Questions for my first build: Fusing, loop-key and vesc configs

Hello, I just finished my first electric longboard (photo):

  • VESC: Flipsky 4.20 50A const 150A burst (based on 4.12 hw)
  • BATT: Lipo 6S 4Ah 30C
  • MOTOR: Flipsky 6374 190KV 3250W 80A Max
  • ANTI-SPARK SWITCH: Flipsky 150A const

atm I configured the vesc like this (if there are some errors in the configuration let me know what’s wrong please):

  • Motor Current: 25A
  • Motor Brake: 30A
  • Battery Max: 60A
  • Battery Regen: 4A (following “1C rule”)

I’ll use a FlexiBMS Lite (max 10A) to charge the battery with a 25.2V 2A charger. So, here are the questions:

  1. Can someone help me finding the best fuse solution for main(if needed) and charge lines? For the last one I recently bought these, they are good?
  2. At the moment I turn off my board with the anti-spark switch but I noticed that the electronics draw a little bit of current even when turned off, do I also need to implement the loop-key as shown here?
  3. I’ve noticed some users maxing out the motor current and adjusting the max battery current as needed, is it better than my approach?


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image if these touch your esc blows a DRV chip

looks good, yeah wire a loop key if you need a holder printed you can find it on the clone clone clone forum.

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Yes I know, I thought they can’t touch due to the heat shrink extra width. Am I wrong? What do you suggest? Electrical tape or other?

Ok, thanks. Can you help me with questions 1 and 3 please?

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Try increasing motor max to 100A and decreasing battery regen to -20A

Battery max at 60A will overheat that ESC almost immediately, try lowering that to 25A

Yes, this works much better.


If the motor is rated up to 85A (source), why do I have to set the motor max over that limit?

How battery regen to -20A can be correct according to my battery?

Ok. What about the motor brake amps? It is enough that I’m feeling good with that value?

Can you sum up a quick explanation please? I like to understand things specially when my safety depends on these.


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try numbers. see how they work for you

Sorry but i think this is the worst method to understand things correctly, with the possibility to even break stuff.

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start low then go higher then

@b264 can you help me here please?

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the motors can take more, just don’t overheat them. If the number you set is low you will get errors when you push the throttle going uphill.

adjust if it is not strong enough or too strong. Don’t overheat the cheap flipsky with too many batt amps.

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Ok, I’ll try.

What about the batt regen -20A? Using a Lipo battery I have to charge at 1C (4A in this case) to prevent damage, what I’m missing about charging it 5x amps more?

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where does it say the max charge is 1C

I used that exact pack for my first build. I killed them from heavy abuse.

You don’t have to, you can set it at anything you desire to. I’ve found this makes it a lot better. You won’t be running at your motor max setting very much if at all. Maybe for a second here and there, but definitely not long enough to heat your motor up too much. If your battery maximum was also set that high, then things would be a lot different.

Typically the high regenerative charge rates achieved by smashing the brakes at a high speed will be so ephemeral that they won’t upset the cells.

If sustained, a charge rate that high could definitely be an issue. But once you start braking hard, you immediately begin losing the momentum that would be needed to sustain such hard braking.

In addition, once your cells are discharged even a little bit, like even 99%, it makes this even less disruptive to them.

Looked fine to me.

Maybe read this thread

Sustained high charge rate could definitely be an issue for the Lipo battery. So I’m a little bit worried about ruining the battery. Anyway thank you, I’ll try higher values.

Ok, thank you. I’ll start testing with motor at 80A and battery at 25A later to rise to higher values if needed (where I live it snowed so I’ll have to wait some day).

Few days ago I ordered the Metr Pro module and I can’t wait to check volts/amps in rt while riding my e-longboard. Just to check how the energy is spread and at which rate to make sure I’m not stressing the devices out.

@Fosterqc @b264 could you please help me with this problem too? :point_up_2:

What kind and rating of fuses do you recommend? Are fuses rated for 250V usable for this situation?

For main line I was thinking about this type rated for 100A(?) :

For charge line I was thinking about this two types rated for 10A :

I didn’t get that memo


I recommend no fuse on the discharge line, and on the charge port, max_charge_current * 1.25 to max_charge_current * 3

Fuse the charge port directly, not somewhere on the other side of the BMS.

So if you’re going to charge at 4A, then a 7.5A fuse would work. Or a 10A or 5A

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ahahahahah unfortunately I live in open countryside :sweat_smile:

so there are more disadvantages than advantages?

The FlexiBMS is rated up to 10A but I’ll use a charger with 2A charge rate so I’ll go with a 3x option so 6A fuse.

This way with that kind of fuse?

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Well, there have been long discussions on this topic, and both ways have pros and cons.

But me personally, I value my body more than my battery or ESC, so I feel this is safest for body. If something terrible is happening, I at least want to have a chance to hit the brakes before the battery goes nuclear, without a fuse popping and killing any chance I have to save myself.

If built and operated correctly, your current should not be going to levels above that anyway.

That’s the short version.

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