Controller max current problem

[harrisonh]

I have a CA3 and 35A 24-48V grinfineon controller, recently put onto my first e-bike.
The last few days, I noticed that the max current is only about 30A.
I don't remember if the max current before was higher at 35A or not.

I've tried changing the throttle_out, changing the max current limit, and probing the phase/battery leads to see if the mosfets are blown.
I think it's something with the controller and not the CA since while running current-control mode, full throttle, the CA says it is not limiting the current, but it still wouldn't go much above 30A.

Any help with what might be wrong would be appreciated! thanks!

 

[motomech]

What battery?
You may be at it's max. discharge rate.

 

[harrisonh]

I'm using two 2.6Ah 6S Turnigy nano-tech lipos in parallel(sometimes in series). No BMS.
They say 45C discharge each,8C charge.

This is the data from a short commute today:
http://www.ebikes.ca/tools/trip-analyzer.html?trip=BJPU0a
Peak 31.19A

 

[motomech]

You need to talk to teklektik .
He is on a related thread(CAv3) that is up right now.

 

[fechter]

If the battery voltage is too low, the motor might not pull full amps.

What's the voltage when you're trying to hit max current?

 

[harrisonh]

It drops to about 23.3V when the battery still had most of its capacity still. The cycle analysts estimates about .03Ohm internal resistance for the batteries.
I've also put my two batteries in series for 48V and still couldn't get 35A.

 

[harrisonh]

I calibrated my shunt. Written value on the outside of the controller is 2.54mOhm
I set it to 2.353mOhm. Max current on last ride: 34.75A
The controller seems to be doing its job. I used 3 different supplies and current measuring devices, they were off from each other by about 2% but seems good.
I might try to calibrate it more in the future, or after I modify my shunt for more current!

 

[fechter]

One other question: What kind of motor are you running?

My original thought was that a lower voltages, the motor might draw less than the controller's limit due to it's resistance.
A motor with a 'slow' wind made for a higher voltage will have a more resistance in the windings and could be the limiting factor.

 

[harrisonh]

9C 3004. I chose the fastest of the three 9C motors from ebikes.ca

 

[fechter]

Seems like that one should be able to pull the limit when starting out from a dead stop even with the lower voltage.

 

[Alan B]

Best to use an external shunt for CA. The internal shunts are often not wired properly to get a good voltage sample, and if you are going to mod the internal shunt it will be even less temperature stable that it was, so using an external shunt will solve that and allow you to see how your mods are changing things.

 

[harrisonh]

Thanks! I will look into external shunts.