Electric rc cars need an ESC (electronic speed controller) to work correctly. The ESC regulates the speed and breaking strength to your electric motor. The signals to the ESC are usually PWM and are based on the inputs from your transmitter.
ESC’s are more advanced than they were 15 years ago. You now have the ability to tweak several aspects of your cars speed controller.
Calibration.
The purpose of calibration is so your ESC can understand the full range of inputs your transmitter has. If you do not complete this step you will either have reduced control or no control at all.
The first thing you will need to do with your ESC is calibrate it to your transmitter. They will be different ways to do this based on the ESC you chose, but the basics remain the same. I would advise you place your RC car on a brick or something which will raise the wheels off the ground. You need to let the wheels freely spin encase the calibration doesn’t work properly. I have had cars go into full throttle before because the calibration has failed.
You will need to calibrate full brake/reverse, full throttle and neutral. To do this you go into calibrate mode on your ESC. You usually enter this mode by holding down the mode/set button until you see flashing lights. Then you set the neutral position and press the reset/set button. After this you will set full throttle and full brake. Press full throttle on your transmitter and press the set/reset button once more. Then hold full brake and press the set/reset button a final time. You should hear a final audible beep or flashing lights indicating calibration mode is set.
For the exact method on your speed controller I would advise you to look through the instruction manual which came with your ESC.
Now your ESC is calibrated we can look at some of the features and options. The more expensive race spec speed controllers will have more options, however you get a good selection on ready to run versions.
Running mode.
- FWD/BR – this means your ESC will control the acceleration and break only. This is the ideal setting for racing rc cars as you are not allowed to use reverse. The other reason to set this for the race track is you can activate reverse while still going forward. Going from forward to reverse quickly can damage gears.
- FWD/REV/BR – this setting will be forward break and reverse. You normally press the break to slow down and once you have stopped press the break again and your car will go into reverse.
- FWD/REV – this option is very rare! If your speed controller has this setting, I would advise you not to use it to avoid damage.
Cell count.
This applies more to Lipo batteries. Most speed controllers have an auto detect setting which can be handy. However I recommend setting it to match your battery exactly. If you are racing 1/8th scale you will be using a 4s battery. Set your cell count to 4s or 14.4v.
The reason for this is lipo batteries can sometimes not correctly charge. They can also have a bad or unbalanced cell. If you have it set to auto detect your ESC could pick the battery up as a 3s, instead of a 4s. If you drive with a 4s detected as a 3s you will further damage the battery. This can cause the battery to swell, burst or catch fire.
Voltage cutoff.
Its advisable to not discharge a lipo battery below 3.0v per cell. Even at 3.0v per cell you are taking it to the limits. When you discharge a lipo battery below this threshold 99% of the time its damaged beyond repair. Lipo battery chargers can detect if a battery is too low and they will not charge a battery below the threshold.
RTR ESC’s will have 3 options low, medium and high.To get the most run time you should opt for the low setting. It is difficult to measure how many volts per cell the low setting is. Through my experience it is often above 3.0v per cell somewhere around 3.3 – 3.1.
On the more advanced ESC’s you are able to set the desired voltage in increments of 0.1v.
ESC thermal protection.
Your ESC monitor’s the temperature if you go above the threshold you set your ESC will shut down. Personally I set my ESC’s to the highest setting usually125°C/257°F. I only choose this setting when there is a fan to assist with cooling.
Sensored speed controllers can motor the motor temperature through the sensor cable. This cable also tells the ESC exactly where the rotor position is for better timing and smoother operation.
Throttle/start punch.
In simple terms throttle punch is the amount of torque available to the motor as soon as you pull the throttle. Think of this like a little delay between the trigger and how the car reacts. if you have a low setting as soon as you hit the throttle your car will start to accelerate slower than with a higher setting. This is either in levels e.g level 1 – level 7 or percentages 20%, 25% etc. High end speed controllers can also have several stages of punch for finer tweaks.
So let’s set it to the highest setting right? – lets go as fast as we can straight away. Well if you have a very high grip track surface this may be a good idea. If you are running on low grip surface your wheels will just spin and spin you will go nowhere. You can be much faster on the track by being smoother.
Throttle curve.
You would use this to tweak throttle delivery. Most ESC’s won’t have this feature and when they do the default is always linear. As you apply to the throttle it builds and builds until full throttle is reached. You could set the curve to be more instant at the start and then slower or slower at the start then build up.
This setting would most likely be track specific and would be difficult to adjust on the fly. You would need to test several different combinations and check your lap times with each change.
Reverse Force.
As mentioned above when you are racing rc cars reverse is not allowed. However if you do use reverse this setting will allow you to set how much reverse speed you want. Usually in percentage increments 25%,50% 75% etc.
Neutral range.
You can set how big the neutral range is. This is the gap between forward and break the highest setting is not normally more than 8%. The lowest is around 4% lower settings will make the throttle and breaking more sensitive.
Motor rotation.
Handy feature to have. A brushless motor is connected to a ESC with 3 wires A, B & C you can change the rotation of your motor by swapping any 2 of the 3 wires. A brushed motor has 2 wires and you can change the rotation by changing these wires around. This is a quicker option if you have bullet connectors. However if you have spent some time soldering your motor connections then this setting quickly becomes your best friend.
- CW – clock wise rotation.
- CCW counter clock wise rotation.
This option will not be listed as forward or reverse.
BEC Voltage.
BEC stands for (battery eliminating circuit). Not all speed controllers have a BEC built in. The BEC coverts the high voltage of your batteries down to a lower voltage like 6.0v or 7.4v. This powers other electronic devices on your rc car like your receiver, servo’s & transponder.
WARNING – be sure to check your other electronics are capable of higher voltages before you change this setting. Your servos, receiver and transponder need to be able to work at 7.4v. If not you can burn them out very quickly.
If your ESC does not have a BEC built in (most do) you will need to purchase a UBEC to power your other electronics.
Break force.
This is the amount of breaking strength available when you put the breaks on. Similar to throttle punch here you want to try different settings and see what works best. This is usually in percentages 25%, 50%, 75% etc. higher end ESC’s have finer increments.
100% full breaks on a low grip surface will cause your car to loose traction and slide out of control. 100% full breaks on a high grip track can cause your car to flip over and puts huge stresses on your drive train.
Drag break.
Drag break occurs when your transmitter is in the neutral position. You can set drag break in percentages 2%, 5%, 7% etc. Lets say you set this to 7%. That means as your racing round the track each time you let of the throttle, 7% of breaking force will be applied instantly.
I still need to play around with this setting. Personally I prefer to control the breaks manually through my inputs. I have used drag break on indoor 1/10th scale tracks. As you approach corners at high speed the extra instant breaking force can help stabilize your car on corner entry. It can also aid in jumping bringing the nose down ready for the landing.
Initial break.
Initial break is often only a feature on more advanced ESC’s. This is similar to drag break except initial break comes into effect when you press the breaks and not in neutral. The default setting is often the same as drag break. Drag break only works in neutral this works in the breaking position. This is also set in percentage increments20%, 30%, 40% etc.
Lets say you have 7% drag break and you leave this at the default setting this will also be set to 7%. When you approach a corner at speed and go from full throttle to full breaks. Your initial breaking will be 7% then your breaking force comes into effect.
If that is a little difficult to understand you would use this setting to smooth out your breaking force.
Break curve.
Just the same as throttle curve except for the breaks. You have the ability to change the break curve from linear. To your desired setting more break strength smoothing out or smoother breaking into a sharper breaking force. This is a track specific setting that would require lots of testing and tweaking to get the ideal setting.
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