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Confused about Battery and Motor Specs

Confused about Battery and Motor Specs

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Old 12-12-2009, 09:24 AM
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Default Confused about Battery and Motor Specs

So suffice it to say, I'm new to RC, trying to build a 1/8 buggy. I don't want some high level competition speed, just something I can run at a local track, with medium level competition and just have fun with.

My confusion comes in when trying to figure out what motor I need and what battery I need.

On the motor, I see a lot of people use a 2650kV motor, and some people use a 2200kV motor. I read a lot about how 2200kV are usually for truggies, as they have more torque for the heavier vehicles. But I also hear that a lot of people use the ESC to dial down the torque and use them in buggies. Given that I am generally new to all of this, am I better off just sticking with a 2650kV motor and not worry about tweaking it so much?

On batteries, I know I want somewhere in the 3S-4S range, and from what I can tell, 4S means a 4 cell battery? Is there something inherently better about a 4 cell battery vs a 3 cell battery (4S vs 3S) if they both have the same capacity? On capacity, I think I want to start with a 5000mAh battery. It seems that 2S doesn't last very long, but some people run two 2S batteries in parrallel and that acts about the same as a 4S battery? Also, on the discharge rate, I see batteries range from 20C to 50C, does this mean they discharge more power/run out faster/send more energy to the motor? So a higher C rate on the battery means they give more power to the motor/make it run hotter/run the battery out faster?

If I'm just trying to get a decent setup I can learn on and maybe do some low-medium level racing (at a local track), am I going to be ok with something like a 2650kV motor and a 3C battery? And if so, is 5000mAh ok? And what should the discharge rate be? 20C? 30C? 40C? 50C?

I don't really want something that is too fast/too hard to control, as I'm basically learning from scratch, but at the same time, once I learn, I don't want a setup that will be too slow to compete with.

So, any clarification/ideas/suggestions?

Thanks ahead of time...
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Old 12-12-2009, 10:04 AM
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I run a 2650 on 3S and it's fine for small to medium tracks. It's only slightly slower than the fastest 1/8 buggies on a large track. The 2200 works fine in buggies. Probably more common than the 2650.

Right now, the Castle 1800 with a 5S seems to be a great way to go or maybe a Tekin or other setup using a 1400 or 1700 motor.

The advantage of more cells is a higher voltage setup which should result in lower temps and longer run times.

I've been doing fine with my 2650/3S setup, but would go with the above if doing it again.

Castle's Monster or Tekin RX-8 ESC + any motor seem to be a popular setup.

The higher the number of cells, the lower the overall capacity to keep weight down. I'd recommend not going any lower than 35C to keep the juice flowing comfortably and getting the highest mah pack you can get. I'd pay significantly more to get a higher mah pack than most people. Just remember that as it gets heavier, it WILL get harder to balance the weight bias of your car (left to right). You only need as many Cs as your setup draws power. There is a difference between burst & continuous. Look primarily at the continuous.

Been running an 8000mah 3S pack that is really heavy, but I like that I don't worry about running it down and rarely drain more than 6000mah at a time which keeps the pack healthy. Check your esc & motor temps if you are going to be running for extended periods of time. Higher cell setups will have lower mah, but should run longer.

I DO run 2S 25C packs (single pack, not in parrallel) with the 2650 and find the speed to be usable if not exactly fireworks on small tracks designed for 1/10 scale. Seems to work okay and the packs have shown no damage from doing so extensively so far.

Read somewhere else that you should decide the voltage (number of cells you want to run) before you decide anything else. The 5s/1800 setup above or something close to it should run fine, maybe 6S and lower kv would be good too. Would not recommend anything less than 2000kv or so with 4S.

My friend runs a 1400 with 5S and is very happy with his setup. 4S/2200 is a REALLY popular setup in my area.

Balance your cells often if over 2S

Last edited by lusifur; 12-12-2009 at 11:15 PM.
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Old 12-12-2009, 08:26 PM
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So as long as your setup does not draw more continuous power (35C being the low end of what it would draw?) than the battery is rated, you don't risk damaging it over time? Or is it that you don't want to run the battery down to empty (such as not going lower than 2000mAh on an 8000mAh pack) to prevent long term damage?

Is it difficult to tune the torque that a 2200kVh motor puts out when used in a buggy?
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Old 12-12-2009, 09:04 PM
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higher voltage often has higher effieciency. But 5 and six cell packs are a bit larger and heavier. You can shrink to slightly less mah capacity to make up for it sometimes. With 30c and up packs you don't have to worry about overloading you 4s as much.

4s just seems to be a good middle ground for voltage and weight. 3s isn't enough, 5s is good as well, 6s is a bit too much.

The trend for the faster racers is to use less powerful motors now. When 1/8th E started, everyone was in a huge hurry to cram as much power in as possible. The cars were too heavy to turn and were nothing but tire eating wheelspin monsters in the infield. With all that power, nitro cars still sailed by and won every race.

Yes its hard to drive a car with aggressive bottom end torque. The Losi drivers with the 2100 Xelmoran syystems on 4s seem to really have thier hands full. Deosn't feel like a smooth esc at all. The MMM is a bit better and the Tekin is butter.

Having a smooth bottom end is very important with E. Stick to the Sensored racing Esc's like Tekin and speed Passion and your set. A Tekin system with a 1700 or 1900 motor on 4 cell 5000 mah 30c should race nicely.

Last edited by Zerodefect; 12-12-2009 at 09:11 PM. Reason: new pet possum
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Old 12-12-2009, 09:22 PM
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Someone posted this beginner's guide to brushless on another forum, and I really found it useful. Have a read there, it will explain a lot.

The idea with higher voltage (like 5S or 6S) is that the motor can have a lower KV rating and also draw less current. Which will help with longer runtimes.

I'm running the 2200 castle motor on 4s in my buggy. And you really don't have to worry about it, it runs great. I've got it geared for just over 40mph and find it really nice to drive. Pretty much the same top end as 1/8 nitro buggies.

Only problem I've got with this setup is that it gives me just on 15min of runtime on a 5000 mah 20C batt. Currently waiting on some 30C batts.
I'm thinking of trying a lower KV motor so the runtime will be a bit better.

The 20C batts run great with no performance problems. I just feel safer running 30C. I'm currently watching the 20C batts like a hawk to make sure nothing goes wrong though.
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Old 12-12-2009, 09:55 PM
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As I read this thread, I'm a little concerned. Dane, you say your new to rc.
then my concern would be a newbe with a 9lb 2+ hp missle in your hands trying to run laps with experienced drivers. I Watched a 16 year old kid take one in the face off a jump a few weeks ago driven by someone with past race experience. Even a somewhat experienced driver can have more power than they can handle. I put my wife into a 1700 kv 4s setup this year after four years of racing 1/10th scale cars. She is a very throttle concience driver, and the smaller motor made the buggy very easy to drive. My suggestion to you, (built my first one over three years ago, on #3) would be to concider less power until you get more experience.... Rick
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Old 12-12-2009, 11:18 PM
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You could try running your 2S lipos for a few weeks to get used to the car.

I run my 2S packs at least for 2 packs to start off every practice. "re-learn" the track at low power, then throw in the 3S and drive harder.

just me.
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Old 12-13-2009, 11:26 AM
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My only negative with building a 1/8 electric buggy was choosing a 2650KV first. Now that Castle has the 1800 out, that is a way-better choice. You can learn with 4S Lipo and then go 5S when you're more capable.

I ran a few races this year with 2650KV and 3S Lipo (5000mAh) and it was fun but too "powerbandy" and not enough runtime. 1800KV or 1700KV with 4S would be my choice anyday. The Castle 1800KV would be a great choice over the 2650KV unless someone is offering you a 2650KV cheap.

BTW - I'll offer you my Castle 2650KV motor cheap - with one Zippy 30C 3S 5000mAh - $120 shipped!
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Old 12-13-2009, 01:04 PM
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From what I can tell from feedback so far, is that there is really no reason to go with a 2650kV motor unless I can get ahold of one for pretty cheap, and really, long term, it's just best to shoot for either 2200kV or 1800kV.

Seems several people have talked about using an 1800kV motor and stepping up from 4S to 5S as I get more experience. I assume the 4S battery will give me less speed than the 5S, and is something better to learn on?

I don't want to go crazy buying several motors and batteries, so if I could get a motor that I could step from one battery to another as I learn, that'd be great. Or alternatively, one battery and two motors, and "upgrade" as I learn, but I'm not quite sure which route is the better of the two.

I guess from what I've read so far, given my lack of experience (I won't be racing on a track until I get experience, the track is available for practice 6-7 days a week) I'll be better suited going with something like an 1800kV motor and getting a bigger/better battery as I get a hang of things.

Is that about right? And I'll want at least a 30C battery as well, but could probably get away with a 20C battery as I'm learning, and step up to a 30C battery when I go from 4S to 5S?

Edit: Also, cost wise, is the ESC needed to run a 2650kV motor vs a 2200kV motor vs a 1800kV motor going to vary much? Do I need a really expensive ESC to run one setup vs another, or can I get some "middle of the line" ESC that could run any of the 3? I'm trying to avoid spending too much money on the initial setup, and depending on how much time I have to dedicate and how competitive I get with it, worry about getting a different (aka more expensive) ESC sometime down the road.
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Old 12-13-2009, 08:04 PM
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You will be able to use a single esc to run those, you won't need to buy a new esc everytime you change motors if thats what you wind up doing. A Castle MMM or Tekin RX8 would run those as well as some other brands of escs out there.
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Old 12-13-2009, 08:34 PM
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1700-1900 kv motors on 4 cell aren't slow, they just aren't "wet you pants" on the straightaway fast. They're still faster than nitro, but have a smoother bottom than the overpowered cars. Thats why nitro's are still kicking but on outdoor tracks in my area. The electrics are usually undrivable in dust.

Most tracks don't have the room or grip to put big power down.

Don't bother with useing a slow setup until you get better at driving. Desighn your car right the first time, its cheaper. Don't bother switching to different voltages and motors unless you mess up and get the wrong stuff. just try to get good compatable batteries and motor. You can slow the car down with epa, or just being easy on the trigger.

But don't rely on epa to calm a way overpowered motor in race trim. It'll still have too much lowend grunt. Trying to tame an overpowered motor seems to kill the drivability of the car in many cases. Its just better to run a tamer motor as hard as it'll go.

Keep in mind, the racers that learn the quickest are the cautious slow ones. Airshow momos never learn.

Just shoot for 15 min runtime and less than 700 grams battery weight.
4s 5000 30c and a 1700-1900 tekin should be able to pull this off.

Like this one:
http://www.hobbycity.com/hobbycity/s...idProduct=9516

http://www.hobbycity.com/hobbycity/s..._35C_Lipo_Pack

http://www.hobbycity.com/hobbycity/s...idProduct=9933

Last edited by Zerodefect; 12-13-2009 at 08:49 PM.
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Old 12-13-2009, 08:39 PM
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Originally Posted by Zerodefect View Post
1700-1900 kv motors on 4 cell aren't slow, they just aren't "wet you pants" on the straightaway fast.

Most tracks don't have the room or grip to put big power down.

Just shoot for 15 min runtime and less than 700 grams battery weight.
4s 5000 30c and a 1900 tekin should be able to pull this off.

http://www.hobbycity.com/hobbycity/s..._35C_Lipo_Pack

http://www.hobbycity.com/hobbycity/s...idProduct=9933
I agree....I run a 1900kv on 4s and it is enough power for the medium size track I run on....
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Old 12-13-2009, 09:12 PM
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I agree with the last few posts. I run a 1850kv nue and get awesome runtime, temps and plenty fast enough. I ran a 43+ min race with nitros a few weeks ago with only two 20C 5000mah turnigy batts. if you stay with a milder setup like this you will not need Crating above 20C my batts come off track after 20+ min runs at 105F max. If you go to 5S on the 1700-1900kv range motors you get even better runtime AND speed. the 1800ish kv range i think is the perfect motor.
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Old 12-14-2009, 03:18 AM
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Originally Posted by Zerodefect View Post
1700-1900 kv motors on 4 cell aren't slow, they just aren't "wet you pants" on the straightaway fast. They're still faster than nitro, but have a smoother bottom than the overpowered cars. Thats why nitro's are still kicking but on outdoor tracks in my area. The electrics are usually undrivable in dust.

Most tracks don't have the room or grip to put big power down.

Don't bother with useing a slow setup until you get better at driving. Desighn your car right the first time, its cheaper. Don't bother switching to different voltages and motors unless you mess up and get the wrong stuff. just try to get good compatable batteries and motor. You can slow the car down with epa, or just being easy on the trigger.

But don't rely on epa to calm a way overpowered motor in race trim. It'll still have too much lowend grunt. Trying to tame an overpowered motor seems to kill the drivability of the car in many cases. Its just better to run a tamer motor as hard as it'll go.

Keep in mind, the racers that learn the quickest are the cautious slow ones. Airshow momos never learn.

Just shoot for 15 min runtime and less than 700 grams battery weight.
4s 5000 30c and a 1700-1900 tekin should be able to pull this off.

Like this one:
http://www.hobbycity.com/hobbycity/s...idProduct=9516

http://www.hobbycity.com/hobbycity/s..._35C_Lipo_Pack

http://www.hobbycity.com/hobbycity/s...idProduct=9933
This is the best advise you can follow as I did. I am a newbie for electric 8th scale and dont know shit about anything about it. I still drive nitro most of the time but its sure is fun to drive e bugs.

As the post say get a combination that is driveable. Before I get to purchase anything I searched and searched and ask and ask every opinion I can possibly get. There is to much unknown to me when i started the project but I am glad I got the best combi can have.

I went with a tekin rx8 with a 1900 kv motor on a caster racing EX 1.5 R. The rig that you are driving is also important as the items you will put in the vehicle and i find its the best setup up for my particular buggy. Using this setup (sensored mode), I still need to tone it down a bit. Cause I spin the tires a lot and two run days will take out a set of tires (heavy nitro fingers). Its useless to have an overpowered motor cause you cant even use the power it can bring. You need a driveable buggy. 1900 kv on a 4s is not slow and can keep up with high end nitro engines out there. plus youll have the advantange of no spool up so making jumps will be a cinch. I just smile whenever i clear jumps that i barely make using nitro sometimes i over shoot it.
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Old 12-14-2009, 02:34 PM
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Tons of great feedback, thanks guys.

The 1800/1900 motor setup sounded like the way to go, but for the price, I have to wonder. I can get an MM ESC and 2200Kv motor combo for $240, but an 1800Kv CC motor will run me $160 by itself. (can't fnid any combo) A Tekin RX8 would run me $200 by itself, an MM ESC would run me $160 by itself. An RX8/1900Kv motor combo would run me about $330.

Is it really worth an extra $80-$90 to run an 1800/1900 motor over a 2200Kv Neu/CC motor? Am I kicking myself as far as learning goes by adopting a more powerful motor that early on?
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