lorenfb wrote:johnlocke wrote:lorenfb wrote:
A further comparison of MS battery heat versus the Leaf's (24kWhr) becomes interesting. Since the Tesla's
and Leaf's overall internal battery impedance is about the same, and the MS weighs about 1.4X the Leaf's weight,
the MS' battery will generate 2X the heat as will the Leaf's battery:
Battery Heat = Rs (internal impedance) X I (battery current)^2
Vehicle Power Losses (moderate freeway speeds - same rolling resistance + moderate drag) =
V (battery) X I (battery current)
Since the battery voltage is the same for both the MS & Leaf, the MS will require about 1.4X (MS weight)
the current than the Leaf at the same speed. Since both the MS & the Leaf have about the same internal
impedance, the MS battery will develop about 2X the battery heat as the Leaf at about the same speeds.
Not true. The model S has only slightly lower efficiency than the Leaf (330wh/mi vs 300wh/mi). So figure 10% more heat not twice the heat. Also there are 7000 cells in a Tesla battery pack as compared to 96 in a Leaf pack. There are a lot of cells in parallel in each module in a Tesla pack so the the current draw from each is much lower. The current draw on a Leaf is though 96 cells in series. Bottom line is that despite being heavier, the Tesla is nearly as efficient as a Leaf and seats up to 7 with the jump seats installed. Weight is less of a factor than aerodynamics particularly at highway speeds.
Here's my data source: https://rennlist.com/forums/mission-e/984855-probable-base-price-2.html
Where're your data to refute mine, i.e simple math based on simple electronics & NOT EPA data.
You do understand internal battery impedance (a common term used in electronics to measure battery
characteristics), right? You have been using TeslaSpy to actually measure the MS' battery output impedance too?
Or maybe you actually used a 18650 cell as was done in the link, right?
My results are NOT based on how each vehicle was driven and under what conditions, i.e. open to question,
but an actual analysis of each vehicle's battery!
Your first error is to equate vehicle weight to power consumption.
Your second error is your source for impedances. They were calculated incorrectly. They forgot to account for the fact that the cells in a Tesla are connected in parallel for the modules and the modules are in series. In a Leaf all the cells are in series even though the cells are packed as pairs. The correct values are 115.2 mohms for the Leaf and 76.5 mohms for the 95 KWH Tesla. That's using your source's figures for the battery's internal impedance. if you are driving at 60 mph on level ground power consumption is about 16KWH per hour or 42 amps current at 375VDC. In a Leaf, that 42 amps flows through each cell in the pack. Those cells had better have a very low impedance. In a Tesla pack those 42 amps are divided among 74 batteries or about 560ma each. The Leaf has a .55 c discharge rate while the discharge rate on the Tesla is .16 c. Which battery do you think is working harder?
Your third error is to dismiss the EPA numbers as irrelevant. They are run under controlled conditions in a lab setting. They do correlate to real world numbers provided by both Leaf and Tesla drivers.
Your fourth error is to state that the battery impedances for both the Tesla and the Leaf are the same. Tesla batteries have about 2/3 of the impedance of a Leaf. Teslas can be equipped with dual 275hp motors. That translates to 1100 Amps current draw and they can actually draw even more on fully charged batteries. See ludicrous mode on Youtube for a demo. Try drawing anywhere near that out of a Leaf battery. I had to do the math 3 times before I believed that current draw. It equates to 15,27 amp draw from each cell in the module.
The purpose of this thread is to discuss whether the 2018 Leaf needs a TMS in hot climates. It's already been proven that Leafs do well in cool climates like England,Canada and the northern U.S. The French Zoe with a 40KWH battery does well in Europe as well.