The i3's plastic jack points are not like those on most cars. The $20 1.5-ton automotive scissor jack and $40 2-ton ratcheting jack stands that I had used with my Mitsubishi i-MiEV could not be used with our i3 because their lifting surfaces do not have the correct shape to fit in the i3's jack points, and they do not have flat lifting surfaces that could be used with a jack pad adapter. So I had to pay almost $400 for a 1.5-ton floor jack with a round, flat, rubber-padded lifting surface and 4 3-ton ESCO 10499 jack stands with custom pivoting aluminum block stainless steel posts that fit in the i3's jack points.
My new floor jack is much larger and heavier than the basic scissor jack that it replaces which isn't ideal for those of us who live in apartments with limited storage space. My new jack stands are way overkill for our light i3 and are considerably heavier than those they replace. However, they are very high quality with wide, stable bases. I was able to use the wheel chocks that I already had. These jack pad adapters do not work with an i3 because the rectangular support surface is only ¼" high whereas the i3's jack points are ½" deep. I removed the rectangular support surface from one of them and glued it to another of them to create a jack pad adapter with the necessary ½" high rectangular support surface. The jack, 1 jack stand, 1 wheel chock, and the modified jack pad adapter can be seen here.
To place an i3 on jack stands, put the car in P and engage the parking brake. Unlock the car to prevent the motion alarm from tripping as the car is being lifted. Place wheel chocks in front of a front and behind a rear tire on the side of the car opposite that which will be lifted first. Position a jack pad adapter on the lifting surface of the floor jack. Roll the floor jack into approximate position below one of the front jack points and raise the jack until the jack pad adapter just touches the jack point. Adjust the position of the jack so that the jack pad adapter will enter the jack point properly, and lift the jack until the rear tire on the same side is off the floor. Place a jack stand under the rear jack point next to the rear tire adjusting the high of the jack and jack stand so that the tire remains off the ground when the car is supported by the jack stand. Lower the jack slowly and move it to the other side of the car.
Position the floor jack with its jack pad adapter under the other front jack point. As before, slowly lift the jack until the rear tire on the same side is off the floor. Because of the stiffness of the i3's chassis, the front wheel on the opposite side will also be off the floor. Because the wheel chocks will no longer be blocking the tires, be careful that the car does not move as the remaining 3 wheels are lifted off the floor. The front of my car moved a bit to the side as the jack was lifting, so watch the jack stand that is supporting the rear of the opposite side to ensure that it remains squarely on the floor and doesn't start tilting. Place jack stands under the rear jack point on the side of the car being lifted and under the front jack point on the opposite side adjusting them appropriately so that the tires remain off the floor as the jack is slowly lowered. Remove the jack pad adapter from the jack.
For some reason, BMW did not provide 2 additional jack points to use to lift an i3 so that jack stands could be placed under the existing 4 jack points. Therefore, the last jack point must be raised by placing the jack under an arm of the front suspension closest to this jack point. Move the jack to under this suspension arm as close to the tire as possible being careful to protect the aluminum suspension arm with the rubber pad on the jack. Slowly raise the jack until a jack stand can be placed under the last jack point keeping an eye on all jack stands ensuring that they don't move or tilt. After the last jack stand is secured, slowly lower the jack and remove it from under the car. The car should now be securely off the floor on 4 jack stands.
To lower the car off the jack stands, just reverse the above steps.