Newbie low battery question

[rambisetr]

Hello! I'm new to the forum and RC scene and just got the 2WD BL Ruckus. My questions are, is it standard for the truck to get herky-jerky when the battery is too low or did I break my truck already? Because I would expect it to just slow down when the battery got low but the truck will just pulsate basically when the battery gets lower. If its normal, does it do that for NiMh and LiPo batteries or just NiMh? I haven't gotten the LiPo yet but am curious if it works the same way. Thank you.

 

[xlDooM]

Maybe it's just cogging? If you drive that slowly on a fresh battery, does it also do it? Unsensored brushless motors will just do that; pulse the power as the motor turns slowly.

 

[X]

I haven't ran into that issue with mine......maybe I should try driving it slower......

Plus I drive it with lipo.

I assume, as @xlDooM does that this is cogging. Possibly made worse by the fact that nimh batteries cannot sustain current as well as lipo.

 

[rambisetr]

Maybe it's just cogging? If you drive that slowly on a fresh battery, does it also do it? Unsensored brushless motors will just do that; pulse the power as the motor turns slowly.

I don't have the issue when I drive on a fresh battery or while driving slow. Only after I've driven a while and it seems to be slowing down. It seems fine until once I have drained the battery down.

I haven't ran into that issue with mine......maybe I should try driving it slower......

Plus I drive it with LiPo.

I assume, as @xlDooM does that this is cogging. Possibly made worse by the fact that NiMH batteries cannot sustain current as well as LiPo.

I'm sure this has been answered somewhere to another newbie but I'm already here on my post and it relates, can you explain what "cogging" is?

 

[xlDooM]

The motor works like this. The rotor, which is the drum like thing that is connected to the output shaft, contains permanent magnets. The can around it (the stator) pushes the rotor around by means of electromagnets placed around the rotor, which are alternatingly being energized. In order for the motor to run, the activation of the electromagnets must be timed in such a way that they attract one of the magnets which is coming towards them, or push against one that has just passed. If the motor is sensored the timing is always accurate, but an unsensored motor has to guess the position of the rotor. At high speeds this smooths itself out, the rotor automatically comes into sync with the stator pulses. At low speeds however, you can have jolts of power because the timing is off. This causes the RC to go forward in a pulsing fashion.

 

[X]

I don't have the issue when I drive on a fresh battery or while driving slow. Only after I've driven a while and it seems to be slowing down. It seems fine until once I have drained the battery down.


I'm sure this has been answered somewhere to another newbie but I'm already here on my post and it relates, can you explain what "cogging" is?

If you hand turn your motor you will find that it jumps from one position (pole) to the next, it doesn't turn smoothly. At low speeds this can cause the effect you speak of.

@xlDooM beat me to it with a more in depth explanation.

 

[rambisetr]

The motor works like this. The rotor, which is the drum like thing that is connected to the output shaft, contains permanent magnets. The can around it (the stator) pushes the rotor around by means of electromagnets placed around the rotor, which are alternatingly being energized. In order for the motor to run, the activation of the electromagnets must be timed in such a way that they attract one of the magnets which is coming towards them, or push against one that has just passed. If the motor is sensored the timing is always accurate, but an unsensored motor has to guess the position of the rotor. At high speeds this smooths itself out, the rotor automatically comes into sync with the stator pulses. At low speeds however, you can have jolts of power because the timing is off. This causes the RC to go forward in a pulsing fashion.

Thank you so much for this education (not being sarcastic). So I don't think its a cogging issue since it only happens when the battery is lower. It will do this off pavement but once on the pavement it will run fine.