# kelly controller kdz48551



## wjdtpghks29 (11 mo ago)

We are using kelly controller kdz48551.peak 550a and continuous current 220a But when we connect the shunt resistor to measure the current, we hit 400a and we go down to 80a in three seconds. Is the controller broken? The battery we use is 52v78ah and the peak current is 400a. The motor I use is agni motor 119r


----------



## Functional Artist (Aug 8, 2016)

Is this happening before use? (like just while doing connections)
...or during use?
...or when programming?

I have a Kelly KDZ 48400 on my Hell-raiser kart

Here is a "shaky" video of some of the power meter readings, while in use


----------



## wjdtpghks29 (11 mo ago)

When we use it, when we press the full accelerator, we hit 400a and the current is linearly lowered to 80a.I don't know why. Why is that?


----------



## kennybobby (Aug 10, 2012)

The controller is throttling back the current because the battery can't supply 400 Amps and maintain the minimum voltage limit. See note [2] on your third photo.

Try lowering your max motor current to something like 100 A [set to 25% in photo 4], then do WOT test and measure the battery voiltage while under such a load. Then try 200A, and repeat. Eventually you will find the point in which the battery can't hold up it's voltage under load.

The battery is the main factor in EV performance; in your case it is the weak link in the chain of battery, controller, motor.


----------



## wjdtpghks29 (11 mo ago)

Thank you for your reply.Keep starting the motor current at 80 percent, and if you keep going down, you're going to hit 380a and go down to 80a. Isn't this an internal problem with the controller? I don't know what the problem is


----------



## Electric Forklift Guy (Dec 13, 2012)

You're just hitting the limit of what your battery can do.

"Peak Current" is not "Continuous Current."

Peak Current is only available for a couple of seconds.

On a 78ah battery the continuous current rating is only going to be about 70-90 amps.
(So the 80 amps you're measuring is spot on )

So while you can do hundreds of amps for a couple of seconds the voltage will rapidly drop down to 40.3 volts and the controller will throttle back the current to prevent it dropping lower ( to protect the battery ).

Nothing is broken.

You can increase the maximum current by setting the minimum voltage lower ( I strongly recommend you don't ) but you won't get much more power out of it than you are getting right now.

The controller you have could handle three of the batteries you are currently using.

So if you have room , and the budget, I'd recommend two more batteries.


----------



## wjdtpghks29 (11 mo ago)

Electric Forklift Guy said:


> You're just hitting the limit of what your battery can do.
> 
> "Peak Current" is not "Continuous Current."
> 
> ...


By the way, our battery bms setting is maintained for 400a 30 seconds. But I'm not sure if 400a stays for 2 seconds and then falls to 80a. Why is that?


----------



## kennybobby (Aug 10, 2012)

Maybe it's a language translation issue?

문제는 배터리 팩에 있습니다. 셀은 부하를 공급하기에 충분한 용량(A-hr)이 없습니다.

팩은 고전류(400A)를 공급할 수 없고 작동 전압을 유지할 수 없습니다. 전압은 컨트롤러의 저전압 설정 아래로 풀다운되고 컨트롤러는 기본적으로 80A로 설정됩니다. 이것은 컨트롤러가 작동하는 방식의 정상적인 작동이며 결함이 아닙니다.


----------



## Electric Forklift Guy (Dec 13, 2012)

The value listed in the BMS is how much current you could draw for 30 seconds if you don't care about how much the voltage drops

So you could draw 400 amps for 30 seconds ,but you'll also drop down to about 8 volts in 30 seconds.

So that number is technically true , but borderline useless for a traction controller.

What's happening is at a 5C discharge rate you're dropping to 40 volts in three seconds ( which is normal ) and the Kelly controller throttles back to 80 amps to prevent the voltage dropping even lower. ( which is also normal)

This is the setting I was talking about modifying 
You could set it to the minimum voltage the controller can operate at but you're already real close to that value 

If you want to do over 200 amps for more than 5 seconds you'll need two more batteries.


----------



## blackterminal (Oct 14, 2021)

wjdtpghks29 said:


> We are using kelly controller kdz48551.peak 550a and continuous current 220a But when we connect the shunt resistor to measure the current, we hit 400a and we go down to 80a in three seconds. Is the controller broken? The battery we use is 52v78ah and the peak current is 400a. The motor I use is agni motor 119r
> View attachment 131008
> 
> View attachment 131009
> ...


Did you try talking to a Kelly rep? I am considering one of these controllers and I am interested in what their after sale service is like.


----------



## wjdtpghks29 (11 mo ago)

blackterminal said:


> Did you try talking to a Kelly rep? I am considering one of these controllers and I am interested in what their after sale service is like.


Kelly's controller's people seem unkind I don't recommend it


----------



## wjdtpghks29 (11 mo ago)

Electric Forklift Guy said:


> The value listed in the BMS is how much current you could draw for 30 seconds if you don't care about how much the voltage drops
> 
> So you could draw 400 amps for 30 seconds ,but you'll also drop down to about 8 volts in 30 seconds.
> 
> ...


Does that mean that the controller is doing a good job to prevent the battery from dropping voltage?
I think it's very difficult And thank you for your answer


----------



## kennybobby (Aug 10, 2012)

The problem is the battery pack is too small for the job. The cell does not have enough capacity (A-hr) to supply the load.

Your pack cannot supply high current (400A) and sustain operating voltage. The voltage is pulled down below the undervoltage setting of the controller and the controller defaults to 80A. This is normal operation of the way the controller works and is not a defect.

If 80 or 100 A is not enough to drive the car, then you will need a bigger battery pack with higher capacity (AHr).


----------

