Blasted capacitor

For my Hummie hubs pretty build, I use a 12s5p Eskating Battery Samsung 30Q 15000mah, like this one :

# 12s5p Eskating Battery Samsung 30Q 15000mah

But the one that I have bought in 2019 also had a ON/OFF button (+ charge port + XT90).

Using this battery for the fist time, I’ve just blasted a 63V capacitor from a Flipsky FESC 6.6 DUAL mini (the one with NO integrated antispark).

I’ve already tested this dual ESC in the past, and there was no issue.

The dual ESC worked fine just after the capacitor was smoked. I have green light and blue light on both ESCs. Motor detection worked fine with wizard using can.

Now I can run both motors in spite of the fact sometime only one ESC is detected over can, and always the same, even if I try to connect to second micro-USB port.

My questions are :

  1. Do this kind of Li-Ion battery pack with ON/OFF button connected to BMS needs other antispark on the circuit (XT-90S for example)?
    I thought the ON/OFF button of the BMS also behaves like an antispak.

  2. Should I worry about the blasted capacitor if the dual ESC works (almost) fine?

  3. Does anybody know about my issue of detecting all ESCs over can? I’ve built more than 10 e-vehicules, mostly e-mountainboards, and have never seen that… I’m not used to Li-Ion packs. I prefer Lipos a lot.



preferably, yes


idk about question 3


Yes. I would absolutely not ignore this and just continue using this device as-if it’s 100% working.


I thought the capacitors were there to smoothen current and stuff for the other components and less capacitance could damage the esc…if the battery wires are long especially


Thanks for helping!

Wires are not very long actually.

I thought it would be easy to remove the capacitor, but unfortunalely all capacitors there are potted in epoxy resin.

Yet, epoxy could be scraped by soldering iron tip set to 450°C.

Now I have to find the same capacitor on Farnel or Mouser…

Fun to think that it the ESC was hidden into an alu case, then I might have believed nothing bad had happened and continued using the ESC with blasted capacitor…


On the positive AWG10 power cable I’ve soldered the wire directly to a 80A strip fuse like that (the fuse is hidden by black heatshrink on above photo).


it’s clean work but there is still quite a lot of solder.

Can it generate to much inductance and explain why the capacitor has been blown when powering the BMS e-switch?

I think inductance in the battery wires is dealt with by the big capacitors on the end. Or maybe if they don’t do the job and ur wires create too much then maybe it stresses other capacitors on the board. I don’t know and @linsus or @jaykup would know.

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Some kind of pre-charge is preferable, the caps are essentially shorts before they’re charged up, meaning current goes brrrr until the potential accross them reach VBAT when connected.
Looks like one of your caps went brrr bit too hard. (could also just be bad luck with shitty components)

A cap fails either open or closed. For paranoias sake I’d atleast remove it.

detection shouldn’t have anything to do with your battery. What error are you getting?

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The shorter the battery cables the better. Loops = more inductance, straight cables = less inductance. Phase cables can be long af


Straightened cables would probably already be arranged pretty closely to each other but I wanted to emphasize that the size of the loop (from battery, out ESC, and back to battery) is smallest if the cables are against each other all the way.

Even better is if the battery cables are twisted together too but that’s tough to do with large gauge wire.


What’s an acceptable inductance for battery wires… when using … maybe the flipsky 75100 or some other esc?

I remember reading long ago that generally people have too much inductance for the Vesc’s main caps but it survives surprisingly well anyway.

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We’re not able to quantify that.
It depends on the ESC’s input capacitance, the ESC’s circuit/pcb inductance, the amount of current flowing, how close the pack voltage is to the component voltage ratings, and how quickly the MOSFETs are turning on/off.

But even if we had an max acceptable inductance number it wouldn’t help much without a meter to measure the inductance of the setup once the wiring was in place.

Check your meter’s voltage ratings (for inductance mode) before you try to measure your pack’s inductance! This number won’t really tell you anything though.

We can do one thing…battery wires made as short as possible and run directly next to each other = more better (lower inductance). Larger wire gauge doesn’t have much of an effect on the inductance (affects wire resistance and power loss a lot though).


Trying to measure inductance of battery will ruin my multimeter I guess


Epically I imagine

Check the specs for the voltage rating in that mode.
Edited my post to add this.

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This cap failed open.

I’ve tested this ESC at 6S without the blasted cap, without motors, just connecting to VESC-Tool and I got no issue with detecting other ESC through can and re-uploading firmwares to both ESC with can. Yet, uploading firmwares was very slow with USB as if I did the process with a bluetooth dongle. I don’t think it is supposed to be slower at 6S compared to 12S.

I won’t do anything else with it until I replace the cap.

I’ll replace the ON/OFF e-switch button with a XT-60 key and I’ll add a XT-90S key system on the positive power cable after the fuse. I’ll also try to make the power cables shorter.

Thanks for your help!