What is Ebike Battery Voltage Sag? Explained!

With the will to add innovation to bicycles by increasing their proficiency, e-bikes have taken over the market. However, the battery’s performance plays a major role when it comes to an e-bike’s efficiency.

One such major issue that ebike riders face is the ebike battery voltage sag. It means the capacity of an e-bike battery to assist the load starts to fall off over a period of time. This is called battery voltage sag in cyclists’ vocabulary.

What is the reason behind this voltage sagging and how could you maintain your battery properly to prevent voltage sagging?

In this article, we will highlight those important parts along with informative FAQs.

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Related: Why is my ebike charger not working?

What is Ebike Battery Voltage Sagging? Answered!

Voltage sagging or otherwise referred to as a voltage dip is basically when there’s a temporary depletion in the voltage of the e-bike’s battery. An e-bike’s battery is quite restricted as compared to any other electric appliance’s battery.

Hence, what happens is when you increase the load on the battery it gets heated and leads to a drop in voltage levels.

48v ebike battery voltage sagging chart

For example, when you are needed to generate a larger amount of power while riding uphill or off-roading there’s an increase in power consumption which leads to voltage sag or drop.

However, the percentage of voltage dip depends majorly on two factors:

Ebike motor

When you are putting a load on the battery, a reasonable percentage of the volt is drawn away to run the electrical power of the motor or the kilowatts. That is when you see the voltage percentage reading lower than usual.

This is an inaccurate reading, and we are not able to estimate how many amp hours are left in the battery. However, once the high power is dropped and the voltage reading is adjusted you get the correct reading.

Electric bike battery

Indeed the battery is one of the major components when we are talking about voltage sag. How it affects is basically when the internal resistance increases while the power is draining.

This limits the flow of current capacity of the battery and in return the voltage drops. The internal resistance’s performance of affected mostly when there’s a heavier load on the battery. Read more.

Why Electric Bike Battery Voltage Sag? 3 Reasons

Now that we are aware of what exactly is battery voltage sagging in e-bikes, it is crucial to understand why does it happen? Where voltage sagging could be absolutely normal, on the other hand, there are multiple reasons that lead to the voltage drop in e-bike batteries.

Let’s see some of the major voltage sag causes or reasons:

1. Due to an old battery

In regard to older batteries, which have been charged and recharged multiple times affect their functioning of it. The draining and regaining of charge so many times disrupt its electrical structure of it, which may lead to voltage sag.

2. When the battery is heated

Often during or after long rides, it is quite evident to see a significant drop in the voltage level of your e-bike. This is because of the battery being warmed up.

3. Unused ebike battery

If you are using a battery that has been laying around in the storage for quite some while, then you might face some unexpected battery voltage sagging as well.

Apart from these, the power level at which you are riding your bike also decides how much of a sag will your e-bike battery face. When you are riding at a higher power, comparatively a larger amount of current is used up which leads your battery to sag quickly as when you are riding at a lower power level.

Weather conditions also play a significant role. When you are charging your e-bike battery, it absorbs more energy compared to what it generates.

Hence, when there’s no sun to absorb this energy or you are not riding it often, then this energy is left stored in the battery unused which is later emitted as heat. Now, this leads to voltage sag in the battery.

How Much Voltage Sag is Acceptable in Ebike Battery?

A major question that most ebike riders ask is whether voltage sag is good or bad. However, you must know that voltage sag is experienced in almost all-electric vehicles.

What really matters is the amount of voltage sag that is acceptable and could be managed when experienced. There are a few estimations that tell you if the sagging percentage of your battery is on the acceptable side or not.

For say, if you are going full throttle from a standstill and it leads to a sag of 2V to 3V, then there’s nothing to worry about. Mostly, cyclists face a voltage sag in the range of 4V to 5V depending on the size of the battery.

Moreover, a 5V battery sag would have a different effect on a 24v battery’s performance than it would on a 48v battery. Apart from this, a voltage sag of 6v or above makes your battery very hot and could hamper the life span.

Related: Are Rad Power Bikes UL Certified? No!

How to Avoid Maximum Voltage Sag in Ebike Battery?

Where voltage sagging is evident in e-bike batteries, it is also important to practice healthy habits for your e-bike battery which will help you avoid maximum voltage sag and will keep your battery young and effective for a long riding period.

Le’s see what are the few simple steps by which you can maintain your ebike battery!

1. A High-Quality Battery

This is one of the foremost ways to avoid voltage sag. You should always look for high-quality batteries that suit your e-bike perfectly. A good battery is more likely to produce a higher density of energy, which in return generates a comparatively consistent voltage range than any low-quality battery.

Consistent voltage production is a key element when we talk about the prevention of voltage sagging in e-bike batteries.

2. Battery Charging Etiquetes

A major mistake that most ebike users do is in the charging habits of the battery. It is crucial to note that keeping your battery plugged-in, in order to keep the battery charged at maximum all the time, damages your battery the most.

Whereas, neither overcharging nor undercharging is a healthy habit for your e-bike along with following the manufacturer’s instructions.

3. Finding the Apt Motor and Controller

Using the correct kilowatts of the motor and controller is the most important and necessary part. Since the energy from the battery is drained, which leads to voltage sag, drives the motor.

Hence, a cohesive power motor that can support your battery’s overload is much for avoiding voltage sag.

4. Range Test of Voltage Sag

As you know that voltage sagging up to a certain level of a volt is quite normal and acceptable, you can do checks on your e-bike to be aware of the danger range. After all, prevention is better than cure.

All you need to do is charge up your e-bike battery to the max, then drain the battery power by riding it to its maximum capacity. This you can do either by riding uphill or against the wind.

Now observe the voltage display monitor on your e-bike to take observations of how many watts it is going down by. 

These were the few methods that you can follow to avoid voltage sagging in your e-bikes and keep the performance level high!

Apart from these a few basic habits like keeping your battery in a cool place and not overloading your e-bike could also help you to minimize the voltage sag!

Conclusion on Ebike Battery Voltage Drop or Sag

Riding an e-bike comes with certain responsibilities if you want optimum performance in long run. Especially when it’s the battery. Charging it correctly, using the right power pod, maintaining the voltage sag range, and so on.

We hope that our article could spread awareness and help you in keeping your e-bike batteries at their best and never let any technical inconvenience ruin your cycling experience.

FAQs on Ebike Battery Voltage Sag

  • How does voltage sag affect the performance of an e-bike?

    Not permanently. However, a voltage sag will naturally make your e-bike slower and reduce the distance range as previously covered by it.

  • Can voltage sag damage an e-bike battery?

    Yes! If you are not taking any of the preventive measures or keeping a track of voltage sag percentage then, over time your battery will get destroyed because of overheating and inconsistent power draining.

  • How to identify that the voltage of my e-bike battery is sagging?

    You can either see the display on your e-bike which shows the voltage levels or you could use a vol reader meter to detect it.

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I am the founder and editor of The Bike Fetcher, a passionate E-Biker. My passion for E-bikes led me to build this blog site where I share electric bike news & updates, my e-biking experience, e-biking tips, e-bike battery tips and help people to get the best e-bike. Feel free to contact me on my social accounts or through the contact form.

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