Technical Articles
  Do Voltage Stabilizers Work?
  Why Capacitors don't work
Do Voltage Stabilizers Work?

Selling sizzle but the concept fizzles… Don’t expect miracles here

Electrical modifications (grounding/stabilising)

Devices of this type include Z-Stab / EZ-Stab, Pivot Raizin etc

As well as the air and fuel related devices described elsewhere on this site, there are also many products that claim to improve economy and/or power via changes to the vehicle electrical system. Chiefly these are grounding wires (to fit between the engine block and the vehicle body) and various voltage stabilisers.

Certainly poor electrical systems can cause significant problems. Most obviously, a poor earth link between the engine and body makes starting very difficult, since there is a large voltage drop when the starter current (100 - 200A) passes through the high resistance. What is far less clear is that a vehicle whose electrical system is in pretty much "factory" condition could benefit from adding an additional grounding strap.

Another class of device is the add-on voltage stabiliser. Now, there is no doubt that vehicle electrical systems are inherently "noisy" (due to ignition, alternator, etc), and it is not hard for me to see how an add-on device could smooth this out. The electrical details of these devices are of course kept secret by the makers but some educated guesswork is relatively straightforward! Assuming that these devices do reduce noise in the electrical system, it would not be unreasonable to expect benefits such as:

• Better sound from the in-car entertainment system
• Smoother idle, especially when switching electrical devices on/off
• Steadier light from headlamps; increased bulb life
• Possibly sharper throttle response, especially from low engine revs and with a nearly-flat battery
• Possibly better starting with a nearly-flat battery

To be fair to the makers, these are among the claims they typically make, and it is up to potential customers to decide whether or not they are enough to justify the purchase price (for some people, almost any expenditure on the sound system is justified, though my ears are not good enough for that!)

Where I am less convinced is when the claims are extended to significantly improved fuel economy or torque / power. Modern vehicle wiring and ECUs are already designed to operate in a harsh electrical environment. They cope with conditions from maybe 8V starting with a nearly-flat battery to 16V on a boost charge, and with electrical interference from mobile telephones etc, without failure. The ECU runs internally at 5V or even less and is heavily stabilised to ensure the processor runs fault-free at all times. Many modern ECUs repeatedly self-check and would shut down the engine entirely if any kind of fault condition occurred. Overall, it is hard to envisage how a more stable electrical supply could significantly improve engine economy, emissions or performance on a vehicle in good condition.

The suggestion made by some sellers of such products, that the alternator on "unmodified" vehicles is always pushing 1 - 2 kW into the battery (and hence "robbing" the engine of this power) also does not fit my experiences. Once the battery is fully charged, the alternator automatically reduces its output (otherwise the continual flow of energy into the battery would cause it to boil and ultimately be destroyed), and the mechanical loading on the engine then drops to a relatively low level - though undoubtedly there is still some power loss.

Equally, extremely precise control of the engine is essential to meet today's strict emissions standards. If electrical problems really did lead to significant errors in fuel delivery or ignition timing on cars in good working order, it seems highly unlikely that such cars could pass emissions tests.

It is also worth noting that engines are generally developed on test beds using highly stabilised power supplies (not using the vehicle alternator), but the test results and ECU settings carry over quite accurately to in-vehicle use - ie there is no obvious worsening in performance with the "less stable" supply.

Improvements of one or two percent may be justified, and again to be fair to the makers of such devices, they do not generally claim implausibly large power or economy gains. Unfortunately benefits as small as this are difficult to precisely quantify without a large number of rolling-road dyno power or economy tests, due to the natural variation inherent in such testing. As with all such devices, while there are many satisfied customers, you can also find people who have tried them and found no obvious benefit.

When it comes to performance benefits, my view is that even quite effective products usually do not justify their purchase on a straight "power increase versus money spent" equation. I would tend to put voltage stabilisers in the same category - but as with all performance enhancers, some people are willing to spend a lot of money on not very much horsepower gain for understandable reasons of "making their car special", "liking the different sound", "because it looks cool", etc, and if you want to buy one for those reasons, that's fair enough.

- Article taken from Tony’s Guide from Fuel Saving Gadgets

3rd Gear
Posts: 259
Joined: 26-March 08

Just to throw in my opinions. Why are people still buying VS? What is the engineering principle behind it? Grounding? There are multiple points of earth throughout the car not just from/to the 2 battery terminals.

As I understand from books and internet articles, the battery is used for starting, lighting and ignition (SLI). When you crank up your engine and the flywheel turns, the entire current supply comes from your alternator to feed onboard electronics ie. ecu, auto gear, lighting, air-con etc. The battery stops delivery of current and now goes into charging phase (recharge by the alternator through i/c regulator). The circuitry is discontinued from main breaker mainly found in your key cylinder rotary switch.

If the above being the case, then how can VS 'stabilise' when there is no meaningful output to all circuitry?

I read from auto manufacturer that in fact our battery is a 'voltage stabiliser' of sorts. If that being the case, how can 4-6 AA sized capacitors be better than the big size battery itself? Especially when its running parallel and not in series?

Moreover, capacitors should be place very near the point of power demand ie. just behind the 2 din headunit power line. This would allow the stored energy from the capacitors to momentarily bring up the voltage should it dip suddenly due to current draw from elsewhere.

Tiny capacitors running parallel with your battery does not do anything. If you feel it does, it most likely psychological. Another pausible theory is that the battery current sensor 'see' a higher voltage, it then does not activate the cycling of the alternator, hence running the car feels better. Alternator is 'bluffed' into thinking battery is always full. However, this is at the expense of not charging the battery adequately. After a while, battery loses its capacity and then kaputs...

I was once a user of Hot Inazma, remembered bought at $420 MR model. After awhile battery died and changed new one, died again all within 3 years.

I began to read more and understand more about the car charging system and how it works. After that, I swore off VS products. The don't work at all no matter how you'll like to call it or package it.

Previously there was a car fire along highway and heard through the grapevine that a VS could have caused it. Capacitors can leak or explode when overcharged and they most definitely have a shelf life. They do not work forever.

Posts: 7,437
Joined: 12-December 06

QUOTE (Smhomie @ Jan 12 2010, 01:55 AM)

Thanks for sharing. Fully agreed with you.


4th Gear
Posts: 927
Joined: 18-April 08

definitely agree

QUOTE (Smhomie @ Jan 12 2010, 01:55 AM)


3rd Gear
Posts: 259
Joined: 26-March 08

QUOTE (Nmnhnlm @ Jan 12 2010, 09:47 PM)

Voltage stabiliser does have its uses though. I don't believe in installing VS for better FC or more HP, but if you are someone who is into car audio and demand the best possible sound quality, then you will want to install a VS. This is because power from our alternator is very 'dirty'. Just use a multimeter and you will see the fluctuations in the voltage. Bad for audio quality.

I don't know if those normal commercial VS will really work or not though.

Btw capacitors do work for ignition. Not talking about those ignition VS but CDI.

3rd Gear
Posts: 259
Joined: 26-March 08

QUOTE (Nmnhnlm @ Jan 12 2010, 09:47 PM)

Voltage stabiliser does have its uses though. I don't believe in installing VS for better FC or more HP, but if you are someone who is into car audio and demand the best possible sound quality, then you will want to install a VS. This is because power from our alternator is very 'dirty'. Just use a multimeter and you will see the fluctuations in the voltage. Bad for audio quality.

I don't know if those normal commercial VS will really work or not though.

Btw capacitors do work for ignition. Not talking about those ignition VS but CDI.


Capacitors do only one thing and that is for filtering purposes. Current from your alternator is not 'dirty' it is AC converted into DC through rectifying and the voltage stability is governed by your regulator. If you do have fluctuations in your readings, either check your regulator since its function is directly dependent on engine rpm ie. 700rpm still 13.0v, 3500rpm still 13.0v or this could be the direct function of the newer cars which uses ecu controlled alternator to help improve fuel efficiency. Help this explains...

As for Capacitive Discharge Ignition like MSD, Jacob's electronic it is useful for hard to ignite fuels or when the fuel mixture introduced is extremely rich. Your stock energy (joules) released from your stock ignition system would not be able to ignite the mixture, hence the need to fire more energy within a spark to help promote combustion. CDI coils store energy and has multiple discharge per cycle with longer durations (dwell time). Regular ignition 1 spark per cycle, CDI 4-9 sparks per cycle. Pistol action vs machine gun action. Help this again explains the concept.

Article taken from ICE guru :

A capacitor WILL:
-Stiffen voltage rails. If you experience very brief, momentary periods of high current demand that cause the electrical system to falter only at these rare, peak draw times, then a capacitor will supply the additional current needed (when bass hits) to keep your voltage rails stiff, and prevent damage to the car or audio equipment.

-Increase response times for musical accuracy by reducing delay caused by transient response times between current demands from the amplifier, and response to this by the electrical system. In other words, your subs will respond more quickly, because they don't have to wait for the alternator to supply additional current at the moment of demand. Amplifiers have to provide a very dynamic and quick response many times. A capacitor can assist in this if the rest of the charging system is up to par and not overtly taxed.

A capacitor will NOT:
-replace the need for a larger, high-output alternator and/or a deep-cycle battery or batteries. If your electrical system is inadequate, the ONLY way to fix this, and again I repeat, the ONLY WAY to fix this, is to replace the alternator. This is the SOLE source of electrical current for your car when the motor is running.

When the motor is turned off, the battery then becomes your source of electricity. When the battery is run down, and when the capacitor(s) is/are depleted, the alternator has to work even harder in order to supply current to the car, the audio system, and also to recharge the capacitor(s) (which deplete very quickly) as well as recharge the car's battery(ies). So by adding a capacitor to try taking the place of a high-output alternator, you are actually causing more work for your alternator, and causing even more damage to that stock alternator. -make your system magically sound 10 times better.

Many people believe that a capacitor adds NO real benefit to an audio system, and this is why you never see before and after demonstrations, or factory capacitor company vehicles at competition events. A capacitor does have it's uses, but it is not a magical fix for a lacking electrical system.

A capacitor is an electronic device which consists of two plates (electrically conductive material) separated by an insulator. The capacitor's value (its 'capacitance') is largely determined by the total surface area of the plates and the distance between the plates (determined by the insulator's thickness). A capacitor's value is commonly referred to in microfarads, one millionth of a farad. It is expressed in micro farads because the farad is such a large amount of capacitance that it would be impractical to use in most situations.

Capacitor and DC voltage:
When a DC voltage source is applied to a capacitor there is an initial surge of current, when the voltage across the terminals of the capacitor is equal to the applied voltage, the current flow stops. When the current stops flowing from the power supply to the capacitor, the capacitor is 'charged'. If the DC source is removed from the capacitor, the capacitor will retain a voltage across its terminals (it will remain charged). The capacitor can be discharged by touching the capacitor's external leads together. When using very large capacitors (1/2 farad or more) in your car, the capacitor partially discharges into the amplifier's power supply when the voltage from the alternator or battery starts to fall. Keep in mind that the discharge is only for a fraction of a second. The capacitor can not act like a battery. It only serves to fill in what would otherwise be very small dips in the supply voltage.

ESR is the equivalent series resistance of a capacitor. An ideal capacitor would have only capacitance. As you remember, all conductors have resistance. In a capacitor, there are multiple conductors like the wire leads, the foil and the electrolyte. The resistance of all of the conductors contribute to the capacitor's series resistance. It's essentially the same as having a resistor in series with an ideal capacitor. Capacitors with relatively high ESR will have less ability to pass current from its plates to the external circuit (to the amplifiers in the case of stiffening capacitors in car audio). Low ESR is desirable when using a capacitor as a filter.

ESL is the equivalent series inductance of a capacitor. Since most electrolytic capacitors are basically a large coil of flat wire, it will have even more inductance than it would have if it were flat. This inductance, along with the small amount of inductance from the wire leads, will make up the ESL of the capacitor. The ESL is essentially the same as having an inductor in series with an ideal capacitor. Low ESL is desirable when using capacitors for filtering purposes.

Even though a capacitor's plates are insulated from each other, there is a small amount of 'leakage' current between its plates. This current is generally insignificant but will cause a capacitor to slowly discharge with no external circuit path between the capacitor's leads.

I hope the above article helps in educating readers and break through the fallacies surrounding capbanks and capacitors in a sound system setup. A capacitor used in ICE setups is not the same as 'Voltage Stabilisers' since the central processor and capacitors used are very different both in form and function. Don't let those two-bit audio shops teach you the wrong stuff. Most of them are chinese businessmen without academic inclinations. Show them this article and I bet they will keep quiet. Enuff said.

By misleading the general populace with half-truths, they hope to lead you into buying more and more equipment and products from them when you claim that your sound system is not 'good' enough or something is not right and needs improvement.

Another time dear foummers

- Excerpt postings from www.mycarforum.com under ‘HKS Grounding Kit' thread discussion dated 12 Jan 2010