Garrett Jax

I'm really getting lost with these new lipo batteries and what they are capable of giving the RC hobbyist in the form of power, run time and speed.

Does any one know a link to a video that could explain all of it to me?

I'm never going to be a racer. I'm in the hobby as something to do and maybe share with my elderly father who was diagnosed with colon cancer a few weeks ago. Once he gets out of the hospital, he's pretty much through as far as working a regular job. So I thought he and I could maybe drive RC cars around the neighborhood and maybe bash them in the backyard or front street as a shared hobby. You know, something to keep him entertained and occupied. He's a work-a-holic and this down-shifting for him is going to be hard.

Back to my dilemma though .... I'm going to be what you would call a casual hobbyist with RC. Iwant a little better speed than the stock motors, but 70+mph of unmanageable speed is not for me. Iwould like to go moderately fast(er) than stock and maintain a nice long run time to avoid changing and charging batteries too often. I've read that lipos are "crazy power" when coupled with a brushless motor which Ithink I would switch to strictly for the durability.

Any help would be appreciated.

If it helps any the vehicles I've been contemplating buying for my father and me would be one or more of the following:

E-Revo (either 1/10, 1/16, or 1 of each)
Slash (either 1/10, 1/16, or 1 of each)
Dark Impact (already bought)
Summit (not sure ... looks more for rock crawling instead of just bashing, but it looks so damn awsome &fun to drive)
E-Firestorm
Savage

Links to other threads that covered this subject, sites, videos, youtube, etc. would be a great help as long as it axplains things in detail.

Thanks

Spetz

I'm really sorry to hear about your dad. I hope the best for you and your family.

As for lipos, I had the same question, because I always read lipo + brushless = insane. What I was told was that unlike other batteries, lipos can supply immense amounts of current, hence you can use crazy powered motors. So basically an insane motor with a battery that can't supply the needed current just wont be that quick. Think of it as the fuel system in a car. A crazy engine with a small fuel pump will never make power.

Garrett Jax

Thanks for the kind words. We're praying as well for a speedious and complete recovery.

Concerning the lipo and motors ... does this mean that Icould take any of the above mentioned vehicles, drop in a 3500 Velineon system (if it doesn't already have one, and control the amount of speed Iget out of it by the size of the lipo battery .... 2S, 3S etc.? Or is it more of a combination of motor, esc, and battery capacity that will keep me sub 50+, maintain a cool running system, but still have loads of fun and run time with it?

On a side note concerning gearing ... is it necessarily important for someone who is not into racing their trucks to be concerned with what gearing that they're using? Iwould think that I need a slipper clutch at least to avoid damage from jumping (if we get to the point where we want to give that a try).

Ifind it funny after seeing some videos and other threads that what Iand my dad will be calling "bashing" will be more like a Sunday drive in the country for some of you.

Druss

The thing to keep in mind about both brushless and lipo batteries. 

Think of motors in real cars, just because you have a turbo charged V8 that can do 250mph doesn't mean you actually have to drive that fast.  Same is true with the lipo, just because you have a big tank with high octane fuel doesn't mean you have to be a speed demon.

Get the brushless for the low/no maintenance and the lipo for the higher capacity then use the controller to manage the power.  The VXL esc also has a training mode which limits you to 50% power until you can control it.

As for gearing, it's still important depending on the surface your running on.  Lower gearing is better for grass so you don't overheat the motor.

Spetz

No you wouldn't control the speed via  the battery you choose. A lipo with just allow you to get the most out of a really hardcore brushless system.

You can control the speed by setting up rpm limits etc on the ESC of a brushless system.

And the gearing, if you're not racing it doesn't have to be spot on, but at the same time it can't be too far off, as too tall of gearing will put a lot of stress on the motor and burn it out prematurely

Garrett Jax

Okay, Iget it!

The lipo gives the motor the energy it needs to reach its peak performance. So ... now I need to know what kind of motor Iwant/need. Right?

Alright ... than what does the cell count do for the motor? Isee 2S all the way up to 6S.

Hmm ... perhaps it would be better if Iask this another way ....

Suppose Isettle on getting a Traxxas Slash? With what Iwant to do with it (which is basically just have a bit of fun with dad) .... what motor, battery and gearing would Ineed to get extended run time, 30-45mph,little heat, and decent power?

Sorry for the goofy question as if I'm a child or something. But I think it would be better if I could learn by an example.

Is there anywhere online that has something similar to a chart or cross-reference that lets amateurs/casual hobbyists sort of "dial in" what they want and a pre-designed set-up is listed to get them started? That would be awesome if something like that existed.

Thanks for the continued input guys. I know its hard dealing with newbies, but Ido appreciate the help.

Druss

First of all, the #S stands for the number of cells in Series.

So 2S is 2 cells in series.  3S is 3 cells.... etc.  Each lipo cell has a nominal voltage of 3.7v so a 2S lipo has 7.4v, 3S as 11.1v.

If you're not looking for all out speed then get a 2S in the 5000mah range.  That will give you near 30 minutes of run time.

For the Slash the sidewinder, mamba max or VXL would do fine.  I use a VXL in mine and it works great with the stock gearing.  If you get a mamba max then get the 4600kv motor.

Keep in mind that most brushless escs are not water proof like the stock XL5 esc is, although I hear that Traxxas is coming out with a waterproof VXL soon, not sure when.

Spetz

Have a look on youtube for the Slash, as I think for someone just getting into the hobby it's definitely fast enough. Keep in mind it's also only RWD so adding more power will make it a lot harder to drive.

To be honest I think the slash does go around 30mph out of the box. And even still you would only reach such speeds on smooth surfaces

locksmack

On the topic of Lipos, what does the C rating mean? I have seen batteries with descriptions such as 20C...etc

MonkeyFist

The C rating is a discription of how much power the battery can out put. the formula is this:


C Rating X mAh rating of battery = total output of battery in mAh.

If you want to convert that mAh number into amps divide your answer by 1000.


Example 30C X 5000mAh =150000 mAh

convert to amps 150000/1000 = 150 Amps

Most batteries will have a constant C rating and a burst C rating. The constant is the more important of the two. If you try to draw to many amps from a Lipo battery it can cause premature failure of the cells. If you are looking at a Lipo pack the doesn't give you a Crating, I'd stay away. it could be a low drain cell that caould puff and die the first time you use it.

The more amps you can produce the faster you can go. Up to a point. The motor is the final piece of that equation. A 13.5 will never draw that much power, a 3.5 with the right gearing in a heavier car might come close.

Garrett Jax

Okay.

So it's the cell count coupled with the mah that gives you a higher voltage?

Does that mean that if I get a modest brushless system and a higher cell li-po than Ican feasibly double or triple the run times?

HomeDawwg

No. Runtime is determined by the Mah rating of the battery. a 3200mah battery wont last as long as a 5000mah battery.

What a 3s will give you in comparison to a 2s is more voltage. More voltage means more motor rpm, which in turn means more speed/power.

Pepethekingprawn

Quoted for greatness...

Now iget what I am looking for in a battery!! Got my new slash, and even though I got the brushed motor atm, I do plan on upgrading near the end of the summer, and this tells me exactly what I am looking for! Great Thread

Foxy

That's a very good piece of basic information, but it is also important, especially with lipo, to look at the discharge capacity. It's all very well having the volts, but if you can't discharge the amps fast enough, you're going to have a blown battery in short order. This unit (used for charge and discharge current) is expressed as 'C', and refers to the number of multiples of the mAh that the battery can simultaneously discharge, or accept as charge current.

eg 5000mAh 3s lipo rated at 50C (burst rating) can discharge 250A in one burst if needed. Sustained C can be much lower, like 30C, and means that it can sustain a discharge of 150A.

This also applies to charging. You will see people say 'charge at 2C', this means if the battery is 5000mAh, you can charge at 10A. Always keep an eye on the temperature of your batteries as they charge and occasionally check them during a run. You can use a simple cheap temp gun for this.

So, to clarify, 1C of a 3000mAh battery is 3A. 1C of a 6000mAh battery is 6A, etc, etc.

A strong brushless setup will often require 30C plus discharge rate. Exceeding the discharge rates will permanently damage the batteries. You can offset the risk to your battery by increasing the risk to your motor. This is done by simply putting a battery with more cells, this puts less strain on each individual cell, but more strain on the motor, due to the increased voltage (and heat generated), racers are always striving for the perfect balance, not necessarily the most power.

I'm no battery expert though, so if any of that is wrong, from my basic understanding of batteries, I'm sure someone will correct me.

EDIT: Ooops, didn't realise Monkeyfist else beat me to that exlanation, that'll teach me to read threads properly! Didn't mean to second guess someone. Might as well leave the post now I've typed it though.

Garrett Jax

I'm looking for Lipos at the moment and came up with another question ... what does the "p" stand for?? (ie: 2s2p or 2s1p)

Which is better?

Figured I'd work my way backwards in choosing the right RC vehicle(s) by buying the batteries/charger first, motor and esc second, and the car last :lol:

I think I'm definately going for this motor system if Iget 1/10 scale.

I'm looking at Team Orion for lipos. (read that they were good for the price)

Not sure what charger and accessories to get for charging the lipos. (I want one that also charges the two NiMh batteries Igot with the Dark Impact)

And I'm on the fence about getting either an E-Revo, Slash, or one each of the 1/16 E-Revo and Slash.

:sigh: decisions, decisions ....

Any suggestions on the batteries, charger, and motor system would be greatfully appreciated.

I can sink about $1000 cash into everything at this time.

Druss

If you read my description above about that the S stands for then you'll understand that while S stands for series, P stands for Parallel.

Just back to basics for a second, mAh stands for milliampere hour, how many milliamps are available in 1 hour.  Because of the complexity of manufacturing batteries, they are all tested as they come off the line.  Some batteries with discharge faster than others, this is where the C rating comes from.  Batteries are tested then placed into the appropriate section based on performance.  One line could produce 20C, 25C and 30C all from the same manufacturing batch.

All batteries are produced from cells.  Similar to nimh packs which are typically 6, 7 or 8 cells, lipo batteries are the same.  They are just named in a different fashion.

A 2S2P battery is made up of 4 cells, take 2 cells and connect them in parallel, take the other two cells and also connect them in parallel.  Then take those two sets and connect them in series.  You now have a battery that's 2S2P.  You could also do it the other way and put them in series first them parallel.

So the voltage is determined by the number of cells in series regardless of how many you have in parallel.  Each cell is 3.7v so a 2S*P battery will be 7.4v.

Each cell is manufactured to a certain capacity in mAh.  In order to find out the total capacity of the battery, multiply the number of cells in parallel by the individual capacity of the cells.  So a *S2P battery made up of 2000mah cells would have a total capacity of 4000mah total.

If you combine what I've said in the last two paragraphs a 2S2P battery made up of lipo cells which are 3.7v and 2000mah you end up with a 7.4v 4000mah battery.  Of course you want to use matched cells with the same C rating as well so that one doesn't get damaged before the others.

Pepethekingprawn

As posted in my other thread, Igot the slash, and although its my first dance, Ican tell you that I have not a single regret!

Garrett Jax

Well, it seems like a silly place to start my endeavor as a "casual" hobbyist .. but I decided on and already ordered a battery charger.

The Thunder AC6.

Looks good. Video makes it sound good. Reads like it's good. Seems like a well rounded charger ... Did I make a good choice??

Now I just have to decide on some batteries and vehicle(s) and I'm in business :lol:

Think I'll hold off on the motor 'til I decide on the vehicle.

A few final lipo questions (I'm sure you guys are tired of them by now)and I'm off on my own to choose one or two for myself ...

Hardcase or no hard case? Just wondering exactly how prone the soft ones are to damage when bashing, racing, playing with your rc's.

If it's one thing I picked up on right away by reading, it's that you don't want to treat lipos roughly or damage them in any way possible. I figured that hard cases are better because of the added protection, but I'm not too sure. If one is cheaper than the other I'll probably be getting those, but I just wanted to check with you guys first as to what preference you have (if any) and why?

Thanks for the continued help. I appreciate it.

Druss

Personally I only use hard case for off road but will use soft for on road.

That charger looks like a chinese knockoff and unfortunately xheli is not the best etailer but I hope it works out for you.

Garrett Jax

Really ....? Damn!

Iwas looking around youtube and found a video by Dave Herbert and he seemed immensely impressed by it.

Oh well ... we'll see how it works out :-).

Druss

I'm not guaranteeing that it's crap, just that it's not a brand known in NA and you won't get much of a warranty with it (if any).  Try using it on some nimh batteries as soon as you get it to make sure it works ok.  If it doesn't try to get xheli to take it back (not exchange it) but that might be difficult too.

Garrett Jax

Do I need a low voltage cutoff switch?

While I know I'm going to decide on a Traxxas Slash or E-Revo ... I don't know if either of these have a built-in LVC for lipos.

While I want lipos for the consistent energy and runtime, I'm starting to wonder if I should just stick with NiMhs until I get better acquainted with them.

If I do need a LVC is there any that are compatible with the Traxxas Slash or E-Revo? I'm reading that the Novaks' are not.

Garrett Jax

*bump*

So I've got a stock Slash (having a lot of fun with it too) and I really want to try these 2s 5000mah Lipo I bought instead of the NiMh ... but I notice that the stock ESC is not compatible with the Novak LVC for 2s.

Are any of you running your stock Slash on lipos? What kind of run time are you getting? What LVC are you using?

Thanks.

Druss

To be honest with you, I don't run a LVC in all my electrics with Lipos. I just don't run them all down. As soon as I notice a slight power loss I stop running and check the voltage. I've never damaged a lipo this way myself but I've had lots of experience with them.

If you're LVC isn't working then what I suggest is that you check the voltage every 3-5 minutes while running and as soon as you get to 6.8, stop running and charge it. See how much mAh you put back into it. 80% is usually the rule there.

HomeDawwg

Just for future reference, this post wasnt meant as a be all and end all description on which lipo battery to get. It was basically just to show a (very basic) example on how to compare 2 batteries run-time, in answer to Jax's question about runtimes and cell counts. Refer to foxy's post for more info