I'm pretty sure that LI-ION has the same problems that LIFEPO4 has in that they can't handle high currents. Ok, try this. When you are first starting off, turn the throttle to the maximum and get up to speed that way. If it cuts out doing that, then it's a battery problem. You still haven't said whether the battery has a BMS or not. I assume the battery has a BMS. In that case, your battery might be just fine and it's the BMS that is the problem. To correct this, what you could do is remove the BMS from the battery by cutting only the wires connect the BMS...Be careful that you don't render the battery useless. Then rewire the battery with anderson connectors or whatever connector is used to connect it to the controller. Then, you will have to use the cycle analyst to determine when the battery is low. I do this on my bike. I have no BMS. I'm not very familiar with LI-ION so you'll need to find out how many cells are in your battery pack. And what the battery reads on a full charge. And then find out what the lowest battery voltage per cell is considered safe. So for example, if 2.8v per cell is considered safe, then I wouldn't take it below 3.0v per cell. So if you had 15 cells then that would be 15 x 3 = 45v so when the Cycle analyst read 45v (at rest), you will want to stop.