If I wanted to make a Tesla Model 3 more competitive, it stands to reason that weight reduction would help. The battery back is good for 300 miles of range, but since I am trailering my theoretical car to autocross events, I only need about 10 miles of range for a day, call it 25 for good measure. So I only need 1/12 the battery pack, a huge weight savings. I can also put the battery where I want it for weight distribution. I could even have another 11 battery packs in the trailer for hot swapping between runs.
The question is, will the motors care if I am running 1/12 of a battery? Will power also be affected? My understanding is that the Tesla uses a collection of hundreds of Lion cells, same as my Makita drill. If I am pulling from 100, 1000, or 10,000, does it make a difference in HP at the motor?
Yes. Each cell can only deliver a certain amount of power, so more cells equals more total power delivery. Think of them as little fuel tanks with a built in pump, and the more "tanks" you have the more fuel you can deliver at a given time. High EV performance levels are almost a side effect of efficient motors and big batteries.
Yes, absolutely. Bigger batteries have more capacity, but also more peak power, as each cell can generate a relatively fixed number of watts. Think of the battery less like a gas tank and more like cylinders in an engine.
And of course Keith tree'd me!
Fewer batteries won't produce enough amps to see the performance you are expecting. In gas engine terms, its like trying to save weight by taking out a twin turbo V12 and installing a lawnmower engine. Sure you will save weight, but the lawnmower engine won't have the same amount of nut as the V12.
In reply to Keith Tanner :
I'm left with the question how would you manipulate battery and motor/controls to deliver lower power levels with greater range? Let's say we wanted the vehicle performance of a 1980 Rabbit GTI? Yes they existed in Canada a round headlight GTI in red, whitenor black.
For a race you want higher power output than power density. Tesla batteries are made for density so the vehicles go long ranges, but battery packs like the Chrysler Pacifica Hybrid cells have the highest power output because they're needed to dump all their energy to move a minivan suddenly.
In reply to Rons :
I think you are thinking in internal combustion engine terms. Making the car slower won't increase its range, if anything the way I interpret the efficiency charts, a lower power motor will make the range shorter because they're less efficient.
In reply to Pete. (l33t FS) :
Exactly. The bigger the electric motor, the more efficient it is. So you get the performance as a side effect. Same with batteries, a high capacity battery can also dump more power. EVs work differently than internal combustion vehicles and we're all learning to think of the trade offs differently.
The hybrid batteries might have a higher "C rating" (basically, how quickly it can discharge) but that's needed because they're smaller. Think of the C rating as a percentage. A big EV battery doesn't need the same C rating to be able to deliver the same absolute amount of power.
Every EV has the performance level of a 1980 GTi. You just don't depress the accelerator very far :) Or you simply limit it in software, then you offer a delimited software based power upgrade and car enthusiasts get all upset...
Now I am thinking of minmax possibilities. Like, a smaller battery sheds weight but increases handling, but the battery is a smaller proportion of weight...
I will need a chart
You could look at different battery chemistries like lithium titanate but Tesla electronics are likely going to keep you from doing any kind of mods.
In reply to Pete. (l33t FS) :
To really berkeley with your chart CATL has announced but not in production they have a battery that is 1 kilo per 500 watts so by math a 100kilowatt battery would weigh 200 kilos or 440 pounds.
What size pack did your car come with? I would look at whether anyone has swapped in the lower range packs and convinced the car to be happy/abuse them enough to get good power out of them. None of the packs are small so I would imagine even a 50KWh pack would be capable of providing some serious umph if the computer was willing to use it.
Nothing says you need a big battery pack- smaller ones have less physical storage of electrons, so for a track toy only something small but high discharge might work great and have quick recharge times, assuming you can cool it properly.
I think if you circumvent the V and A issues of using a smaller pack, you're on to a great idea. I don't know how Tesla does their series/parallel configuration, but it's worth a look.
The battery composition and construction dictates how many amps it can deliver and the batteries' configuration (series or parallel) will dictate how many volts. Three 4v/10A batteries in series will make 12v/10A. Those same batteries in parallel make 4V/30A. As a really simplified example, if Tesla uses those batteries in series, you can't just remove two of the batteries because the Tesla is expecting 12v and you'd be giving it 4v. In the parallel example, you can't remove two of the batteries because you'd cut your amperage (and therefore acceleration) by 67%. The Tesla, I'm certain has redundancy. That is to say, maybe the Tesla has a gajillion amps on tap and taking away 90% of it might still leave you enough amperage to satisfy peak demand, but I don't know the numbers there.
Long story short, you'll have to find a way to maintain the voltage the electronics expect to see, and maintain the amperage flow to maintain peak performance. If you can remove batteries and still keep those numbers the same - albeit for a shorter time - then your idea is sound.
Rons said:
In reply to Pete. (l33t FS) :
To really berkeley with your chart CATL has announced but not in production they have a battery that is 1 kilo per 500 watts so by math a 100kilowatt battery would weigh 200 kilos or 440 pounds.
What's the charge/discharge rate on that, though?
There are so many new variables to play with while trying to find the best compromise!
In reply to Pete. (l33t FS) :
There are many many "announced but not in production" batteries that are always just around the corner. I don't take them seriously until there's actual production.
A Model 3 Performance produces the most horsepower with a fully charged battery, so that makes me believe the limitation is not the motors/controllers ability to take the power, but the battery's max discharge rate. If that is the case, you're definitely going to lose performance by installing a smaller battery of similar specification. Something more exotic might do the trick but they tend to get a little more exciting in their failure modes and require special care and handling.
In reply to Keith Tanner :
What about the modifications Tesla is doing to the Motors in the new series 2 just released.
500KWH Still has a top speed of 130 mph. Due to the lighter weight battery pack and lighter more dense motor
Keith Tanner said:
Something more exotic might do the trick but they tend to get a little more exciting in their failure modes and require special care and handling.
I think even the normal stuff that Tesla uses is fairly exciting if not treated properly -- the difference is that it was all designed and integrated to work together. Swapping out one component of the system without reengineering the rest of it seems like a not-great idea to me.
I expect it's going to be a while before we've got the EV-equivalent of a $5000 turbo kit.
I think we'd need to look at something like formula E for real electric hop up tricks and approaches.
Although it wasn't long after I saw Tesla adapt a similar approach to electric motors.
Is it possible to 'simply' drop the battery pack out of a Tesla Model 3, open up the case, chuck some stuff out to make it lighter, reinstall the pack back into the car, and come out ahead? Nope. Definitively. B/c Tesla batteries have all the modules in series (cannot remove any modules w/o losing voltage), and all the cells inside each module are glued together into a true monolith using 3x types of adhesive. Realistically you either use 'em as-is, or you start over and completely DIY your own pack. See "disassembly" vid1, vid2
I am not saying that a lighter battery is impossible, I am only saying that you cannot get there by starting with the OE battery.
Coincidentally, "b is for build" is disassembling a Model 3 for some sort of body swap, and went 1 sec faster 0-60 with extreme weight reduction: https://youtu.be/z27t9uHp7nY?t=1101
You could swap in a low range model 3 battery:
or you could get a pack like they use in something like this:
which has a pack that weighs 125lbs, is good for about 650hp, and has a super short cycle life.
Either way the issue is convincing the Tesla to either use a smaller Tesla pack and push it in ways that will shorten it's lifespan, or use a completely unknown battery.
When you are running battery packs harder than designed how to you keep them cool ?
I know there have been speed runs at Laguna Seca but do not know how many laps and if the batteries got close to Max temp ,
Does the dash screen show battery temp ?
In reply to californiamilleghia :
I think it does in the Performance, but not in the boring Model 3s. If you watch Randy Pobst's Pike's Peak run from...2021? the one where they crashed...you can see the car overheating on the central display because they didn't get the cooling system properly filled.
Very intersting stuff, thanks for the education. To be very clear, I do not have a Tesla nor do I plan to have one any time soon, this was a thought exercise to learn about battery technology. I hope to be able to be hot rodding EV's in my retirement someday.
