9xl, 5s, Quark 125b + Lipo battery holders?

I have to admit that I too am guilty of quoting specs and numbers. I've often used 30K rpms as a "sweet spot" to shoot for and adhere to that more closely with the Feigao motors. The fact of the matter is that there are variables that will also play a substantial role in the amount of success that you have with a particular setup.

The two most substantial variables to consider will be the type of terrain that you will be running on that the ambient temperature of the area of the world that you are in.

Although the better Neu motors are more forgiving of these considerations, the Feigaos are not.

I'm in southern Louisiana and it's always hot down here. I think that winter lasted all of two days last year. LOL.

Anyway, the 9XL might perform well for you and the temps might not get too bad if it is relatively cool where you are.

Down here where I am, a 9XL does fairly well on 4S, but will jump up to 200*F on 5S pretty quickly. Although I run Neu motors in almost all of my vehicles, I still run a MM/Feigao combo in my Monster GT conversion. Running the 9XL on 4S makes for plenty of power and loads of fun.

In my experience with the Compro controllers, they run cool no matter what you put them through. If you can run 6S, you could look to an 11XL or 12XL.

If you are new to brushless, you may just not know what to expect. Here's a link to a video of my 8ight T running a 9XL on 4S geared 14/46...http://s154.photobucket.com/albums/s...DSCF0303-1.flv

It is, of course, not stupid powerful, but still much more powerful than a nitro setup.

[jhautz]

I gotta pee too...

[MTBikerTim]

Originally Posted by jhautz

I gotta pee too...

I was wondering what you on about. That 8T is pretty quick. If I got that sort of performance out of my savage and the electrics stayed cool I'd be happy. The 350Z in the background is quick too I bet.

The temp here vary from about 5-15c (41-59f) in middle of winter to around 25-40c (77-104f) in summer. I have used BrianG's speed calculator and I may try an 11xl. It will be mainly off road work that the savage will do. Dirt and grass. It is going to probably be a basher so I still want heaps of torque. Here is what i put in:

Vehicle Weight (approx): 15 (I assume this is in pounds, I have no idea what my truck weighs)
Desired top speed in MPH: 40
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.6956521739130435
Additional Ratio: 0.967741935483871
Spur Tooth Count: 47
Pinion Tooth Count: 16
Battery Voltage: 22.2
Tire Diameter (inches): 6
Total Ratio: 15.94407 : 1
Tire Circumference: 18.85 inches (478.779 mm)
Required Motor RPM: 35729.102 RPM
Required Motor KV: 1609.419 RPM/V
Good Motor Choices: BK Wanderer 12 XL (kv=1390) BK Wanderer 11 XL (kv=1516) BK Wanderer 10 XL (kv=1668)
Better Motor Choices: No motors of this class fit the parameters you entered.
Best Motor Choices: Neu 1515 2.5d (kv=1700) Neu 1515 1.5y (kv=1500) Neu 1512 3d (kv=1700) Neu 1512 2y (kv=1400) LMT 1940/10 (kv=1588) LMT 1940/9 (kv=1742) LMT 1950/9 (kv=1452) LMT 1950/8 (kv=1634)

I'd love to get a neu motor in the future but for the momment I'm going to stick to feiago's. If I try to get a neu now this truck will never be finished. I have almost enough parts to build the chassis now, so pics should be coming soon. Just waiting on a couple of bits.

Getting a 15lb truck to 40mph may be a bit of a chore. I think that 35 would be more realistic and practical.

In any event, you should prepare yourself for some fun.

As a side note and perhaps a piece of advise, if you are venturing into the unknown, it is usually better to err on the side of being conservative than getting things that are too hot. It really sucks when you put something together only to find that you can't run it the way that you want to, because of excessive heat.

[MTBikerTim]

Originally Posted by AAngel

Getting a 15lb truck to 40mph may be a bit of a chore. I think that 35 would be more realistic and practical.

In any event, you should prepare yourself for some fun.

As a side note and perhaps a piece of advise, if you are venturing into the unknown, it is usually better to err on the side of being conservative than getting things that are too hot. It really sucks when you put something together only to find that you can't run it the way that you want to, because of excessive heat.

Thanks for the advice. 35mph is probably a better target and I would be happy with that. I just kept reading all these posts saying they want their trucks to do 40mph. Being in australia we use kph so 40mph didn't mean much to me.

I would prefer a more conservative setup, one that is easy on the batteries (longer run time) and runs cool then some thing that can do 40mph. But I don't know what would be a more conservative setup. 5s or 11/12xl.

I have to say I really appreciate all the help you guys are giving me.

[BrianG]

For 5s, I'd say 9XL or 10XL. Don't forget that those XL kv ratings are unloaded. Once you load the motors, the kv can drop a couple hundred thereby lowering the total speed.

If you enter an estimated current draw into the speed calc, it will show you the approximate loaded kv (and the adjusted top speed).

[MTBikerTim]

If I run 6s will this keep the motor cooler if I get a motor with the same top rpm? eg:

5s on 9xl is max unloaded rpm 30839
6s on 11xl is max unloaded rpm 30303
so they are very similar rpm will the 6s setup run cooler under the same conditions then the 5s? I'm thinking that I might as well go 6s if it will be better as the compro esc sounds like it can handle it, no worries.

[BrianG]

Yes, the 11XL/6s setup will be better because you are getting around the same power, but using less current. High current is what makes things run inefficiently. The only downside with the higher voltages is the expense of the battery pack, and maybe a charger that will do 6s...

[MTBikerTim]

I would have to run two 3s packs on the savage and I would charge them as 2 seperate packs. Even though just looking at the specs of my charger it will do 6s. If I could get a special balancing lead I could do both at once. My charger won't go up to 8amps (for the 8000mah packs) but they will just charge slower.

As far as batteries go I was looking as the true rc custom packs. I am planning on getting two TrueRC 10c 11.1V 3S2P 8000mAh packs and running them in series. I assume 80A continuous is plenty for the savage on 6s on an 11xl. 60A max on the 11xl on the feigao data sheet if that means anything.

[BrianG]

80A on 6s is around 1700w. However, you will probably be drawing around 12-15A average with peaks around 80-90A. No one pays much attention to the current ratings on those motors since car current requirements are different than flight current requirements.

As far as a special balancing lead goes, you might want to check the bottom of this page.

[MTBikerTim]

BrianG that link points to your E:. I'm definitely interested though. The balancing lead would half my charge time.

[BrianG]

lol, yeah, I was doing some development and forgot which browser window I was in. Oops.

Link fixed.

[Arct1k]

How close does the voltage on lipo packs need to be for parallel?

[BrianG]

Exactly the same would be best. If the packs are different, there will be a decent spark when you parallel them. I would charge both up fresh, and then let both sit until the voltages settle down to within 0.05v of each other. Even then, there will be a spark.

[MTBikerTim]

That's probably a good reason to charge them at the same time. then they will be balanced across both packs (at least at the end of the charge).

edit: thanks briang for the link. The problem I have over here is getting the right balancing plugs.