Random power cut issues

I am encountering some issues on my electric car since some months, and nobody here appears to be able to figure out what is going on, even the shop which sold it to me; they totally replaced the BMS and the service battery, thinking that they could in some way affect the electrical system of the car, but the problem persists, so I would like to know if, in your opinion, it can depend on motor controller.

Problem is that when the car is moving, suddenly and for no apparent reasons, sometimes the power gets cut: from the usual 5 kW at 60 km/h (it’s a microcar), power is cut at 3 kW, with pedal at full throttle; than power is cut down to 2 kw, and eventually to 0.8 kW (10A/80V), always with pedal at full throttle.
Weird thing is that if I stop the car (without turning it off) and the I run again, at the beginning I see the motor drawing 150A for some seconds, while car is accelerating; but as soon as car reaches 20 km/h, current is cut down to 0.8 kW, and speed goes down to 10 km/h.
The problem also sometime shows at start: I turn on the car, I leave the parking, but I am not able to go firther than 20 km/h due to power limitation.

I did dozens of tests in different conditions, but I am not able in any way to reproduce the problem at my wish, it only happens randomly. Problem temprarily disappear if I swithch off/on the car.

My controller is a Kelly KHB72701. Battery is 72V/150Ah. Motor is rated 6kW continuous, 8 kW peak. Problem happens with battery at any state of charge from 50% to 100%. Cells are perfectly balanced (max 0.010V difference).
In which conditions exactly does this controller cut the power to the motor?
Is any firmware upgrade available for this controller?
Can I read any diagnostic data via canbus?
The car is a Zhidou Xindayang A1, but I am not getting any help from the company.

Sounds like the controller is detecting (or thinks it is) some condition that it's programmed to reduce power for.

Usually this is either overheating in controller, motor, or battery, or a battery condition problem.


If the controller does not have sensors for any of these things, then maybe it has inputs for those sensors that are supposed to have pulldown resistors or other disabling mechanisms, that are not connected or not working.


It could also just be another bit of kelly flakiness; some of their controllers have been known to just...stop working correctly.... :/

As for firmware or other software for it, you'd have to get that from Kelly.

How can I usae CANBUS to read data from a kelly controller?

I don't know; kelly would be the place to ask for a manual of their canbus commands and responses (there are no standard ones; it's just a protocol; everybody can use whatever actual data they like for their products, and don't have to tell anyone what it is, either).

Reference this thread
https://endless-sphere.com/forums/viewtopic.php?f=30&t=93345
for your previous discussion on the topic.

Best I can tell you is these posts have Kelly and CANBUS in them, so they might reference the info you're after (or might not).

https://endless-sphere.com/forums/search.php?keywords=canbus+kelly&terms=all&author=&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

This is topics with those words in the first post or title:

https://endless-sphere.com/forums/search.php?keywords=canbus+kelly&terms=all&author=&sc=1&sf=firstpost&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

There may be more info on google, but the company taht made the product is your best bet for accurate info on a specific model (because they may all be different).

You don't need CAN to do a readout, only the kelly program and a programming cable.

Ask sales@kelly-controls.com, they'll help you.

I've had some kelly kls controllers die in a similar way to what you describe. First some random cutouts, later totally dead. Checked inside but no blown fets or magic smoke so i guess a dc-dc converter or some other component just stopped. It'll be interesting to hear what error you can readout from the program, if any.