Help with SWXH and KT36 controller

[_ro_]

Hi All,

I have just finished building a recumbent trike based loosely on the Atomic Zombie Warrior.


I've laced a 201rpm Bafang SWXH into a 26" rim and am using a 20A (max) KT controller powered by a homemade 14S 30Q battery.

It all works, and pulls nicely from a stop, with the display showing 1000W, but as the speed approaches 10MPH the power drops right off. At 10MPH the display shows 300W, at 12MPH at shows about 150w.

I have set the speed limit to it's max value and even tried setting the wheel diameter to 18" instead of 26" in case there is another speed limit that i'm hitting somewhere, but the behaviour is exactly the same. This happens on all PAS modes and I've tried connecting a throttle as well, but this doesn't change anything.

By my calculations the 201rpm SWXH should be good for 18-19mph on a 14s battery so I'm not looking for a huge top speed, but for it to pull well up to 15MPH

I'd like to keep this build legal and will be reducing limits and removing the throttle once I have (hopefully) resolved this problem

Can anyone help with what I've done wrong.

 

[vfr400]

Before anything, 20A at 14S is too much for that motor. You'll shred the gears before long. I wouldn't go any higher than 16A.

How do you know it's 36v and 201 rpm? What's written on it?

 

[_ro_]

Before anything, 20A at 14S is too much for that motor. You'll shred the gears before long. I wouldn't go any higher than 16A.

OK, cool. Thanks for the advice - I take it setting C5 to 6 (Maximum Current Value ÷ 1.25) should do that for me.

How do you know it's 36v and 201 rpm? What's written on it?

That's what I ordered from greenbikekit, but I can't be sure that's what I've got. This is the serial on the motor.


Thanks for your help

 

[vfr400]

Did you try it on all PAS levels? If you have your controller set to speed control on the PAS, each level will give a different speed.

 

[Nealh]

Your issue is down to the P1 Parameter being to low, what is it's current value ?

 

[_ro_]

Your issue is down to the P1 Parameter being to low, what is it's current value ?

P1 is set to 88 and P2 is set to 6

Did you try it on all PAS levels? If you have your controller set to speed control on the PAS, each level will give a different speed.

It happens on all levels.

 

[PC2017]

Maybe try a 15a controller perhaps sinewave, I had trouble with the 20a KT and the amp draw setting(LCD3), my problem was never found, I believe the controller was faulty however my problem was indicative of a failing battery(36v) however on a 14a sinewave and the 17a square my batteries work fine to LVC - I know nothing about battery BMS but could that be faulty?

 

[Nealh]

P1 88 doesn't sound to bad.
My original reasoning was I had a similar issue when I swapped my Yose hub wheel over to my AKM128c, I forgot to change P1 and my AKM did exactly the same. 10mph was the max in any PAS and throttle when out on a journey, It took me about 1/2hr in to the ride before I realised my error. Increasing the P1 up to the higher value it should have been at had it back to normal operation and speed read out.

 

[Nealh]

The KT dual controllers aren't configured for 52v so that may be where the issue lies.
Try the controller with 36 or 48v max to see if things correct them selves.

 

[Nealh]

Does your new controller display have the extra L settings ?

 

[_ro_]

Wow, thanks for all the suggestions - this is really helpful.

however my problem was indicative of a failing battery(36v)

I know the battery and BMS are good as they work fine on another bike with a BBS02

P1 88 doesn't sound to bad.

OK, I'll still try changing this tonight. I'll set P1 to 176 and P2 to 3 - this should give me the same speed readout (right?)

The KT dual controllers aren't configured for 52v so that may be where the issue lies.
Try the controller with 36 or 48v max to see if things correct them selves.

My 14s4p is currently at 48.9V after a blast on my other bike last night. I'll try that tonight (after a bit of a run it should be at 48V).

Does your new controller display have the extra L settings ?

Um, no idea What are they and where would I find them?

Thanks again for all the help!

 

[vfr400]

The problem is not caused by any current limit because he gets 1000w at low speed, which is consistent with 20A 14S.

If none of the setting changes do anything, have a look at the motor connection sequence. Maybe you have a false positive. Try other combinations to see if it sorts it out.

This manual explains the L parameters that aren't in all LCDs:

 

[Nealh]

When you have entered P & C settings, some LCD now have a further setting to enter of L. If you have L setting and L2 is set wrong then it can half the P1 value.

 

[_ro_]

Thank you all for your help. I tried all of your suggestions and finally (as it meant disassembling my wiring harness, I left it to last) changing the hall sensor connection sequence worked. It now accelerates under full power up to 18MPH!

Thanks again, I can't believe how helpful the folks on this forum are

 

[harrys]

This manual explains the L parameters that aren't in all LCDs:

Hi vfr400, appreciate the LCD4 manual, but that particular one doesn't discuss the L parameters. They are in this link.

https://cdn.shopify.cn/s/files/1/1430/3254/files/KT_LCD8_DISPLAY_USER_MANUAL_12676e67-7c33-4036-b255-78a4ac6beed2.pdf?v=1589875045

Want to keep L2 =0 unless one has a really high speed motor.

KT LCD3 L-settings

L1 = 0, LVC is auto sensed
L1=1 , LVC =20V
L1=2, LVC = 30V
L1=3, LVC =40V

L2=0, the actual P1 is used
L2=1, P1 is divided for half

L3 default is 1
L3=0, controller chooses some backup if hall sensors fail

L4 used for auto shutoff of display
Default at L4=5 for 5 minutes. Add 1 minutes for every incrememt
If L4=120, you get two hours

 

[vfr400]

Hi vfr400, appreciate the LCD4 manual, but that particular one doesn't discuss the L parameters. They are in this link.

https://cdn.shopify.cn/s/files/1/1430/3254/files/KT_LCD8_DISPLAY_USER_MANUAL_12676e67-7c33-4036-b255-78a4ac6beed2.pdf?v=1589875045

That's weird. In the index it says they're on page 37. I just looked in my library of manuals and found a later one that said they were on page 39. That didn't have them either. Thanks for the link.