I think for a swappable battery, one should look at using a small truck, like a Ranger, S10 or the like. Have a few battery packs and a forklift or some sort of crane to swap the packs at the track. The pack would be an easy shape to make and would be easily accessible. Heck, you could probably even put it on some slides with a matching rack that it gets put into for the swap. I'd imagine one could swap packs in 5 minutes and then the recharge rate and size of generator or shore power supply can go way down.
RX8driver said:
I think for a swappable battery, one should look at using a small truck, like a Ranger, S10 or the like. Have a few battery packs and a forklift or some sort of crane to swap the packs at the track. The pack would be an easy shape to make and would be easily accessible. Heck, you could probably even put it on some slides with a matching rack that it gets put into for the swap. I'd imagine one could swap packs in 5 minutes and then the recharge rate and size of generator or shore power supply can go way down.
See earlier comments in this thread. I think with your CG up that high you'll have a hard time putting down the lap times needed to run at the front of the field.
Now if you are using a Tesla style motor/diff/assembly and you don't need a driveshaft or exhaust, I wonder if you can create a hot swappable section behind the cab that is down low enough to be parallel to the frame rails. You can do the same thing under the hood (even just slides to pull the pack out forward).
In reply to ProDarwin :
I was actually going to go back on my "2nd Gen Prius", and suggest some kind of pickup setup after seeing this...
https://jalopnik.com/chevrolet-somehow-makes-one-1-electric-pickup-truck-1839643120
yes, Virginia, that's your 120kWhs of battery pack
I still think you'd want something like the Leaf drivetrain, up front. Dunno if you'd want to put packs up there too. But you'd need to take some time to lower the weight/CG/Aero of the truck
Robbie
MegaDork
11/6/19 8:56 a.m.
You should use airjacks in reverse.
Pull in pit, airjacks drop battery on ground. Roll car 15 ft forward above new battery, airjacks up. Go!
The battery pack can then be almost the entire bottom of the car up to 5-6 inches thick. You also get a flat bottom for aero and a massive battery cooling surface when in motion.
STM317
UltraDork
11/6/19 9:20 a.m.
sleepyhead the buffalo said:
In reply to ProDarwin :
https://jalopnik.com/chevrolet-somehow-makes-one-1-electric-pickup-truck-1839643120
yes, Virginia, that's your 120kWhs of battery pack
I still think you'd want something like the Leaf drivetrain, up front. Dunno if you'd want to put packs up there too. But you'd need to take some time to lower the weight/CG/Aero of the truck
If there was no stick axle in the rear, you could keep the batteries on trays between the rear frame rails and simply drag the trays in/out the rear of the truck like that seadoo boat thing. No bed floor. No tailgate. Lower the whole thing to a ride height appropriate for a race car and your CG would be fairly low with plenty of space/easy access for battery swapability. The open nature of the bed would let one(or more) crew members deal with electrical battery connections from either side of the vehicle while one (or more) crew members dealt with physically securing/removing the battery.
A Tesla Model 3 pack is composed of 4 separate modules that are 11" wide, 3.5" thick and 67.5"-73" long. Those sound like dimensions that are really compatible with most truck beds. Run 2 of them side by side between the rear frame rails of a truck with a 6ft bed. You could stack the other 2 on top, or deal with less capacity/more frequent stops. All 4 modules combined would be about 800lbs dry.
Whatever solution someone comes up with for swappable batteries, it would be important that it be a fast swap since they're probably going to have to be swapped every hour(?) or so. If it's 2 seconds a lap slower on track, but 2 minutes faster a change in the pits, then that's probably a good tradeoff.
Robbie said:
You should use airjacks in reverse.
Pull in pit, airjacks drop battery on ground. Roll car 15 ft forward above new battery, airjacks up. Go!
The battery pack can then be almost the entire bottom of the car up to 5-6 inches thick. You also get a flat bottom for aero and a massive battery cooling surface when in motion.
I like this. You may could even build a custom ramp/fixture to roll the car onto for the drop, roll forward, raise up, and go. Everything is fully staged. If the packs have studs on them and the reciever in the bed has holes, you have 2 or 4 guys with impacts run the nuts on and it could be done very quick.
It also means you could do multiple packs without much additional complexity.
If you can get your pit time down to the length of a driver change, you can make up for a lot of time lost from either A) more frequent stops or B) slower lap times.
RX8driver said:
Whatever solution someone comes up with for swappable batteries, it would be important that it be a fast swap since they're probably going to have to be swapped every hour(?) or so. If it's 2 seconds a lap slower on track, but 2 minutes faster a change in the pits, then that's probably a good tradeoff.
A good lemons pit stop is about 2 minutes. Also, teams are allowed to have 24 gallon gas tanks. That means that they only need to pit like 3 or 4 times in a 14 hour race.
Gasoline has a crazy awesome power density!
ProDarwin said:
Robbie said:
You should use airjacks in reverse.
Pull in pit, airjacks drop battery on ground. Roll car 15 ft forward above new battery, airjacks up. Go!
The battery pack can then be almost the entire bottom of the car up to 5-6 inches thick. You also get a flat bottom for aero and a massive battery cooling surface when in motion.
I like this. You may could even build a custom ramp/fixture to roll the car onto for the drop, roll forward, raise up, and go. Everything is fully staged. If the packs have studs on them and the reciever in the bed has holes, you have 2 or 4 guys with impacts run the nuts on and it could be done very quick.
It also means you could do multiple packs without much additional complexity.
If you can get your pit time down to the length of a driver change, you can make up for a lot of time lost from either A) more frequent stops or B) slower lap times.
I like this too... and I think it's a version (better) of what I poorly described one page back.
however, I think one of the biggest challenges is going to be ensuring alignment of everything. Also, I figure 45sec for replacement is going to be the ballpark to work towards.
wvumtnbkr said:
A good lemons pit stop is about 2 minutes. Also, teams are allowed to have 24 gallon gas tanks. That means that they only need to pit like 3 or 4 times in a 14 hour race.
well, berk. I think we were working from a ~5min pitstop in the past. Even at 30sec for a pack change, that'll probably won't be enough to balance the more frequent stops.
LeMons world HQ has an update about the prize. Apparently "Kcar" is the answer, currently...
