🔍 How to Use the Voltage Sag Simulator (Full Guide)
The Voltage Sag Simulator is a fully interactive tool designed to help e-bike and scooter riders, builders, and enthusiasts understand how battery voltage behaves under load—especially during acceleration. Voltage sag is one of the most important yet misunderstood concepts in electric mobility, and this simulator makes it easy to visualize and explore.
Understand Real-World Battery Behavior in E-Bikes & Scooters
This guide walks you through how the tool works, how to use it, and why it’s extremely valuable for anyone involved in the micromobility world.
What Is Voltage Sag?
When you accelerate on an electric bike or scooter, the motor demands a high amount of current (Amps).
This sudden load causes the battery voltage to temporarily drop, a phenomenon known as voltage sag.
- A battery that normally sits at 52V might drop to 46–48V under heavy acceleration.
- A weaker or high-resistance battery may drop even further.
- Once the load is reduced, the voltage rises back up.
Voltage sag affects:
- Acceleration strength
- Top speed
- Overall riding efficiency
- Heat generation
- Battery lifespan
The simulator visualizes all of this in real time.
How the Simulator Works
The tool combines three dynamic elements:
1. Adjustable Controls
You can influence the behavior of the simulation using three main controls:
● Battery Voltage (V)
Represents the nominal voltage of your battery pack.
Higher voltage = less sag and stronger acceleration.
● Load Current (A)
The amount of current the motor draws during acceleration.
Higher load = more sag, more heat, and slightly more speed at the start.
● Battery Type
Different battery chemistries have different internal resistances:
- Li-ion: Balanced, moderate sag
- LiFePO₄: Low sag, very stable
- Lead Acid: Very high sag, outdated technology
The internal resistance dramatically affects how much voltage drops during acceleration.
2. Real-Time Graphs
The chart displays two curves:
● Actual Voltage Curve
This is the real, dynamic voltage under load.
It changes frame-by-frame based on your inputs.
● Voltage Drop History
A secondary trace showing how quickly the voltage is falling during hard acceleration.
These two together show:
- How stable the battery is
- How severe the voltage sag becomes
- How changing load or battery type affects performance
3. Animated Vehicle Visual
The small animated vehicle at the bottom is a visual representation of the performance:
- The vehicle accelerates based on calculated speed.
- Wheel rotation shows motor load.
- The body color changes depending on voltage health.
- A glowing acceleration trail appears during heavy load.
It connects the technical data to real-world behavior.
How to Use the Simulator
Here is the recommended step-by-step workflow:
1. Set Your Battery Voltage
Choose your real battery:
- 36V
- 48V
- 52V
- 60V
- 72V
Higher voltage results in:
- Better acceleration
- Less sag under load
- More stable operation
2. Adjust Load Current
Move the “Load Current (A)” slider to simulate:
- Gentle acceleration (10–20A)
- Normal riding (20–40A)
- Hard launches (40–70A)
- Extreme controllers (70–100A)
As you increase current:
- Voltage sag becomes deeper
- The vehicle accelerates faster at first
- But voltage stability worsens
3. Choose the Battery Type
Select the chemistry you want to test:
- Li-ion (typical e-bike battery)
- LiFePO₄ (premium stability)
- Lead Acid (strong sag)
Each type has a different internal resistance, which changes the sag model.
4. Click “Start / Pause Animation”
This begins the simulation cycle.
You can:
- Pause it
- Adjust sliders
- Resume and instantly see the effect
This makes it perfect for testing combinations.
What You Learn Using the Tool
✔️ Why your e-bike slows down during uphill acceleration
Voltage sag limits motor power when current demand spikes.
✔️ Why two 52V batteries behave differently
Even with the same voltage, internal resistance determines sag.
✔️ How battery age affects performance
Old batteries have higher internal resistance → more sag.
✔️ Why your display sometimes shows voltage “jumping”
You’re seeing sag in real life—this tool shows the same effect visually.
✔️ Why LiFePO₄ or high-quality cells feel “stronger”
They maintain voltage better under high load.
Why This Tool Is Useful
Whether you’re a rider, technician, or builder, the simulator gives immediate insights:
For Riders
- Understand why your scooter feels weaker at low charge
- See how battery sag affects real-world speed
- Learn how different loads change performance
For Builders & DIY Enthusiasts
- Compare battery chemistries
- Test how much current your pack can realistically handle
- Visualize internal resistance effects
- Plan better battery/controller pairings
For Technicians & Sellers
- Educate customers about battery behavior
- Demonstrate performance differences
- Explain why quality cells matter
Conclusion
The Voltage Sag Simulator transforms a complex electrical concept into a clear, dynamic, and visually intuitive experience. By adjusting just a few sliders, you can instantly see how battery voltage, current, chemistry, and load interact to shape the performance of your e-bike or scooter.
It’s the perfect tool for anyone who wants a deeper understanding of real-world battery behavior—and for making smarter decisions when choosing or upgrading battery systems.
