8+ Min. Ep Races; Higher Capacity Batteries

[chambalero]

I've been hearing news of races that will last much longer than the usual 5 min. I am aware that there are enduro races using brushless motors that last for hours. But 8+ min races using a single 6 cell pack? New battery technologies with more that 4000 mah capacity? I've read about Li-ion and polymer batteries which are pretty much common in cellphones. But it seems these kinds of batteries are still far off for race use... or is it? Li-ion batteries are much much lighter than Nimh and is capable of even much higher capacities. Polymer batteries are even more freaky- they can be formed into any shape and placed anywhere in the car. At least this is what some periodicals say. Guys and gals how true is it?:confused: :D

[Grizzbob]

Well, I'd still say that Lithium-Ion or Lithium-Polymer cells are a ways off for our use(R/C cars definitely put more stress on batteries than just about anything), but even with the NiMh's we have now, we can run a good 6-7 minutes at speed(at least 7 minutes with stock motors). However, motors definitely do NOT like to run for that long, I've doen some 6 minute races with stocks, & at the end of a race, the motor would get pretty darn warm(definitely moreso than they should), so they will wear faster in longer runs. On the other hand, from a driving standpoint, I did like driving longer runs, that was fun......:cool:

[InspGadgt]

Some enduro races are ran with brushed motors as well though brushless survives it a lot better in most cases. Yes I'll bring it up again...lol...our F1 race uses Sport Tuned Mabuchi motors and races for 40 minutes. Typically that's 3 battery packs at about 16 minutes apiece.

[Grizzbob]

I'm not surprised, I know that with the 1100mah NiMh packs for micros, we can go for at least 15-20 minutes on a charge, & because of that, at my local track we started running 10 minute mains. I like those runs, though I don't know if I could stay mistake free for any longer than that, at 10 minutes my left hand already feels like it's about to fall asleep......:p

[End Overend]

The latest issue of Xtreme RC Cars magazine has a test of a prototype Lithium Poly battery, page 177.

They tested it on an HPI Super RS4.

The battery was a stack of 4 cells and had a voltage of 8.4 volts. Total mAh was 8000. The motor they tested it with was a Hacker 5T motor/ESC. I would guess that this set up would really test the battery.

After 15 minutes of very hard driving (I'm guessing near race conditions) they had to stop the test because of a bad switch. At that time the motor was 150 degrees, the ESC 180 degrees and the battery 120 degrees!

The next day with a fixed switch they ran for 20 minutes with no degridation in performance and only stopped because they didn't want to run the battery all the way down.

Sounds to me like they are making pretty good advances with the technology.

Their are problems with Lithium Poly cells from my understanding though. If they are charged too much they tend to release Hydrogen, which can lead to an explosion. How large that may be is not known to my self.

The performance benifits seem great though. They compared the results with a set of GP3300 matched packs.

Here are the comparisons:

Weight: Lithium Poly 287g, GP3300 366g (3 ounces lighter)
Run time: Lithium Poly 20+ minutes, GP3300 6 minutes
Acceleration (60 feet): Lithium Poly 1.67 seconds to 39.8mph, GP3300 1.82 seconds to 32.8mph
Top Speed: Lithium Poly 47.2mph, GP3300 41.2mph

The speed increase is due to a combination of increased voltage and lighter weight.

Anyway, interesting article. I hear fuel cells may have a future in RC vehicles also.

I can't wait to see what the next 5 years brings with battery technology in RC cars.

[crono man]

i understand lithium cells put out more voltage and this leads to higher top speed but lets say were comparing same voltage(lithuim) VS same voltage(nimh),im curious then on a drag race because i heard that lithium cells have higher IR i wonder how it would effect acceleration!??

[TEM]

12th scale is 8 mins but it's only 4 cell. As said in the above, the motors are NOT going to like to run for a long time on 6 cells. Expecially when you got motors like the monster that gets damn hot even after a 5 min race. We still can't pull so many amps from lithium cells right now. And when we can, those cells are toast after very few cycles.

I haven't yet run an enduro, but if I do, and if it's brushed, I won't be going by the same game plan as with just normal stock or mod. The motor will get killed. Maybe as a team and if people are willing to dish out the bucks. I'll do it with a stock silver can motor(order a whole box of them first!) or use spec motor and brushes. those motor seem to take a good beating and keep on ticking. Ofcourse it still depends on the rules. You kind of got to play by them.

So to lenghten races; not a big problem. It will only hurt the people who can't afford it. Just like how races went from 4 min to 5 and some places 6. Technology went up, our $$$, not necessarily..

[End Overend]

crono man,

My guess is that with the same voltage they would be pretty close. I'm doubting that the internal resistance would be so much higher that it would make a serious reduction in speed.

TEM,

One thing impressive about the test in Xtreme RC cars magazine was the fact that they used a Hacker 5T Brushless Motor. I don't think you are going to get much more of an amp draw than that out of a motor.

The simple fact of the matter is that if battery duration gets much higher Brushed motors won't survive long, and battery life is advancing at a rapid rate right now. A 10 Turn motor will have a melt down if it runs for 20 minutes at race pace.

Brushless motors are the future of RC cars, it's just a matter of how long it will take before they surpass brushed motors in frequency of purchase and the low entry cost of brushed motors. In the next year or two you will see brushless motors come down a long way in price and you will start to see more companies producing them.

Sanctioned racing may take the longest to make the change as racing leagues are historically slow to change with technology. But if it gets to the point that only racers are using brushed motors, racing will start to whither.

On the plus side of racing you could start to see more endurance oriented races come about. 20-30 minute races that involve more people in a heat. More confusion, but not so much stress for 5 minutes. Some of the guys that I run with that's their biggest complaint with racing. It's just too much concentration and stress to run 5 minute races. Most of the time it comes down to who screws up the least not who has the fastest car or best set up. All it takes is one idiot to try a bad pass and take one or both of you out and your race day is over because you didn't qualify for the next race. With a 20-30 minute race you would have time to work your self back into the race and hence less stress and more enjoyment.

Nitro mains can run 20 minutes to an hour already, the problem there is that you need a pit crew to fill up your tank as the main goes on. With the length of nitro mains, I can see electric mains going the same length when battery technology gets there.

Anway, as I said before the next five years could be pretty exciting for electric RC. When battery technology gets to the point that we can get 20-30 minute run times out of batteries and we can charge at a high rate (so waiting for a charge won't be all day), I'm buying something like an E-Maxx and selling my nitro truck. Or maybe I'll just try and convert my CEN MT2, that would be cool. :D

[rcguy2477]

Our mains are 7mins long and at the end, my 3300's still have plenty of juice. The problem is the motors. Around here, everyone gears high, and that causes some major heat, which is bad for an extended period of time.

[TheSilverFox]

Arn't Lithium Poly & Ion like $150 though?

Bit pricy if you ask me...I'd rater get 4 GP 3300 packs pre assembled at my LHS.

[chambalero]

they have a review on new battery tech on page 116 on the october issue of r/c car magazine. they didn't talk about new extended run times for NiMH. But they talked about Li-ion and Li-ion polymer batteries. Seems the only rc application they have right now is in the receiver packs of nitro vehicles. But that has also proved significant because the receiver pack weight was reduced dramatically thus proving to be an advantage.

Li-ion polymer batteries are not too far off because they are now mass produced for cellphones. they have much bigger capacity than NiMH and are much lighter. the drawback is that they are also much more expensive. but expect the price to go down as they are used for more applications. here is something quite interesting that i'm quoting from the magazine: "...with the polymer technology, your car body could also be your battery. Polymer technology will allow future batteries to be molded into any shape, and farther into the future, a battery will be as thin as a piece of paper which could be rolled up and put in your pocket!"

i know i'm kinda straying from my topic in the beginning when i posted this thread. but my point is a 4000 mah NiMH or so will further put a greater weight on the ep car!! this will in turn affect more the balance of the cars who have the battery slots on one side. could there be higher capacity NiMH on the way or shouldn't there be other battery technologies to be applied to rc? lighter batteries, batteries with much greater capacity, and batteries that can be placed anywhere on the car? i agree with end overend when he said brushless motors are the future. and i agree that there are disadvantages with 5 min only races. i know because i have joined 40 min nitro races. i think significantly exteded ep race run times (without pitstops) could only come about with new battery technology and brushless technology

[chambalero]

Originally posted by TheSilverFox
Arn't Lithium Poly & Ion like $150 though?

Bit pricy if you ask me...I'd rater get 4 GP 3300 packs pre assembled at my LHS.

are these batteries available already for race applications?

[ChumsGum]

I get 10-15 runs with my Micro RS4 with an Elite Modified.

[SausaGe_LinK]

i read something about lithium batteries saying that the hotter they get the less power they release.... this is to prevent damage to the cells

[Maverick Racer]

In a race situation a good brushed motor will out draw any brushless motor when pulled on hard enough. In very light load situations 6 and 7 turn brushed motors will pull well over 100 amps. And that is spinning a small aluminum dyno flywheel.

This is in most cases to much for the Li-Pol cells to handle.

[highroller]

In 1/12th races it 8 minutes, has been since the 1200sc batteries, only change has been to using lower turn/wind motors.
Most of the tracks I race at still run 4 minutes heats, a couple of offroad tracks run 5 minutes. In 1/10 modified oval it is still possible to dump even with the best 3300 pack and I had the feeling that 3300 would give us that padding of added runtime - but racers have found a way to extract every last ounce of energy from the battery packs.
We went from 3 minute heats (7cells), to 4minutes (6cell limit) and as battery capacity increased some tracks have gone to 5minutes and motors are using less turns. If battery technology does change as if has it wil only cause a change in motors and ESC technology. Motors changed for 19-21 turn singles (mod) 28-30 turn (stock) which were divided into enduro and sprint races with 1200 saft batteries then to 17-20 turn as battery capacity increased to the 6 single turns we normally see today don't forget the specially wound 5 turns that some guys can't use because of track conditions not having adaquate traction to hold that much power.

[bad_company_9]

Didn't Novak make Li-ion packs for the micro RS4? Due to a possibility of those packs leaking, i think, they issued a mandatory product recall. Oh well, if you own these you can get free stuff from Novak or for cheap...

[InspGadgt]

Wasn't that they were leaking...a few of them caught fire while charging.

[chambalero]

oh wow!