parallel regenerative braking project

I am doing a heavy vehicle project and putting a regenerative braking system into the vehicle. It also has a supercapacitor module in parallel with the battery (which has the same voltage), and the goal is to

  1. Share the current during acceleration (s1 and s2 closed)
  2. Charge the supercapacitor (only) during braking (s1 open and s2 closed)

Because I am a student and have limited money, I don’t want to blow up anything. Will this circuit work as I want it to be? Also, does this circuit need a dc-dc converter?

Materials

Battery: 12 V 10 ah

Supercapacitor: 15 V (only using up to 12 V) 55 Farad

Switch: 30 V 10 A relay with diodes

Motor: 775 DC Motor

H bridge: DROK L298 Dual H Bridge

I would really appreciate some type of help and if interested, I can share more pictures of the project.


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The voltage across a battery is roughly constant, depending on chemistry, from fully charged to discharged. The voltage across a capacitor is exactly proportional (by an equation I have long since forgotten, but someone will post it soon I expect) to the energy stored in it. The prectical effect of this is the voltage across the capacitor is highly unlikely to be the same as the voltage across the battery when S1 is closed. When S1 is closed there will be a short burst of very high current while the capacitor charges or discharges to equal the battery voltage, which will most likely damage or destroy S1.

I see a few problems with this.

1st, the L298N doesn't have a way to do regenerative breaking. 2nd, That motor isn't very efficient as a motor, even less as a generator. You're not going to get enough back out of it to justify that work to do it. If you want to do regenerative breaking brushless is the way to go. 3rd, The Mabauchi RS775 is way to big for a L298N, as they are rated at 2A continous 3A peak. https://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf but a RS775 (There are two versions) pulls more current than that with no load. https://product.mabuchi-motor.com/detail.html?id=129 4th, a RS-775 likes more than 12V. If your vehicle is geared low enough, and its light enough, it will still work, if you can get enough current to it.

I have a robot platform I built a few years ago that runs on a pair of RS775's on each side (lateral steering). It is powered by a pair of 12V 5A gell cells, or a pair of 5AH 4cell LiOn's. The motors have gear reduction attached to them. Each side has a RC car electronic speed controller. It works well.

To use a L298, you want to be using something more like a 280 motor. I have a small dev toy based a L298. Google Arduino Yellow Wheel to see what works well for a L298.

A good place to start would be some reading on how regenerative braking is done in the real world.

I don't want to blow up anything

We can tell that you haven't tried to wire this circuit up, because the L298 H-bridge will instantly go up in smoke with a 775 motor (stall current 90 Amperes at 12V).