RC10Talk - The Net's Largest Vintage R/C Community

True the car did run faster on the lipo. So I thought It was the extra heat generated from turning faster.

Lipo's are generaly 7.4v and tend to stay around that voltage throughout each discharge cycle. The older Sub C packs would discharge at lower voltages. While we did our best to have a pack ready before a race with the highest volts (PEAK) the motors back then didnt get the full high voltage right the way through like the way they do now.

Brushless is king and will no doubt fade brushed systems out in the future. Thats not to say I dont still run many brushed motors though, but hey- I run vintage cars.

bormac wrote:Lipo's are generaly 7.4v and tend to stay around that voltage throughout each discharge cycle. The older Sub C packs would discharge at lower voltages. While we did our best to have a pack ready before a race with the highest volts (PEAK) the motors back then didnt get the full high voltage right the way through like the way they do now.

True, but Modified 2wd in the days of the 6-gear was also 7-cell NiCd, which was 8.4v, regardless of the discharge curve. That's still more power than a 2S LiPo can provide. No, there is no slipper on a 6-gear, but R/C cars raced for years without slippers. It's not the death of a gearbox if you know what you are doing. Hell, We raced Stealths, JRX2s, MIPs and many other trannies with direct gear mounts to remove the slipper, and we did it on surfaces that would allow wheelstands off the corners with the right tires.

The point is, the 6-gear is not some fragile paper transmission that can't handle contemporary electronics. If you manage to "blow up" a 6-gear on Lipo and brushless power, you would have blown it up with a vintage electronics setup in 1985, too.

Agreed.

I remember when 7 cell packs were around. Im pretty sure they were phased out here somtime around the 1200-1700mah cells were around. Those cells were cool though, thats why I have a small collection of them now.

Ahhhhh, those days of 7-cells on 10-turns trying to last 4 blistering minutes on a bullring dirt oval are dearly missed. Wicked fast racing for the technology of the cars we had. I think we were using 1400 SCRs when most mod guys were using the 1700 SCEs, so it was even a bigger accomplishment to make it 4 full minutes with a sprint car.




I think I need to build a killer 6-gear and run it with an 7.5 on a 40C LiPo to put this to rest once and for all.

Having learnt the hard way Lipo tech matched with Brushless Tech certainly deliveres some pretty potent torque at time. The issue is no longer how to set about finding that amount of power or even duration any more, its more about how to manipulate it to work in your favour.

I think the average basher doesnt even realise what a 'throttle profile' is- LOL! Seriously anyone can get access to some decent horsepower these days but its the racers that usualy know how to set their gear up to manage it.

Case in point, many people could set up a six gear and work the throttle profiles to make the trans last. The average basher however wouldnt know where to start.

Yes yes yes I am a basher. With my work schedule I cannot race. And I do think it was my fault and not the batteries that killed my motor. Running wide open is so fun though. My nimh batteries are 7.4v 3000mah and the lipo is a 7.4v 4000mah. So there was some extra juice involved. I know voltage is constant but current changes a lot of things. Oh yeah and what is a throttle profile?

Throttle profiles are settings on the esc and some radios that allow for various changes to the amount of power to throttle.

Kayne wrote:My nimh batteries are 7.4v 3000mah and the lipo is a 7.4v 4000mah. So there was some extra juice involved. I know voltage is constant but current changes a lot of things.

No, mAh is current capacity, it changes NOTHING. Current capacity has zero to do with the amount of power at all. It's the rating of how long a battery will last given a full charge. 1200 or 6000 mAh batteries all still deliver the same power (1.2v per cell for NiMh or 3.7v per cell for LiPo), just for different periods of time.

Think of mAh (current capacity) as the size or capacity of your gas tank, not the amount or rate of fuel you can use or the horsepower of the engine.




If you melted a motor, it was likely due to improper (over)gearing more than anything else.

Eau Rouge wrote:

Kayne wrote:My nimh batteries are 7.4v 3000mah and the lipo is a 7.4v 4000mah. So there was some extra juice involved. I know voltage is constant but current changes a lot of things.

No, mAh is current capacity, it changes NOTHING. Current capacity has zero to do with the amount of power at all. It's the rating of how long a battery will last given a full charge. 1200 or 6000 mAh batteries all still deliver the same power (1.2v per cell for NiMh or 3.7v per cell for LiPo), just for different periods of time.

Think of mAh (current capacity) as the size or capacity of your gas tank, not the amount or rate of fuel you can use or the horsepower of the engine.




If you melted a motor, it was likely due to improper (over)gearing more than anything else.

Thank you for the lesson. I really mean that. I have asked questions at my lhs and it seems like they are more interested in selling traxxas products than anything else. I probably made myself sound stupid with my previous posts. I haven't been doing this that long. I am learning as I go. I guess I just need to ask more questions before I type. Thank you Eau Rouge for taking the time to clarify my mistakes. I am sure it was frustrating to read my blabbering.
I am not being sarcastic I really do appreciate it.

Sorry for the hijacking. I think brushless is the way to go maintenance wise. Especially for some like me who is mostly plug and play.

No problem, it's easy stuff to get confused with. It's definitely a misnomer that people believe that LiPo batteries and brushless motors are some sort of supercharged better than old technology just because it is newer and everyone uses it.

Voltage is voltage, mo matter where it comes from. That 9-volt battery in your smoke detector will run like a banshee in your RC10... for all of about 20 seconds.

The truth is, brushless is better because you don't have to cut comms every four runs, change brushes every three or springs every 5. You don't have to "zap" can magnets, and you don't have to screw with comm drops or other hocus pocus. Brushless and brushed motors will run virtually identically (with a few notable exceptions) on the track—brushless motors just require almost ZERO maintenance and run the same indefinitely. If you maintain a brushed motor after every run, it will run at the top level for a long time. It's just a lot of work and wasted time you could be driving the car. Think of it as carbs versus fuel injection. They will run the same when perfectly tuned, but the FI will be the same every time no matter what variables around it change.

LiPo vs NiMh/NiCd cell technology is similar. Flat discharge curves for the LiPo and zero memory make the batteries almost baby-sitter proof. No maintenance other than a balance one in a blue moon, and don't over discharge the pack—don't dump it—and it will run the same indefinitely. If you let the most recent NiMh cells sit on the shelf for a couple of days without cycling them, they lose potential, power and capacity. It was like having a supermodel for a girlfriend that would never put out. Just too high maintenance to be something you could enjoy using more than once or twice.




Brushed motors are dead. For everything but crawlers, their benefits outweigh the cost of entry in massive chunks. I have a bunch of rocket 27t and 19t brushed motors in my motor case that will never get used again if anyone would like to stock up their vintage electronics collection.

Well with the capacity and voltage talk, it may seem that this thread is going a bit off topic, but...

I just picked up a second brushless motor and a pair of Lipo batteries. And I still have questions. I had no idea that brushless cans come in sizes. My first brushless was a Novak ballistic/havok pro 6.5. My second is an Orion Experience 2 pro. I had asked the guy at the shop for a good motor speed control combo for my TC5 and he recommended the Orion. When I got it home it was bigger than the Novak, but still fit on the car and looks great. So I ran it this weekend in a lot with a 5300 Lipo and it was fast, fast, Fast! There wasn't much in the way of information on this combo though. The instructions just tell you how to install onto a Traxxas Slash, and the web site doesn't offer much info either, just says its plug and play. Is it too much for a TC? Can I program the esc? I didn't know you could do that now (My next newest esc is a Tempest Pro). I need to install the Novak into another car and run them together. Given the duration of run time (seemed like forever) and speed brushless is the real deal. I guess a good comparison is records vs. digital downloads. I still have my vinyl, Cds and an Ipod, have my entire Cd collection on my computer, yet I still listened to Abbey Road the other day on record. I just like it that way. (And I still can't find a digital copy of my Irish War Pipes on 78). I think brushed will never completely go away, just continue to become more obsolete, same as records.

Now about batteries, mahs I've always understood, and voltage I get. What are C's? Specifically a 25C vs. a 30C or even higher? From what I understood a C was related to Mah in charging (charge at 1C = 5 amps for 5000mah) so what's the other C number mean?

It seems like I should be able to ask these questions at the hobby shop, but I am in agreement that at least here where I live, if its not a traxxas or truck that I'm buying, they're not interested in helping much. Prior to getting the batteries, I had asked questions like this and the response I got was something like "It's what everyone is running now so you should just get them. And make sure you buy a charger that can handle them. What are you going to put them in? Oh a touring car... well those aren't popular around here so I guess you could do whatever you want." So as always I'm glad to have found a forum that is very helpful and informative.

C rating on a Lipo is how much "punch" it has available (and allegedly at that)...

5000 mah @ 30C = 150 amps

5000/100 = 50, 30C/10 = 3, 50*3=150

Hope that makes sense...


i say allegedly because there are some shady sellers out there that post "peak" C ratings and not "constant" C ratings, so you think your getting a good pack, but it is only mediocre at best.

just to add a little more info to this thread.....

the C rating is the maximum discharge current through a pack that is safe and allows for maximum efficiency. C stands for capacity. So as said, 30C means 30 times the capacity(in mAh). If you try to draw excess beyond 30C, you will begin to overheat the pack and risk damage to the cells. This is directly related to the internal resistance of the cells, and is determined by how the cell and pack are constructed. You pay more for a higher C pack much like you would pay more for highly matched nicd or nimh cells.

Lipo cells are discharged just under 3.7v per cell, and will be fully charged up to 4.2 volts per cell(roughly speaking). the flatter discharge curve means that a 2S lipo pack is more like a 7 cell pack on steroids, which is why a lipo battery has a much better performance 'feel'. it holds a higher voltage longer, even longer than an 8.4v nicd pack.

OK... brushed motor vs brushless. the brushed motors major downfall is that there is a mechanical commutation that must take place. the magnetic coils are switched on and off through the commutator and brushes. This is a wear point, and the overall motor construction uses more parts than a brushless motor(hence the name). this required constant maintenence, as you all know, and provides many points of failure, including adding resistance which directly relates to lower performance.

a brushless motor relies on electronic commutation of the magnetic fields, and that is why brushless motors are 3 wire systems(sensors are a whole different topic and not relavent for right here), the motors still have 3 magnetic poles. If you have a motor with more poles, you would need more wires. The core on the main shaft is a permanent magnet, so overall a brushless motor only has 3 moving parts. The main shaft, and the 2 bearings supporting it.

the electronic commutation is done with semiconductors that never change over the life of operation(again, for these purposes), so the performance of a brushless system is always consistent. the only things that can go wrong are bad bearings, and occasionally, the armature will become demagnetized and need replacement(usually this is directly related to overheating).

hope that helps and is not confusing.