Wednesday, May 8, 2013

Beyond Unboxing: Chinese E-bike Controller (chatparts.ltd)

This post is a preliminary to a much more comprehensive post detailing controller capability that will be made when I am nearby more legit diagnostic equipment. For now, this post will contain my conclusions from observation, use, and light modification.

The "Beyond Unboxing" series is inspired by Charles Guan's posts concerning these same type of escs.

The Thing:
I have purchased a marketed 24V, 250W brushless controller for e-bikes hopefully as a replacement for Jasontrollers. What caught my eye was the cheaper shipping, faster delivery time, and the seller whose English was grammatically correct. It arrived just yesterday and after some observations, I am very excited about this controller.


The seller even included pre-stripped connectors!


Its casing was a interesting trapezoidal feature. Still a single tube of extruded aluminum, still two silicon pads on either end captured by two stainless steel brackets. I even think they used the same screws...

The chatparts esc also has fewer wires. The seller includes a diagram of the connectors (without labeling the individual wires) but there are unfortunately more than 9 connectors on this controller.


In short, it is incomplete. However the function can be deciphers from the connector ends since these are meant to be direct drop-ins for existing EV systems.

The Comparison:
Now lets have a closer look at a jason and chatpart side by side.


Its smaller... Less thick by about 1/8"


Board looks less janky. The chatparts ESC (bottom) has only SMT components whereas the jason (top) does not. I was also intrigued by the 7 labeled vias at the top left of the esc (in this picture, in this orientation). Those look like programming pins. It may be possible to reverse engineer the software and find out REALLY how this guy works.


Again, fewer wires.


Ah the processor! Everything in here is ST Mirco stuff.

MOSFETs:   STP75NF75
Processor:     STM8S903K3

Performance:
My test rig is just my latest GigaRazor scooter (that none of you know about yet) with a watt meter inline with the power source. Note that this is a sensorless configuration. I will not be able to conclude as to what functions it has but I can at least detail its behaviors.

Unmodified Test runs:

  • No-load behavior: Ramps up until near max throttle where controller experiences cutoff. Not choppy intermittent behavior, simply cuts-off. Repeatable behavior. However does not affect throttle behavior for subsequent runs. Lets consider this feature Controller Protection.
  • Load behavior: ~20 Amps current limit stock. Does not experience high speed cutoff under load (perhaps I am not traveling quick enough to reach no-load speeds). ESC is cool to the touch.


The controller was then modified using the solder-blob shunt method.

Modified Test Runs:

  • No-load behavior: Experiences intermittent cutoff at higher speeds. It is choppy, unlike the unmodified behavior before.
  • Load behavior: increased acceleration as expected. Choppy behavior as described in no-load experienced in load behavior. Watt meter reads ~50 Amps peak. Case is hot.


The controller shunt was then lowered to 40A and then 35A afterwards. The choppy behavior still persisted. I took this opportunity to measure to case surface temperature and discovered it was in excess of 120 degrees F AFTER a run at higher current.

My scooter uses an 8s3p A123 LiFePO4 pack and a Turnigy Areodrive SK3 6374-149 motor. This means at nominal voltage I should be rotating ~3933 RPMs. However at charged voltage I would be ~4172 RPMs. For comparable controllers in this application, it exceeds the infamous RPM limit determined by Charles and Shane years ago. To validate the RPM limit cutoff, I will test no-load conditions again using a 24V nominal battery or PSU.

Conclusions:
I will withhold my final judgement until I can more easily explain its behaviors and features. For now I can summarize the main takeaways:


  • Runs sensorless (sensored TBD although it has wires for it)
  • Possibly has high eRPM controller protection
  • Possibly has a second method of current limiting
  • Possibly has over temperature cutoff control
  • Smaller and cheaper than Jasontroller
  • No self-learn


More to come.

2 comments:

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  2. It appears that the controller they're selling now is different, do you have any experience with it?
    http://www.ebay.com/itm/120964489876
    Also, is the one you reviewed here the same as the ones on ELifeBike?

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