Tuesday, March 12, 2013

☈ Ultra Capacitors VS Car Battery ☈

Unlike ordinary capacitors, batteries store energy in a chemical reaction. And because of this the ions are actually inserted into the atomic structure of an electrode. If we take your ordinary capacitor or super capacitors that can be seen below for that matter, the ions simply "cling". This is an important thing and the key factor behind the success of storing and releasing electricity in capacitors because storing energy without chemical reactions allows ultra capacitors to charge up and discharge much, much faster than normal batteries.

And because the capacitors does not suffer from wear caused by chemical reactions like oxidizing like in lead batteries or ageing like in new lithium-ion batteries, means they also last a lot longer.

Normally if you would  drain a car battery too much and try to start the car afterwards even when it's nearly empty it will cause more damage to the car battery. Eventualy because of this the battery will not take charge and charge back up to it's maximum again. However this is not true for ultra capacitors.

For example, if we take a capacitor the size of a small D-cell battery, it would have a capacitance of about 20 microfarads. But if we take a similarly sized ultracapacitor, it would have a capacitance of 300 Farads. What this means is at the same voltage, the ultracapacitor could in theory store up to 15 million times more energy. 

Ultra capacitor VS Car Battery

However if we take your typical 20-microfarad capacitor it would be able to handle as much as 300 volts, while ultracapacitors would be rated at only about 2.7 volts. At a higher voltage, the electrolyte inside ultracapacitors starts to break down. So in reality an ultracapacitor have the ability to store about 1,500 times the energy of a similar sized capacitor. This is something you need to take into consideration in you're attempts at storing energy in a capaciator.

Ultracapacitors are very effective at accepting or delivering a sudden surge of energy, and it is this that makes them a good alternative for our regular 12v car battery.

With electric cars for example ultra capacitors provide the power needed for acceleration and give that sudden boost in energy needed, while a battery provides range and recharges the ultracapacitor between surges. They normally also go by the name "Boost Capacitors" or "Boostcap" simply because that's their normal usage in industry. The Maxwell product line have the name BOOSTCAP® ultracapacitors, and these supercapacitors are the ones you would normally find if you are searching for big ultra capacitors or super capacitors around the web.

While some electric vehicles are using ultra capacitors or boost capacitors for acceleration. The devices also appear in hundreds of other applications, from cell phone base stations to alarm clocks to audio systems.

Why not use capacitors instead of your 12 volt car battery!

If you like to use ultracapacitors instead of you're ordinary car battery they could provide power during stops (running the air conditioner, lights, radio etc.).” They would also provide power for the restart, and then be “recharged during the next interval of travel.”

Building you're own DIY car battery replacement with ultracapacitors for your cars with supercapacitors for automotive applications is not that hard.

So where could I buy a +12 volt capacitor to replace the car battery?

Actually this is what you and most people would need to do. Get 6 ultracapacitors connected together (normally they have about 2.5 Volts each)

So 2.5 Volts x 6 = 15 Volts fully charged. You could do with only 5 capacitors giving you 12.5 Volts but it's not recommended, you need the extra volts to be there. Besides you're alternator will put out more than 12.5 volts when it's charging anyways. Most new cars charge anywhere between 14-15 volts, so having that extra super capacitor in your electrical system is not going to go to waste. Most cars have some electronics that drain you're battery like the car alarm. So if you leave you're car standing for a week a ultracapacitor might have drained to much and you will not be able to crank over the engine.

With 14-15 Volts and 6 of them in a bank you wont be having any problem starting you're car even if you leave it for 4-5 days. However any drain can be stopped with a simple solar panel to recharge the ultracapacitors, so if that is done you should always have them fully charged and ready to start you're car. And if you for some reason would find your supercapacitors drained charging them back up takes seconds and not hours / days like charging up your 12 volt lead car batteries.

Another interesting thing replacing you're car battery is the weight difference between a ultracapacitor pack and a battery. A normal lead acid car battery have a weight around 30 pounds. However installing ultracapacitors in it's place you will actually save around 25 pounds in weight.

What all this boils down to is you will save weight = Better gas milage
Super fast charging = Small drain on your alternator =  Better gas milage
Never wears out = Never need to be replaced = More money for you.

To break down things a bit. The ultracapacitor will charge up very quick and not load the engine as much. They will also probably last the entire life of the car, that will save you maintinance and money. They will also prevent voltage drop when restarting the engine that could be causing aftermarket electronics to shut off like the stereo. Or if you have a big sound system or other equipment that use more than the avarage electricity in your car, super capacitors would prevent voltage drop and keep it working.

In reality it does not have to be a car battery that gets replaced with supercapacitors, it might as well be your, bike, mower, atv or any type of battery. It will work just the same.

What About Using Lithium Batteries Instead?

They only weigh 1.5Kg (3lbs), will stay charged for a year, survive 1000+ discharge cycles and can be fully charged in 1-2 hours. They cost around $300-500.

While it's true that the lithium battery does have some advantages over using supercapacitors. Like it can stay charged for a year, you also need to consider the life of the lithium battery (about 3-5 years max). And today the cost is about the same, today $300 will get you 6x 3000f farad super capacitors that can make you a very strong supercapacitor car battery replacement that in theory should last you over 200 years..

Here's a few things that are good to know. Porsche AG, Stuttgart was the first car maker in the world to offer a starter battery with lithium-ion technology. Weighing less than 13 lb or 6 kg, the new battery is more than 22 lb or 10 kg lighter than the conventional 60 Ah lead battery.

While the most used batteries today are rechargeable Li-ion, Li-Poly and Lithium Iron Phosphate (LiFePO4) batteries. Li-ion and LiPo batteries have a recommended per-cell safety zone between 3V (fully discharged) and 4.2V (fully charged), although they can normally discharge down to about 2.8V without any problems. Discharging below these levels may cause irreversible/irreparable damage.

Therefore, these batteries must have a built-in safety mechanisms, preventing over-discharging. Conversely, overcharging can also be very dangerous.

The Li-Po batteries have a lower number of recharging cycles than LiFePo4 (1000@0.2C rate, IEC Standard). The projected/estimated life of a Lithium-Ion battery is approximately 3 years from production.

The LiFePO4  batteries exhibit slightly different properties. The LiFePO4 is a kind of Li-Ion rechargeable battery intended for high power applications, such as EV cars , eBikes, electric bike, Power Tools and RC hobby.

The LiFePO4 batteries have more constant discharge voltage and are considered to offer better safety than other Lithium-based batteries.

Other advantages of the Lithium-based rechargeable batteries include the ability of a much faster recharge and higher discharge rates than other chemistries mentioned and usually higher number of recharge cycles (>2000@0.2C rate, IEC Standard) , meaning longer life when not fully discharged, but its energy density is lower than normal Li-Ion cell (Li-Co) LiFePO4 life expectancy is approximately 5-7 years.

The supercapacitors on the other hand can do 10 million times of charging/ discharging. The supercapacitor can be charged/discharged more than 20 times a day for 136 years of continuous usage. It is about 1000 - 2000 times of Li-Ion/Ni-MH/ Ni-Cd batteries. And to fully charge a supercapacitor takes seconds instead of hours for a lithium battery.

This ultracapacitors car article is also found on ☈ Super Capacitor Vs Car Battery ☈

Read the full specifications about to the most common 2600 farad Boostcap BCAP0010 ultracapacitor below
☈ BoostCap BCAP0010 2600 farad Specs ☈


  1. whats with the 2600 farad is that mandatory or can i use the 10 farad 2.5v ones what will the difference be

  2. Hello

    If you are going to replace your 12 volt car battery with ultra capacitors then the bigger the capacitors you can get the better.

    The 2600 farad ultra capacitor is not mandatory to use but have been easier and more affordable to get. However 3000 farad supercapacitors are becoming more affordable now also. You can go as low as to use 300 farad capacitors to use as a 12 volt car battery replacement however you are running a greater risk of running flat using so small capacitors.

    The 10 farad capacitors would not have enought power to crank your engine or run much of the electronics in todays car, but you might be able to use 10 farad capacitors to replace a small battery but that's about it.

  3. I have tried 6, 3000 farad capacitors in series. It started my car just fine, but seems to have burned out my 65 amp alternator. I'm guessing that because there is almost no internal resistance, charging the caps drew more amps than the system was designed for. Has anyone had trouble with this? I'm thinking of trying a 4 ohm resistor on the wire from the alternator.

  4. I have tried 6, 3000 farad capacitors in series. It started my car just fine, but seems to have burned out my 65 amp alternator. I'm guessing that because there is almost no internal resistance, charging the caps drew more amps than the system was designed for. Has anyone had trouble with this? I'm thinking of trying a 4 ohm resistor on the wire from the alternator.

  5. Hello Jeff, sorry to hear you got problems with the alternator.

    I know for a fact that running 6 of the 2600 farad ultra capacitors pictured above in series have worked for years without problems to the alternator. I can only guess that perhaps having 6 even bigger 3000 farad capacitors pull a bit too much amps for the alternator if it's only rated for 65 amps. If you left the car sitting for a week you might be down to 10 Volts and charging them back to 14 Volts would take 30 seconds, so not that long of a time but who knows maybe it would be too much for the 65 amp alternator to charge them up in one go. You could give the resistor a try considering the price of a resistor is nothing compared to having to buy a new alternator. But I would not rule out a faulty alternator either.

  6. I'm interested in combining supercaps with a conventional battery in my motorhome. How many ah do you get from your array?

  7. Hello Zephod, that's a good idea if you can find a good deal on these for the right price.

    The specs for the BCAP0010 2600f ultracapacitors say they are rated at 600 Amps and the rated discharge 0,3 - 30 seconds. So considering this they are much more suited for high load situations for a limited time.

    If you charge the six of them up in an array to 14 volts you can run a small microwave in your motorhome for a few 3 - 4 minutes with the 2600f capacitors. And by the end they will have discharged to about 11 volts.

    So they are not empty by that time but it really shows that you won't get much Amp Hours from them.

    Someone else did a test with a 9 watt led bulb and that lasted for about 40 minutes with six 2600f supercaps. I would advise you if you have room for solar panels on your motor home you could use that for charging them up, that way you could make sure they always stay charged and you would always have power to heat some food or perhaps make some coffee.

  8. I am wanting to replace my car battery with supercapacitors. I placed 6 2.7 V 500 F supercapacitors in a series to get a total of 16.2 V and 83.3 F and it did not turn my car over. the voltage instead dropped from roughly 14 V to about 6 V. I do have a V8 though, I also tried this on a 4 cylinder and got the same results. I am wondering how big the supercapacitors have to be in order to start a V8 or if I just have bad supercapacitors.
    Thanks, Clayton

  9. Hi Clayton, It's hard to say what's wrong with your setup. There are people starting cars with only six 20 F capacitors (that's twenty farad x six). And six 350 F capacitors have no problems starting a cold V6 on a winter morning.

    So it does not take much to crank an engine with supercapacitors. Perhaps you have a bad capacitor and that's what causing problems for you.

    You could check how they are connected, some super capacitors have 3 post in a V shape and on the newer capacitors the terminals are negatives not positive, and only the center terminal is the positive.

  10. Can the car's alternator charge the ultracaps like normal? Or is there any procedure that i need to take into account

  11. Hello Fauzan Izhar, generally speaking if you use the ultracapacitors as your car battery then your alternator should be ok with charging the ultracapacitors like normal. But it's better to have a large alternator if you also use large capacitors like the 3000 F ones because they need more Amps to charge.

    So I would only see a problem if you have very large capacitors like the 3000 F ones and they are almost empty (like way less than 10 volts, but somehow managed to start the car). And then you have a small alternator. Then it would take a much longer time (about 1 minute) for your alternator to charge them back up.

    If you are worried and you know you have a very small alternator fitted to your engine that can supply much less than 65 Amps. But also have very large capacitors that need to charge back up from empty then I would try and help the alternator with an ordinary battery to take some of the load off the alternator. Best would be to fit a bigger alternator, or use smaller capacitors. Even six 300 F capacitors will start an engine.

  12. Thanks for your reply. My ultracaps would be 2.7V 350F and will be charged by a 45amps alternator. The number of ultracaps i'd be using is 6 in series arrangement. Do you think it will have a problem?

  13. Hi Fauzan Izhar, that should work fine. Your 45 Amp alternator should have no problems charging 6 350F ultracapacitors.

  14. This comment has been removed by the author.

  15. can i add Ultra Capacitors to my car battery

  16. Hi Simon, yes you can add ultra capacitors to your car battery. In fact many people that use aftermarket car audio amplifiers will also install a car audio capacitor to help stabilize the voltage.

    The thinking behind this is that high power amplifiers draw large amounts of current from the vehicle's battery and alternator. And when adding capacitors to store electrical energy to transfer that power to the amplifier it is easing the burden on the alternator and electrical system.

  17. Hi Simon, I have a VW Touareg with two batteries--one for starting (110Ah, sealed gel-type) and one for consumer electronics (94Ah, sealed AGM type), alternator is rated at 190 Amp. I would like to replace the consumer electronic battery with super/ ultracapcitors. I'd like your advice re.
    1) amount and size of capacitors
    2) The rather sophisticated electronic control unit charges batteries according to their chemistry and capacity (which can be adjusted). Won't supercapcitors damage or at least confuse this control module?

  18. Hello

    First of all, you are asking to do something that capacitors never really where designed for in the first place. I would advice you if you are going to replace your cars consumer battery with ultracapacitors you really need to do some calculations and measurements first, as to how much power the onboard car electronics really are pulling and for how long you are planning on using them between engine starts.

    It's been said in the comments that a 9 watt led bulb lasted for about 40 minutes with six 2600f capacitors. So you will then only get around 10 minutes of use if that load is around 35 watts. So in this case an ordinary battery would do a much better job.

    There are no guarantees when it comes to new types of car electronics and control units that it will work without problems. But your 190 Amp alternator should not have any problem charging the ultracapacitors even if you decide to go big. To keep things safe you can also add what's called a Super Capacitor Balancing Limit Voltage Protection Board.

  19. With a standard battery I can crank my car over for 10 seconds again and again and again and again, if I'm trying to figure out what's wrong with it. How many times would I be able to crank the car over for 10 seconds with a super capacitor set up?

  20. Hi Victor, it differs from car to car like the kw rating on the starter motor. Check out wiggys shop youtube channel he have some good videos on the matter.

    Starting an aircooled VW without a battery (maxwell ultracapacitor) (part 2)

    So from that video around 10 seconds of cranking time.

  21. Replies
    1. But... You don't replace your battery with just supercaps. If you did, you only get that one shot. That's silly. You use a small LiFePo battery or a small lead-acid battery WITH supercaps. The supercaps will recharge in a matter of seconds to a few minutes and you'll be able to try over and over. Actually, you should in theory get substantially more crank attempts with a small battery/cap combo than with a standard lead-acid. The cranking current comes from the surface charge of your lead acid battery and you use that up very quickly at high current. Not to mention, greatly reducing the life of your battery. The caps on the other hand don't need the battery that's recharging them to be all that powerful. If you charged them in parallel and discharged in series, you could, in theory even charge them with a few AAs (would take a long time though).

      Btw, if you can't get the engine cranked in the amount of times a supercap+battery setup gives you, there's a problem somewhere else.



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