Need help/tips on what electronics to buy

[Daniel Norée]

I want to put together a "kit" of electronics need for the "universal" RC Car project. Now, i´m no RC expert so i just want a kit of electronics that i can put in a Touring Car but also in something like a "Truggy" or something else. So it should be easy to put together and not to expensive. It all seems so complicated these days with programmable ESC´s and chargers and such..

Here´s what i have pu together so far with the help of Hobby King Support:

Transmitter / Receiver: Hobby King GT-2 2.4Ghz 2Ch Tx & Rx - $ 14.99

PRODUCT ID:

http://www.hobbyking.com/hobbyking/store/__10608__Hobby_King_GT_2_2_4Ghz_2Ch_Tx_Rx_.html

ESC: Turnigy Brushless ESC 35A CAR ESC

SKU: TR35A-V2 - $ 24.99

Link: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7186

Engine: PRODUCT ID: S2848-4370

S2848-4370 Brushless Inrunner (4370kv) - $ 22.26

Link: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15188

PRODUCT ID: TG-Prog

Turnigy Speed ​​Controller Programming Card - $ 6.13

Link: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7187

What i need is some tips on batteries... It would be awesome if one could choose either a NiMH or LiPO battery.

Any help on this is appreciated. These are the parts i will "reverse engineer" and put in my CAD models...

/Daniel Norée

[jtktam]

these days you would want to use lipo.. nimh is outdated

-joe

[Daniel Norée]

Ok, so let´s say we go for a LiPO, can you help me and specify one from HobbyKing that would go well with the other stuff? 

[Kevin Harrington]

As an engineer I can give some insight into battery selection. First, a few people mentioned LiPo, this is NOT a good idea. The power density of ground vehicles is not as much as an issue as flying things, so the higher energy density is not that useful. On the other side, large LiPo batteries are VERY dangerous when drawing lots of current and doing deep discharge cycles. The biggest danger is when a LiPo is discharged all the way and left like that for any significant amount of time (it happens, especially with hobbiests). What happens is the copper electrode starts to dissolve into solution of the electrolyte and plate back out all over the place. This cause internal shorts. When you try to charge it back up later, the shorts heat up a small section of the battery, hydrogen and oxygen are kicked off and build up in the battery and it eventually explodes. In professional uses of LiPo, there is careful charge/discharge circuits that monitor all of this and prevent damage. 

NiMh is a good chemistry, it can be charged in series, it has excellent thermal characteristics thanks to a low internal resistance, and they are dirt cheap. You get a reasonably good energy density without special charge monitoring and no risk of explosion. 

[Joseph Tam]

I think those are valid concerns but as an avid RC racer, I disagree with two points

RC cars performance has increased greatly with the introduction of lipo batteries and for racing it has lower the barrier of entry, the weight savings alone is worth it

as with any item, certain precautions should be taken and safety in mind, I have seen nimh batteries in explode due to over discharge so it's not 100% safe

any modern speed control these days will have under voltage protection and once it stops your car, you should recharge the battery to a safe level 

Sent from my iPhone

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[Kevin Harrington]

NiMh can only explode when short circuited, not through "normal use" deep discharge like LiPO. It only happens when the battery gets so hot the electrolyte boils off suddenly and can cause the cell to burst. The gas escaping is water vapor, snd will not burn. In contrast, the LiPo will electrolyticly degrade hydrogen and its own oxidizer and actually explode, not just burst. 

As for the performance, yeah, that is of course why they even exist. I would suggest that if you are trying to build kits for hobbyists, the safe option over the high performance option might result in a lower likelihood of someone getting hurt. Once someone knows enough to work with raw-cell LiPo's safely, they can upgrade. In fact, it might be worth looking into making a managed LiPo cell for this purpose as its own product. 

[Daniel Norée]

Ok, so i doesn´t sound as easy as i was hoping. Do you guys think that to make things easy one could do two "recommendations" one NiMh and one LiPO to get things started? If so, could anyone recommend two batteries on HobbyKing for me? If so that would be super awesome and i would be very grateful!  =)  

[Joseph Tam]

if you build a pack of 6 nimh cells in series, if one of the cell become deep discharge and the other cells overcharge, I have been at races where the over charged cells flew off and hit like a projectile

the lipo in hard cases, which is roar (international racing association) approved will not just exploded as you are trying to say

should not rule out a tech because it might be a danger 

Sent from my iPhone

[Kevin Harrington NR]

Just came across this, might be interesting to this thread:

http://grabcad.com/library/tamiya-special-racing-buggy-kit-rc

Kevin Harrington
Neuron Robotics, LLC

Acting President and Founder

99 Prescott St, Worcester MA

http://www.linkedin.com/pub/kevin-harrington/8/a24/358

[Gary Crowell]

Hi, 

I like your project!

A lipo in a  hardcase available from hobbyking or a hundred other rc oriented places would be great.  Lipo is now the industry standard, chargers have the correct charge profile, electronic speed controls have lipo friendly voltage cutoff to shut down the ESC before lipo damage occurs due to overdischarge, the hardcase prevents damage to the cells,  charging in a lipo scak is a good idea. 

For this model  i would advise to take it easy on power and use 13.5 turn or even 17.5 turn and above , to be a gentle as possible with the drivetrain.  This is assuming your using 540 or 36x50mm motors used in 1/10th scale RC.  There are many other sizes that may be good optons, like a 28x48, though you'd have to be even more careful about what wind you pick with that.

A sensorless ESC will drive a sensor equipped motor, but a pure sensor based ESC will not drive a sensorless motor.  Though some ESC's will work either way, with or without a sensor connection to the motor.

[Wagner Aranha Bueno do Prado]

Hey there,

IMHO, as a brazilian hobbist, you should try the NiMh at first... not for safety of the battery or the price... but to test if the model will work properly...

Also, if you use waterproof eletronics (wich will be a good choice, as you're doing a off-road model), you can use the NiMh batteries and run in the rain... LOL... And will be much easier, with waterproof eletronics, wash the model after play in the sand or mud...

Another personal opinion, DON`T USE the HK GT-2... I had problems with this radio system... Sometimes (not always) this 2.4 GHz works as a Crystal one... Losing the comunication and interference are just two of all the problems I`ve seen this radio system shows... GT-3, wich should be even better, is the same problem... If possible, usa the Tactic... No problems reported by the ones the use this one... and the price isn't much higher...

Regards,

Wagner Aranha