Regenerative braking model

Thread Starter

rattleraj2000

Joined Jul 11, 2010
17
I tried out the circuit with the Scalextric motor and the car with tyres. Its showing the capacitor charging as wel as braking in a very wel manner. Thanks a lot.
I then connected an LED directly across the capacitor and now my LED is glowing for sometime.the capacitor is charginf enough very fast each time i brake but when i connect the LED it drains of the charge immediately.but the light glows for sometime. I am now trying to build the Step up DC converter to boost the voltage and then collect it in a rechargeable battery. and then light the LED.
is it possible? please help
 

Thread Starter

rattleraj2000

Joined Jul 11, 2010
17
I have been trying to connect a capacitor to a dc-dc converter but I am not able to take any output at the output of the converter please help.I am attaching the converter circuit.Please check.How do i connect the capacitor to the dc-dc converter circuit??
 

BMorse

Joined Sep 26, 2009
2,675
I have used this IC in several of my projects and it is very easy to use even for a novice... anyway, do you have the proper rated Inductor, Schottky diode and capacitor for the output? these components are critical for this circuit to work, in the datasheet they give you the part numbers and manufacturers for each component that will work with this IC.....

In your circuit you should have pin 1 pulled high on the IC if left floating or connected to ground, this will put the device in shutdown mode, and will not have an output....

and even if the circuit was not properly working, you should still see the voltage from the battery on the output.... if you are not getting any voltage at all, then something is wired wrong, and you need to double check all your connections....

B. Morse
 
Hi RattleRaj,

This is a very interesting topic to me. I like regen braking. I worked on the MIT solar car team, and all solar cars use regen braking to recapture the energy. Some new trains and buses are using regen braking, and the electric cars of course use it now.

Often, supercapacitors are used for storage. However, they have a maximum voltage of 2.5 or 2.7V, so either the power is stored at low voltage, or the caps are put in series.

On your circuit -- why do you need the resistor in the path? It is limiting the energy that you can store into the capacitor. Maybe you need it to protect the capacitor from overvoltage, because it's a very small capacitor for the size of power you are putting in it. Just so you are aware you are losing a lot of power there.

For the DC-to-DC conversion, the MAX chip may work, although note that the startup voltage is typical 1.1V but up to 1.8V. So it is not guaranteed to start up at 1.5V. There are other DC-to-DC chips that start up at lower voltages.

But try this -- charge up two capacitors in parallel... then put them in series and you have doubled your voltage. This should work.

You can use supercaps, then you can use something like a pair of 1F capacitors. Then the LED will light up for more than a quick blink. Just make sure that you don't charge them above the rated voltage 2.5V or 2.7V.

Hope this is helpful.

Have fun with this
 

Thread Starter

rattleraj2000

Joined Jul 11, 2010
17
Hi ,
Many thanks for the suggestions. I have made some changes in the circuit and its working better now. please find the attachment of the circuit. now each time i provide braking by throwing the DPDT in different position i get the voltage being recovered during this braking at each intervals of different voltage levels. and each time the charge goes on increasing very fast. Now i guess as sage.radachowsky said i wil ve to switch to a capacitor of higher rating. but still when i connect the LED it glows initially but then immediately switches off since it drains charge til 1.5 v in seconds. now i built the DC-DC converter. I Will be connecting it across tomorrow and checking the output. but when i connected the DC-DC converter step up circuit to a battery without any input to it , the battery holder started burning which i am confused as to why it burnt. and this happened each time i connected it to the battery. please help. Once again i have not connected the input from the capacitor. please help
 

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Thread Starter

rattleraj2000

Joined Jul 11, 2010
17
hi,
hw do i discharge a capacitor to a a battery. please help. i have connected it directly across the terinals of the battery.it does drain all the charge in the capacitor but it doesnt charge the battery. have even tried by puttin a switch,but it sint working.
please help
 

Potato Pudding

Joined Jun 11, 2010
688
The capacitor is not likely to hold enough energy to make charging a battery worthwhile.

At battery charging currents a capacitor will discharge within a second or two unless it is extremely large.
The battery probably needs about a hour of charging at least.

You don't actually want to charge most batteries in the short bursts like you are talking about. There is a big exception to this. Lead Acid storage cells can tolerate random charge and discharges fairly well.

What the capacitor is good for is for supplying a large surge current that the motor can use when you start it back up again.

If this were a proof of concept demonstator I would set up side by side two otherwise identical working motor systems that just endlessly cycle 5 seconds on and 2 seconds off, one with regenerative braking and one without. Have both fitted with revolution counters. The test is to see which one works longer on the battery charge and how many total motor revs you can get out of a full charge. More total revs is a much better indicator of efficiency than time, because the more advanced motor controls will not just extend the battery life, they make the low charge regime do more work, while the simpler controls are working poorly and wasting power on stall currents.
 
Last edited:

Potato Pudding

Joined Jun 11, 2010
688
I thought of some exceptions where it might be worthwhile to charge the battery.
What I said about most batteries tolerating random charging and discharging poorly still applies.

Potential energy capture is not a single motor stops worth of charge on the capacitor.

You have to be talking about something like a battery powered hoist that hauls a bucket up several hundred feet and then uses regen braking when the bucket is lowered again. Or you could be talking about a car rolling downhill on a long steep slope and using regenerative braking to keep from going overspeed and out of control.

You are storing the energy from gravity, or some other long lasting force that the braking can capture.
 
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