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Super-capacitors instead of a battery?
Happened to see the following video on Youtube... Just wondering if their would be any worth-while efficiency benefits by using capacitors instead of a chemical battery??
Towards the end, he talks about being able to quickly recharge the caps using a solar panel, when the car is stationary. Could you perhaps uses a smaller and lighter battery - with the main whack of starter current provided by the charged capacitor bank?? http://www.youtube.com/watch?v=GPJao1xLe7w |
To take advantage of any improved efficiency in recovering stored energy, the electrical system of the car would have to be changed. Your alternator would not work very well without a battery any more, as you cannot charge a capacitor without the voltage rising and alternator regulators are designed to maintain a constant voltage.
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I asked around about this a couple months ago and along with what UFO said, the computers on modern really need the constant full power a battery provides. With the capacitors dropping down to 10 or 11 you could possibly get voltage spikes that would destroy the sensitive computers. However, if I had a cheap old CRX or something of the like I wouldn't hesitate to give capacitors a try.
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fyi
the youtube 4 lasersaber boostpack has been updated....clearly ultracaps have a higher cycle life and store/release dc power differently than agm battery |
I'll be updating my post on this soon...
My motorcycle, with its very low 1.25mA parasitic drain, only takes about 3 days until the 400F capacitors discharge to the point that it won't start the bike. Using the 3000F capacitors in the video would be very expensive, but would likely give about 3 days of sitting time before they failed to start a vehicle. Combining the "Boostpack" with a small LiFePo4 battery is certainly the proper way to eliminate the lead-acid battery. My hesitation with the LiFePo4 battery is that charging them in sub-freezing conditions will cause permanent damage. To extend the life of the battery, one would need to either ensure it's warm enough to accept the rapid charge an alternator would supply, or limit the charging to a sufficiently low amount as to avoid damage. I have not found a source of info that lists the safe C-rate to charge. My question is- Could a power resistor be put between the LiFePo4 battery and the capacitor to limit the rate of charge/discharge to the battery? Would this still allow the battery to eventually come up to full charge, and maintain the charge of the capacitors when the car is idle? The goal is to get the car to rely on the capacitors for starting/charging, but have the battery maintain the capacitor when the car is off for extended periods of time. Quote:
I would imagine that in a car, the alternator would detect full voltage and then turn charging off until voltage sagged below a certain threshold... another thing for me to test. I'll buy that LiFePo4 battery today so that I can test, and answer some more lingering questions on this topic. |
If you want a light weight battery, have you guys considered a Dyna-Bat from Performance Distrubutors? Weighs 13 1/2 pounds.
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Some motorcycles have alternators. Solid state components have a working range of voltage between the indeterminate condition and burn through. A small battery is used in a computer to maintain a voltage while the power supply is off. Dampening capacitors are used in circuits to prevent spikes in voltage or current. Regulators can control generator output by limiting current to the field windings. Old tractor generators had a cut out switch to do this. A heating element could be used with the LiFePo4 battery to bring it to temperature and act to limit current as well. Time to do some electrical engineering homework.
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I keep getting distracted by other projects and then get chicken to just put the darn LiFePo4 in my car... kinda wanted to wait until a battery died to do this.
I've been running just a supercap in the motorcycle since January. Rode it to work tonight, in fact. It will still only go 3 days before draining down too much to electric start. I've noticed zero issues with the charging system, maintaining voltage, etc. Runs as if I have a battery in place. I'll take your prodding though and get that battery in soon. It's ready to go, just haven't actually installed it yet. I also wanted to put a current limiting resistor in, but maybe I'll skip it and see if I fry a battery. I suppose risking $70 in the name of science (tinkering) is worth it. I still don't know why this is in the unicorn corral. My motorcycle, and posted videos, prove you can replace a battery with super caps. That said, I'll probably let this thread die and post updates to the thread I started, or the original thread on this subject. |
Its probably in the unicorn corral because there is no real fuel saving to be achieved by doing so.
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this has already been done by Mazda i eloop. Don't know why its in the corral
http://www.mazda.com/technology/env/..._sec1_pht1.jpg |
Again, without a variable alternator and a dc to dc converter to convert the higher voltage to 12V replacing your battery with a supercap is useless to get any real fuel savings. Also starting with a super cap you risk burning out your starter motor due to an undervolt condition. In the unicorn corral it stays
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Various sources suggest that lead acid batteries have about a 50% charge efficiency. There is an inverse relationship between charge efficiency and state of charge. At about 50% state of charge, the charge efficiency is over 90%. However, lead acid batteries are normally operated at nearly full charge, which has a charge acceptance efficiency of 50%. Capacitors have almost a linear charge efficiency of 95+ percent. This should translate into fuel savings, albeit very small. I'll also note that LiPoFe4 batteries are more efficient than lead at accepting a charge, especially near the full state of charge. I believe they are somewhere around 80% efficient. No unicorns here, just science. |
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On your typical car trip, the energy used in starting the engine is negligible. The Mazda system uses the capacitor system in an intelligent manner. It doesn't even try to use it for starting. It charges the supercap under braking which reduces energy wasted on the brake pads and rotors and stores it in the cap. It may also charge the cap up at idle taking advantage to try and boost the break thermal efficiency of the engine. It then releases it reducing alternator load on the engine and thus putting the power to the wheels saving fuel. It is thus a light duty hybrid. I'm not saying that replacing a battery with a cap might not reduce fuel consumption in some infinitesimal amount, but you will never be able to show it. |
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Unicorns don't exist, but supercaps do, and they are capable of replacing a battery. I saved about 10lbs in weight by eliminating the battery in my motorcycle, which isn't much, but if you consider that the bike is only 400lbs, it's 2.5% of the total vehicle weight. If I could eliminate the 2 enormous batteries in my diesel truck, I could save 80 lbs. The advantages of eliminating the traditional battery extend beyond the tiny gains in electrical efficiency. We're also talking about weight reduction, better weight distribution (handling), longevity of the energy storage system, and long-term costs. The discussion isn't about perpetual motion or spontaneous creation of energy. |
Thats alright bro, I believe you. :thumbup: I know a few gen 2 insight owners who have seen a change in ima performance and an improvement in mpg when replacing a bad starter battery and upgrading to a slightly bigger battery.
How about you edit all your posts and replace the comments with a few spaces? :D |
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Good luck with that. Until then its a unicorn just like these dimpled car wraps. |
Well Red, with the gen 2 insight it cycles the dc to dc converter from the ima system off and on to charge the 12 volt system under regen and when the voltage falls below 12.5. Ive had some measurable improvement using an agm u1 battery. I added 2 to help firm up the audio system and it had a noticeable negative effect.
I see you can buy small lithium packs in the power sports section of walmart and advance auto and am thinking about giving that a try. Then of course relocating it to the rear by the ima system so it has a smaller window of operating temperature. A bad 12 volt starter battery will still test good, but cause the gen2 to loose 10-15 mpg and see the ima system dip into regen and little assist. :eek: |
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...still hasn't read the title of the thread, or the posts within. :rolleyes: |
@redpoint5: Hi, that’s true that batteries can be replaced with the Ultra caps but modern ultracaps still have many disadvantages over traditional batteries like the capacitors are good to provide sudden surge of energy but it cannot hold the energy for long time and discharge quickly than the batteries and that is the hurdle in replacing batteries with capacitors.
pcb price |
I think the real benefit in the Caps in this situation is that they do not store unneeded energy continually recharging a battery with excess power that you will never use.
Where as in the Capacitors you store only the energy you need at any giving moment and not energy for storage. Its the fast recharge of the small storage that gives the gains, the alternator is not On as often is my deduction and I think its promise. |
The basic problem of the lead-acid battery is not voltage drop. In fact, on most cars voltage drops under cranking towards 9 volts, and truck industry rate the CCAs as the amps a battery can give under freezing cold while dropping to 7.2 volts. Neither is the (renowned) sluggish charging. Or water loss. Or limited life.
The basic problem which is unsolvable as long as we stay on this side of the laws of physics is weight. Lead-acid does not allow deep discharge below a certain threshhold, and in flooded lead acid this threshhold stays up, no more than 30% frequent discharge. Which means that we carry a battery 3 times as heavy as needed. Only to achieve a reasonable service life out of it. AGM, which is deep cycle by construction, for the same amps is even heavier. Which negates any advantage. Plus, even if by some magic we can size the battery to the exact amount needed to start the car and no more, lead is still heavy. As, well.. lead. Supercaps alone are only a thread above useless. They can give a start, but they self-discharge in time, store miserable amounts of energy, discharge dangerously when some metal tools hits them inadvertently. But once lashed to a battery, they can draw, store and fire the exact amount of current needed for a start - while allowing a small, lightweight battery to store energy needed for the car's systems. A 60Ah lead-acid is 15-18kg (33-39lbs), the lightest batteries rated for road cars are in the 10-11 kg (22-24 lbs) range, highly specialized racing batteries like Odyssey or Varley are a bit below 20 lbs. A combo of supercaps and motorcycle lead batteries is barely above 10-11 lbs and can start just fine. |
Dia duit
I work on wind turbines they have large capicitors to even out the grid load they really do have serious storage potentional power in them what you need is a way to charge them up take out the regulator of alternator and put a higher capacity one in say 100volts instead of 14volts I always thought these would be a great addition to a ev battery pack if you watch the amp meter when the load changes it drains the charge from battery with a capicitors set up it would drain them instead of battery and you could extend range milage greatly Over |
Self discharge appears to be a myth.
I pulled my supercap bank out of my Renault when I sold it four months ago and it still sits at over 12v and I've been using it to test a power window install in my TJ. In that regard self discharge appear to be better (or at least no worse), than PB batteries. |
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Anyone who has picked up a charged capacitor that has been lying for a spell will tell you just what a myth self discharge really is.
I pulled a piece of kit off a shelf, where it had been sitting for a couple of years, and got the motherf..... of all belts. It had a couple of 1500v, large capacity, capacitors mounted on the rear, and unbeknown to me the bleed resistor was open circuit. I accidentally came in contact with the ungrounded terminal and it nearly killed me. |
Since this miserable thread won't be left alone to die, I'll add this even though it's apparent that many aren't reading the posts before they comment...
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The real problem with caps as a battery replacement is the constant parasitic draw of the vehicle. Since caps have such low energy storage to begin with, it doesn't take much time for a 25 mA parasitic drain to pull the voltage below a useful level. |
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