Electric karts by Rob Smedley

[izzy]

https://www.racefans.net/2020/01/10/sme ... otorsport/

Smedders is launching two new kart series, which are electric. One of the advantages is that it's easier to make all the karts exactly equal, and it'll be cheaper. And to help get it noticed he mentions Lewis, obviously

Great idea

[flynfrog]

I have been taking part in a local electric kart series. https://www.k1speed.com/challenge-gp.html That being said I can assure you they are not all equal. During qualifying you have the option of removing your kart from the pool. But the electrics do make for great tight circuit karts. Low end grunt out of the corners helps cover my terrible driving skills.

[izzy]

I have been taking part in a local electric kart series. https://www.k1speed.com/challenge-gp.html That being said I can assure you they are not all equal. During qualifying you have the option of removing your kart from the pool. But the electrics do make for great tight circuit karts. Low end grunt out of the corners helps cover my terrible driving skills.

lol, well electric is terrific to drive. What's unequal in your series? The drivetrains or is it something else?

[theblackangus]

You have mostly the same problems you have with gas karts just a bit different.
Battery wear slightly differently ending up with slight different power delivery.
Mechanical setup of each kart being close is a big task, and even with alot of work some karts will be faster than others as each kart becomes unique in its setup needs after a few months of use.

At least that is my experience with my local electric karting.

But I do think they are a blast to drive.

[paipa]

My $50 electronic cigarette can regulate power delivery to 0.1W precision regardless of battery wear or state of charge, why would it be difficult in an electric kart? Serious question, is it an issue, assuming you put some form of an ECU in there?

[theblackangus]

Dunno it could be motor wear, battery wear, manufacturing variance, heat dissipation/airflow, maybe the throttles get a bit off?

Seems like you get two problems with arrive and drive karting fleets:
1. slight straight line speed differential between karts
2. handling problems where the karts vary more widely in response

Guess my only real point is that two karts with the same battery, charge time, and total weight don't always seem to accelerate the same. Its close but close is still an advantage one way or the other.

So be clear I have raced both gas and electric karts in events and I dont think either is worse than the other, its just that keeping any fleet of karts like for like performance w/o super frequent parts replacement is pretty hard. There are always a couple faster karts and a couple slower karts if the karts aren't close to brand new. If you had infinite time and parts to tune the karts sure you *can* do it, but the owners want to have a life and make some money too =)

Also I would guess comparing your lighter to the energy draw needed to move all that weight quickly and fast isn't really the same level of "likeness" you need to have truly like to like competitive karting.

[flynfrog]

I have been taking part in a local electric kart series. https://www.k1speed.com/challenge-gp.html That being said I can assure you they are not all equal. During qualifying you have the option of removing your kart from the pool. But the electrics do make for great tight circuit karts. Low end grunt out of the corners helps cover my terrible driving skills.

lol, well electric is terrific to drive. What's unequal in your series? The drivetrains or is it something else?

It's mostly down to handling but also charge state and general battery state. We had some karts that just get walked on the straights. Its all just for fun anyway.

[izzy]

lol, well electric is terrific to drive. What's unequal in your series? The drivetrains or is it something else?

It's mostly down to handling but also charge state and general battery state. We had some karts that just get walked on the straights. Its all just for fun anyway.

yes if it's more serious i suppose they can fit some kind of regulator, for the power side of things

[Andres125sx]

How long does it take to fully deplete an electric kart battery more or less?

Batteries reduce their power delivery with use, but you must be using the battery to its discharging capacity limits to notice so I´m curious about the discharging rate of those electric karts

[theblackangus]

The karts at my local electric place can run for about 10 minutes max.
But it really depends on how fast they are allowed to go and the track layout.
For instance the local karts (indoor) can hit 70 mph if turned all the way up, but they would last about 4-5 min.
At a speed limit of about 40 they last around 7-8 minutes and change be fully charged again in 7-8 minutes. (Not sure on headroom here).
On different track layouts you see longer possible run times because you are doing less start/stop and more high speed running.
There are two groups of karts that alternate running while the other group charges.
Not really sure the battery tech or if there are better batteries at a reasonable cost.

[theblackangus]

yes if it's more serious i suppose they can fit some kind of regulator, for the power side of things

They mostly (if not all) have regulators already. They have speed controllers for the fleet that set the karts "regulators" to a given power output.
For instance on the out-lap at our local place all the karts are set to about 10 mph until everyone is on the track as which point they are set to about 40. Even with this system some kart will still be slightly slower straight line.

[izzy]

yes if it's more serious i suppose they can fit some kind of regulator, for the power side of things

They mostly (if not all) have regulators already. They have speed controllers for the fleet that set the karts "regulators" to a given power output.
For instance on the out-lap at our local place all the karts are set to about 10 mph until everyone is on the track as which point they are set to about 40. Even with this system some kart will still be slightly slower straight line.

oh, interesting. Still, i bet there's scope to do it more precisely, if there's money for it. They can measure torque and power can't they, tractive effort, and feed that back to the motor control, so ultimately they can reduce the tolerance to something insignificant. With speed, it must depend on driver weight and how you come out of the previous corner for example, plus assume all the carts can get to 40 at the same rate

[theblackangus]

yes if it's more serious i suppose they can fit some kind of regulator, for the power side of things

They mostly (if not all) have regulators already. They have speed controllers for the fleet that set the karts "regulators" to a given power output.
For instance on the out-lap at our local place all the karts are set to about 10 mph until everyone is on the track as which point they are set to about 40. Even with this system some kart will still be slightly slower straight line.

oh, interesting. Still, i bet there's scope to do it more precisely, if there's money for it. They can measure torque and power can't they, tractive effort, and feed that back to the motor control, so ultimately they can reduce the tolerance to something insignificant. With speed, it must depend on driver weight and how you come out of the previous corner for example, plus assume all the carts can get to 40 at the same rate

I agree with the right monetary incentive you could likely do it. I'd bet there a likely systems that can already do it just too costly for the average karting market (at least in the US).

[Tommy Cookers]

the adjustable 'speed controller' restricts the voltage available (at no load) as an indirect means of restricting the motor
it still rewards the kart with the best battery - which under load still gets more volts and so current into the motor
(we can regard good battery characteristics as equivalent to low internal resistance)

direct (torque) limiting can only come from current limiting (each motor gets the same deal regardless of battery quality)
in basic form this equalises performance from rest only - but equalisation throughout is possible (still open loop)

a system with a torque sensor would be a closed loop aka feedback system - more costly and complicated

[joshuagore]

k1 speed carts have variation, just went there, but 95% felt like ego preserving butt dyno results. Meaning I was definitely in a slow cart on my slow laps, and my friends were certain I was in a fast one during my fast laps.

Also shunt based current limiting controllers are pretty par for the course in any brushless controller setup with modern batteries. The ebike community(and many ev conversion projects from karts to cars), use something called a cycle analyst to act as throttle manipulator based upon shunt reading and what current you want(and dont want). Dialing back the throttle despite you asking for more(closed loop?). Sure there are phase currents and all sorts of other fun stuff, but I could just as easily tie my throttle to m/s of acceleration and recalibrate each cart as they leave the pits, got a low battery, well everyones acceleration is fixed at x m/s or whatever the fastest cart was benchmarked as it left the pits?