Li-Po setups

[klims]

hey guys,

i know that there are a bunch of threads around about Li-Po setups and what some of you guys are running, but what i’d really like is to find out what seems to work best.

i’ve been looking at some kits for sale on ebay, but they seem to all be pretty crap. they all say that it can be run in my mini z mr02 with no problems, but from what i have read on some threads it can cause problems. has anyone had problems with the higher voltage in the mr02’s?

initially i though these would be sweet but then i saw the crap discharge rate. i like the idea of using standard size batteries because it wouldnt be a too much of a problem to go back and forward from lithium to ni-mh. has anyone seen AAA size lithiums with better stats?

so i guess what im getting at is what can you guys recommend for a noob that wants to go lithium.

thanks for your help guys

Andrew.

[ph2t]

Hey Klims. Here’s some pointers mate.

1) Mini-z’s will work out of the box with lithiums but the steering will be a bit jittery. This is due to the increase voltage driving the steering motor and the eletronics not conditioned to control it at this speed.

2) Polyquest 600mAh lipos fit into a mr-02 with no problems. Hell you don’t even have to remove the battery prongs. Only need to trim the underside of the battery holders so to not damage the lipos. (see my templestowe vid just posted)

3) AAA 300mAh liths are not bad, just don’t run any motors less then 35 turns (approx) with them. This is just to ensure the longevity of the liths. Even at 35 turns you’re still most likely to draw more than the rated current.

4) atomicmods.com has 450mAh lipo cells that should fit fine as well. I say this since the polyquests are bloody rare to come buy.

5) be carefull running turbos on higher voltages. This isn’t a limitation in the turbo so to speak (nelly EVO & Spider 2.x) but a limitation on how the MOSFETS are driven by the ‘Z PCB. you should be OK, just keep above 35 turns as a starting point.

6) traction traction traction! Get foams on the rear dude. Otherwise don’t even bother with an upgrade. (pm me if you want custom foams made to a special offset, otherwise get the gandini’s from the ausmicro shop, bloody great RTR foams, betty and I used them for ages before I spent too much $$ on the tyre truer).

7) Using the AAA li-ions will require the wiring on the battery layout to be changed to make it into a 2s2p arrangement. That makes the setup 7.2V @ 700mAh. Given this, you then can’t (easily) change back to 4 cell nimh if you wanted to.

I’ve listed a lot of points but I’m sure it’s not too hard to go through.

cheers,

ph2t.

[klims]

thanks for the info ph2t.

in response

1) steering jitters are ok for me now. after making myself a loaded antenna i dont have any more problems.

2) sounds good. any idea where i can get some, besides scouring the internet

3) i like running my pn anima so i guess thats out

4) …

5) i have a spider so i guess i will have to see how that one turns out

6) i invested in the foams from ausmicro. love em!

7) when i say easy i mean that i wont have to destroy my bat mount, but i guess i didnt really explain that one

sounds like some great advise. now all i have to do is wait a week for my net to be uncapped so i can watch the vid. bastards!

[ph2t]

lol….

allow me to retort….

1) looks like your jitters were signal/range based. the increase in voltage will introduce them again, but a little more subtle, and stil controllable. You may most likely find an INCREASE in range with the increase in voltage.

2) http://www.trickrc.com hand them I think, can’t get ’em anywhere but the net mate.

3) Try it out and see how you go. The worse thing that cna happen is that they bomb out from too much current draw.

cheers,

ph2t.

[klims]

i like the sounds of the polyquests. if anyone has any experience with other brands and styles etc. do tell.

thanks for your help

Andrew.

[klims]

does no one else have a lipo setup?

[ph2t]

they’re not the most popular thing….

[klims]

i dont believe it! why not? it seems like a logical progression for someone who has done all the mods and wants more speed!!!!

[betty.k]

because once you do all the mods it’s fast enough:approve: :8ball:

[ph2t]

lol, that’s what I like to hear!

actually most people are satisfied with the (relatively) fast speeds you can get with 4 cells + turbo + hot motor….

here’s some other lithium modded Z’s to grab inspiration from, lol….

http://www.xmoding.com/ftopict-1432-.html

http://p221.ezboard.com/fxmodrcfrm41.showMessage?topicID=35.topic

cheers,

ph2t.

[klims]

so then tell me betty k what are ALL the speed mods?

i have a spider turbo (cant afford the nelly), 800mAh sanyos and am running a iwaver pro at 10T… im convinced its better than my pn anima. i think i might also need a power capacitor. tell me what else i can do?

[betty.k]

well i guess it depends how fast you wanna go.
i’m happy with a top speed of between 30 – 40 kph and to achieve that i run 4 nimh cells, pn racing s03 or s04 motor (35 – 37 turn, neo mags), 9 – 10 t pinion, bearings all round (motor can too), nelly 1.0 (the spider is plenty good too).
then there’s things like suspension, tyres, camber, etc to tweak so it handles the excess speed. you can read all about my mr02 and how i set it up here:
http://www.ausmicro.com/forum/showthread.php?t=10447

i spose if i wanted to go faster i would add a larger pinion, my motors have wads of torque to spare. at a guess i could go up to a 14t pinion and maybe clock 45 – 50 kph.

i’ve just never felt the need to go faster, a car that’s too fast to handle is less fun than a car that’s too slow. :8ball:

[klims]

sounds good. i dont have a speek checker so i have no idea how fast i am going. would probably be a good inverstment.

i guess if you actually have a decent place to race 30-40 is plenty, but seeing as i am down at my local factories thrashing it around the car park i wanna see more speed… and besides the mm i have only allows me to go to 12T.

[klims]

PH2T have you seen these? waht do you think? they seem pretty sweet at a max 13C (6.5A) continuous discharge. the guy seems to think they will fit in an mr02 but after measuring mine i dont know how…

i have also been looking at these but they have a max discharge of 2C each so about 2.5 A with 2s2c. any advice would be greatly appreciated

[merc-blue]

both of them have incredibly low capacitys

[klims]

i know this isnt really a lipo question, but if i had a 6 cell setup with 4.8v running to the pcb and 7.2 running to the turbo would this work? i figure its the same as having a voltage reg on the turbo isnt it?

[klims]

so i figured by the overwhelming response that either no one knew or i asked a stupid question… so i started doing some hunting around. i now see the error of my ways.

BETTYK i see what you were saying. i’ve done some more mods and its fast enough, although i guess it can always go faster lol.

so anyway i was talking to the electronics guy at work who tells me that it is possible to run a load of 7.2v with a 5v gate voltage, however it does require some circuitry. i’ve been trying to figure something out using a configuration like this one (does’t seem to be up), but to adapt it to 4 input signals. what it does is use transistors and some pull up resistors to trigger the gate. i’ve been told that the right combination of resistors can make it happen, but i’d need to do some circuit analysis.
Has anyone tried to do something like this? is it a waste of time trying to get it to work?

thanks for the input guys.

Andrew.

[ph2t]

Klims, don’t listen to betty. If the guy drove it would ba a VW and would never leave 2nd gear, lol…..

You can go as fast as you want to but there are limits to what is feasible when you have a 1:28 scale car runnign along at 50-60kph on the ground. lol….

Suspension is a big thing. It can just be too fast to dampen well.

Grip is also an issue. You need some really nice soft n sticky foams to get that power to the ground and keep it there.

As for the two ebay links I would stay away from the JDR li-ion since they won’t give you the punch you need for the hot motor you will run to get the speed you want. I’ve run li-ions before and they will dump power very quickly. You can try the li-polys in that other link mate and see how you go. If you were to do that though just by the free standing cells at http://www.atomicmods.com and fit them to your mr-02.

that’s what I did with my polyquests….see the attached pic.

Quote:

i know this isnt really a lipo question, but if i had a 6 cell setup with 4.8v running to the pcb and 7.2 running to the turbo would this work? i figure its the same as having a voltage reg on the turbo isnt it?

That won’t work. The reason why is that the mosfet gate voltages don’t fully alternate between GND (0v) and Vcc (4.8v for 4 cell nimh). Whilst I won’t go into the full details, you will find that both the p-chan mosfets on your turbo will always be on. When you apply throttle you will create a short circuit along one path of the h-bridge and blow the turbo.

Found this out myself during the course of my nelly turbo development. I know it’s a shit to read but if you do get the chance read my nelly development thread. I go over this very problem is overwritten detail. lol…..

Quote:

so anyway i was talking to the electronics guy at work who tells me that it is possible to run a load of 7.2v with a 5v gate voltage, however it does require some circuitry. i’ve been trying to figure something out using a configuration like this one (does’t seem to be up), but to adapt it to 4 input signals. what it does is use transistors and some pull up resistors to trigger the gate. i’ve been told that the right combination of resistors can make it happen, but i’d need to do some circuit analysis.
Has anyone tried to do something like this? is it a waste of time trying to get it to work?

Yes it should work. You need to use pull up AND pull down circuitry on the pchan AND nchan mosfets respectively. Then drive the spider from the 4 inputs as usual. I use MOSFET drivers on my nelly deluxe to achieve a similar (but more effective) result. (MOSFET drivers are suited to turning on MOSFET really well, really fast, really hard!)

good luck dude……

[klims]

thanks for that PH2T

Suspension is a big thing. It can just be too fast to dampen well.

i just got in my kyosho oil damper from hobbyjapan. it kicks arse! i noticed both you and BETTYK had one without a spring. works wonders.

Grip is also an issue. You need some really nice soft n sticky foams to get that power to the ground and keep it there.

i have a pair of medium foamies on the back so thats not too bad. the setup i like best is getting the pinion gear right so that at full throttle from stand still i dont spin out. its getting some great speed. im not really to good at handling it though. today i turned my 0 deg knuckles into 10 deg knuckles with the help of those reflectors on the road lol. got some serious air!

That won’t work. The reason why is that the mosfet gate voltages don’t fully alternate between GND (0v) and Vcc (4.8v for 4 cell nimh). Whilst I won’t go into the full details, you will find that both the p-chan mosfets on your turbo will always be on. When you apply throttle you will create a short circuit along one path of the h-bridge and blow the turbo.

yeah this is one of the few things i remembered about transistors from 2nd year lol.

I use MOSFET drivers on my nelly deluxe to achieve a similar (but more effective) result. (MOSFET drivers are suited to turning on MOSFET really well, really fast, really hard!)

yes i like the sound of that! that is originally what the electronics guy was telling me to do. he didnt like the idea of using a p and n chan mosfet though. what mosfets do you use? im not too sure how you feel about sharing your hard work but if you were willing to tell me how exactly you set it up i would really appreciate it.

and about those polyquests. i have been doing some research and found these. they dont seem to be the same as yours though. are the dimensions the same?

thanks for all the help

Andrew.

[klims]

anyone????????

[klims]

ok, so i figured out that my circuit doesn’t work when a heap of smoke escaped from one of the mosfets.
does anyone have any thoughts or suggestions? anyone at all????

[betty.k]

well if it’s definately a drive fet (or both) you can buy the upgrade fets at the shop and replace them. i’d recommend doing a double or triple stack.
whenever you do a drastic upgrade like lithium cells you need to monitor things like fet and motor temp at first in order to avoid these sorts of disasters. :8ball:

[klims]

oh sorry i guess i didnt explain myself too well. i haven’t actually run the setup with LiPo. i only tested my circuit and found that the mosfets (7317 from the shop) were shorting for some unknown reason. i guess i’m gonna have to buy some more and keep testing.

also the two mosfets running at 7.2 volts was supposed to be a crappy representation of my spider…

[klims]

so over the summer break i finally took the plunge and went the Li-Po upgrade.
not wanting to spend 60+ USD on polyquests, i went the low budged chinese knock off brand Li-Pos seen here.
I know the dimensions aren’t exactly right, but for $40 bucks delivered i was willing to give it a shot.

when they arrived i found they didn’t exactly sit too well in the battery holders but with some imagination it actually worked out ok… lol it looks like it has wings! it all fits pretty neatly under the body as can be seen, and the body actually holds the Li-Pos in place pretty well. haven’t fallen out on me yet!

the only thing really holding me back atm is the spider. it really doesn’t seem to be up to the challenge. was running fine on nimh but just giving it a little squirt on the floorboards with the Li-Po setup and they are quite warm. i’m trying to order in some more efficient MOSFETS but am so far unsuccessful.
i don’t suppose anyone wants to part with a nelly do they?[ATTACH]269[/ATTACH]

[betty.k]

he he, the “gullwing lipo mod”:D :8ball:

[Author]

Posts