How to Reset an Ebike Battery BMS in 5 Simple Steps [An Ultimate Guide]

You can’t enjoy riding an electric without a battery, right? It means your electric bike is nothing without a battery as it is considered the heart of an electric bike.

But What if your charged battery stops supplying power to the motor? It can happen as it’s a machine. Obviously, you need to get this issue fixed i.e., You need to reset the ebike battery.

Don’t worry! I have fixed many faulty BMS of ebike batteries, With that knowledge I will guide you through this article to learn How to reset ebike battery BMS in easy steps.

Knowing the symptoms of a faulty battery BMS is very important otherwise you would never know when you should reset the battery. Along with that, I will answer some common questions about e-bike batteries.

I hope you will love reading this article. Let’s start with the basics of an electric bike battery.

Understanding an Ebike Battery

What do you expect out of your e-bike? A powerful bike with amazing speed and riding distance. That’s exactly what your battery does.

A battery pack is made up of a number of smaller battery cells all stacked to deliver the required power that your ebike system needs to function.

The battery is the soul of your bike as it performs many important functions such as the range of riding. The battery is therefore the most expensive component of your E-bike after the motor.

The ebike battery is made up of 3 components – Battery Meter, Battery cells, and Battery Management System (BMS). Among these, only by resetting the BMS, you can regain the battery efficacy.

What to Consider in an Ebike Battery?

1. Battery power

You should invest in the most battery power you can afford. But how do you determine the battery size (voltage) for an ebike? Apply this simple maths;

Size of the battery or Watt-hours = Volts x AMP hours

For eg; Volts = 48; AMP hours =14 Ah. Therefore, Watt-hours= 48×14= 672 WH

This watt-hour determines the range and power you get out of your E-bike battery. Higher watt hour gives more range and supplies more power to the motor.

2. Type of battery charger

Normal battery chargers take around 6-8 hours of charging time. However, efficient chargers can take as little as 3 hours to reach maximum charging points. Don’t use high-amp chargers, it may damage your battery bms.

3. Battery location (on/in the frame)

it’s easy to remove the battery in some ebikes making it feasible to charge the battery even in the comfort of your room, they are known as detachable batteries.

But, some batteries are fixed in such a way that they are difficult to remove without a tool, making the charging even more complex. They are charged along with the bike. In that case, resetting the battery is complex.

Related: How long to charge a 48-volt ebike battery?

4. Battery life

Generally, an ebike lithium-ion battery lasts for 3 to 4 years. Also, the battery life depends on the following factors:

• Your charge cycle (50% efficiency reduces at around 300th recharge).
• Way of riding (Slow, Economy mode, or race mode).
• How you take care of your bike.

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What is a BMS in an Ebike Battery and How Does It Work?

BMS stands for a battery management system which is considered the brain of a battery pack as it manages all the battery functions. In other words, BMS is a set of electronic components that monitors and manages the battery’s operations.

Additionally, It also keeps the battery from operating outside its safety limits such as protecting it from overcharging and overheating. Hence, the ebike battery is nothing without its BMS.

A BMS takes in several inputs such as voltage, temperature sensors, and current. The outputs of a BMS after taking in various algorithms such as:

• SOC (state of charge ),
• SOH (state of health), 
• SOE (state of the envelope), and 
• Faults.

BMS can be used in single-cell or multicell lithium-ion batteries. Some major functions of BMS are:

• It monitors voltage as it resides very close to the cells.
• Monitors overall pack voltage.
• Measures input and output current of the battery.
• It has a master disconnect that allows it to terminate the recharge of the battery if any fault is attacking the system.
• The BMS of a battery disconnects the charger when the battery is fully charged.

Importance of BMS in Ebike Battery

BMS is an indicator of the battery’s health and the protector of the battery under operation. It also performs various functions and is highly important for the following reasons.

• It monitors each lithium cell and ensures that it operates within the limit.
• Preserves and keeps the battery safe.
• Performs cell balancing.
• Maintains stability of the whole pack.
• Monitors and controls the charge demanded from each cell in the chain.
• Major role in battery pack testing.
• Helps detect faults and weaknesses in each cell of the Battery pack. 
• Monitors current, voltage, and temperature.

Faulty BMS Symptoms in Ebike Battery

4 different kinds of faults can happen in your Battery Management System. Let’s have a quick look at what these are along with a summary.

Note: We are considering voltage and temperature as the two determinants for the defect.

Fault	Expected Reason	Symptoms
Thermal Runaway	Over Temperature	Lithium-ion cells heat internally and run away.
Overcharge	Cells can’t hold the charge	Triggers Thermal Runaway
Over-discharge (Drained)	Microfilaments create shorts with inner cells	The chemistry of lithium-ion cells becomes unsafe.
Undertemprature	Electrochemistry is no longer able to move the ions.	This can lead to an over-discharge scenario.

If you experience any faults in your ebike battery, you need to reset your ebike battery’s BMS. Let’s learn the BMS reset process step by step.

Related: What is voltage sag in ebike batteries?

How to Reset Ebike Battery BMS: Step-by-Step Guide

If your battery is no longer charging or getting easily discharged, follow these procedures for an easy BMS rest with the use of minimal tools. There are 2 ways of resetting your BMS:

• External Reset procedure
• Internal Reset procedure

1. How do I Reset my Ebike Battery BMS Externally?

Step 1: Procure tools

For an external Reset, you will need a voltmeter or multimeter, wire cutters, soldering iron, and safety gloves. Get all of these before performing the BMS reset procedure.

Step 2: Collect materials

Once you have got the tools, you will need electrical tape, Electrical wire (red and black), and a DC Barrel Jack Receptacle. Get these as well.

Step 3: Create an adaptor

To create an adapter, you need to solder the red wire to the positive terminal (+) and the black wire to the negative terminal (-) of the DC receptacle.

Step 4: Plug the battery charger into the adapter

The ends of the wire shouldn’t touch. You shall test your adapter with a voltmeter to make sure that the wire is correctly inserted. In this case, you need to plug the red pin with the red wire and the black pin with the black wire. 

Your voltmeter will start showing a positive reading. By chance, if the reading is negative then you have probably connected the wires to the wrong terminal.

Step 5: Attachment with a discharge port

Since the adapter is ready, you need to insert the wires of the adapter into the correct terminals on the discharge port. You must connect the red wire to the positive terminal and the black wire to the negative terminal of the discharge port.

Step 6: Resetting the BMS

Once a red light appears on your charger you can be sure that the battery is charging. Hold the wires in place for at least 15 seconds to ensure your BMS is reset.

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2. How to Perform Internal Ebike Battery BMS Reset Procedure?

In case you weren’t successful in resetting your battery via external procedure you can go for an internal Reset procedure. Here it is:

Step 1: Procure tools

You need some basic tools like a screwdriver and a flat-head precision screwdriver.

Step 2: Take out the BMS chip

Remove the cover of the battery by removing the screws with the help of a screwdriver. The BMS chip will come out with a gentle force.

Step 3: Disconnecting the harness

Now you need to remove the wiring harness from the BMS chip. Do it gently or you will break one of the connections.

Step 4: Connect the charger cable

In this step, you need to connect the charger cable to the battery and fix the harness to the BMS chip.

Step 5: Put back the batteries

Your BMS chip will now be reset. You can put back the batteries and tighten the screws.

Conclusion: Ebike Battery BMS Reset

As a rider of an E-bike, it’s vital to understand the BMS reset as it comes in handy, easy, and economical. BMS reset is the only option when your battery is showing errors, not getting charged, or not supplying power to the motor.

I hope you have understood how to reset ebike battery BMS externally and internally. If you have any doubts, ask us in the comment section below!

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FAQs: Ebike Battery BMS Reset Procedure

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