how to release a burst of energy over time?

[jason41987]

hey.. i was wondering what kind of circuitry i would need to release a quick burst of high energy over a longer period of time in the form of less energy...

for example, taking 12 volts at 10 amps generated in a second, to 12 volts at 1 amp over 10 seconds of time...

what sort of circuit would i need to do something like this?

also.. im not very educated in electronics engineering, im working on a degree in mechanical engineering, but having more knowledge in electronics engineering would help greatly, are there any good text books you would recommend for understanding electronics and circuits?

well, thanks for the advice/help

 

[kubeek]

You would need to store that energy somewhere, for example a flywheel or a capacitor.

 

[ChrisP58]

Store the burst in a super capacitor.

 

[jason41987]

ive thought about the supercapacitor as being the best way to store a short burst... but how do you get the capacitor to release the current over a longer period of time? they typically dump their energy rapidly

 

[ChrisP58]

The discharge, or energy dump, is mostly dependent on the characteristics of where the energy is going to.

What is load?

 

[crutschow]

You could use a series resistor or, if you want higher efficiency in delivering the energy to the load, a series inductor.

 

[jason41987]

anyway.. heres what im working on.. its a motorcycle with a kickstarter being converted to EFI for better performance and efficiency.. battery and alternator being removed for a generator.. problem is you need to fuel pump to start and pressurize the fuel rails (but i could install a system to maintain fuel rail pressure when its shut off... but it will need time to turn on the ECM, detect tempature, calculate air/fuel ratio, open the injectors, and create the spark... but the power from the kickstarter moved the engine itself, so the electricity will have to come off the generator, and im not sure one short burst of a larger amount of power is enough to power these systems long enough... so i wanted to take the energy generated from the generator, store it, then release it back at 12v around 10a over a longer period of time...

my idea is to maybe pump the kickstarter a couple times to charge capacitors, then while the systems come online, kick it and its started without a battery

 

[ClydeCrashKop]

To start with, generators are not very efficient, that's why they use alternators.
Capacitors usually lose their charge over time.
Auto EFI needs at least 10 volts to operate the electronics that signal the injectors.
The injectors are solenoids that use more than a little power.
If you want EFI, keep the alternator and battery.

 

[vlad777]

For charging the cap use diode, for discharging use current limiter (or both current limiter and lin reg).


Edit:

It's important that load resistance * limited current is less then total voltage on
full capacitor. As long as this is true (cap is not empty) voltage will also be constant.

 

[jason41987]

ok, so a capacitor releases its energy once the release of energy is initiated, but the rate at which the energy is actually released can be controlled, is this correct?

 

[vlad777]

ok, so a capacitor releases its energy once the release of energy is initiated, but the rate at which the energy is actually released can be controlled, is this correct?

Yes, that's correct.

 

[Mr RB]

anyway.. heres what im working on.. its a motorcycle with a kickstarter being converted to EFI for better performance and efficiency.. battery and alternator being removed for a generator...
... so i wanted to take the energy generated from the generator, store it, then release it back at 12v around 10a over a longer period of time...

my idea is to maybe pump the kickstarter a couple times to charge capacitors, then while the systems come online, kick it and its started without a battery

You may need to re-think this. Motorcycle alternators and generators won't produce any significant output during a "kick" which is maybe 200 RPM for a second or so. They need the RPM to get up >1000 RPM continuous to deliver a couple amps at 12v and maybe 2000+RPM to properly charge the battery.

However you could keep the same idea and just put a small modern battery somwehere on the bike. A 2.5Ah battery is pretty small and will give you enough power for kickstarting, at least if the weather is warm...

 

[jason41987]

i had the idea of using the kickstarter, or a handcrank to charge the capacitors for an electric start.. but it seems way too many amps would be needed to start the entire engine.. or pump the kickstarter a couple times first to build a charge prior to releasing it... or have a capacitor bank along side the main ignition system that can store power generated from riding the bike, and keep it as an auxilery power source in case the main battery dies and it seems a supercapacitor would have better performance than a flooded cell battery

 

[ChrisP58]

Let's get some numbers before we move along.

In a worst case condition, how many amps for how many seconds does it take to start the engine? What minimum voltage can the supply drop to before it is too low to crank the starter?

 

[jason41987]

thats a number of i have issues with right now... it varies by alternator model, ECM, plugs, coils, injectors, fuel pump... its hard to tell how much is needed for what period of time... i dont have the bike to do this too yet as i was trying to figure out the likeliness of this working before buying it... so im not able to plug a multimeter and read the current needed to start the bike at the battery, then measure the amount the alternator draws to subtract from the first reading.. that would tell me how much is needed with, and without the starter motor