Too Many Amps or voltage cutoff?

ESK8 Electronics
1

Hi!

I spent this summer to build an electric longboard and it works good, most of the time. The only problem is that my motor draws too many amps when going uphill and exceeds the max amp rating on my ESC. Since my ESC “safety feature” for this is stopping immediatly, I get thrown of the board.

I have searched for a solution for a long time, and I got a suggestion to go dual drive. Two motors would split the amps and I would therefor not exceed the max amp rating on the ESC. Is this a good solution?

Specs: Ntm Propdrive 5060 V2 X-Car Beast ESC 120A

2

Have you measured how many amps you really pull? That motor can max draw 90 amps, while your esc is good for 120. I have never heard about amp limits on that esc too?

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4

Well at this point it´s my theory of whats happening, and im not sure how to test how many amps the motor draws.

Someone also mentioned it could be that im voltage sagging the batteries. I bought a voltmeter but it displays the voltage in percent. Going uphill at 100% charge, the display will show about 80 to 70%. Is that ok?

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5

Im not sure about the voltmeter, but if you want to check how many amps youre pulling, you can buy a turning wattmeter or similar. What exact batteries do you use?

6

Im using 2x Zippy flightmax 5000 mah 3s 20c.

7

if this only happens going up hill could it be a heat related issue? maybe it cuts out cause it goes into thermal protection.

8

Your batteries are rated for 100 amps max, and when you most likely pull 90, you will have some serious voltage sag. again, if you get a wattmeter, you can check the voltage when going uphill. I guess you hit the voltage protection.

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9

It happens during regular acceleration too. If i pull the trigger too hard it stops immediatly. It´s quite annoying really…

10

Pretty sure you hit the voltage protection.

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11

Could batteries with better c-rating solve the problem, since they would not voltage sag as much?

Maybe something similar to this, but for 6s (upgrade to 10s later):

https://www.electric-skateboard.builders/t/high-power-10s-lipo-battery-pack-with-bms/10014?u=teslaalex

12

Yes, high C batteries like those will help a lot on voltage sag. But before investing 100$+ in new batteries, i would have bought a wattmeter to check if it really is the voltage sag that is the problem.

13

Well, ok. Im having a hard time finding a wattmeter that supports up to at least 120a. Could you link me one that is commonly used?

14

https://hobbyking.com/en_us/turnigy-180a-watt-meter-and-power-analyzer.html This one support 180 amp, up to 12s

1 Like
15

Thanks mate! I really appretiate it! Finally some progress, been trying to solve this for months!

16

How about getting a cheap battery checker. The alarm will go off when battery cells drop below 3.7 to 3.2v. I had a lot of battery voltage sag with my 25c rated lipo.

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17

I would also recommend Bluetooth module and phone app like Metr ( there is thread about it here on the forum ). I will show you like your amps and also you can record your trips. Below is my today’s trip where up a Hill I tripped low voltage limit in vesc and shut off my board. It is 37V at the momemnt but with a sag up a hill it went below 35-33 and shut off my board.

Highly recommended for diagnostics and fun!

18

That is cool. Any reason motor temp isn’t showing?

19

I think temperature displayed is the Vesc temp. Not sure if motors can be shown. You’ll have to ask @rpasichnyk who developed the app.

Also @emmaanuel has iPhone app (paid ) which works with cheap hm10 Bluetooth modules. I have both apps but haven’t checked out properly @emmaanuel one yet as it just got updated to ackmaniac 3.1 and vedder 3.0 firmware.

20

I’ll have to check into those for my build. Has some great information.

21

Yes the motor temp is one of the data available across the app:

Your motor need to have a temp sensor for that. This data is not in the default view, but you can add it.