12 volt Battery

[serialk11r]

I don't think alternator load is a problem with this kind of mod. The battery is only there to provide reserve power when the engine is off or when the accessories overwhelm the alternator, which is very rare. At all other times, the alternator pretty much puts out full voltage and powers everything in the car.

I think there may be a benefit to having normal electrolytic capacitors in a car, as the ripple from the alternator is substantial and you could smooth it out with capacitors, possibly improving efficiency? Depends on how the regulator circuit works, but if it doesn't measure RMS voltage correctly then this would be useful.

The way I see it, the primary use of ultracapacitors is to take load off the battery for starts as they have much higher power density than batteries.

[redpoint5]

Originally Posted by TexasCotton

The price issue makes the 66 dollar 20 farad look promising canadidate componet.....
New Hybrid Planet Audio PC20F 20 Farad Digital Power Car Auido Capacitor | eBay

I wouldn't bother unless I had about 20 times that farad amount.

[serialk11r]

Originally Posted by redpoint5

I wouldn't bother unless I had about 50 times that farad amount.

To be fair, this guy:

http://www.youtube.com/watch?v=z3x_kYq3mHM

is using 6 350F caps in series for a capacitance of 58.3F, which is not a whole lot more. A good battery supplement, IMO. I'd shoot for more like 100F though.

[kennybobby]

Originally Posted by RobertISaar

i don't know what kind of ESR the "Stinger" would have, but let's assume it is something quite usable.... 1,666 watt-seconds could almost entirely replace a battery. if it were all drawn within 1 second, that is almost 120 amps, which is enough to run a starter motor on nearly anything that isn't a semi or larger.

Can't imagine what sort of starter motor/engine could start with only 1 second of 120 amp cranking, especially on a cold morning. The current in the starter motor will be limited in rise time by the inductance and resistance of the motor windings, and the motor speed will be dropping faster than debutante panties on prom night as soon as the voltage sags.

Remember that a capacitor is a passive electrical component primarily used for filtering and can't source energy like a battery, which is an active chemical reaction device.

[redpoint5]

Originally Posted by serialk11r

To be fair, this guy is using 6 350F caps in series for a capacitance of 58.3F, which is not a whole lot more. A good battery supplement, IMO. I'd shoot for more like 100F though.

I revised my statement since 1000 F is a bit high, but I still wouldn't bother unless I had at least 400 F.

The series capacitance would not be less than the rated 350 F, unless you are accounting for the fact that only a fraction of it is usable due to voltage drop. The series configuration increases the voltage capacity to > 14V so that it's usable in automotive applications.

EDIT: The above statement about series capacitance is incorrect. The farad capacity does drop with each capacitor added in series due to a charge plate being effectively canceled out when the series connection is made.

[ksa8907]

Iirc, you have to wire capacitors in parallel to add the capacitance. Otherwise you get effectively half the capacitance.

[Mustang Dave]

Originally Posted by ksa8907

Iirc, you have to wire capacitors in parallel to add the capacitance. Otherwise you get effectively half the capacitance.

You remember correctly.

[serialk11r]

Yep. To check that it's consistent, just look at conservation of energy: 1/2CV^2. Wiring them in series keeps the total energy constant but raises the voltage, so the capacitance has to be lower to keep the energy the same.

From the charge holding perspective, having greater distance between the plates decreases the capacitance, and that's effectively what you get when you wire caps in series.

[TexasCotton]

Originally Posted by serialk11r

I don't think alternator load is a problem with this kind of mod. The battery is only there to provide reserve power when the engine is off or when the accessories overwhelm the alternator, which is very rare. At all other times, the alternator pretty much puts out full voltage and powers everything in the car.

I think there may be a benefit to having normal electrolytic capacitors in a car, as the ripple from the alternator is substantial and you could smooth it out with capacitors, possibly improving efficiency? Depends on how the regulator circuit works, but if it doesn't measure RMS voltage correctly then this would be useful.

The way I see it, the primary use of ultracapacitors is to take load off the battery for starts as they have much higher power density than batteries.

Thanks
Just for some clarification (4 myself)....The post with the youtube by lasersaber is dated. He used RC lipo battery/maxwell ultracaps. and has made no current posts...
As I have early stated voltage stabilizers are sold on ebay from 40-200 plus dollars.
Can someone further my understanding of series/parallel in relation to a bank of capacitor Example battery in series increase voltage and battery parallel increase the ah/amp hour

[serialk11r]

The "voltage" you are concerned with is the dielectric breakdown voltage. If you put capacitors in series, the voltage drop is split between the capacitors. So if you put identical capacitors in series, the new peak allowable voltage is the number of capacitors times the breakdown voltage of a single capacitor.

The capacitance is the harmonic mean of them, which in the case of identical capacitors is just 1/(number of capacitors).

It's analogous to resistors in parallel, except instead of adding current you add voltage, and instead of taking the harmonic mean of resistances you take the harmonic mean of capacitances