Trex, Qik Motor controller selection

I have a number of TreX and Qik motor controllers that I bought last year and haven’t yet used. I’d like to use them on a robot with a 4S Lipo battery. The battery is nominally 14.8V but when fully charged will likely slightly exceed the 16V voltage limit of the TreX and Qik controllers. I am using your 25D HP motors so a Trex Jr (with a higher maximum voltage but lower maximum current) will not work. Am I correct that the 16V limit on the TreX and Qik is an absolute limit and that using either controller with a 4S lipo would be inadvisable? I could buy a new motor controller that matches the voltage/current requirements (e.g., a RoboClaw) but would love to save some money by using the controllers that I have laying around. Thanks.


The voltage limits listed under the “Specs” tabs of those respective product pages are the absolute maximums for those drivers and should not be exceeded. A 3S LiPo battery would be a better choice for those drivers.

By the way you should consider limiting your duty cycle to bring the effective motor voltage down to the rated voltage to get the best lifetime out of your 25D motors, especially if you are using the 6V versions.


Thanks Derrill. No surprise there but thanks for confirming. We are using 12v motors and will limit the duty cycle to a narrow band around that.

Hi. We have a follow on question relating to this. We would like to come as close to 16v as possible, which with a standard LiPo battery is only reachable by a 4S battery. And, as you know, a fully charged LiPo is 16.8v and will damage the controllers. We are now using motors that are nominally rated 12v but are recommended up to 18v. They would have a stall current of about 6a. So we are a bit stuck as to how to run the motors at or near 16v rathan than 12.6v, which is the maximum a 3S LiPo can provide.

Is there a way to boost a 3s LiPo given our parameters? (We didn’t see a step up voltage regulator in your store that would work.) If not, can you think of any option that gets us to 16v using a high discharge rate battery? We were wondering about discharging the LiPo to 4v per cell but were thinking that might damage the battery. (Our thought was it’s better to discharge by .8v and thereby leave some inefficiency there, than run everything at the 12.6v max of a 3S battery.) Thank you.

None of the our regulators can source enough current with a 16V output to run your motors, but in general, it is not a great idea to try running the TReX controller right at its absolute maximum anyway, since spikes on the input (which are common with motor systems) could damage the controller.

Why do you want to run your motors near 16V?


Perhaps misguided, but we were hoping to get the most power out of the motors as possible. It’s for a competition where speed and power are key. The competition limits the voltage. If we run a 3S LiPo, we get 12.6v. So perhaps we charge the batteries in “storage mode” on the balance charger, which will take them to 15.5v or so. What do you think of that idea? Or we could buy a boost converter step up regulator, use a 3S LiPo and run it at 15v. Any thoughts on those options would be appreciated! Thank you for the help!

I do not have any recommendations for a regulator that can source that much current at 16V or higher. If you decide to try a regulator, you should probably step down from a 4S Lipo rather than try to step up a 3S LiPo.

You will probably need to try your battery strategy to see if it works; as long as it never exceeds 16V, you should be fine.

If higher voltages are important to you, you might consider a different motor controller like our Simple Motor Controllers.