Hand Cranked Generator Charges Supercaps, Starts Car

Pity the lowly lead-acid battery. A century of use as the go-to method for storing enough electrons to spin the starter motor of a car engine has endeared it to few.  Will newer technology supplant that heavy, toxic, and corrosive black box under your hood? If this supercapacitor boost box is any indication, then we’d say lead-acid’s days are numbered.

To be fair, we’ll bet that number is still pretty big. It takes a lot to displace a tried and true technology, especially for something as optimized as the lead-acid battery. But [lasersaber]’s build shows just how far capacitive storage has come from the days when supercaps were relegated to keeping your PC’s clock running. With six commercial 400F caps and a custom-built balance board, the bank takes a charge from a cheap 24V hand generator. The output is either to a heavy-duty lighter socket or some automotive-style lugs, and the whole thing is housed in a simple box partially constructed using energy stored in the bank. Can the supercaps start a car? Stay tuned after the break for the answer.

Although we’ve seen supercaps replace a motorcycle battery before, we’re a little disappointed that the caps used here only have a 1500-hour life – lead-acid wins that fight hands down. But this one gives us lots of ideas for future builds, and we’re heartened by the fact that the supercaps for this build ring up to less than $70.

82 thoughts on “Hand Cranked Generator Charges Supercaps, Starts Car

    1. Because engine compartments tend to stay cool (especially during summer), right? Not that it’s really an adequate product for most people to begin with.

      The lead acid battery is here to stay for a long time still…

      1. The caps cost $60-70/ea on digikey, not including the balance board, and there’s ~5 of them.

        He’s a nice guy, but keeps doing a thousand variants of “put together a bank of supercaps, charge them in some way, then experiment with how long they’ll run things.” He’s been at this for *years*, changing little.

        You can calculate the exact energy available, so all of his experimenting is pretty pointless. The issue isn’t technical. It’s cost.

        1. I am not sure what capacitors you’re looking at but the caps he uses in his project are selling for $12.00/each at mouser. A bit pricey for me, but not an outrageous cost for a hobby project.

          1. I see, however a freewheel implies that the output is going faster than the input… most cranks already do that. The problem is kickback where the engine runs in reverse… I don’t think you could solve that with a simple freewheel.

          2. If you are going to bother manual starting an engine… the easiest, safest and most long term reliable way might be a spring starter http://www.springstarter.com/ …. no it doesn’t self recharge but it doesn’t really have any of the other issues an electric starter or direct crank has either. And once would it does stay wound… with starting performance similar to an air starter.

          3. @Gh0stWriter88. Do the math on the amount of energy stored in that spring. Very cool device. Never heard of it before but now I think I’m going to buy one. However it would be absolutely terrifying if that spring snapped… I know its in a steel shell to protect from that, but that much stored mechanical (spring) energy in one place makes me nervous!

          4. Yes, I think they have been around a very long time though… so the technology is not new. I’ve seen people using them on old generators or other equipment that isn’t started often enough to use a battery…

          1. That’s not a solution because in a kickback the crank flies backwards and hits your arm with its momentum. The clutch could be disengaged – it would still break your arm.

      1. Being fully aware that I am stating a FACT in the face of what some KNOW ABSOLUTELY to be the truth:

        Automotive–and aircraft; and shipboard; and choo-choo train, and farm tractor, and…–alternators are A.C. MACHINES and are NOT self-exciting.

        Time to come into the real world and learn about ALL those electricity parts which you’ve ignored all these years, because you just KNEW that hacking together a (not-well-understood-anyway) program for a not-well-understood microprocessor would solve all of your electrical and electronics shortcomings.

        Not to put too fine a point on things: the operative word here is “LEARN”.

        1. Finally some sense, while we’re talking sense and learning, air, air start is used on many emergency vehicles and cold climate trucks.
          one very good reason for not hand cranking is that few if any modern vehicles come with a manual ignition retarder, it’s kind of necessary on a petrol engine,and all the hand start diesels I’ve ever come across have some form of decompression device, it holds the exhaust valve open while you spin the stupidly heavy flywheel, once spinning you release the decompression lever and either the engine starts, doesn’t or kicks back and rips your arm out of it’s socket.

        2. Alternator can self-excite, I have it in my car.

          The key there is remanent magnetisn in the rotor. It’s decaying with time grom the last excitation. So if I start my car after 5 minutes, it just works, but after more than 2 days it needs to push the pedal and get much higher rpms, than normal driving, because the voltage on output is constant times rpms times magnetic induction.

          Whole loop contains the alternator, 6-way output rectifier (in the alternator’s casing), 3-way auxiliary rectifier (in the casing too) and semiconductor regulator (external). The regulator is powered up from the auxiliary rectifier and exciting the alternator.

          Even when the engine is insanely small for USA (yeah, I’m in Europe), I don’t want to crank it up manually. There is no decompressing lever like old diesels has. I consider totally impossible to boost it manually to 4000 rpm needed for starting the self excitation after a few days without usage.

          If I need to crank it up manually without battery, I’d do one of these 3 things:
          1) 3-phase transformer attached to the alternator (yes, it’s 3-phase inside) to step up the voltage, 6-phase rectifier on the secondary, big capacitor and DIY semiconductor regulator able to handle 3V – 100V on input optimized for the task. Whole transformer should be switched off by 3-pole relay just after it excites.
          2) add some permanent magnets into the alternator’s rotor. It will need some experiments – too small will not excite and too big will not allow regulation down enough.
          3) secondary generator with permanent magnets for power up the excitation – that’s the way, how several kilowatts to several thousands kilowatts generators are excited.

        3. Fortunately once started most piston engine planes have mags, actually dual redundant magnetos. Sure your avionics will take a dump and even some of the old dials with electrical gyros will stop, this is why many small aircraft pilots carry along a handheld air band radio and all carry a red flashlight to read remaining instruments at night. My radio even lets me read VOR navigation beacons and do an instrument approach. Bigger planes have more than just the one alternator and battery system.

        1. @[Thinkerer]–
          Thank you VERY much; what a beautiful response, at so many different levels!

          As I was reading this article’s responses, I kept saying to myself, “What a tragedy that all these highly intelligent young people have (obviously) never, EVER heard of the aircraft inertial starter, which made such a difference in the WWII war effort.”

          Never stop learning; never stop sharing; never grow old (and that goes for you young people, too)…

        2. I just had an Happy Moment listening to that. Inertial star, Air-start, recoil/spring/whatever. Electronics are fun and lovely, but nothing except NOTHING compares to the sound of fine iron becoming power sans electronica.

      1. Modern engines are lower compression than older engines because leaded fuel had higher octane. Today’s lead free fuel has a lower octane and ‘pings’ in higher compression engines.

        1. I’m not sure this is universally true regarding modern engines. My motorcycle has, if I remember correctly, 12:1 compression and runs without pinging on 89 octane at summer temperatures, is completely stock and puts out about 190HP. My car is totally stock, has port injection, an 11:1 compression ratio and is able to run safely on (as stated in the owners manual) 87 octane and puts out 435HP from only 302ci. Those compression ratio numbers are ballpark similar to older motors from the days of leaded fuels. I believe advancements in engine control makes all that possible without detriment to the engine. Motors with direct injection can run at even higher compression ratios.

          1. A high compression engine can run low octane fuel by retarding the ignition. That’s what modern ECUs do when they detect engine knock. It just reduces power output.

            A pre-computerized engine with 11:1 or higher compression ratio will run on 91 oct (95 in the EU) but it won’t stop! I’ve tried – I once accidentally put it in an old Saab 90 and while it did run, turning the key to off, the engine would just keep chugging along by dieseling the fuel. It had to be fueled with 93 oct (98 EU) minimum.

        2. Actually no the J35Z engine in a Pilot has a compression ratio of 10.5 to 1 which is much higher than cars that had hand crank start engines such as a Model T which was 4.5 to 1 stock.

  1. Starting the engine requires, say, 200 Amps during two seconds from a nominal twelve volt battery. The battery (or the capacitor bank) then needs to be recharged. Supposing the hand powered generator supplies around one Amp when cranked, that means a minimum of 200 x 2 seconds = about 7 minutes of cranking, minimum.
    I like it, sure there is a long way to go to be competitive with batteries but it’s a cool gadget he has there.

    1. And if the temperature is cold (it is 3 degrees F outside right now) the engine cranking requirements can easily approach 500 amps, and maybe be needed for more than 2 seconds.

    2. Bear in mind he shows solar panels being used.

      Say a dying battery is fitted and you are stuck the opposite side of the country to your house (hypothetically speaking),
      7 minutes at night of manual labour is better than trying to get a recovery vehicle at midnight and/or them replacing your battery under your insurance policy thus affecting your no-claims (making your insurance higher).

      back to the solar panels, They would be the most beneficial during daytime, however I’m not sure what the BMS board leakage resistances are, though I’d guess the pack may not have enough charge left at night (will presumably cut down on the 7minutes quite a lot I’d guess/hoped)

      1. Good idea, and a high amperage relay to bypass the resistor when immediately need (Engine cranking and ECU stuff) and when the engine is running (bank presumably recharging).

  2. I think a hybrid would be best a cap bank to supply the short high current to start the engine, combined with a chemical battery to provide the storage capacity to run the radio or lights while the engine is off. It could even be smart enough to turn off the power if the battery is getting low enough to endanger starting the car.

    1. One of the largest uses for supercaps is in fact meeting surge current demands for hybrid and electric transit vehicles. The caps provide a sink for regenerative braking and acceleration. The main traction pack provides more energy density, and lasts longer because of lower currents.

  3. the principle of operation of the device he built is the same as these pound shop lamps that are powered by a hand crank, with the same issue: the DC motor is more or less a constant voltage source that depends on the speed.. this means you need to know how fast you can spin the crank, otherwise you may overcharge the capacitors and make them die. Of course I guess this takes some time on a big bank of supercapacitors, which leads to the next problem: the voltage at the terminals of the DC motor depends on the level of charge of the capacitors.. if this is very low, it means you have to spin the crank very slowly, otherwise all your energy is wasted heating up the motor, plus the torque of the motor might be quite high… This makes this a less than ideal way of charging the capacitors. I think this systems needs a power converter somewhere that turns the DC motor into a constant current source, limits the voltage of the supercapacitors, etc…

      1. It’s a balancing circuit based on diodes. If you crank the handle hard enough, it will still overcharge the caps because the diodes pass milliamps of current while the motor can supply amps – you saturate the overflow tube and the sink runs over.

  4. I downloaded all of the supercapacitor data from digikey into excel, reformatted a ton of numbers, and calculated the capacitor with the best energy to cost ratio. It was the capacitor he used, at 121 Joules per dollar, ignoring the capacitors in the $70+ each range. If you are making some giant setup, use www digikey com/product-detail/en/maxwell-technologies-inc/BCAP3400-P285-K04/1182-1037-ND/4896902 at 194 Joules per dollar (With a 0.28mohm ESR). Add some dots to make it a url.

  5. Looks like a marketing potential here to replace those lead acid gell cell booster packs. Just give this puppy some crank, hook it up to your car’s jump terminals and turn the key.

    No need to keep it topped up so it won’t go bad like the battery boosters. Won’t go bad just sitting around. Won’t run out of juice until *you* run out and become physically unable to crank it.

    Only four easy payments of $49.95!

    1. Not really.

      I’m 99% certain that particular crank generator’s output is DC to begin with, given that when the diode is not present the motor runs in a single direction.

      A diode bridge helps when your input is AC not DC. The generator (likely just a brushed motor being used as a generator…) is already outputting DC. The diode is just to prevent the pack from causing the motor to spin when not cranked.

  6. How would the super caps work for a kids 12v car. It has now 12v 12AH led acid sealed battery. Problem is that they use the car it sits there with dead battery which kills the battery for not being recharged. Supercaps seems perfect, let it uncharge then with 12v charger recharge quickly. Only not sure how long it would run on the supercap.

    Any thoughts on this?

    1. If you’re in the US, Lowes sells Kobalt 24V 1.5Ah lithium ion cordless tool battery packs for $10 each. I have a few I’ve used for various purposes (none of which involved Kobalt tools) and they even have 6 genuine Samsung cells inside. I think harvesting a few packs worth of cells, then rebuilding those into a single 12V pack would be a pretty good option. For $40 you could have a 12V 12Ah battery that would hold it’s charge for a long time. You’ll have to do a little work to protect the batteries, but I think that problem is relatively easy to solve. Maybe a battery management board from a 12V lithium ion battery pack may be sufficient?

  7. Great idea. However, if you need a real jump starter, then you can buy one here http://topproducts.com/reviews/best-jumpstarter.htm. We enjoyed your blog post, and we work for http://www.topproducts.com ‎and we will be putting your website in excel to come back later and bookmark. We thank you for your approval consideration. We are a good company, and we give back to the community, as we are not spam. We take the time to come to a few web pages like your, please and thank you. Rhea.

  8. my thought was, #1- back current though small through the diode- long term, an isolation switch in series with the diode, #2- the cranks when installed in the end panel ie opposite the cigarette lighter socket, would be better use of the internal space, leading to more room for extra caps or narrower box… i would like 4 of these for my cars

  9. Self-exciting alternators are very old news. They’re “permanent magnet AC generators” to be precise and two very common examples are the Lucas alternators used in vintage British motorcycles and the alternators used in every Harley big twin since 1970. They cost more than alternators which get their excitation from an external battery, but they’ll generate enough power to kick start those motorcycles with only a capacitor for storage. A Kubota alternator is very compact and self-contained (unlike the other two) so if you want one to experiment with I recommend those. A modified version (takes a Harley drive gear) is used to convert from old DC generators.
    Regarding hand cranking auto engines, that’s stupid vs kicking but designers found it extremely cheap to place the ratchet on the end of the crankshaft and the Kettering starter was invented so early in automotive history it wasn’t considered necessary to do better if it even slightly increased production cost/ Automobiles should have had KICK starters with positive stops and slipper clutches like contemporary motorcycles, since legs are far more powerful than arms. Since only one or two cylinders are on the compression stroke at a time kicking an auto engine would be easier than say a Harley with high compression but fewer cylinders. Small engines like Maytag washer motors and Cushman scooter engines have simple kick starters should you want one for a generator etc and don’tt care for pull starting or have medical issues. Pull starting is cheap (see a theme?) but kickstarting works far better.

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