FAULT_CODE_UNDER_VOLTAGE (VESC problem)

ESK8 Electronics
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1

Hi all,

I was test riding my DIY electric skateboard the other day and after a while of testing, it started to cut in and out, I hopped off the board immediately. I thought it was just running low on battery but the issue was much larger than that.

The electronics on the board:

-10s 5Ah lipo battery -45a 10s BMS

  • 2x Maytech Vecs
  • 2x Maytech hub motors.

I am using the classic “key” design (A xt60 plug that shorts the positive wire to complete the circuit - if that makes sense) to turn off and on the board. After recharging the board, I went to plug in the “key”. It sparks every time I plug it in, however this time, it didn’t spark. This concerned me.

I span the motors to see if it still worked. They both span up fine for one second then the power cut then VESCs blink red about 5 times. This happens every time I try to use the motors and has nothing to do with a broken remote as the motors only span for a second using the BLDC tool.

I typed “faults” into the terminal on the BLDC tool and this came up:

Fault : FAULT_CODE_UNDER_VOLTAGE Current : -0.2 Current filtered : 0.4 Voltage : 7.88 Duty : 0.49 RPM : 4718.0 Tacho : 165 Cycles running : 4345 TIM duty : 3895 TIM val samp : 1960 TIM current samp : 5937 TIM top : 7955 Comm step : 6 Temperature : 31.08

I’ve checked all of my solder joints on my board they all seem fine. These are two brand new VECS’s which makes me really annoyed with Maytech, as I have not had good experience with them.

can anyone help out?

Max.

2

Firstly the “classic” loopkey uses an XT90S

3-Pairs-Amass-XT90S-Anti-spark-connector-male-female-with-two-soldering-protection
3-Pairs-Amass-XT90S-Anti-spark-connector-male-female-with-two-soldering-protection910×640 170 KB

And the vesc is seeing less than 8V that’s why it’s giving an error, can you check voltage coming from battery?

1 Like
3

I do have an antispark xt90 plug coming in the mail,

I checked my battery voltage with a multimeter and it is 34.1V

voltage
voltage1228×934 98 KB

4

Do you have a bms? For 10S that’s empty and would trigger low battery shutoff which would trigger low voltage shutoff on vesc

5

I have it set on 33V battery cutoff. I’ll give it a charge and see if it changes anything

6

Your battery is at 34V that’s pretty much empty…it needs to be 41-42

You don’t have a problem other than needing to charge your battery…

7

Update: the battery doesn’t charge. :tired_face:

8

There we go :wink: Likely need to replace BMS

Can you take some pics of that?

9

Actually want to die

10

Out of all the problems you could have thats one of the simplest and cheapest to fix…don’t be too down

11

It’s like the 5th time replacing the BMS

12

Using the same charger between all the BMS?

Also as a general rule, sparks aren’t good for electronics

13

Yeah it’s an evolve charger, works fine.

20180122_172939
20180122_1729394032×1960 2.58 MB
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20180122_1729584032×1960 2.63 MB
20180122_173005
20180122_1730054032×1960 2.79 MB

14

Gonna need to see the PCB of the BMS to spot any damage I don’t know if i would feel comfortable with lipos that look like that under my feet :thinking:

1 Like
15

Thinnest diy board man! Haha the lipos are inside the deck!

16

I get that but how did they get all the almost puncture marks on almost every cell?

2 Likes
17

Magic hahaha

18

I cant get into the BMS. It’s soldered shut

19

Have you been getting the same BMS model each time or diff ones?

20

Pls isolate your cells dude! Sooner or later you´re gonna have magic smoke comming out that deck! Lipos like it best in a soft environment, not wiggeling around like that.

Also your wiring confuses me a bit with that bms. In your picture, you´ve connected the top two contacts together?