Hi,
I would like to make a super capacitor based jump starter for my car in case of an emergency.
I saw a video of a guy doing that with a 6X super capacitor module.That module is not available in my place, however individual 2.7V 100F super capacitors are available.
So can I make the charging/balancing circuit with the help of an arduino without additional controller ICs? and can I use lower capacity caps to do the job?
My car battery is 48Ah battery and I live in a tropical area, so engine is never frozen.
Yes, you certainly can use supercaps to charge your car battery. It's fairly elementary to do so. You merely need to put the caps in the correct configuration to get the voltage right. Anything between 13.5 and 15V (or even a bit higher) would be fine. The only issue is the initial surge. You have to limit the current going into the battery until it settles down to about 1.5C (in most cases this would be about 100 amps). If you employ a simple hall-effect sensor on the charger side, away from any vehicle noise, you should be able to calibrate it to detect when that happens. There are a number of ways you could control the current (by controlling the voltage). A rheostat is one. High current power mosfets are another, if you want to go computer-controlled but you'll need a boost stage to power such FETs because their gates take more charge to saturate than the Arduino pins can provide.
Yes you could. But adding the Arduino doesn't make it any simpler / simple...
Just making an analog circuit to prevent a cap from overcharging is simpler.
I can't watch the video because I'm at work...
In general, series capacitors in a DC circuit are a bad idea. They won't charge (or discharge) equally because of varying internal resistance and varying capacitance. You'll probably exceed the 2.7V rating of at least one capacitor somewhere during charge, hold, or discharge.
With 6 in series you'll get 1/6th the capacitance.
Capacitors make terrible batteries because the [u]discharge curve[/u] is the opposite of an ideal battery. The voltage drops rapidly and immediately at first, and then levels-off as you near full-discharge.
Are you sure the capacitors will self-discharge more slowly than the battery? i.e. If the battery is dead the capacitors may be dead too.
Are the capacitors designed for enough current to turn a starter motor? A starter motor is almost a short circuit and the caps may fry themselves.
DVDdoug:
Are you sure the capacitors will self-discharge more slowly than the battery? i.e. If the battery is dead the capacitors may be dead too.
My idea at fist as well but after watching the video it's clear he wants a way to hand-crank the motor. Aka, hand-crank a small generator, store in a super-cap and then start the car.
DVDdoug:
Are the capacitors designed for enough current to turn a starter motor? A starter motor is almost a short circuit and the caps may fry themselves.
And yes, there are caps beefy enough 
septillion:
Yes you could. But adding the Arduino doesn't make it any simpler / simple...
Just making an analog circuit to prevent a cap from overcharging is simpler.
I asked about Arduino because i couldn't get hold of IC's that control the cap module.
If I could do it without arduino then it would be better. I also need led to glow up when each cap reaches full capacity.
What all components will I need?
Gahhhrrrlic:
The only issue is the initial surge. You have to limit the current going into the battery until it settles down to about 1.5C (in most cases this would be about 100 amps).
Ok, I think I can get hold of mosfets. What power rating and what should I do with them?
DVDdoug:
In general, series capacitors in a DC circuit are a bad idea. They won't charge (or discharge) equally because of varying internal resistance and varying capacitance. You'll probably exceed the 2.7V rating of at least one capacitor somewhere during charge, hold, or discharge.
In the video those capacitors are connected to some ICs and resistors to balance their charge.
septillion:
My idea at fist as well but after watching the video it's clear he wants a way to hand-crank the motor. Aka, hand-crank a small generator, store in a super-cap and then start the car.
Yepp, I already have the hand crank ready. I just want to use the cap module in case of emergency. I'm not going to replace my car batteries with a ultra cap module.
Those IC's are nothing more then a transistor, an opamp and a voltage reference. If you do some Googling you can find it.
septillion:
Those IC's are nothing more then a transistor, an opamp and a voltage reference. If you do some Googling you can find it.
I guess you're correct. The guy in this video says that.
also this picture shows another kind of circuit
But can an arduino do this without these components?
Will a TL431 do the job for the voltage reference?
Noobian:
But can an arduino do this without these components?
No, not really. You would still need (power) resistors and en beefy transistor. So you only save on an opamp which is so generic and cheap.
Noobian:
Will a TL431 do the job for the voltage reference?
Something like that will probably work fine
Well, for an op amp will the regular LM741 do the job? I can get hold of power resistors of up to 20W rating
but I'm not sure about the beefy transistor. Only a few types of transistors are available here, If you can give me a model maybe I can look for it.
We made a capacitor jump starter 2.7V/ 350F *5, it can start 5000cc gasoline car and 2500cc diesel car.
