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I have a system which uses this board: Arceli Motor Control Speed. It's supposed to run for a maximum of 5 hours continuously.

It has an electrolytic capacitor (black vertical tube) on which is written 100 µF, 25V.

I want to know if there's any risk that this capacitor may explode? I could explain why, but I'm not sure that's relevant to the question.

I've been looking on the web for information, and had a lot of trouble finding information on this specific matter.

What I have in mind:

  • It's not very probable that this happens, because the voltage is very low, and I learned that capacitors explode only because of overvoltage, or reverse-voltage
  • This board is of low quality, generic design, so the components may be faulty, but I'm not sure of that
  • The problem may not the an explosion, but may be more of a leak of chemical components

I've found some information thanks to Bard, saying that "[...] in general, it is likely to be in the range of 140-160 dB [...]" (its source is a few books I'm not sure are relevant.)

Would you have any knowledge on the probability that this might happen?

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    \$\begingroup\$ Leave it running for a day not by your ear and see if it explodes. \$\endgroup\$
    – DKNguyen
    Commented Jan 4 at 20:13
  • \$\begingroup\$ In addition to @DKNguyen suggestion, to complete the experiment, leave it running for a day not by your ear and see if your ear explodes. \$\endgroup\$
    – Chris Knudsen
    Commented Jan 4 at 20:20
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    \$\begingroup\$ I've never seen an e-cap that was not abused by being deliberately exposed to relatively high reverse voltage explode. Doesn't mean it couldn't happen, but it's certainly not a common failure mode. \$\endgroup\$
    – Spehro Pefhany
    Commented Jan 4 at 20:33
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    \$\begingroup\$ I’m voting to close this question because its about medical issues, not electronics \$\endgroup\$
    – Davide Andrea
    Commented Jan 4 at 20:58
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    \$\begingroup\$ I don't understand how "how likely is it that a 100 µF capacitor charged to 5 V will explode and make a deafeningly loud noise?" is a question about medical issues rather than electronics. I do want to mention that the amount of energy stored in that capacitor is equal to the energy a penny gains by falling 2 inches. So if you try to imagine the loudest possible sound a penny could make by falling 2 inches (onto a metal cabinet, perhaps), it's pretty much impossible for the capacitor to ever make a louder sound than that, if I'm not mistaken. \$\endgroup\$
    – Tanner Swett
    Commented Jan 5 at 5:47

1 Answer 1

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The risk of a capacitor explosion causing deafness is negligible. But it's true that an aluminum can electrolytic capacitor, when it overheats (due to a short circuit, which can be caused by overvoltage or decades of degradation over time) can pop open, and some contents could leak out. A simple risk-reduction might be to squeeze a glob of ordinary silicone sealant out to cover the capacitor's can. It would probably muffle the pop and reduce the likelihood of crud being ejected.

Setting aside the capacitor issue, I wouldn't like having a circuit with a 30 watt power source next to my head/ear unless it's well protected against an overcurrent situation. A simple fuse or other circuit breaker component should be included.

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    \$\begingroup\$ I have an on/off power button. Is that enough? EDIT: I'll upvote when the reputation is high enough! \$\endgroup\$
    – talhos137
    Commented Jan 4 at 20:36
  • \$\begingroup\$ A power button is essential, but if your circuit developed a dead short, 30 watts might be enough to burn your skin or singe your hair a bit before you got to the switch. What is the power source for this circuit? \$\endgroup\$
    – Mark Leavitt
    Commented Jan 4 at 20:43
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    \$\begingroup\$ Application notes for handling capacitors are strictly against obstructing the pressure relief vents with glues of any kind which prevent their normal operation, so in case of pressure buildup, it definitely not vent safely and is more likely to explode. \$\endgroup\$
    – Justme
    Commented Jan 4 at 21:21
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    \$\begingroup\$ Don't use bathroom silicone sealant as when that cures it releases acetic acid which corrodes the circuitry (especially the Cu in the board). Better to use silicone for fixing the capacitor on the board. \$\endgroup\$
    – D Duck
    Commented Jan 4 at 21:38
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    \$\begingroup\$ You want neutral cure silicone. It doesn't produce acetic acid. And it tends to be noticeably more expensive than most silicone you find at the hardware store aka "regular silicone". \$\endgroup\$
    – DKNguyen
    Commented Jan 5 at 3:31

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