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Cranking a Car with Super Capacitors (Supercap)

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Kind: captions
Language: en

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Hi.
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I have jump started my car with AA batteries before, but now I want to try and see if I can jump start with supercapacitors or supercaps.
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As we know, capacitors hold electric charge like a battery.
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What's so super about these?
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This is a 100 millifarad, 6.3 volt electrolytic capacitor, but this is a supercapacitor rated for 2.7 volts, and it is 400 farads!
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(Outside voice) Stop yelling at the camera!
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Sh*t.
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So, at the same voltage, this supercap can hold 4000 times more charge compared to this electrolytic cap.
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Can you digest that? Of course not. It's filled with with chemicals.
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But that's a lot of charge for a capacitor, that is. Still, this AA battery can hold 20 times more charge compared to this supercap.
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The upside? The supercap has a much smaller series resistance of 3.2 milliohms compared to a typical AA battery, which is around 200 milliohms.
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So if I charge this to 2.13 volts and short it, it can deliver up to 666 amps of current.
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Coincidence? I think not. Because the current is equal to voltage divided by resistance.
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Let me charge it and short it.
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I'll charge this cap with a fixed 10 amps from my power supply.
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Bluhuhuh! Ha ha ha! You thought the cap was gonna blow, oh no no no! Sir, these expensive, I careful! (kiss)
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I scope the voltage and for the fixed 10 amp current, the rate of voltage rise is around 25 millivolts per second.
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OK. Let's first short the AA battery and see how much current it can deliver.
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9.6 amps.
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Now, let's short the supercap.
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Of course the resistance of this wire is gonna limit the current through the supercap.
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Oww! Sh*t! F*ck!
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Sh*t! I totally burned my finger!
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The clamp registered 376 amps and we still have 2.2 volts on the supercap.
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I think we are on the right track for the jump start.
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The downside of the supercaps is that they are generally rated for low voltages like 2.7 volts.
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So in order to increase my capacitor voltage, I have to put 6 of them in series in a bank to bring my voltage up to a maximum of 16.2 volts.
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But that means that my total capacitance will drop by 6 times to 66.6 farads.
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And I have to use high gauge wires to solder them together to make sure...
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ooh sh*t
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Never solder when your capacitor is charged. It could damage the capacitor or the circuit.
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I'm gonna discharge the capacitor with a low gauge wire to limit the current.
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Wow! This thing can deliver!
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Done. Now let's charge this capacitor bank to 14 volts like a fully charged battery.
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Supercaps have high leakage current.
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This one is around one milliamp that will drain the capacitor in around 13 days.
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I still have lots of time.
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First, I'm going to measure the normal current draw of the crank motor from the battery, and I'm gonna use my current clamp and connect it to my scope.
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First I have to set up a spot for my scope so it doesn't get dirty.
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(kiss)
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There will be a Keysight scope giveaway at the end of the video.
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My assistant here will help me demonstrate a point while I crank the engine.
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You hold on to the battery contacts while I crank the car. And we measure the current on the screen.
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[car starts]
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@#$%!
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Let's try again.
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Are you okay?
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Yes.
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You can see here that the inrush current into the crank motor is around 750 amps, and quickly drops to around 200 amps while we are cranking the car.
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When the car starts, it charges the battery, here, so that the current goes to negative 30 to 40 amps.
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Now if we look at the battery voltage we see that it starts around 12 volts, and when there is the inrush current,
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the voltage drops to 8 volts, and goes back up to around 11, and then when the car charges the battery, the battery voltage goes to 14 volts.
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So as I suspected, even if you hold on to the wires that carry a lot of current, you won't be electrocuted.
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So you weren't sure?
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Ow! You little...
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Of course I was 100 percent sure, because the voltage across the body is very small.
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Now I disconnect the battery positive to replace it with the capa...
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Dogsh*t!
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I have to remember not to short the battery.
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Now I connect the capacitors to the power lines with these clamps...
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Let's crank.
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Done! Perfect!
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Seems like the capacitor bank is good for one crank, as you can see the current jumps to 450 amp, and then quickly drops to 150 amps.
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And also the voltage drops a lot.
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You see here that uhh...from 14 volts almost, it drops to around 6 volts and then goes back up.
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Of course it charges quickly back up to 14 volts as soon as the engine starts going.
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So this can crank a car.
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So I have a new Keysight scope.
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It's like somebody took God and shoved him into a plastic box and gave him a touch screen too.
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It's oozing with power. It's a 1 gigahertz four channel scope, a 16 bit digital analyzer,
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an arbitrary waveform generator, an 8 digit frequency counter, and more.
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Wowwww!...
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(outside voice) Stop yelling...sshhh
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Now, I have a brand new lower model Keysight scope with most of the same features that I don't need since I have this one.
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So I'm going to give that one away to my supporters at Patreon.com as an ongoing token of appreciation.
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If you want to know how scopes work though, that's not what I do.
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But you can find very good information in the Keysight Oscilloscopes YouTube channel.

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