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teddillard
24 March 2011, 0602
Great instructional interview with some very detailed build detail type stuff, also Mark's motor at the end:

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Nuts & Volts
24 March 2011, 0805
Cool video. The bike is super simple in a good way. Only complaint :) is that they definitely have more room for batteries. But then again the headways are not the easiest to fit in the nocks and crannies.

thanks Ted

markcycle
13 October 2011, 1626
Jon sent me some statistic on how the bike performed and basic bike specifications
These are Jon words

we had a top speed of 155kph on a Race track(Eastern creek @40% power).
We have the lap record at wakefield only 5 sec of the two strokes 10 sec of the superbikes @35% current limit.
Catavolt only had 4.3kwh others had 6.5 and 8kwh of battery.
The hub motor didnt hinder cornering at all just needed an adjustable rebound shock.
Catavolt bike weight 190kg voltron 170kg riperton 145kg

And my favorite picture
https://www.sugarsync.com/pf/D336079_7080550_33591

evmotorcycle
13 October 2011, 1904
Hey guys,

Heat is the enemy of the electric motor! Catavolt, Voltron and Ripperton teams all battled with the same problem. Keeping the motor cool. There were a few issues with controllers etc but the main problem was heat in the motor. If Catavolt had a better mechanism for dissipating the heat then I am betting that it would have smoked the 125 lap times for sure.

So that's where markcycle comes in. You gotta get some liquid in there dude! >:)

Nuts & Volts
13 October 2011, 1929
Hey guys,

Heat is the enemy of the electric motor! Catavolt, Voltron and Ripperton teams all battled with the same problem. Keeping the motor cool. There were a few issues with controllers etc but the main problem was heat in the motor. If Catavolt had a better mechanism for dissipating the heat then I am betting that it would have smoked the 125 lap times for sure.

So that's where markcycle comes in. You gotta get some liquid in there dude! >:)

True dat, either cool the **** out of it...or make it more efficient :D

markcycle
14 October 2011, 0524
No matter how efficient you make the motor these guys will just pump more and more amps into it and we'll wind up having to get rid of the same or more heat. It's an endless circle until the motor is no longer the weak link in the power chain and just improving the efficiency a few percent not going to do it. So I agree liquid cooling for next year, gets the motor out of the thermal loop. After all it's what all the big boys in racing are doing, every high end bike is liquid cooled.

Let me add if all goes as planed a 20 to 30 percent weight reduction is also possible

Nuts & Volts
14 October 2011, 0547
No matter how efficient you make the motor these guys will just pump more and more amps into it...
Totally agree about the increase in amps. So one way or another you'll need some liquid cooling when going racing


Let me add if all goes as planed a 20 to 30 percent weight reduction is also possible
Sweetness!

Totally agree about the increase in amps. So one way or another you'll need some liquid cooling.

lugnut
14 October 2011, 0747
Jon sent me some statistic on how the bike performed and basic bike specifications
These are Jon words...

Catavolt only had 4.3kwh others had 6.5 and 8kwh of battery.
.....
Catavolt bike weight 190kg voltron 170kg riperton 145kg

Curious that the heaviest bike has the least battery (kWh). Any info as to why? Cell energy density? Heavier motor? Heavier donor bike to start with?

markcycle
14 October 2011, 0847
Basicly LIFEPO4 Headway VS foil pouch cells

Round steel cans don't package very well
Look at the naked bike and all those cells and it ads up to 4.3Kwh Kinda answers the question. I think 4.3Kwh is with the cells removed from under the seat.

teddillard
14 October 2011, 0924
I'm pretty sure the Headways are heavier, too, for the energy of the lipo (at least one of the other bikes is running lipo, no?), to the tune of about 30% if memory serves. I'd have to look it up...

podolefsky
14 October 2011, 0940
Headway is about .2 kWh/L, 0.1 kWh/kg (that's assuming they are tightly packed in a square configuration). Turnigy Lipo is .28 kWh/L, .14 kWh/kg.

So yup, about 30-40%, both in volume and weight.

frodus
14 October 2011, 0943
sounds about right, Headway is about 102Wh/kg.... lipo is much higher.

They're also not flat, so it's harder to package, but there is a bonus.... built in cooling paths. Lipo in a tight setup could have issues with overheating the cells in the middle.

teddillard
14 October 2011, 0952
... but there is a bonus.... built in cooling paths. Lipo in a tight setup could have issues with overheating the cells in the middle.

Is this seriously an issue? Do the large bikes running lipo have "cooling paths"? First I've heard of it. My understanding was that if your batteries were heating there was something seriously wrong... damage, overcharging, like that, but normal hard running?

Warren
14 October 2011, 1033
Brain Richardson has no cooling channels in his pack.

http://www.facebook.com/photo.php?fbid=210399532325066&set=pu.110022072362813&type=1&theater

Battery heat was never his problem. It was always motor and controller heat....finally solved by gearing lower.

frodus
14 October 2011, 1049
Is this seriously an issue? Do the large bikes running lipo have "cooling paths"? First I've heard of it. My understanding was that if your batteries were heating there was something seriously wrong... damage, overcharging, like that, but normal hard running?

Yeah, absolutely. Not sure about how each bike pack is designed, so I can't comment. When you draw high current from cells, they can really heat up, so it should to be taken into consideration.

Just did a a test the other evening on a cell that I drew 22C from, for about 2.5 minutes, the temp rose from 17C to 37C (50C cutoff for the cell), voltage went from 4.2V down to 2.8V. After the test ended, the temperature kept rising up to about 44C, almost hitting the cutoff. So for people using cells that are high power Lipo, they'll definately heat up. Anything over about 1C and you'll get some degree of heating, even with a low IR. Remember, power = I^2 * R, so even with a low IR, the power dissipated is a function of a square of Current. I'm really loving my discharger....

So when you have a cell, that is essentially insulated by the warm cell next to it, it's not really helping keep that cell cool, so the heat has nowhere to go. With Headway though, they're separated by air, so it's slightly easier.

teddillard
14 October 2011, 1056
Just did a a test the other evening on a cell that ...

What flavor cell was that? Which begs the followup, do different chemistries have different "heatup" rates at a give discharge rate?

podolefsky
14 October 2011, 1126
Different chemistries will have different heatup rates...but it depends on a few things.

- internal resistance (Ri)
- surface are
- heat capacity
- thermal conductivity

Ri is what goes into I^2*Ri, but it also decreases with temperature. I've seen graphs where the I^2*R losses increase with C-rate, and then they go back down, I believe because Ri is decreasing with temperature.

Surface area: more area exposed to air, easier to get rid of heat. Actually, it's surface area as a fraction of volume. Smaller objects have a higher ratio of area / volume. (Why mice have to keep moving to stay warm, elephants have big thin ears to cool off.)

Heat capacity: how much energy is needed for a given temperature increase. It take more energy to raise 1 cup of water 1 deg than to raise 1 cup of aluminum 1 deg (about 1.7 times)

Thermal conductivity: higher means you can get rid of heat more quickly. Aluminum has about 250 times the thermal conductivity of water.

frodus
14 October 2011, 1142
What flavor cell was that? Which begs the followup, do different chemistries have different "heatup" rates at a give discharge rate?

I can't tell right now, not until the client publishes the data.... it's lipo.

Yes they do have different heat up rates, mostly due to the things Noah mentioned.

teddillard
14 October 2011, 1428
Thanks, Noah, I guess my question was more about the inherent heat produced by different specific chemistries, not the basic construction. That is, does lead heat faster than lipo, for example, all else being equal. But I realize that's a pretty academic question.

What's not academic, though, is the question of battery cooling. I basically assumed that if the batteries weren't being pulled at their maximum C rate that they wouldn't heat over an acceptable level, and that, regardless of external cooling, if you pull them too hard for too long, the internal temps will be high enough to cause permanent damage. Did I get this wrong? I'm not doing the TTXGP, but my Turnigys stay cool to the touch, way past the motor getting very warm.

I understand that what you're doing, Travis, is to bench test the actual C rates, which is maximum safe, but is this something that we need to worry about on our bikes, esp. fast bikes?

Again, I'm confused... I hadn't seen any mention of cooling batteries on any of the big badass bikes. Motors, controllers, sure, but not batteries. I also get that, like Tesla for example, there's an advantage to heating and cooling packs to keep an optimum temperature, but that's not what I'm talking about.

Thanks, Travis, lipo was all I was looking for for "flavor". Not the brand.

My head hurtz.

frodus
14 October 2011, 1546
Thanks, Noah, I guess my question was more about the inherent heat produced by different specific chemistries, not the basic construction. That is, does lead heat faster than lipo, for example, all else being equal. But I realize that's a pretty academic question.
They're all different, it's based on multiple things, so one chemistry might heat the same rate as another, depending on it's IR, surface area, etc.


What's not academic, though, is the question of battery cooling. I basically assumed that if the batteries weren't being pulled at their maximum C rate that they wouldn't heat over an acceptable level, and that, regardless of external cooling, if you pull them too hard for too long, the internal temps will be high enough to cause permanent damage. Did I get this wrong? I'm not doing the TTXGP, but my Turnigys stay cool to the touch, way past the motor getting very warm.

I've observed that cells run at their max C-rate will go thermal (go over their max temperature) before they hit LVC. Every cell I've tested at 5C heats up, but when running a cell at it's max continuous rating (10, 20C, etc), I've usually hit thermal before seeing it hit LVC. Some companies might derate the "max continuous" so that it never goes thermal, so it should be measured on one battery at least.... but I haven't seen any yet. A123, headway, Kokam, and a couple others, all went thermal or very close to it when running them at the max from the datasheet. Now, higher C rated batteries are better for people like you that use them mostly in that lower current area.... Compare 100A on a 10Ah headway (10C) with 2 5Ah turnigy batteries... same C rate, but the turnigy are made for more current, and may not heat up as much... I'll know more when I test them next week. Might be a couple weeks, depends on how much rain we get :)

True about the internal temps though. When I stopped my test, the temp rose another ~8 degrees C, telling me the temp inside was much higher than 37C when the test stopped. That's what really kills it, but maybe the manufacturer already rates the external case as teh temp not to go over.... who knows.


I understand that what you're doing, Travis, is to bench test the actual C rates, which is maximum safe, but is this something that we need to worry about on our bikes, esp. fast bikes?
It's something to consider absolutely. C rate is only one thing to consider, voltage drop and temperature rise is another. I don't really worry too much because my BMS monitors cell voltages and has a temp sensor on the cell boards..... if you don't have that luxury, then you should design such that you're not going above certain continuous rates, so they don't heat up. I've heard of packs overheating/going thermal..... Packs get hot during a race.


Again, I'm confused... I hadn't seen any mention of cooling batteries on any of the big badass bikes. Motors, controllers, sure, but not batteries. I also get that, like Tesla for example, there's an advantage to heating and cooling packs to keep an optimum temperature, but that's not what I'm talking about.
They may not need it because of how they're running the bike, they may control the current from the controller so they're always below the value that causes them to run thermal. There's a sweet spot, that can really only be seen by testing the battery, which many of us can't do. I can promise you, Zero and Brammo test batteries.


Thanks, Travis, lipo was all I was looking for for "flavor". Not the brand.
no prob.... I didn't wanna say much, so I just stated the 4.2-2.8V range.... it's a pretty good lipo from what I've seen.

podolefsky
14 October 2011, 1903
Thanks, Noah, I guess my question was more about the inherent heat produced by different specific chemistries, not the basic construction. That is, does lead heat faster than lipo, for example, all else being equal. But I realize that's a pretty academic question.

The answer is...yes, but it is sort of academic since all else isn't equal. But it's interesting to think about.

You have to think about heat (or energy) and temperature as two different things. A battery works on a chemical reaction. When that reaction takes place, it produces energy. Some of that energy can heat up the cell, but the temperature will only increase if it heats up faster than it can cool off.

It's like a bucket with a hole in it. If you pour water in at the same rate it comes out, it won't get any more full. More pouring is like more heating. Bigger hole is like more cooling.

So maybe what your asking is, all else being equal (like volume, surface area), does the reaction in lifepo4 produce more heat than lipo? I don't know...I'm going to guess yes, which is part of why lipo has such a large discharge rating. (But that's just a guess).

The thing to remember about batteries is that the resistance isn't like the resistance in a, uh, resistor. In a resistor, it is due to the atoms in the material getting in the way of electrons. Battery resistance is mostly due to the rate that the chemical reaction takes place. At a higher temperature, the reaction can go faster, supply more electrons which acts like lower resistance.

(In a resistor, higher temperature leads to higher resistance...because the atoms bounce around more and it's harder for electrons to get through.)

teddillard
15 October 2011, 0103
Thanks, guys, sorry for the hijack. Maybe we should start a new thread, I find this stuff really interesting.