 2017 7:56 am

lorenfb wrote:
GetOffYourGas wrote:
Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.


Did you overlook this?

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


No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.

SageBrush wrote:
BrockWI wrote: Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.
Reference ?


I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.
~Brian

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

lorenfb
Posts: 1245
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?

Wed Sep 13, 2017 8:22 am

GetOffYourGas wrote:
lorenfb wrote:
GetOffYourGas wrote:
Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.


Did you overlook this?

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


No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.

SageBrush wrote:
BrockWI wrote: Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.
Reference ?


I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.


My original post:

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


The first equation indicates 1/4 power for each 30KWh when used in parallel to produce a single 60kWh;
P = (I/2)^2 X R = I^2 X R divided by 4

BrockWI
Posts: 527
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?

Wed Sep 13, 2017 9:49 am

Yes it is half the total heat generated, but assuming two separate 30 kWh packs (unrealistic I know) each of those packs would be 1/4 as hot as a single 30 kWh pack would be, ignoring ambient heating. Realistically it would be a single 60 kWh pack that would get 1/2 the heat.
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

GetOffYourGas
Posts: 1607
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?

Wed Sep 13, 2017 9:56 am

lorenfb wrote:
GetOffYourGas wrote:
lorenfb wrote:
Did you overlook this?



No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.

SageBrush wrote:Reference ?


I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.


My original post:

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


The first equation indicates 1/4 power for each 30KWh when used in parallel to produce a single 60kWh;
P = (I/2)^2 X R = I^2 X R divided by 4


It seems you are having trouble with me agreeing with you. I don't understand why you are pushing this? You misread my (admittedly poorly written) statement in which I agreed with you. And when I clarify where the 1/4 figure came from (someone else - not you), you pull up an older post of yours in which you state 1/2. Seems defensive from this end of the 'net and I'm wondering why.
~Brian

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

lorenfb
Posts: 1245
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?

Wed Sep 13, 2017 6:00 pm

GetOffYourGas wrote:
lorenfb wrote:
GetOffYourGas wrote:
No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.



I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.


My original post:

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


The first equation indicates 1/4 power for each 30KWh when used in parallel to produce a single 60kWh;
P = (I/2)^2 X R = I^2 X R divided by 4


It seems you are having trouble with me agreeing with you. I don't understand why you are pushing this? You misread my (admittedly poorly written) statement in which I agreed with you. And when I clarify where the 1/4 figure came from (someone else - not you), you pull up an older post of yours in which you state 1/2. Seems defensive from this end of the 'net and I'm wondering why.


Sorry for the back-and-forth, and also sorry if I caused you to get a headache too.

lorenfb
Posts: 1245
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?

Wed Sep 13, 2017 6:01 pm

BrockWI wrote:Yes it is half the total heat generated, but assuming two separate 30 kWh packs (unrealistic I know) each of those packs would be 1/4 as hot as a single 30 kWh pack would be, ignoring ambient heating. Realistically it would be a single 60 kWh pack that would get 1/2 the heat.


Great, everyone's on the same page.

internalaudit
Posts: 66
Joined: Wed Aug 09, 2017 9:34 am
Delivery Date: 09 Aug 2032

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

Wed Sep 13, 2017 6:14 pm

So a 60 kWh battery will heat up half as much as a 30 kWh battery?

Sorry for being crappy at physics.

DaveinOlyWA
Gold Member
Posts: 11958
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 10 Nov 2016
Leaf Number: 314199
Location: Olympia, WA
Contact: Website

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

Thu Sep 14, 2017 6:30 am

internalaudit wrote:
EatsShootsandLeafs wrote:Because I can't help myself, I thought I'd look into this more.

Here is a nicely detailed write up from a guy with a 2015 Leaf. The 2015 Leaf has a supposedly better heat-resistant battery than the early models. In two years and 14k miles he has a 10% range reduction. http://www.wind-works.org/cms/index.php ... ad0bbfc94d

He says "This isn’t out of line with what others have seen.".

As for Tesla, a big matrix here shows that the average model s has projected loss of 23 miles over 100k (10%), with an actual loss reported of just under 6% @ 66k combining all results.
https://www.teslacentral.com/worried-ab ... 000-driven

The tesla data is more reliable because it's a large pool of drivers.

I don't know if relative geography of leaf and tesla is the same, but I imagine it's similar.

One of the teslas after 60k miles had a range reduction from 265 to 264. Anybody think any leaf can do that? The worst, and this was a significant outlier, had a 10% reduction after 54k miles.


Does the Tesla data include battery degradation for battery packs that Tesla had replaced?

I have read a couple of comments over on TMC as well as additional information from a friend who has a Model S that Tesla proactively replaces components that it thinks may fail.

Maybe it's like the old Rolls Royce where there are very few customer complaints because RR fixes the issues and word doesn't go out about them?

I'm not biased for or against Tesla or Leaf but just want to make some informed decision making when it comes to buying a BEV, in late 2018 at the earliest.


well from the chart, its easy to pick out the ones that live in Mojave and Phoenix... ;)

The one consistent parameter is time so having driven 100,000 miles and seen 1% degradation is easy if in a decent climate and you drive 10,000 miles a month.

Can I say my 10/2016 build date 30 kwh pack is bullet proof because I have gone over 22,000 miles with zero quantifiable degradation? That extrapolates to 1% over 100,000 miles, right?

So the graph tells half the story, a story we know but most do not.
2011 SL; 44,598 miles. 2013 S; 44,840 miles. 2016 S30 (build 10/2016); 22,003 miles. 363 GIDs, Ahr 82.34, Hx; 101.21% kwh 28.1 QCs 190, L2's 213
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

SageBrush
Posts: 1107
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

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

Thu Sep 14, 2017 8:14 am

Here is more extensive and up to date data from the Tesla owners Battery Life database:

https://docs.google.com/spreadsheets/d/ ... =154312675

Image



As related to battery age (notice the scale -- this one starts at 85% SoC):
Average 94% SoC remaining after 5 years. Also note that after the first ~ 5% loss further degradation is negligible

Image
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
Car is now enjoying an easy life in Colorado

Return to “LEAF Gen 2 & Infiniti EV”