Tried Running a 72V Motor on a 52V Battery — Here’s What I Learned

[JL0256]

Hey everyone,


Just wanted to share something I tried recently that a lot of DIY e-bike builders have probably wondered about:
Can a 72V motor work with a 52V battery?


I’ve been putting together my own builds for a few years now, and this time I wanted to see if I could reuse my old 52V battery with a 72V hub motor instead of buying a new pack right away. Here’s what I found.

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My Setup​

I’m running a 5000W rear hub motor with a 52V 20Ah battery from my previous build.
The controller was originally configured for 72V, but since most programmable controllers have a voltage range, I figured it might still run fine.


Startup went smoothly. The motor spun up without issue, throttle felt okay, and for a moment, I thought I’d found the perfect money-saving workaround.

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On the First Ride​

On flat ground, it rode fine — just slower than expected.
Torque was noticeably weaker, and on inclines, it became obvious that the motor wasn’t getting enough current.
Performance dropped about 25–30%. My 5000W e-bike suddenly felt like a 3000W version.


Under heavy throttle, voltage sag hit hard. After around 15–20 minutes, the controller began cutting power intermittently — probably low-voltage protection kicking in.

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What I Learned​

You can run a 72V motor on a 52V battery, but only if your controller supports it.


Expect:

• Lower top speed
• Softer torque
• Quicker heat buildup

It’s fine for short tests or light commuting, but not ideal long-term if you care about efficiency or battery health.


When I finally upgraded to a proper 72V pack, the difference was huge. The bike felt powerful and consistent again — just like it should.

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Final Thoughts​

If you’re experimenting, that’s part of the DIY fun — just know what you’re getting into.
If you want a deeper technical explanation of how voltage matching affects power and efficiency, this detailed guide from EM3ev explains it really well.


It’s worth a read if you’re considering mixing voltages or planning your next upgrade.

 

[6zfshdb]

I occasionally run a 52V motor with a 48V battery. The performance is a bit sluggish, but not as severe as your experience. Probably because it's just a 4 volt drop compared to the 20 volts you're dealing with.

 

[harryS]

Good topic, but many DIY guys are looking to try increased voltage , Going from 36V up to 48V and even 52V won't hurt most hubmotors. Just make sure the controller can handle the higher voltage and use some restraint. I routinely run my hubmotors on my 36, 48, and 52V packs, accepting that they're a little slower at 36V.

For fun, one time I used a voltage booster to run 60V into my Ecotric fat tire folder. It was fast, but the efficiency of the DC-DC booster was losing a third of the battery capacity to heat. Then I blew the fuse on the battery, something I've never done, No restraint that day, Had to pedal home w/o power. That soured me on fat tires. Now I prefer light bikes with tires that roll forever.

Most of my controllers are designed to put out a certain current at a given assist level. Lowering the voltage lowers the wattage (watts is current x volts), I only have one that tries to keep the power constant. That's in my DM02 mid drive kit. WIth a 36V battery, I get the same assist power (per the display wattmeter) as 48V in the lower assist modes. That's pertty nice.