RC-Monster Forums - View Single Post - What kind of performance would the Tesla have

othello · 01.13.2010, 05:30 PM

Lutach i can understand your feeling that considering Teslas car price level you want the best cell powering this car. C rate of the cells used is only one criteria when it comes to define "best" cell. Of course a higher C rate allows higher power levels and an efficient cool running battery pack also translating in a higher range. On the other side Teslas rather small motor can't cope for long with high power levels. The motor if i recall it right is only air cooled and will simply overheat when pushed to hard (one of the reasons why they limited top speed to around 120mph which requires around 80KW according to their mathematical model). Pushing a street legal car to 60mph in around 4 seconds is not that bad after all ;-)

When reading articles about their battery pack and cell choice i got the impression that many other criterias (beside C rate) had to be considered: safety, cycle life, energy density are among the important ones. Don't forget that their cell tests, R&D of battery pack, passing safety tests and so on dates already a few years back and implied high costs. You can't simply switch to another cell now that the car is beeing sold and every component is optimised around a certain cell design.

Facts gathered from Teslas articles about their battery pack:
. Cells have a capacity of 2.2Ah
. 99 cells in series: around 366.3V (3.7x99)
. 69 bricks in paralel: around 151.8Ah (69x2.2)
. 151.8 x 366.3 = 55.6KwH on board (roughly comparable to 8 liters of gasoline)

Tesla states that the battery pack is able to provide up to 200KW.
. 200 / 69 = 2.89KW per paralleled string
. 2890 / 366.3V = 7.88A

If those cells were able to hold voltage at 3.7V each string must provide less then 8A to achieve a power level of 200KW (or 544A @ 366.3V).

To optimise cycle life cells are operated between 3.0V and 4.15V. To achieve 200KW with a minimum cell voltage of 3V (system pack @ 297V) one would need 673A (673 / 69 = 9.75A per cell). Amp draw per cell should never exceed 10A under those circumstances.

Lutach, i'm looking forward seeing your built.

	(#11)
othello HV basher Offline Posts: 392 Join Date: Jun 2007 Location: Austria (Europe)	01.13.2010, 05:30 PM Lutach i can understand your feeling that considering Teslas car price level you want the best cell powering this car. C rate of the cells used is only one criteria when it comes to define "best" cell. Of course a higher C rate allows higher power levels and an efficient cool running battery pack also translating in a higher range. On the other side Teslas rather small motor can't cope for long with high power levels. The motor if i recall it right is only air cooled and will simply overheat when pushed to hard (one of the reasons why they limited top speed to around 120mph which requires around 80KW according to their mathematical model). Pushing a street legal car to 60mph in around 4 seconds is not that bad after all ;-) When reading articles about their battery pack and cell choice i got the impression that many other criterias (beside C rate) had to be considered: safety, cycle life, energy density are among the important ones. Don't forget that their cell tests, R&D of battery pack, passing safety tests and so on dates already a few years back and implied high costs. You can't simply switch to another cell now that the car is beeing sold and every component is optimised around a certain cell design. Facts gathered from Teslas articles about their battery pack: . Cells have a capacity of 2.2Ah . 99 cells in series: around 366.3V (3.7x99) . 69 bricks in paralel: around 151.8Ah (69x2.2) . 151.8 x 366.3 = 55.6KwH on board (roughly comparable to 8 liters of gasoline) Tesla states that the battery pack is able to provide up to 200KW. . 200 / 69 = 2.89KW per paralleled string . 2890 / 366.3V = 7.88A If those cells were able to hold voltage at 3.7V each string must provide less then 8A to achieve a power level of 200KW (or 544A @ 366.3V). To optimise cycle life cells are operated between 3.0V and 4.15V. To achieve 200KW with a minimum cell voltage of 3V (system pack @ 297V) one would need 673A (673 / 69 = 9.75A per cell). Amp draw per cell should never exceed 10A under those circumstances. Lutach, i'm looking forward seeing your built. Brushless 1:5 custom 4wd Baja based on 1:8 truggy chassie Jazz 55-10-32, Neu 1515/2Y (1100kv), 9s2p A123 (27v), up to 3.1KW Latest video with eagletree Data inserts: Run on asphalt