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Advice on adding 'reverse' to electric cart

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svenonderbeke

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Hi everyone,

I made an electric cart. Therefore I bought a chinese 48v 1600W ESC, a 2000W 20Ah 48v lithium pack and a 48v 1600W bldc motor (and other electronics not related to my question).
The cart works well, but I would like to add the ability to drive in reverse. Therefore I see three 'options' to achieve this, being:

- Reprogram the microcontroller inside the esc (picture of µc attached)
difficulty: nothing to found about the microntroller so no original firmware found and no info on how to pogram it

- Hack the esc by using my own microcontroller to switch the mosfets.
difficulty: drawing electric scheme of the esc and writing a good program (that not only switches the mosfets but also measures the currents and acts accordingly and more things)

- Use relays to twist a correct phase wire and the right hall sensors wires. (seems most achievable to me)
difficulty: making sure that the relays exactly switch at the same time so I don't creat a short. (using DPDT relays) + safety: making sure I don't apply full throttle forward and then full throttle backwards (I think it would make the motor generate power and that would kill the esc but i'm not sure about this).

Q:
What would you suggest I do to add a reverse? Are there more options? Are there things a didn't think about regarding safety?

extra Question:
I would measure my cart speed using a hall sensor and a magnet and be sure that my velocity is 0 before I'm am able to drive in reverse. But could I also use the switching to reverse when I'm driving forward and by this creating eletric braking?
 

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Last edited:
Cross-wiring the corner tabs on a center-off DPDT switch is the most common way to reverse polarity and change motor direction. If you go online and seek out "DC motor control circuits", you'll see this and other solid-state designs using an H-ladder ( 2 or 4 opposing cross-connected transistors), and may include another switch to power up the control circuit.
 
Thank you Shokjok,
I will do it that way, changed my mind from achieving this with relays to doing it mechanically: ordered this drum switch :
**broken link removed**
Though I never saw anyone use it on a motor WITH hall sensors. But I guess I'll just have to mind switching those with another switch as well.
 
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