Using the VESC & The S.P.A.C.E Cell together to build your esk8 is a great combination!.. It gives you a system which is not only very safe, simple to build and easy to use whilst being super slim, but one that is offering a level of technology that is unmatched in many of the commercially available boards the have been born from various crowdfunding campaigns. The technology available in the VESC alone puts you in a league of your own when it comes to eboard performance and configurability. In this article I will explain how to configure the VESC to get maximum performance.
First, let’s discuss the limitations of the S.P.A.C.E. Cell
- It has a 30A fuse, this is a safety feature to prevent you from ruining your battery if you make a mistake with wiring or if there is a short in the circuit after the battery. 30A fuses can actually throughput bursts of current that exceed 30A for a few seconds, any longer than this and they will blow and protect the other components. You can expect bursts of up to around 40-60A for 1-2 second without it blowing.
- The BMS inside the S.P.A.C.E. Cell Can handle 30A continuous throughput and peak of 60A for a few seconds, anymore and it will blow also. This protects the cells from over discharging, overheating and self destructing leading to a catastrophic thermal runaway event…
- The cells inside the S.P.A.C.E Cell in a 10S3P configuration can easily support a discharge of 60A continuous but will never be able to as the Fuse & BMS will prevent it.
Why is the S.P.A.C.E. Cell limited?
- It is limited by the FUSE & BMS to save itself & save you money just incase something bad happens.
- It prevents you from inadvertently punishing the cells & the other componentry to the point of early failure. For example; some people might think it is a good idea to tow their friends on a non-powered skateboard… in most cases this will be ok, but if you then decide to tow them up a steep hill, without current protection, the electronics will just keep heating up and eventually the weakest link will catch fire or melt. The S.P.A.C.E Cell won’t allow this and you will blow a $2 fuse instead of a $200+ worth of electronics…
- This is DIY & Accidents do happen, with a fuse in place if you accidentally short circuit your wiring the fuse will blow & save you $200+
How can I ensure I don’t blow up my S.P.A.C.E Cell?
- Firstly, you should always be thinking about your system and how you are using it, knowing its limits and being respectful of them is important. This is the same for any electric vehicle.
- Most importantly - Use a Motor Controller, like the VESC, that has built in protection features such as current control.
So what are the best VESC settings to use to ensure your S.P.A.C.E Cell lives a long and happy life?
As I mentioned the VESC has current limiting functionality which is what we will focus on. It also has built in temperature sensors and rpm limiting and a whole bunch of other really useful features that need to be discussed in another topic.
NOW Let’s configure the VESC for S.P.A.C.E Cell
Open BLDC tool / Motor Configuration TAB / Motor TAB
You should see this screen:
We will be working on the “Current Limits”
- This is the MAX amps you want inside your motor, set it at 80 Amps
- This is the MAX amps you want inside the motor during braking, it’s set to (-60) 60 Amps by default, leave that.
- This is the MAX current draw from the battery, set it to 30Amps which matches the BMS inside the S.P.A.C.E Cell
- This is the MAX regen-charging current you want to flow into the battery whilst braking. (-12) 12 Amps is the Maximum safe level for the Cells inside the S.P.A.C.E Cell. The lower you make this setting the weaker your brakes. You could go higher if you want stronger brakes just be aware that high sustained regen current can reduce cell life.
NOTE: This is the setting you would use for a single VESC, for Dual VESC you might need to reduce “Batt MAX” to 15A in each VESC making the combined total across two VESC equal 30A Max battery current. NOTE: The negative “-” value indicates power running backwards through the VESC back into the Battery.
With these settings you cannot blow your fuse or damage the S.P.A.C.E Cell by riding aggressively. However a short will still blow the fuse no matter what settings you have inside the VESC
So how does the Motor MAX & Batt Max settings work? The VESC is able to independently measure & control the current at the battery & at the motor simultaneously! This means you can achieve impressive start up power whilst keeping overall currents low when cruising at higher speeds.
I can’t explain to you exactly how this works because I am not an electrical engineer… but for fun I will take a guess! I think it has something to do with ohm’s law V = I R if the battery can output a peak of 1080 Watts total it means current in the motor can be high whilst the voltage is low. This means when you have a lower RPM and less voltage in the motor you can have higher current. As the RPM increases and Voltage increases the motor current will become more & more limited.
In a propulsion system that is geared for a top speed of about 45km/h the motor current can reach the 80A peak up until you reach 3/8s of your top speed which is about 16km/h… Once you have reached this speed the current will begin dropping down.
With this functionality you can have high starting current and not blow your battery up!