Quark fried, blown capacitor...

[smhertzog]

Originally Posted by AAngel

Serum, I tried every possible combination that I could think of. Drag brake on/off with the freewheel on/off. I could not get the Compro to freewheel.

Did you try increasing your neutral range? It seamed to help mine a little but it didnt solve the problem just masked it.

Yes, I did do that, but all that does is make the neutral range easier to hit. It doesn't make the freewheeling work. Besides, it still leaves the possibility of not letting off of the throttle enough to hit the neutal range.

It shouldn't be this way with a $200+ esc.

What can I say, I'm just bitter. LOL

[smhertzog]

Originally Posted by AAngel

Yes, I did do that, but all that does is make the neutral range easier to hit. It doesn't make the freewheeling work. Besides, it still leaves the possibility of not letting off of the throttle enough to hit the neutal range.

It shouldn't be this way with a $200+ esc.

What can I say, I'm just bitter. LOL

I dont blame you, I wreck enough on my own I dont need any help from my brake happy ESC. :031:
They must have had brake issues during R&D and released it anyway.

[zeropointbug]

Seems like the more expensive the controller the more problems they have, eh AAngel... :005:

zpb, it sure seems that way. There is still more stuff to try though. Castle is taking its time with the MMM, but I think that it will be good when it does come out and the Tekin controllers should be interesting.

There has also been talk concerning the Kontronik motors and Mega is releasing motors for rc cars too. The future is either looking brighter or the money pitt is about to get larger.

[plumslow]

I have a question, many people on the forum say that they want to run 5S to get longer run time. I was looking at the batteries and cell counts. I was thinking of them as watts = V times A and a 4S 8000 mah battery and a 3S 11000 mah battery has about the same watts and both batteries would weigh about the same so where is the advantage of a higher voltage battery by using more cells. They both have the same amount of energy on tap. You would need a hotter motor for the lower voltage. What is the real advantage of the more cell packs please enlighten me.

[bdebde]

Speaking of other motors, Great Planes (Tower hobbies brand), has a few that look decent. They look like the fiegao's but have a screwed endbell.

[suicideneil]

It all depends on the application. MAh capacity isnt the overriding factor though. In a small vehicle you want to match the battery to the motor- so say a 5600kv motor on 2s is fast, but a 4700kv motor on 3s is amazing. In a big truck the same applies. A hot motor like a 7xl is great on 4s say, but you would run a 9xl on 5 or 6s. Capacity is just a matter of price- the more $$$ you spend the more mah you get really, though the smaller the cell the less mah you can physically squeeze into it- think 2500mah AA batteries vs 4200mah C cells- but the AA cells have greater limitations on the current you can draw. Wattage is seperate really, thats to do with the power of the motor- Watts divided by volts = max amp draw of the motor I believe...

[suicideneil]

Originally Posted by bdebde

Speaking of other motors, Great Planes (Tower hobbies brand), has a few that look decent. They look like the fiegao's but have a screwed endbell.

Hmm, they are rather intersting. The long can model is good, but only 1280kv- I wonder if they have a larger range somewhere else.:024: *begins searching...*
Edit: found their site.... no joy. Only the one xl can motor, but lots of other smaller ones.

Saying that you are going with more voltage for longer runtime can be a bit misleading. If you are going to run higher voltage, you have to setup for it from the get go.

The advantage of running higher voltage is to reduce current draw. As current draw increases, so do inefficiencies. These inefficiencies (losses) are the source of most of the heat generated in a brushless system and the heat is a sign of wasted energy.

If you take a 4S system that turns a maximum rpms of 30,000 you will get a certain amount of current draw while accomplishing a specific task. On the other hand, if you take a 5S system that also turns a maximum rpms of 30,000, the 5S system will be doing the same amount of work as the 4S system with a substantially lower current draw. Since the current draw is lower, there are fewer losses and less heat. Everything runs more efficiently.

In real world application, it's harder (for me) to figure out exactly what battery to go with when going to a 5S configuration. When running 4S I usually run a 4S2P 8Ah pack, so I have about 118.4Wh of stored energy. When running 5S, I should be able to go to around a 6Ah pack and get the roughly the same runtime, with some gains due to less stress on the pack resulting in less voltage drop. Although these gains may be debateable, since you've gone to a pack with less capacity and we don't know how the load will affect the voltage drop.

It all seems to go around in circles to me at this point. Assuming that the 4S 8Ah pack can deliver 20C, which is 160A and the 5S pack can deliver 20C, which is about 120A, each pack is still going to be stressed just about a like in either system. To me, the only real advantage is that the whole system will run cooler on the 5S setup than it will on the 4S setup.

What kills the whole deal with 5S for me is that the nicer motors run cool no matter what, whether they are being run in a 4s setup or 5S setup.

Oh, I also liked the idea of being able to run a cheap 5S2P 8Ah battery pack because the current draw was so low that it didn't stress the cheapie 10C pack. Of course, the battery is a brick and I can't race with it because it knocks my suspension out of whack.

I personally think that it is pointless to beat your brains out over the 4S to 5S issue. I've found 4S to be great in the right setup.

I don't think that going to higher voltage will really payoff until we can reliably run a 6S or 8S setup that only draws 60A peaks so that we can run cheap battery packs without stressing them out. That's on the practical side.

As I said, all of this keeps going around in circles. For me, I am satisfied for the moment with 4S systems. They are a good compromise among weight, runtime, heat, and cost.

Once technology catches up, then I'll turn all of my 4S2P packs into 8S1P packs and run much lower kv motors just for the efficiency.

[zeropointbug]

Well said AAngel. :dft009:

Theoretically, the higher the voltage, the better... but like AAngel said, it's more to do with what actual equipment we have that has not been made to up most standards (in my books), in particular the Feigao motors. They are going to run quite hot no matter what you do, basically, the more power you pull from them, the more heat, and sometimes not even that, they are very picky what kind of load they have on them... won't go into that now.

Look at it this way for Feigao's, say you spin an XL motor under load at 30,000rpm, one at 4s and the other at 6s lipo (making the appropriate Kv. rating choice for each voltage). Now, Artur says the Feigao 7XL motor runs at ~70% efficiency under max power, just as an example... now say that the 4s setup will get you ~71% efficiency at max power, then going to a 6s setup(with appropriate Kv. motor to maintain 30Krpm) will get you ~72.5%... you gain 1.5% efficiency (example) when running higher voltage (normally this is a large difference), but since the 'overall' efficiency of the motor tech is poor, the higher voltage setup will not make that much of a difference as far as heat output. IIRC, 1200 watts for XL motors, so the 4s setup will put out 490 watts of heat (max power...how long do you think it can do that for:005: :013: ), and the 6s setup will get you 455 watts output of heat. Mind you, you are not drawing max power all the time, but you get the point.

Now if we look at a Lehner or a Neu motor which normally run ~88% efficient under max load, now impose the last 'Feigao' example to this, the 4s setup might get you 88% efficiency, then the 6s setup might increase this closer to 90%. As you can see, this same 'percent increase' will give you larger payback as far as running temp. But, at the same time, the Lehners and Neu are supposed to run cool at any voltage setup, but simply, the higher voltage, the cooler it will run.

NOTE: These brushless motors also have different efficiency curves at different voltage setups as well... hence real world applications may vary. On the same note, efficiency should NOT be confused with motor running temp, as they don't really go hand in hand. ex. You can have a 90% motor running at 1800 watts, that's 180 watts of waste heat (motor will run hot)... as well you can have a 80% motor and running 800 watts power, and have 160 watts of waste heat (still hot, but a tad cooler), the 90% efficient motor is going to run hotter.

I say run a 4s lipo setup or 5s2p A123 pack and you are set, go for an 8 or 9XL for the low end, or a Lehner or Neu for cool running. If you want to run high voltage, get a Neu or Lehner if you want to maximize benefits.

I am currently switching to a Neu 1512/3D (1700Kv.) running on 7s2p A123 (23.1v/4.6Ah), this is going from a 5s2p and 7XL, I am expecting huge benefits from this change.

[wallot]

added 2 more caps so 4x470uF total with nice small spark when connecting batteries. 2 caps helped a lot with race tires so i hope that 4 will help with heavy bigjoes



oh and no more yellow/green shrink wrap for your entertainment :)

[no mods]

so whats the verdict... is there an ideal cap to buy for the quarks?

[suicideneil]

Ideally, it should be 35v, low esr, and work at upto 105*. UF rating is personal choice- either go for lots of smaller ones (say 220-370uf), a couple bigg'uns (2200uf etc). It all depends on how much space you have to mount them as to which size you get, but the 1st three factors are vital.

[zeropointbug]

Yes. Also, when running 4s lipo or below, 25v caps are all that is needed.

http://search.stores.ebay.com/JEA-CA...580994QQsofpZ0

There is a good place to get some good caps, you get 200 caps though... :eek: