Bonzaianswered grow question 1d ago At 90–100 seconds, I would first check the distance from the ground to the lower coil. In the picture, it looks to me like there might be too much distance there. The ground should be pretty close to the lower coil, of course without touching it.
At 70% battery, it could also be that the Cuboo is already reducing the power a bit. So I would test with a full battery and see if the heat-up time changes significantly.
If it still takes around 90–100 seconds even with 100% battery, I would rather play around with the distance or ball filling.
It would also be interesting to know how many 2.5mm 100Cr6 balls you have in there.