How Long Does the Sinden Lightgun’s Capacitor Take to Discharge?
When working on a Sinden Lightgun, whether you’re fitting a trigger mod or doing other maintenance, you’ll usually hear the same warning: be careful around the big capacitor in the handle.
That capacitor powers the recoil solenoid, and when fully charged it holds around 20 volts. If you accidentally short its terminals with your hand or a tool, you could get a sharp (and very unpleasant) shock.
But that raises a sensible question: how long does it take for the capacitor to discharge after you unplug the gun?
It’s easy to say “wait before you open it up,” but what does “safe” actually mean in practice? I decided to put it to the test.
Setting Up the Test
To measure the discharge rate, I connected my multimeter directly to the capacitor’s terminals and watched the voltage over time.
Since the capacitor was already flat, I first needed to charge it. Plugging the Sinden into my PC and enabling recoil in the Sinden software sent the voltage climbing almost instantly. Within just a few seconds it reached its peak: about 20.8 volts.
With the capacitor fully charged, I unplugged the gun from USB and started a kitchen timer at the exact same moment to keep track of time. (My timer only runs up to 20 minutes before looping back to zero, so in the video I made a note of that when it happened.)
Watching the Voltage Fall
Right away, the voltage began to drop:
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After 5 seconds: Already down from 20.8V to around 15V.
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After 45 seconds: About 8V, so the rate was clearly slowing.
This is potentially an important point. The capacitor doesn’t discharge at a constant speed. The rate of discharge is proportional to the voltage. When it’s full, it drains quickly, but as the voltage drops the rate slows down.
The best way to think about this is like a barrel of water with a hole near the bottom. When the barrel is full, water gushes out with high pressure. As the level gets lower, the pressure drops and the flow slows to a trickle. Capacitors behave the same way.
Key Results
Here are the main milestones I observed:
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At 11 minutes: The voltage had fallen to about 1 volt. That’s less than a standard AA battery (which is about 1.5V), and completely harmless to touch. At this stage, the capacitor is effectively safe.
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At 1 hour: The voltage was down to 0.09V — less than a tenth of a volt. You could leave it another hour and it would still never quite reach an absolute zero, but at that level it’s functionally discharged.
So in practice:
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After about 1 minutes, the capacitor should already be safe to work around. Make it 15 to be safe.
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If you’re extra cautious and want absolute peace of mind, leaving the gun unplugged for an hour will guarantee it’s flat.
Double-Checking the Test
One last concern I had was whether the multimeter itself might affect the discharge by providing a path for current. To check, I repeated the test without the meter connected and spot-checked the voltage at intervals. The results were essentially the same, so the meter wasn’t influencing the outcome.
A Note on Safety
It’s worth pointing out:
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This test applies only to the capacitor inside the Sinden Lightgun in its normal setup.
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It is not a universal benchmark for all capacitors in all situations. Capacitors can behave differently depending on their type, value, and circuit design.
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And of course, your mileage may vary. If you don’t have the means to measure voltage yourself, always err on the side of caution and wait longer than you think you need.
Conclusion
So, how long does the Sinden Lightgun’s capacitor take to discharge?
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In about 11 minutes, it’s already down to 1V and safe to handle.
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After an hour, it’s essentially flat.
That means if your gun has been unplugged for any reasonable amount of time, you don’t need to fear the capacitor when opening it up.
If you’d like to see the full test, including the live measurements, timer, and results, you can watch my video here:
And if you’re interested in modifying your Sinden, you may also want to check out my guide to the V3 Sinden Trigger Mod: