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I have an electric wheel designed for an electric bicycle conversion. By my understanding, the wheel is essentially a 48V, 1000w rated brushless DC motor. It comes with a thumb throttle and kill switch built into a break lever.

I am looking to set it up as part of a stationary rig to do some testing and want to run the wheel on AC power. The wheel has no regenerative breaking so only draws power from a battery (not included in the kit).

Instead of wiring the positive and negative terminals of the motor to a battery, can I wire them to the appropriate terminals of an AC-DC transformer adapter such as this one and plug this directly into mains?

If not, what extra components do I need to include?

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  • \$\begingroup\$ You need the ESC electronics not just a power supply. Contact supplier \$\endgroup\$
    – D.A.S.
    Commented Jan 22, 2019 at 16:12
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    \$\begingroup\$ "regenerative breaks" is my Chemical Brothers cover band. \$\endgroup\$
    – user156429
    Commented Jan 22, 2019 at 16:58
  • \$\begingroup\$ There's no economically practical way to do this, at least not to power it to perform anything near its rated mechanical work. The power supply you'd need would be quite expensive. Further, the battery is a key part of the system - you should test that and the motor as their joint performance determines what you can actually get. Monitoring the battery voltage under load will give you some idea of how it is performing. \$\endgroup\$
    – Chris Stratton
    Commented Jan 22, 2019 at 22:09

4 Answers 4

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You can wire the + and - connections of the included controller to a power supply. Bear in mind that the current, which will be limited by the controller can initially be quite a lot higher than the rated current. A battery will tolerate that, but the switch mode supply you ink to may well limit or shut down when it sees that current, so you often need a large margin on rating the power supply.

Given that the battery's characteristics - it has a finite internal resistance, and the supply will droop under load - will affect the performance of the motor, so if you're using the rig to evaluate available power, you're better either using the intended battery, or a supply that has matching characteristics.

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  • \$\begingroup\$ What sort of current margin would you typically expect? \$\endgroup\$
    – JP19774028
    Commented Jan 22, 2019 at 17:56
  • \$\begingroup\$ Typically 50%, so 30A in this case. \$\endgroup\$
    – Phil G
    Commented Jan 22, 2019 at 19:12
  • \$\begingroup\$ If you can find and afford a suitable power supply. Which the OP probably cannot. \$\endgroup\$
    – Chris Stratton
    Commented Jan 22, 2019 at 22:10
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If you're using the same control electronics (thumb throttle and kill lever), then yes you can just hook it up to a Switch Mode Power Supply like the one you show.

You'll likely want some sort of very low ESR decoupling capacitor where you hand over power to the controller.

Make sure the power supply you choose is up to providing the instantaneous current required by your motor drive electronics, as that may be much larger than its average consumption. (The decoupling capacitor will help you here)

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  • \$\begingroup\$ A switch mode power supply capable of powering that is a non-trivial item. \$\endgroup\$
    – Chris Stratton
    Commented Jan 22, 2019 at 22:10
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Interesting, although I would be interested what kind of application you have in mind.
My suggestion would be to take a hybrid approach. Use the 48V (nom.) battery that is commonly used for the motor, which is able to provide the peak load currents at starting and accelleration. In addition connect a mains-fed power supply in parallel to the battery that can provide roughly the average current needed for the setup (note: no need for precise balancing of the two current contributions!). The voltage of that supply should be set such as not to overcharge the battery; as well the supply should have a properly adjusted current-limiting circuit in its output line, preventing shorting etc. Note that the supply does not need to be capable of delivering the instanteous peak currents: the battery takes care!
In this way one also ensures that the voltage applied to the DUT is well stabilised by the (low Ri) battery.
Main concern is to keep a solid eye on all (!) safety issues around Li-battery (dis)charging!

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    \$\begingroup\$ There's too much that can go wrong with the idea to make attempting wise. \$\endgroup\$
    – Chris Stratton
    Commented Jan 22, 2019 at 22:11
  • \$\begingroup\$ @Chris Stratton I tend to disagree: if combining the power supply with a CV/CC regulator like the DPS5015 of -5020 full and safe control is provided. \$\endgroup\$
    – Kees_DCRF
    Commented Jan 23, 2019 at 15:28
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What you want to do sounds feasible, with one notable problem: the power supply that you have chosen may not handle startup current. The great advantage of using a large battery pack is that the battery pack can supply enormous amounts of current for the short time that it takes to get the wheel spinning.

This isn't a problem if the wheel is not loaded but is definitely a problem if the load is at all similar to a rider on a bicycle.

All you can do is try it. If the power supply collapses under startup conditions, consider adding a battery pack in parallel with your power supply via a suitable isolation diode. You can keep this extra battery pack on a charger all the time.

Just be sure to set the output voltage of the power supply to be somewhat higher than the fully-charged voltage of the battery.

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