Formula E

[machin]

Given that the longer events are up to 140 seconds in length and that a day's racing consists of 3-7 minutes behind the wheel, I'd rather bet on 15C discharge in real terms. I could go for something like these cells, which have a greater energy density but a lower peak power output. To match my current engine, I'd need ~80kg at 10C, which would let me run a whole event without recharging, but that pack would be capable of 450bhp peak, which is somewhat over-specced. My current engine is 69kg, but by going electric, I can ditch the engine, gearbox, exhaust, ECU, fuel tank, radiator, coolant, oil, etc. All that's needed to replace all of that is a motor, controller and battery pack.

Looking at the Formula E battery pack (here) (which is admittedly slightly over-engineered for reliability), it weighs 200kg, and has a useable energy storage of 28kW.hrs (100.8MJ) and has a maximum output of 200kW. If you were using the full 200kW output that battery pack would give you just 8.4 minutes of full power use! If you factor in a couple of red flags and therefore a couple of re-runs at one of your events, I wouldn't want to have a battery pack much smaller than this at one of the longer venues....

As we've established a few pages back you also wouldn't want to be chucking out the gearbox if you want to maximise performance... and you'll still need the heat exchanger and coolant....

Add the weight of the motor of 40kg (5kW per kg according to this source, and the weight of the controller ??kg, and you're probably looking at somewhere around the 280 to 300kg mark for a reliable electric propulsion system giving 200kW of power for 8.4 minutes. Maybe 200kg total weight if you pared down to 5 minutes of full power?

....I don't think I'd be throwing your ICE away just yet....

Now someone like Autogyro will probably say it is all a big conspiracy and the Formula E battery weights could be much lower than this if the series weren't a fixed spec formulae... hopefully in year two the weight rules will be made such that the bare chassis must weigh something like 450kg, but with no lower limits to the battery weight... (with say a 200kg maximum battery weight). That would really promote battery development.

(In defence of the Formula E battery pack; the battery pack in the Drayson-lola LMP1-based EV supposedly has a capacity of 30kWhrs (108MJ) (source here), and weighs approx. 300kg (source here). In short: I don't think scaling up those RC batteries gives a fair representation of the actual weight of pack required for full-scale automotive use...)

[Richard]

Trolling that Formula E is not as <insert spurious characteristic in here, eg noisy> as Formula 1 has been deleted.

For the avoidance of doubt: Formula E is not Formula 1. It's a fallacy to say one is better than the other, just like pears do not taste like apples, chalk is not cheese, electricity is not petrol.

[Andres125sx]

Add the weight of the motor of 40kg (5kW per kg according to this source, and the weight of the controller ??kg, and you're probably looking at somewhere around the 280 to 300kg mark for a reliable electric propulsion system giving 200kW of power for 8.4 minutes. Maybe 200kg total weight if you pared down to 5 minutes of full power?

....I don't think I'd be throwing your ICE away just yet....

You should take into account the energy recovery system too. I don´t know how effective it is tough. Anyone has more info about the recovering system? What´s the power it generate?

About the battery/weight compared to the listed RC batteries, you should take into account the batteries we linked are bare cells, but the FE batteries have the added weight of the casing to protect the cells, the battery managment unit, and the cooling system, with the liquid and I guess the radiator is also included into the battery weight.


And no, I wouldn´t throw my ICE away yet. Its LiS batteries what will be revolutionary, with double energy density (five times better in theory, but that´s the theory) that will be the inflexion point both for more useable road cars, and for better racing. But they will be here soon, so the cars, systems, motors, etc should be tested and developed to make the most of those batteries when they arrive. That´s the reason FE is starting in 2 days, this all is new and need some development

[andylaurence]

Looking at the Formula E battery pack (here) (which is admittedly slightly over-engineered for reliability), it weighs 200kg, and has a useable energy storage of 28kW.hrs (100.8MJ) and has a maximum output of 200kW. If you were using the full 200kW output that battery pack would give you just 8.4 minutes of full power use! If you factor in a couple of red flags and therefore a couple of re-runs at one of your events, I wouldn't want to have a battery pack much smaller than this at one of the longer venues....

The longest event is ~420 seconds for the whole event. Assuming ~70% full throttle, that's ~300 seconds at full power, so a pretty reasonable estimate. We could add a 5-10% reserve for regenerative braking. A guy did turn up with an electric car at an event this year and he ditched a practice run to keep his battery topped up (with a generator) for the timed runs. Agreed that range would be an issue, especially as you wouldn't wish to fully discharge the pack.

As we've established a few pages back you also wouldn't want to be chucking out the gearbox if you want to maximise performance... and you'll still need the heat exchanger and coolant....

Agreed, although the heat exchanger and coolant could be less as heat soak would account for a lot of cooling given that the car can start from cold with cold water in the coolant and the longest run would be just 140 seconds.

Add the weight of the motor of 40kg (5kW per kg according to this source, and the weight of the controller ??kg, and you're probably looking at somewhere around the 280 to 300kg mark for a reliable electric propulsion system giving 200kW of power for 8.4 minutes. Maybe 200kg total weight if you pared down to 5 minutes of full power?

....I don't think I'd be throwing your ICE away just yet....

Agreed - there's a reason I still have my ICE!

Now someone like Autogyro will probably say it is all a big conspiracy and the Formula E battery weights could be much lower than this if the series weren't a fixed spec formulae... hopefully in year two the weight rules will be made such that the bare chassis must weigh something like 450kg, but with no lower limits to the battery weight... (with say a 200kg maximum battery weight). That would really promote battery development.

(In defence of the Formula E battery pack; the battery pack in the Drayson-lola LMP1-based EV supposedly has a capacity of 30kWhrs (108MJ) (source here), and weighs approx. 300kg (source here). In short: I don't think scaling up those RC batteries gives a fair representation of the actual weight of pack required for full-scale automotive use...)

As already pointed out, I linked to bare cells. When a BMS and case is added, the weight goes up. Having said that, I think these batteries are probably heavier than needed, simply because of the weight regulations. That regulation might be in the interest of safety as no minimum weight would lead to less robust casings and the associated chances of a rupture in an accident. As a comparison, those cells I linked to would weigh 165kg for 28KWh. 35kg for casing and BMS seems appropriate.

On the flip side, a more powerful motor isn't much heavier (as you've quoted above) and on lower speed events, such as hillclimbs, that gives the opportunity to use a larger motor with a higher maximum torque (and power) and dispense with the gearshift, trading amps for volts in the knowledge that torque will fall with speed as the battery pack is the limitation. Aside from the obvious benefit in drive-ability, that reduces drive-train weight, which in turn reduces the need for power, which reduces the need for batteries. Utilising two motors (one per wheel) removes the need for a differential, further reducing weight. As an example of this concept taken to extreme, the Delft Formula Student car this year weighed in at just 155kg. I'd wager that car is quicker at Crystal Palace than mine. The motors are effectively part of the hub and I think I read in Racecar Engineering that the whole assembly is under 10kg (hub/upright/brakes/whatever).

[FW17]

Battle of the sexes

Trulli has a team mate Michela Cerruti. It is going to end badly for him.

[machin]

Battle of the sexes

Trulli has a team mate Michela Cerruti. It is going to end badly for him.

http://upload.wikimedia.org/wikipedia/c ... erruti.JPG

Are you implying that she'll get more fan boost for some reason?!

[machin]

As an example of this concept taken to extreme, the Delft Formula Student car this year weighed in at just 155kg. I'd wager that car is quicker at Crystal Palace than mine. The motors are effectively part of the hub and I think I read in Racecar Engineering that the whole assembly is under 10kg (hub/upright/brakes/whatever).

That is an impressive car.. from what I can see it is lighter overall than many of the ICE cars..? I wonder what useable energy capacity their battery has? No mention on the link. Would it be sufficient for a day's sprinting, or would you need to have 4 or 5 packs? I have no problem with that if the cost isn't too prohibitive and it is easy to change. (I would not like to be forced down the route FE has taken and have to take multiple cars along to the event!!!!)

It is also worth noting to those people who don't believe in the need for gearboxes, that even that Delft car has an integral single-speed planetary gearbox for each of its in-hub motors. Clearly there is a big benefit in keeping the motor small (but high reving), and then gear it down (10 to 1 in this case).

[mzso]

As an example of this concept taken to extreme, the Delft Formula Student car this year weighed in at just 155kg. I'd wager that car is quicker at Crystal Palace than mine. The motors are effectively part of the hub and I think I read in Racecar Engineering that the whole assembly is under 10kg (hub/upright/brakes/whatever).

Why do they need planetary gears?

Something like this doesn't need them:
http://www.electric-vehiclenews.com/201 ... firms.html
http://green.autoblog.com/2013/07/29/ev ... own-under/

Also the delta E4 with it's YASA motors doesn't need them.

[andylaurence]

As an example of this concept taken to extreme, the Delft Formula Student car this year weighed in at just 155kg. I'd wager that car is quicker at Crystal Palace than mine. The motors are effectively part of the hub and I think I read in Racecar Engineering that the whole assembly is under 10kg (hub/upright/brakes/whatever).

That is an impressive car.. from what I can see it is lighter overall than many of the ICE cars..? I wonder what useable energy capacity their battery has? No mention on the link. Would it be sufficient for a day's sprinting, or would you need to have 4 or 5 packs? I have no problem with that if the cost isn't too prohibitive and it is easy to change. (I would not like to be forced down the route FE has taken and have to take multiple cars along to the event!!!!)

The endurance part of the Formula Student competition is 22km. However, it's worth noting that the speeds are lower in Formula Student competition than would be seen on even the slowest sprint (132kph top speed). That reduces the energy requirement - they have 6.3KWh from a 43kg pack. As a further point, the car has motors capable of over 100Kw (27KW per wheel), which makes it almost as powerful as my car, although I believe they are limited to a total of 80KW by regulation. I believe a car of this type would be viable for me at Crystal Palace, Clay Pigeon and possibly at Curborough or Prescott, but it'd be completely outclassed at Castle Combe or Abingdon where I find I'm short on power and average speeds are higher than this car's top speed.

It is also worth noting to those people who don't believe in the need for gearboxes, that even that Delft car has an integral single-speed planetary gearbox for each of its in-hub motors. Clearly there is a big benefit in keeping the motor small (but high reving), and then gear it down (10 to 1 in this case).

They have chosen this route (a final drive ratio), but others have chosen direct drive (I think Drayson did with their Lola, as have other Formula Student teams) and others have chosen a multi-ratio gearbox (Formula E and Formula Student). I'm not sure it's a big benefit, but it's the compromise they chose.

[mzso]

They have chosen this route (a final drive ratio), but others have chosen direct drive (I think Drayson did with their Lola, as have other Formula Student teams) and others have chosen a multi-ratio gearbox (Formula E and Formula Student). I'm not sure it's a big benefit, but it's the compromise they chose.

I think it might be the easy way. (I may be wrong) Few motors are designed to be direct drive. It's just easier to use stuff off the shelf.

[Pierce89]

Battle of the sexes

Trulli has a team mate Michela Cerruti. It is going to end badly for him.

http://upload.wikimedia.org/wikipedia/c ... erruti.JPG

Are you implying that she'll get more fan boost for some reason?!

No, he's implying Trulli will look stupid being outclassed by a female.

[Pierce89]

Actual racing this weekend. The neverending speculation can finally be put to bed.

[Andres125sx]

It is also worth noting to those people who don't believe in the need for gearboxes, that even that Delft car has an integral single-speed planetary gearbox for each of its in-hub motors. Clearly there is a big benefit in keeping the motor small (but high reving), and then gear it down (10 to 1 in this case).

Not sure if comparable, but on high perfomance rc planes we´re using electric motors for many years and here the power/size (or weight) ratio is really important because the fuselages are pretty small, maybe 8cm diameter and 30-40cm long, that´s what you have for the motor and battery (and receiver)

Everybody is using high rev motors with planetary gearboxes. It looks like it´s more efficient because a high rev motor use thicker wire (less turns of wire), so it handles a lot more current, what means a lot more power. Even with the added weight of the gearbox they´re more powerful for the size than direct drive setups. I´m talking about 2-3kw for 2kg planes. They climb much faster than a rocket

[autogyro]

It is also worth noting to those people who don't believe in the need for gearboxes, that even that Delft car has an integral single-speed planetary gearbox for each of its in-hub motors. Clearly there is a big benefit in keeping the motor small (but high reving), and then gear it down (10 to 1 in this case).

Not sure if comparable, but on high perfomance rc planes we´re using electric motors for many years and here the power/size (or weight) ratio is really important because the fuselages are pretty small, maybe 8cm diameter and 30-40cm long, that´s what you have for the motor and battery (and receiver)

Everybody is using high rev motors with planetary gearboxes. It looks like it´s more efficient because a high rev motor use thicker wire (less turns of wire), so it handles a lot more current, what means a lot more power. Even with the added weight of the gearbox they´re more powerful for the size than direct drive setups. I´m talking about 2-3kw for 2kg planes. They climb much faster than a rocket

I am interested in sourcing a small rim drive electric motor at present.
I am doing some comparisons with conventional high rpm model motors.
Something similar to the available boat rim drive thrusters on the market but in miniature should do.
I can find plenty of pancake motors which are not the same.

[machin]

Everybody is using high rev motors with planetary gearboxes.

Exactly; the starter motor on my hilclimb car is an absolute beauty compared to the standard starter motor; it is a high speed motor mated to a little gearbox. The whole assembly weighs much less than the original direct drive motor, takes up less room and has better starting capability.