kt-lcd power cutting out

Hey

Just cobbled my ebike together finally and took it on a few runs

It runs well for a short time and then the battery level gauge on the top left of my kt-lcd goes empty and flashes and then the power cuts out for a few seconds then comes back and cuts off again when i apply over like 25% throttle

Note: the display doesn't actually turn off, just the power cuts off briefly

Anyone know why this is?

I just hooked up a watt meter

It pulls 35 amps and seriously sags like 6v under load so i guess i was hitting lvc on the controller

Is this normal for a 13s5p pack?

what cells are in the pack?

do you have a BMS?

nieles said:

what cells are in the pack?

do you have a BMS?

Click to expand...

Sanyo's and yes

do you know the cell type? 35A is 7A per cell.
a 6v drop is 0.45V per cell

we need to check the datasheet if this is normal or not.

could also be there is a cold solder joint or the BMS is faulty
both could introduce extra voltage drop.


the voltage drop could also be bigger than the wattmeter shows, because the are not very fast from what i have seen

https://lygte-info.dk/review/batteries2012/Sanyo%20NCR18650GA%203500mAh%20%28Red%29%20UK.html

Hitting LVC is very likely. (either from the controller or BMS)

maybe think about beefing up the wiring to lower the losses and voltage drop.

EDIT: is the pack rated for 35A? (or better, is the BMS rated for 35A?)

I had a KT controller doing this, ended up redoing all the wires to the motor thinking it was the halls because I could max out the throttle on startup if the wheel was unloaded but had to put a curve on the throttle and take off slowly to go (doing the halls did fix the cutting out at startup but I also put 12awg phase wires on at the same time as the originals had melted into eachother).
Only did that last weekend and have ridden that bike once since and it was still doing funny things.
(but I also put a domino throttle on at the same time and think it might need a resistor or it tops out to high)
Keep in mind this is on a 18fet kt controller with an 18s battery

If you give it time after it cuts out do you get an error message?
It will be like info_03 or info_06 or info_02

Could be a bad throttle these controllers seem to wig out with a throttle voltage over 4.2v iirc

Also how soon into a ride does this start? GA cells with 5 in parallel can source a lot of current and the sag is normally pretty reasonable

It starts within 5 minutes

I think maybe these sanyos are not good for high discharge even though 35a is not super high

I guess they're more of a range battery than a power battery

Also the other reason its cutting out is because i looked at the battery and it has a 20a continuous bms, which is ridiculously low

To keep it working and healthy could set the controllers max amperage to just below the bms rating.
I set my kt lcd-5's display to just under the batteries BMS rating doing this have only had 1 bms shut down which happened running in speed 2 against the wind after a incline. This is using a 12AH 48v 15A max battery at about 1/3 discharge level on a 350w motor limited to 14.7A via the display which is about 750w peak.

Im probably going to rebuild the battery with cells that can put out more amps and get a better bms or just bypass it

It would be the KT-LCD/controller re-evaluating the batteries status based on the large voltage sag you are causing when pulling heavy amps.
If you have a P4 18650 battery pack I would be surprised if you didn't get that happening when pulling 35a

This is normal, you can just take off more slowly, or you could try playing with the P5 setting, normally I just have mine on "0" which means automatic.

You could also try lowering your "C5" parameter setting, which the manual describes as "Controller Maximum Current Adjustment Mode", , try changing its levels to something lower, the default is maximum.
I have a 7P 18650 pack and I can still manage to get it to cause the battery status to re-evaluate when taking off hard enough, not sure if I have ever caused the screen to blank out, but possibly when the battery is very low.