LiPo LiPo LiPo!
 

Ok, I'm trying to figure out this hole LiPo thing. I really want to go LiPo in my dual 9L setup because the thing ways so much.

So I am running 28cells in it now, wich is obviously four 7cell packs. Each motor gets it's own two packs. The specs say that a 9L can handle up to 16cells (19.2v) but I hear alot of people say they wouldn't recomend it. Why would they publish that if it is not recomended?

Anyway, if I were to go LiPo, I was thinking about going with two 5s packs (one for each motor obviously) wich is 18.5v per motor vs. the 19.2 of the 16cell nimh packs. (do you see were I'm going with this) Is voltage voltage, or does it matter if it is coming from nimh or LiPo. If some people think that 16cells (19.2v) is a bit much for the 9L then a 5s LiPo (18.5v) must be a little bit easier on it?

Hopefully all that made sense, PLEASE HELP!:D

When a lipo cell is rated at 3.7v each it will realy go up to 4.2v on a full charge, so your total would really be 21v at full charge on both packs, im not sure if im 100% correct though.

With the weight lost would make it easier on motor to or motors in your case. It is going to push the motors pretty hard though. 3.7 volts a cell at 5 cells on a motor with a 2731 kv. your look at alomsot 50,000 rpm. of course that is unloaded rating to. I think the 4s may be better for you. You could probably step up in gearing for the lose of weight. So you gain the speed that way. That is 4s per motor.

I second the 4s packs. You'll more than make up the difference in voltage with the weight savings.

28 sub c cells (2.2oz ea.) - 61.6 oz.
4 2s Kokam 3200 packs - 28.2 oz.

Voltage drop under load is also less with lipos.

5s Lipo unloaded, fresh from the charger could put out 4v/cell, at 20v. But then again, 16 NiMh cells fresh off the charger without much load (just tires spinning) could put out 1.3+v/cell. 4s Lipo wouldn't be a bad choice, as it would be easier on your motors. The punch delivered by 4s Lipo would be at least equal to 14 NiMh cells (depending on the actual cells), and you wouldn't be dissappointed.

So if a 4s pack would at least equal 14 nimh's does that mean that I will not gain any top speed by going to the LiPo's?

Your top speed with 4s probably won't be as good as with 14 NiMh cells, but the acceleration will be better. 5s Lipo is just a bit high for a 9L. The difference here between Lipo and NiMh is the voltage of each cell. IMO, you wouldn't be dissappointed with 4s Lipo. Or, you could move to 10Ls and then use 5s Lipo (not sure if you want to spend that much money though).

The specs on the 10L say 16cell maxx also, so why would a 5s work on that motor? Top speed is my main concern, so if I have to go to a 10L for that, I would.
Thanks.

the only reason i can think of is that the 10L has a lower kv rating which would allow you to run on 5s without putting as much strain on the motors
fiego 9L=2731x20=54620rpm
fiego 10L=2458x20=49160rpm

boss 302 is correct. The 10L would just spin slower, which would be less likely to damage the rotor or bearings. But then, the 7XL would be a better choice, due to its lower kv than the 10L.

yup, i second the 7xl. i would through 2 of them on there with 10s lipo and see what happens....

thatr would be crazy and very powerful hopefully you have a bulletproof drivetrain :eek: :eek: :eek:

You could put some really tall gearing on the truck with dual 7xls. I could see a 60 mph pass with the 7xls and 5s lipos. And that would be geared good. See about getting some bigger pinions for that setup.

Or I could just go dual Lehner 40 series?

I don't think they make a 40 series yet. :D I think you talking 1940 series. If you got the money You can run anything really. ;)

im thinking with the weight savings and the torque.....65mph should be realistic.

Which setup you talking about squee? My current setup or the duall 1940?

you need over 2000 watts to go over 60 mph. Make sure your lipos can give out that kind of power w/o ballooning.

Yeah, HINT! hpi Nubz have got threads, that prevent them from balooning..

i think he was talking about the lipos balooning not the tires :027:

johnny, i was talking about the 7xls. 2 7xls on 5s lipo each 60mph range should be very do able maybe more becuase you can gear higher.

LOL, yeah i guess he was Boss!

What does a hpi nubz look like? I can use a none ballooning tire myself. hard to drive at 90 mph on pizza cutters. ;)

i will need some non-balloning tires this summer but i dont think i will be going 90mph though that would be to fast for me i would be worrying about hittng a tree or running into a car

This sounds intriguing, anybody else have any thoughts on this?

go for it. it will definatly be fast

A little off-topic but; Balooning tires are actually a plus! It's like having a constantly varying transmission since the final drive ratio goes up as the tires balloon! :D

just like dragsters the tires balloon and make them go faster :026: :026:

But a dragster don't have to turn either. The tire ballooning is little excisive some times to. I have done the duct tape but hey it can't hold but so much pressure before the adhesive lets go.

It would have up in the 3000 + watts range with the 5s and 7xl combos johnny.

[QUOTE=coolhandcountry]But a dragster don't have to turn either. QUOTE]
that true and it is also a good thing they dont have to turn at high speeds otherwise the drivers would be the passengers on one wild ride :020: :020: :020: :007: :mad:1

With a 4wd without centerdiff, you really don't want the tires to balloon, the front tires get a larger diameter than the rears, this causes a huge stress on the drivetrain.

and usually it breaks :035: :035: :026:

Is it the Wanderer 7XL http://www.rc-monster.com/proddetail...WAND_XL&cat=20 that I should go to?

yes the wanderer is good :cool: :cool:

Don't forget your bigger pinion gears. Need to step it up on that step up if you going with twin 7xls. Are you running a strobe,stock, or robinson slipper? I think the strobe is much better out of them three.

You meen to tell me that the stock slipper that I am using is not good for dual brushless?:D
I am running 20t pinions on the 9L's now, what should I step up to on the 7XL's?

As tall as you can find!! :018:

Thank you,
Promod

Hey, would a 1950/10 pull a 5k truck to 60+ mph with 20 cells?

I ran a 22 66 on 18 cells with a single motor. I would get a bout 22 -24 at least maybe look at a smaller spur to. IF you get the strobe and 20 51 gearing should make it fly.

Actually, Mike suggested a 24/51 gearing for 44-50mph. I'm not really looking for high high high speeds with a big machine.