In the ebike industry, unlike more mature industries, there’s a distinct lack of standardization. This means that components from one e-bike might use different technology, voltages, and connectors than similar parts from another e-bike. Replacing, upgrading, or adding electronic parts to e-bikes can get complicated, and fast.
If you’re building your own bike, you want to replace a battery, or you just have a spare lithium battery you’re thinking about using on your e-bike, you might be wondering how compatible these different parts are with each other. So can you use a 48v battery with your 36v motor?
You can use a 48-volt battery with a 36-volt e-bike motor as long as the controller is compatible with 48-volt (or higher) setups, and the electric motor is compatible with and does not overheat by the increased Wattage (volt x amps) output generated by the 48-volt battery.
Let’s go over all of the reasons why this might not work from an electronics perspective and talk about what you should look for before plugging in a battery that’s not designed for your bike.
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Can I Use 48v Battery With 36v Motor?
Yes, you can use a 48-volt battery with your 36-volt e-bike motor, but it might not be a good idea. Your motor probably will work with a wide range of voltages and is unlikely to be the source of any problems you run into.
Increasing the voltage to the motor will increase the rate at which it spins, which can have interesting mechanical implications and will cause the motor to generate more heat, but it won’t break anything short-term. In fact, some people deliberately over-volt their motors in order to get their bikes to go faster.
Before throwing a high voltage battery on your e-bike, you’ll want to do a bit of research. First, if you can, try to figure out the exact specifications of your motor and see what voltage ranges it was designed for.
If you’ve got a motor that’s designed to be used at 36 volts, the 33% increase in voltage to 48 volts is probably fine. If you’ve got a motor that’s designed to be used at a lower voltage, however, it’s probably being stretched already when it’s pushed to 36 volts. In this case, going to 48 volts is much more likely to cause issues.
Alternately, if you’ve got a motor that’s being used under its rated voltage, going to 48 volts will be totally fine.
Second, and more importantly, you’ll want to examine the other components of your bike and make sure that they’re compatible with your 48v battery.
Your motor will generate more heat and spin faster when it’s exposed to more voltage, but your controller is much more sensitive to changes in how electricity flows through your bike. This means that the controller is the component you’ll want to examine first if you’re trying to put a 48v battery on your bike.
Can I Use A 48v Battery With a 36v Controller?
You might be able to use a 48v battery with your 36v e-bike controller, but you’ll need to do some research first. Most modern e-bike controllers are designed for a very big range of voltages, so a 36v controller is a bit of an oddity.
Look for the model number of your controller (often found on a sticker on the unit) and try to find out the full range of voltages it’s compatible with. If the range ends in 36v (24-36v, for example), you’ll definitely want to avoid using a 48v battery. If it’s 36-48v or higher, however, you should be fine to plug in your big battery.
If your controller isn’t listed as being compatible with 48v or higher setups, do NOT plug the battery in. Controllers tend to have sensitive components like capacitors that will break very quickly when exposed to a higher voltage than they’re designed for.
Plugging a 48v battery into your 36v controller and turning on your bike has a very high chance of blowing your capacitors and breaking your controller.
What Happens When I Use A 48v Battery With A 36v Motor?
The terms “volts” and “amps” describe the flow of electricity through a system. If we think of electricity as water running through pipes, voltage describes the pressure of the water in the pipe, while amperage describes the volume of water flowing through the pipe.
A big, wide pipe with slow flow would have high amps and low voltage, while a thin pipe with high pressure would have high voltage and lower amps.
Your motor needs both pressure and volume in order to function. The more electricity it gets, the more torque it can generate. This means that in order to get up hills or start from a stop you’ll want to increase the amps that your motor has access to, but not necessarily the voltage.
If you want it to spin fast, however, it needs a supply of high-pressure, fast-moving electricity in order to quickly power and de-power the magnets that make your motor work. This requires a lot of voltage.
Motors are sensitive to changes in both amps and volts, but they’re generally totally safe to operate as long as the two don’t combine dangerously.
To continue with the water analogy, this means that your motor doesn’t care if you’ve got a thin pipe with high pressure or a thick pipe with low pressure. Your motor will simply produce lots of torque at low speeds with one setup and high speeds with less torque with the other setup.
If you give it a thick pipe with high pressure, however, you risk exposing your motor to more total electricity than it can safely handle, which could cause problems. In other words, you’re mostly worried about watts, or voltage times amps, not the distribution between the two. This is why many people who overvolt their motors will modify their setup to reduce amperage, keeping their motors safe.
As mentioned above, supplying your motor with more volts than it is designed for will cause it to generate more heat. This often means that you’ll reduce the lifespan of your motor, although not necessarily by a huge amount.
Motors are designed to handle some amount of heat generation and are usually over-engineered, meaning that they’ll have generous tolerances in terms of their ability to handle the voltage, dissipate heat, and deal with wear and tear.
In practice, you’ll probably be fine with a modest increase in volts of 25-35%, especially if you don’t run your motors at peak output all the time. Again, though, be mindful of your total watt output and make sure that you’re not pushing an unsafe amount of energy into your motors.
