Error fault_code_under_voltage & Weak Breaks

I’m experiencing some issues with a DIY eSkate that I built.

It is a dual setup with 6355 Maytech’s motors, Focbox and a 10s3p Samsung 25R battery pack with Bestech BMS for charging & discharge and an anti-spark switch… few days ago the battery started to act weird, it dropped voltages from about 39v to 32v in the middle of the ride. I opened the battery and found out that few nickel strips got disconnected from few 18650 cells so I re-soldered them with my DIY spot welder.

Now the battery shows the right voltage, however I’m facing some two serious issues:

  1. The brakes became very very very weak, I can barely stop the board completely even at low speeds ride. However acceleration and top speed are still fine and I don’t feel any difference.

  2. When I climb a hill or accelerate hard, sometimes the whole system shuts it self down. If I turn the board off and on everything is fine until I’m repeating the hard acceleration/going up a hill. I was connected to the Xmatic app to record the ride, when the board got turned off I received an error “fault_code_under_voltage”.

At this point I’m not sure if the battery is the problem, or the BMS (due to it also discharge my battery) or the anti-spark switch.

If anyone have any idea what could be the source for this problem I’ll very appreciate it. :beers:

@BillGordon can you pump @Style to builders level (Tomer over there if i´m not wrong)

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Yes, this is me :slight_smile: Appreciate it brother

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Done. Thanks for the heads-up and welcome, Style!

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  1. What are your brake settings?
  2. I assume, that your pack has a massive voltage sag under load. That cell type is known for this. They are used widely in the evolve gtx. You get cutouts, because it reaches the battery cutoff voltage under load.

Did you check the wires to your esc? It could be a bad connection

Thanks! :slight_smile:

  1. I didn’t change the settings whatsoever, they used to work pretty well.


2. I thought about it as well, however this battery has been in use for the past year and 3 months.
Does it make sense?

I’m pretty much sure the connection is okay, will double check it again.

your motor max and min are low for 6355 you have the 170kv

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Tried to increase it but it didn’t help.

I guess I’ll test this eBoard with a different battery to verify if the issue comes from the battery or the Focbox/motors.