Lets discuss super capacitors

Seems to be more talk of this going around but I'm not seeing a whole lot on ADV. I finally decided to give it a go since the battery on my KTM is shot and I've been watching super/ultra capacitor videos on YouTube for a few weeks now. Ordered my caps today and will post the details of the build once they arrive. So have any inmates made the swap? What was your impression?

If you're saying, "WTF is a super capacitor and why would you put one on a bike?"
-Its basically a rechargeable battery that is capable of enough charge/discharge cycles to be the last one you'll ever install in your bike. The downside is they have less capacity for a given size and a much faster leakage rate than batteries so on their own they probably won't start your bike if left alone for a day or two. On the upside they suffer no ill consequences from being drained flat. In fact the only way to really hurt them is by reversing polarity or exceeding the maximum cell voltage (which can be largely mitigated during the build). They can be charged and discharged extremely rapidly (seconds) or in a pinch from a small source. One example I found the guy had made a hybrid battery/SC combo for his car using 10 rechargeable AA batteries to keep his SC topped off. Many others are using cheap $10 solar panels. Once the engine starts the SC is recharged quite rapidly.

Some vids:

Build:
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In the bike:
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Here's a SC/LiPo hybrid starting a car after 10 days (he ends up destroying his LiPo pack due to not installing voltage regulation between the LiPo and SC:
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Most Google searches on this subject seem to result in a lot of troll posts so lets try to keep this informative and not get into a "why would you want to do that??" flame war.

For me, the reason is simple: I enjoy knowledge. Batteries are evolving extremely fast right now and I believe super caps are going to play a major role in that evolution over the next few years. SLA's and even LiPo's are hardly the end-all solution to our power needs on a bike. The KTM is a good platform for me to experiment on since:

1. It has a kickstart backup so flat caps aren't a big deal.
2. Convenience. It needs a new battery anyway so why not tinker?
3. Its a light bike already so shedding a couple pounds has more effect than on a 500lb bike. A LiPo would be even lighter but I've had bad luck with them on bikes. Not to mention the fire hazard.
4. Its doesn't have much of an aux load with its limited accessories.

They are capacitors, not batteries. They will only hold a charge for hours, maybe days. You can't park it for a week or two and expect it to start.

Super capacitors are neat. A few years back I saw a jump start pack that used them in combination with a Joule thief. You connect it to a nearly dead battery, and it pulls what little power there is left in the battery and charges the caps. At that point the caps are then fed into the vehicles electrical system with enough kick to start an engine.

That Buell bit was on Hackaday a few months back. The charge rate on the caps can be so high that it will act like a short circuit. Not all bike will accept such abuse. I also recall that the discharge rate on the caps was beyond the manufacturers recommendations.

I've ordered 6 of the 350 Farad caps:
http://www.mouser.com/ds/2/257/Maxwell_BCSeries_DS_1017105-4-341252.pdf

Wired in series this gives a maximum voltage rating of 16.2v. As I mentioned caps can be damaged by exceeding their maximum voltage. Well bc of manufacturing differences and such, its possible that some cells might accept a charge more readily than others, creating an imbalance. With a charging voltage of 14.4v, it might be that the extra 0.3v per cell gives me enough wiggle room to avoid adding a balancing circuit, although I think I'll add one just so I'm not feeling paranoid about needing to test individual cell voltages all the time. The simplest method of balancing the cells would be to wire a resistor to the +/- of each cell thereby increasing its leakage. This is rather undesirable however since that means I'd be amplifying the biggest drawback that this system has by making them discharge even faster when not being actively charged. Probably the best passive method of balancing is wiring in LED's and diodes to create a circuit that only discharges an individual cell when that cell voltage exceeds a certain amount.

Maxwell's are on the pricey end of SC's but they have a good reputation whereas the cheap ones do not. I'm hoping to make this a once-and-done battery replacement so I don't mind spending a few extra bucks. I ended up about $75 for the caps. Plus I'll still come in well below what I would have spent on a Lithium.

All correct. I referred to them as batteries only to keep it in layman's terms for somebody tuning in that has no electrical knowledge. Yes, an SC pack alone won't start a bike that's been left in a garage after a week not on a tender, but then there's a lot of guys that have that same problem with an SLA that's a few years old. Keeping it on a tender, using a solar panel, or making a hybrid battery/SC combo are all cheap ways to solve this issue.

The guy that puffed his LiPo has another vid starting a car with a dead battery on a cold morning simply by hooking up his uncharged cap bank. They have some very practical uses.

Also correct that a discharged SC pack will act like a direct short. That's why the LiPo died - he drove the LiPo cell voltage below their tolerance when he shorted it to the caps. This can be dealt with in a variety of ways so as not to tax the bike's electrical system. I'm still figuring this all out but with a shunt type voltage R/R like many bikes have, all unused load is dumped to ground anyway so might not need additional protection.

I have a pack of seven Maxwell BCAP0010 2600F 2.5V I use as a jump start pack. It kind off scares me when it's fully charged.

Ha. Could double as a field welder. Doing anything to keep the cells balanced or don't bother since I'd imagine they're mostly discharged?

My understanding of capacitors is that they are an open connection in direct current (DC). Under alternating current (AC) they have a reactance and impedance related to the frequency of the AC voltage. The current in all cases is the product of the capacitance with the derivative of the voltage with respect to time. Some electric cars have incorporated 'super' capacitors as energy storage components due their high power to weight ratio. A capacitor can turn an electric motor.

For DC electrical systems (such as those used on motorcycles and cars) the capacitors will only come into play during transients. However, if the entire electrical system was converted to AC then capacitors could act as energy storage components (like a battery). There may be a circuit for DC/AC conversions and vice versa that is highly efficient which would make capacitors comparable to batteries, but I don't know of any. A battery is necessary for a DC electrical system to store energy.

Some google searches show the energy storage capacity (energy/Kg) of super capacitors is only ~ 5% of a comparable Li-ion battery with the cost per watt hour (energy) ~ 40x that of a Li-ion battery of the same size. But, the super capacitor lasts > 100000 cycles and has much higher specific power (watt/Kg). Current research using nano technology is hopeful that super capacitors will replace conventional batteries.

I am afraid you are a little confused. The energy stored in a capacitor is 1/2xCx V^2. They do not store AC energy, though they can pass AC current. A capacitor is just a type of rechargeable battery with the properties you discovered with your Google search.

A capacitor won't store DC current, only transient current - such as AC or a DC voltage over a short interval of time. As such, only transient voltages apply to capacitor power - such as AC. Unfortunately, I can't explain this without going into calculus but maybe someone else can. Wikipedia has an accurate description: http://en.wikipedia.org/wiki/Capacitor

In a DC electrical circuit, the battery is constantly storing and discharging current to supply power to the spark plugs, lights, etc. A capacitor can operate similarly in an AC system. But, a capacitor in a DC system will not behave like a battery.

Wrong again pal...capacitors have been used as battery substitutes on motorcycles for many years, for example the classic British bikes of the 60's and 70's were equipped a Lucas 2MC capacitor and will run without the battery thanks to that because IT STORES ENERGY from the charging system (an alternator, full wave rectifier, and a zener diode) and its output approximates DC well enough that the points/coil ignition system can function without a battery. Whether a modern bike equipped with fuel injection and electronic ignition would work with a capacitor substitution gets much more complicated...
A discharged capacitor DOES in fact look like a dead short when first connected to a DC supply and the inrush current can be a problem if it is not limited in many cases, especially with a very large capacitance like the OP is experimenting with.

I am certainly familiar with the calculus used to describe the operation of capacitors. The voltage is the integral of the current into the capacitor divided by the capacitance and the current is dV/dt x C. However, that does not change the fact that the capacitor stores charge (i.e. electrons, i.e. energy) A charged capacitor or anything that has capacitance, like cable has energy stored in it, and when discharged through something like a motor, can do work, or it kill can you if the voltage and capacitance is high enough. Is this starting to make sense? I think what may be confusing is that when capacitors discharge you notice the voltage changing significantly because the capacitors you normally deal with have such low capacitance, like millionths of a Farad. When you start to deal with capacitors with lots of Farads, the voltage does not drop that much. The 350 F caps he is talking about could supply 350 amps (plenty to start a large truck) for a second and only drop their voltage by one volt.

Well thankfully we're all humans here and our skin is resistant enough that we can handle 16v of capacitance without gloves and The Minion Suit. Also you missed that I'm wiring 2.7v 350F caps in series, so it works out to only 58 Farads for the entire bank [(1/C_TOTAL) = (1/C₁) + (1/C₂) + (1/C₃)]. But just in case I get the urge to go licking some terminals here's a self portrait so you can rest assured that I'll be safe:



Can't lick for shit in that thing.

A DC capacitor most certainly works on a DC circuit - had a smaller one on my XR400 which I converted to DC and used a single >15v cap in lieu of a battery since I just wanted a voltage sink. Also if you'll notice on the videos in the 1st post, there is one of a Buell having its battery replaced by a supercap assembly and started. No muss, no fuss, no collapse of 1/3 of the universe.

Here's another on a Honda/Lafawnda:
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The technology is already here and it works (well technically its been around for 100 years or so) - just hasn't quite made it into mass production yet. A few more years and cell phones, cars, etc etc are going to be utilizing hybrid systems. I certainly wouldn't mind a phone that needed charging 2-3x/day if it only took 10 seconds to charge.

Balancing resistors.

It has a board with resistors to balance them.

I got bored and conducted a rudimentary experiment. I connected a crappy 35 watt hid ballast and lamp to my capacitor bank and a voltmeter. After 13 minutes the voltage dropped from about 16 to 11. These are 2600 farad capacitors.

I'd really like to hear from somebody familiar with volt reg/rec on bikes. As I understand it, being a shunt type, which means to me that the stator is always making maximum output for a given RPM, any unused amperage just dumps to ground. So would a cap bank at 0v in place of a battery cause issues? I don't think the VRR would mind, but would there be anything left for spark? This is all assuming the caps have gone completely flat. I really don't want to have another bike with a strange kick start ritual. Obviously they'd only drop a few volts at most during a charged e-start and wouldn't cause any issues at all.

I don't think there'd be any issues. Vespa racers have used battery replacing caps for decades and I don't recall any problems associated with flat caps.

I think what you're describing is a magneto ignition. I must stand by my statement that a capacitor will never behave as a battery in a DC electrical system. However, I am not saying that any electrical system cannot operate with a capacitor as an energy storage device - just not a DC system as used on current motorcycles and automobiles.

Edit: Maybe this will explain the difference between batteries and capacitors better than I, but probably not for those true believers: http://engineerexplains.com/answr/CapacitorvsBattery1.html
I recognized my statements have touched a nerve. While I would like to think my education and experience could explain my statements better, they apparently cannot. This is yet another topic I have learned not to breach on an internet message board.

12v DC is 12v DC. A battery stores a charge chemically while a capacitor does it more-or-less mechanically, but as far as the circuit is concerned its exactly the same - its stored energy and therefore has the potential to do work. Caps are often added parallel to the battery in modern-day vehicles to deal with demand spikes when running high powered amplifiers to keep the lights from dimming - had one in my car 20 years ago and again in my 2004 truck. I'm really not sure where your information is coming from mate. Spend 30 seconds on YouTube and you can see capacitors used in lieu of batteries in a wide variety of DC applications.

Here's an ultra basic explanation of a capacitor in a DC circuit:
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Edit in response to your edit/link: Yes, normal capacitors suffer from an extremely rapid leakage rate meaning their voltage will return to zero in a matter of minutes even if unhooked from any circuit and just sitting on a table. Super capacitors however, have much less leakage and therefore are able to maintain voltage for several days or even weeks. Granted after a week it probably won't have enough voltage left to start an engine, but that can be addressed by adding an external power source (battery tender, small 12v battery, etc etc). And no nerve struck, just a misunderstanding/miscommunication. There are several videos in this thread alone showing exactly what you're saying is impossible. I'm assuming you didn't watch them and therefore are sticking to your guns but meh, I can't make you watch them.

Back on subject...

I'm adding several of the videos that inspired me to try this just so anyone reading doesn't have to dig around as much as I did.

Here we have a 2.7v 350F SC bank rigged as a hybrid with a $40 4.2 Ah LiFePO4 battery through a 0.2ohm 50w resistor. Good vid in that he actually posts real world numbers when used to start a small car. In summary: 213A drawn by starter, battery supplied 14A max (3.33C), alternator supplied 3A back to battery once idling (0.7C), minimum voltage @ caps was 9v. I don't expect his battery to last long without fairly frequent balancing. A simple commercial balancer could be added for about $10 and left in place although it would discharge the pack faster.
<iframe width="560" height="315" src="https://www.youtube.com/embed/LX_o3hl2Dv4" frameborder="0" allowfullscreen></iframe>

Same guy starting a CBR 600F4i (fuel injected bike) using a 2.7v, 400F bank (that would be 66.7F) with no battery backup charged to 10v. 77A drawn during cranking. In one of his vids he says that he can still start the bike after 3 days of sitting on caps only. By the 4th day he has to bump start it since he lives on a hill. So at least one person is managing to start the bike even though the caps are empty.
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Same CBR at idle with 55w headlight on and cap bank sitting at 12v. He didn't specify how long the bike had been idling but does mention in the comments that the cap voltage increases to 14.4v while riding. He also states that he normally runs an HID conversion and had to add a switch since the high current draw of the HID warmup was causing the caps to dip too low to start the bike. Once running he can switch the HID on and use normally.
<iframe width="560" height="315" src="https://www.youtube.com/embed/MlMdeyt5yWA" frameborder="0" allowfullscreen></iframe>


This one the guy is testing the actual Ah of two cheapo 2.7v 400F SC's wired in series (makes it 200F). TLDW? Ends up having a peak of 277mAh. Not bad for rattle can caps.
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Maybe because it's incorrect? If somebody else doesn't jump in here and correct this, you touting education and experience is going to derail the thread into a debate over witchcraft and sorcery.

Capacitors are DC energy storage devices. That's what they do. That's ALL they do or ever did. That's precisely what they do in an AC circuit or a pulsing DC circuit: collect and release their electrons. There is no way to make that description any more simple. There's no calculus involved, except to describe how much energy a capacitor might be holding at any given time.

I'm personally blown away that such large storage capacitors have become reality but, people are posting videos of them working and you still don't believe it. No, the capacitors on motorcycles were not magneto ignitions. Magneto ignitions directly charge the ignition coil and nothing else. The examples cited had normal, 12V charging systems, with regulation of some type and all the associated losses. They were most often single-phase systems that had relatively long periods of no available voltage (in terms of crank rotation). In order for the bike to still run without a battery, a capacitor was used to temporarily store the energy created by the charging system, to be available for the coil at ignition time.