selfmade homemade DIY supercap ultracap bcap boostcap

[Red_Sunset]

Having built the capacitor, when using it as a replacement battery,  how do we regulate the output voltage to give a fairly constant voltage as the cap discharges?

(Obviously, a voltage regulator would do this but will waste most of the power).

Paul,
By definition a "voltage regulator" in the old school understanding did waste a lot of power, they were also caller "series regulators" because the regulation was done in a semi analog fashion by venting excess power into a transistor regulator as heat. They were heavy due to the transform iron block inside and not efficient at all due to the analog power venting.

The integrated circuit age provided much more efficient regulation using switching regulators using the "buck/boost" principle,  now commonly used in all electronic appliances, one common one you handle every day is your mobile charger. 
No big iron block transformer, so very lite an efficient due to the digital power switching duty cycle which regulates according to need. Power regulation is done from DC to DC (AC is rectified first).  Voltage regulation can be done in both direction, the output voltage can be smaller or greater than the input (Buck/boost) and is very efficient due to the low power loss switching (the reason for using power FET's).
Some Gooling will find you all you need

Red_Sunset

[Pirate88179]

Paul,
By definition a "voltage regulator" in the old school understanding did waste a lot of power, they were also caller "series regulators" because the regulation was done in a semi analog fashion by venting excess power into a transistor regulator as heat. They were heavy due to the transform iron block inside and not efficient at all due to the analog power venting.

The integrated circuit age provided much more efficient regulation using switching regulators using the "buck/boost" principle,  now commonly used in all electronic appliances, one common one you handle every day is your mobile charger. 
No big iron block transformer, so very lite an efficient due to the digital power switching duty cycle which regulates according to need. Power regulation is done from DC to DC (AC is rectified first).  Voltage regulation can be done in both direction, the output voltage can be smaller or greater than the input (Buck/boost) and is very efficient due to the low power loss switching (the reason for using power FET's).
Some Gooling will find you all you need

Red_Sunset

Or, could you not just use the proper supercap for the application?  In other words, I use a 2.7 volt supercap (650 F) to light an led.  The voltage is fine as it is and the led only draws what it needs and it will run for a very long time.  No other components required that would waste energy.

Or, am I missing something?

Bill

[Red_Sunset]

Or, could you not just use the proper supercap for the application?  In other words, I use a 2.7 volt supercap (650 F) to light an led.  The voltage is fine as it is and the led only draws what it needs and it will run for a very long time.  No other components required that would waste energy.

Or, am I missing something?

Bill

Bill,
I am not sure if I understand correctly the question or issue at hand. So I might also be missing something.
Voltage or current regulation is required to keep one or the other at a specific value. 

To charge a cap to max. 2.7 v,   a regulator would limit the voltage

To drive a LED, you need to control the current, depending on LED type,  20-30ma for a common variety bright LED.  The LED junction voltage is determined by the LED type and color.  This LED power control is usually done by a series resistor which limits the current and picks up the excess voltage.
A current regulator could be used to do the same thing and save on the wasted energy by the resistor. In addition it can compensate for a discharge descending voltage.  Because if the CAP voltage drops below the LED junction voltage, the LED will switch off. The regulator could compensate for this simular to a MPPT charger/regulator used with solar panels (Maximum power point tracking (MPPT)   It is a technique that solar battery chargers and similar devices use to get the maximum possible power from one or more photovoltaic modules. 
MPPT is a type of intelligent buck/boost according to need to extract most power at any time and extend the usable charge time.

Red_Sunset

[Doug1]

I know what your saying Bill. it's just a communication difference. Bill is using the cap as a battery with a near matching voltage to the load in which case no regulation would be required. On the charging side there is need for regulation if the supply is ac and or over/under the target voltage to be put into the cap. I think Bill would first look for a source that is matched  to the target voltage then move on to other sources requiring more exotic components to regulate and step up or down as needed. The cap will deplete over time but not above the voltage it was supplied with. The load usually has a window or spread that it will function with in, example led working at full bright at 3v down to 2v but with lower brightness as voltage decreases down to the point it will not light any more.
  Just like the cap battery replacement on his car. The caps will still start the car even with less then optimal voltage.
  Bill have you looked at the self charging cap idea yet? I found the pdf link without paying for the abstract lol .
http://www.nanoscience.gatech.edu/paper/2013/13_AEM_01.pdf . I think the pizo thing was considered back in the days of the CC forum.

[Pirate88179]

Bill,
I am not sure if I understand correctly the question or issue at hand. So I might also be missing something.
Voltage or current regulation is required to keep one or the other at a specific value. 

To charge a cap to max. 2.7 v,   a regulator would limit the voltage

To drive a LED, you need to control the current, depending on LED type,  20-30ma for a common variety bright LED.  The LED junction voltage is determined by the LED type and color.  This LED power control is usually done by a series resistor which limits the current and picks up the excess voltage.
A current regulator could be used to do the same thing and save on the wasted energy by the resistor. In addition it can compensate for a discharge descending voltage.  Because if the CAP voltage drops below the LED junction voltage, the LED will switch off. The regulator could compensate for this simular to a MPPT charger/regulator used with solar panels (Maximum power point tracking (MPPT)   It is a technique that solar battery chargers and similar devices use to get the maximum possible power from one or more photovoltaic modules. 
MPPT is a type of intelligent buck/boost according to need to extract most power at any time and extend the usable charge time.

Red_Sunset

Red:

I may be missing something here also, and I know that you know your stuff but I never use a current limiting resistor when using supercaps.  My 650 F cap has enough current available that it will melt the wires I use if shorted. (ask me how I found this out, ha ha)  But, I can light a single led from it that only needs 20 mA  (Like you said) and it will only draw that 20 mA's.  I have found that as long as the voltage is correct for the given led, then they only draw the current they need and do not fry.  As Doug said, I am using supercaps like I would a battery, and have been doing so for many years now.  Now, if I had a 12 volt supercap and only wanted to run my 3 volt led from it, of course I would need to use the right resistor in that circuit, or that led will fry in less than a second.  (ask me how I know this too, ha ha)  Doug is also correct in that as the voltage drops in the cap, the led will dim over time and finally go out when the cap voltage is below the led's minimum voltage requirement but, with so large a cap, that can take a really long time to happen.  I like using them as they charge up very fast.

Doug:

I will look at that pdf.  Nice job on getting it for free, ha ha.  I had never heard of anything like this.

I have been following Lasersaber's work on replacing his car battery with the cap banks and, the latest version uses some pretty small caps
compared to what he started out with yet, it starts and runs his truck just fine...so far anyway.  They appear to recover from the starting draw very fast as well.  His meter on his last video (I think it was the latest one, maybe the one prior) showed they charged back up in a matter of seconds after his truck started.  He does some interesting work.

Thanks,

Bill