I need help!  I asked a question on the OpenRC Google Group ( https://groups.google.com/forum/#!topic/openrc/R-DxkdXfHeE

I need help!

I asked a question on the OpenRC Google Group ( https://groups.google.com/forum/#!topic/openrc/R-DxkdXfHeE ) on what battery to get for electronics I have listed there. This is because I want to prupose (and design for) a basic set of electronics for people (like myself) not knowing so much about the electronics as they seem quite advanced these days.

As I’m spending a lot of time designing the mechanics it would be really awesome if someone could just tell me exactly what battery to add to my list.
Right now i´m trying to finish a “proof of concept” so at this stage I just modeled everything to fit my old Nimh battery because I can´t wait.

But if there is someone that could help out with this!


Regular sized Lipos are roughly the same size as a six-cell NiMh stick pack. When I get home, i’ll measure the exact size of my LRP pack, the Turnigy pack I have and the battery “slot” size of the B4.1. Hobbyking has many packs that fit and a couple that have the perfect size and weight.

The most imortant thing is that i want a recommendation on a specific bettery on the HK website.
And this is because i want to leave no questions on how to get this thing up and running if your a RC newbie (just like myself). Meaning i will present a complete list on the non printable parts and where to get them. So if you have a 3D printer and want to print your own car it will be easy to get everything needed without hassle.

I´m not sure whats up with the battery thing but i have asked alot of people and no one wants to say “get this one”, it will work with rest of the stuff you suggested", not even HobbyKing who helped me with the other stuff. This only makes me feel batteries for RC stuff is extremely complicated.

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

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

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

Turnigy Speed ​​Controller Programming Card - $ 6.13
Link: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7187

If someone could provide a link to a compatible battery on the HK website it will truly make my day! This has really become a headache for me…


The thing with batteries is that, as long as they are the right size, voltage and have an adequate discharge rate (which rarely is an issue nowadays), they all work.
Here’s one that is a typical 1:10th mid-range battery: http://www.hobbyking.com/hobbyking/store/_21006__Turnigy_5000mAh_2S2P_40C_hardcase_pack_ROAR_APPROVED.html

2S is the de-facto standard for 1:10th batteries.

I just assumed it’s 1:10th scale we’re talking about. 1:12th or 1:8th have vastly different layouts and sizes.

Btw, that motor you chose is not a typical 1:10th car motor. 1:10th exclusively uses 540-sized motors, the one you chose is a 380, commonly used in 1:12th scale cars.
An adequate motor for a buggy has around 350W at about 4500kV, that’s what i drive for fun.
Less kV and more power for a truggy.
More kV and more power for an on-road car.

Creating a shopping list at HK is a great idea. It would be nice to place an HK order, and start printing your car. Don’t forget about other things that you probably had on hand already, like shocks, and screws. 100mm shocks from HK:

@Thomas_Sanladerer Ok, thanks i´ll go for that battery! =) I had no idea about the motor, i asked HobbyKing for advice and that´s what they sent me. And your right it´s a 1:10 car. Can i just pick out any 540 motor to go with the rest of the parts?

And another thing… what is needed in terms of tuning and “programming” for this stuff?

@Tyler_Cooper Yes i think so. It will help alot for people not into the whole RC-thing (yet).

Don´t worry about the other stuff, got that already, some parts like the shocks are from my old (very old) Kyosho Ultima Outlaw Truck so they might not be ideal but will do for now. =)

Any 540 brushless motor will work (as long as the ESC can provide adequate current). ~350W / ~4500kV is the sweet spot for enjoyable buggy driving in my opinion, though.
This one looks quite nice: http://www.hobbyking.com/hobbyking/store/__21957__Turnigy_TrackStar_9_5T_Sensored_Brushless_Motor_4120KV.html
And for a bit more power: http://www.hobbyking.com/hobbyking/store/__21959__Turnigy_TrackStar_8_5T_Sensored_Brushless_Motor_4620KV.html

I don’t know if that ESC is going to hold up, though. 25$ for a brushless ESC is still very, very cheap (usually 100$ and up), so i’d just get one size bigger to make sure that it won’t melt down mid-use.

The ESC i use (basically an LRP SPX bullet reverse, but with Nosram branding) has on-board programming with two tiny buttons. You can set up things like motor timing (more power at higher revs or more torque at lower revs), brake sensitivity and aggressivity, limit power to the motor, enable/disable reverse and so on.
I chose an ESC with reverse because it makes driving more enjoyable since you often don’t have to run up to the car to get it unstuck. This is not an option racers go for, since races do not allow a reverse function anyways.
Programming the ESC is not something a beginner would want to do. I’d say its more important to get the geometry of the chassis and suspension right - those two will influence the driving properties much more than how the ESC is programmed, since many things that can be programmed into the ESC can also be done with a sensitive throttle finger.

You’ll also need to make sure that the ESC does indeed supply power to the receiver. I’d expect it for a car ESC, but you can never be sure about the hobby king stuff unless it says so explicitly.

And, of course, you’ll need a Servo for steering. Here’s what i use and can recommend (those will last forever, so it’s worth the investment): http://www.hobbyking.com/hobbyking/store/__8778__BMS_621MG_High_Speed_Servo_Metal_Gear_6_4kg_13sec_47g.html

But they’re also available (but not in stock) as the better and surprisingly also cheaper digital version, which i would recommend for OpenRC: http://www.hobbyking.com/hobbyking/store/__9439__BMS_621DMG_HS_High_Speed_Digital_Servo_MG_7_2kg_10sec_46_5g.html

Thanks to @Thomas_Sanladerer i have put together a list of electronics that will go well with this project. Below is the list, please have a look and comment if you think something is totally wrong or if you have any suggestions.



For anyone not to familiar with RC electronics, here is a list on everything you need and will be well suited to run with your typical 1:10 RC Car.

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

ESC: PRODUCT ID: 9052000032 Not sure on this ESC, can anyone confirm it´s ok?
Turnigy Trackstar 1/10 45A Sensorless Car Esc


PRODUCT ID: 9192000037
Turnigy TrackStar 9.5T Sensored Brushless Motor 4120KV

Or if you want a bit more power go for this one:

PRODUCT ID: 9192000038
Turnigy TrackStar 8.5T Sensored Brushless Motor 4620KV

Battery: PRODUCT ID: T5000.2S.40HC
Turnigy 5000mAh 2S2P 40C hardcase pack (ROAR APPROVED)

BMS-621MG High Speed Servo (Metal Gear) 6.4kg / .13sec / 47g

An ESC programming card is optional and not needed/recommended for beginners:

Turnigy Speed ​​Controller Programming Card - $ 6.13
Link: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7187

Looks fine to me. There usually is some confusion concerning sensored / non-sensored motors and ESCs for newcomers, so i though i’d write a quick paragraph about them.
A “sensor” is a small PCB at the end of the motor that carries three hall sensors - these detect the exact position the rotor is in. An ESC made for sensored motors can use these sensors for optimizing the motor control - this often gets you a smoother acceleration in speeds between stand-still and a couple km/h. When the car is moving, there is barely any difference between a sensored and unsensored setup. Unsensored ESCs are generally cheaper and therefore a popular option when there’s a budget.

Since the sensors are not required for the motor to receive current, a sensored motor can be used with both a sensored and unsensored ESC (this is what we’re doing). However, since a sensored ESC relies on the sensors to determine the rotor’s position instead of calculating it from the motor’s current draw, a sensored ESC will usually not work with a sensorless motor.

Ok, so much for that. There is one more thing that we’ll need for the electrics: Battery plugs. The usual system is 4mm bananas, with the battery providing the female terminal and the controller having male plugs. Hobbyking uses 5.5mm on most of their batteries - i’m not sure about the male-female parts of the plugs. It looks like the battery is female for the positive side and male for ground - i’d inquire hobbyking about this.
You’ll need to solder corresponding plugs to the ESC - some like these: http://www.hobbyking.com/hobbyking/store/_2087__Polymax_5_5mm_Gold_Connectors_10_pairs_20pc.html . A fairly large soldering iron (large tip or at least 60W, preferrably 80 or 100) is required to get a good solder joint to the ESC leads. Heatshrink tubing tidies the solder joint up and makes sure you don’t get a short while driving.

I would also ask Hobbyking about the pre-set LiPo cutoff in the ESC - ideally this would be 6V for 2S and 9V for 3S. The cutoff makes sure you don’t accidentally deep-discharge the battery.

Have you considered including a battery charger in the list?

I like the idea of a standard, easy to come by, average priced set of components that can be added to a 3D printed car. This list once totally completed should be used on all the up and coming designs for this community! You’ve saved me a lot of leg work finding and sourcing a generic kit for my up and coming design, which is based around your idea of model from what you have kicking around and once proven altered for generic, easy to source components. Great to see the input from the experienced RC community as well! :slight_smile:

A suitable, yet cheap charger would be this one: http://www.hobbyking.com/hobbyking/store/__22410__HobbyKing_B3AC_Compact_Charger.html

Most mid/high-end chargers expect a 12V supply, so you’d need a separate PSU for it and deal with two boxes and a lot of wiring.
The B3AC just plugs into your wall outlet (US users only need a new power cord) and charges the battery through its balancer plug. For the recommended battery, it will take around six hours to charge instead of less than one with a “bigger” charger. But on the other hand, there is no way you could set up that pocket charger in a way that would destroy the LiPo (which is pretty easily done with an advanced charger).

I’d never store or charge a LiPo without one of these: http://www.hobbyking.com/hobbyking/store/__4134__Lithium_Polymer_Charge_Pack_18x22cm_Sack.html
LiPos have the potential of starting fires under certain circumstances (so do NiMh), so 2$ of safety equipment is not a bad investment in any case.

@Thomas_Sanladerer Ah, yes of course a charger can come in pretty handy if you actually want to be able to eventually drive the car… :wink:

Didn´t think of it since i already have one. Anyway i will add the charger you suggested which by the way is unbelivable cheap. I think mine cost like ten times that price… =)

Ok, i have posted the list here: https://groups.google.com/forum/?hl=en&fromgroups=#!topic/openrc/pnhBCD3rr-o

I will edit the list later if needed.

Looking good!
The charger I’m using personally is a lookalike to the ubiquitous Imax B6, but sold and branded by the German company Jamara - they specialize in R/C planes and solar panels :smiley:
I think i paid like 30€ for it, which is also quite cheap for a mid-range charger. The only problem with it is that it is quite fiddly to use, but you get used to it.