What Does Motor Start Capacitors Have to DO With EVs

What does motor start capacitors have to do with electric vehicles. Not a very common question but the answer to it is very fulfilling. But Before all of that lets just first discuss the basic working of a capacitor. That way the answer will make much more sense.


Basically, A capacitor works by storing energy on one plate, then releasing that energy to another plate. This article will outline the operation of the parallel plate capacitor. The discussion is simplified for clarity, and leaves out the Calculus.

Picture two close together metal plates. The distance between the plates may vary from nanometers to centimeters. The plates may be round, square or cylindrical, or other shapes.

The medium between the plates can be air, vacuum or some other material. The material between the plates is called the dielectric medium. The amount of charge or Capacitance varies with the distance between the plates, the permittivity of the medium between the plates, and the area of the plates.

Capacitance then increases with plate area and permittivity. It decreases with distance apart from the plates.

The resulting equation is: Capacitance is equal to the permittivity (dielectric) x plate area / distance between the plates.


When the battery or energy source in the capacitor circuit is switched on, charge starts to build up on the nearest capacitor plate. When the maximum capacitance is reached the plate will not accept any more charge. The charge will be maintained on the plate as long as the power supply is maintained. Once the power is switched off, the charge in the capacitor will begin to discharge its energy to the other plate.

The stored energy will continue to flow across the plates, and on down the circuit to the device needing power.

After the capacitor discharges, it will simply recharge if the switch is opened. This cycle will repeat itself hundreds, thousands or millions of times. That is the great part about capacitors. There are no moving parts. They last a long time.

While capacitors are great at storing and releasing charge on cue, they have a couple of practical limitations. First, they can not store charge for very long, and they have low energy density. They can not hold as much energy as say lithium ion storage batteries. Research is ongoing to improve both limitations.


So, now you know the basics of how a capacitor works. How do motor start capacitors help electric vehicles? The main use right now is for braking. Since capacitors can accept energy at a fast rate and batteries take a long time to charge, they are well suited for storing energy normally lost to heat during braking.

Take hybrid vehicles for example. As hybrids brake, their on board alternator can also be used as a generator. As the brakes are applied, the generator kicks in, slowing the car and recharging the batteries and capacitors at the same time. Some hybrid taxi drivers for example have reported a lot less brake wear due to the use of regenerative braking. Pure electric vehicles like the new Nissan Leaf also have regenerative braking.

Future Of The Capacitors

In the future, it appears possible that large capacitors called ultracapacitors or ultracaps could replace batteries altogether. Large ultracaps can be very quickly charged. However, ultracaps today will not hold energy for long, and cannot yet be relied on for long term storage like batteries. Research is ongoing.

Banks of ultracaps have found use in some city buses however. Currently in China, ultracap powered Sinotec buses can travel around 5 miles between charges. The buses connect to overhead power lines at bus stops. Since the bus needs to make passenger stops anyway, as they are stopped, they charge up their capacitor banks.

Do I Need Motor Start Capacitors

Car enthusiasts would generally ask this query, “Do I need motor start capacitors“? To answer this particular question you should know the kind of vehicle system you got. If you are the kind who frequently upgrade your car’s audio system but do not know whether the current electrical system is designed for its power needs, chances are you may need one, because some vehicles are not able to handle high energy systems.

Tsunami HCAP-5 Capacitor is a reasonable addition for your system due to the fact that not all vehicle batteries can handle high capacity car audio systems. You will observe fluctuation of power whenever your headlights dim during peak usage or when a largemouth bass drum strikes. It also filters the AC voltage for amplifier power that can produce disrupting noise.


A car audio capacitor such as the Tsunami HCAP-5 Capacitor basically amasses power for the car’s electric usage. It provides additional needed energy in order to power the amplifier to produce awesome sound especially when producing a bombastic largemouth bass sound.

Just one Farad of capacitance is actually recommended for each 500 w of amp power nevertheless, you can never have too much capacitance for the car’s electric program. The Tsunami HCAP – 5 is a 5.0 Farad high-powered hybrid capacitor that accompanies a digital voltmeter. It’s two 1/0 or even 4-gauge inputs as well as four 1/0 or even 4-gauge outputs for any multi-amp system with as many as 3 amplifiers. The Tsunami capacitor can provide a total of 5,000 watts RMS. This is more than enough to power your car amp.

The Tsunami HCAP-5 electronic hybrid car capacitor is available in an aluminum outer shell with stainless plastic highlights. It includes a hinge that hides the terminal contacts. It has a blue electronic LCD volt meter. The flashing red-colored LEDs implies high or low voltage. The working current of the Tsunami capacitor is 20 volt or 24 at volt rise. Its terminals have a 1/10-gauge nickel plated, higher current terminal blocks along with 4-gauge reducers. The HCAP-5 includes one positive, one negative input, and a pair of positive, and two negative outputs.


In conclusion, regardless of whether you need motor start capacitors or otherwise, they are clarified by how much power you need for your car audio system. If it needs too much power then it will likely be starving your cars of additional electric gadgets which will result in low performance. If you have a sophisticated car audio system that needs additional power, then it’s time for you to get the Tsunami HCAP-5 Capacitor.