camasleaf
Posts: 608
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 8:35 am

Long tread, but I likely go with the Leaf since I do not believe I cam lease Model 3. I only need a car for next 3 years.
2011 SLe 06/17/11 Over 71000 miles, GID 213 49.88 AHr; 76%SOH; 16.5kWh
2015 SV 09/02/14, Over 15000 miles, GID 287; 61.12AHr; 98%SOH; 22.2kWh
5.7kW DC System:

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?

Tue Sep 12, 2017 8:40 am

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


Heat is proportional to the square root of the current. Twice the current means four times the heat.


And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?

That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.
~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?

Tue Sep 12, 2017 9:38 am

GetOffYourGas wrote:
camasleaf wrote:
SageBrush wrote:Reference ?


Heat is proportional to the square root of the current. Twice the current means four times the heat.


And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?

That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.


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
Posts: 608
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 9:44 am

GetOffYourGas wrote:
camasleaf wrote:
SageBrush wrote:Reference ?


Heat is proportional to the square root of the current. Twice the current means four times the heat.


And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?

That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.


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."
2011 SLe 06/17/11 Over 71000 miles, GID 213 49.88 AHr; 76%SOH; 16.5kWh
2015 SV 09/02/14, Over 15000 miles, GID 287; 61.12AHr; 98%SOH; 22.2kWh
5.7kW DC System:

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?

Tue Sep 12, 2017 9:49 am

camasleaf wrote:
SageBrush wrote:
BrockWI wrote: Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.
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 ;-)
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

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?

Tue Sep 12, 2017 9:50 am

camasleaf wrote:
GetOffYourGas wrote:
camasleaf wrote:
Heat is proportional to the square root of the current. Twice the current means four times the heat.


And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?

That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.


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."
It also is defined at discharging the full capacity in one hour
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

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?

Tue Sep 12, 2017 10:12 am

camasleaf wrote:Heat is proportional to the square root of the current. Twice the current means four times the heat.


Typo?

Power (heat) = I^2 x R

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?

Tue Sep 12, 2017 10:48 am

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.
~Brian

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

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?

Tue Sep 12, 2017 11:46 am

GetOffYourGas wrote: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.


Trying to wrap my head around this but if I understand this correctly the 60kWh pack is supplying twice the power of the 30 kWh pack in the quote above correct? What I was suggesting is the same load for both packs at the same Ah draw given the same operating voltage, then larger pack would have less internal resistance and thus less heating. Also the larger pack would have more mass (for better or worse) to absorb the internal 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?

Tue Sep 12, 2017 11:56 am

BrockWI wrote:
GetOffYourGas wrote: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.


Trying to wrap my head around this but if I understand this correctly the 60kWh pack is supplying twice the power of the 30 kWh pack in the quote above correct? What I was suggesting is the same load for both packs at the same Ah draw given the same operating voltage, then larger pack would have less internal resistance and thus less heating. Also the larger pack would have more mass (for better or worse) to absorb the internal heat.


No, both packs are supplying the same amount of power. 83.3A * 360V = 30kW. For the 30kWh battery, that is 1C rate. For the 60kWh battery, that is C/2 rate. Same amount of current.

Both packs are also assumed to have the same internal resistance. This is a characteristic of the battery, more or less, and does not change with C rate of discharge.

Therefore both pack have the same internal heating.
~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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