How Do I Reset My Ebike BMS battery? (Guide With PIC)


The battery is one of the very important parts of an electric bike, not only because it is the second most expensive part after the motor, but also because without it the bike would not be an electric bike.

Since the battery, as we mentioned, is one of the most expensive parts, replacing it will be expensive, so knowing a little about maintaining your battery may save you a lot of money.

The good thing here is that the internal contents of the battery are not complicated at all. The internal parts of the battery in most batteries are as follows.

1- Battery cells
2- BMS System
3- The battery meter

Since you searched for how to do a BMS reset for your electric bike battery, you may have checked your battery and made sure that the problem could be in the BMS.

Therefore, in this post, we will explain the possible ways in which REST for BMS can work, as well as how to test the BMS.

Warning: In this post, we will use some electrical tools and also deal with electrical parts, so you must take all safety measures for dealing with electrical tools and parts

Anything you will try in this post will be at your own risk, without any responsibility on our website.

Now that we have mentioned all the necessary precautions, let’s start first with the BMS test method.

How To Test your ebike BMS battery?

As a general rule, you can test the BMS of an electric bike battery by measuring the voltage of the negative BMS connection going to the controller and the motor and between the main positive side connected to the battery cells and the BMS together.

If the measurements are equal to the voltage of your battery and the numbers are constant, then The BMS works well, but if the numbers are jumping, there is a problem with the BMS.

Now let’s explain the test details in steps with some light information about the BMS function.

What is the function of the BMS on your ebike?

 

The function of the BMS is to protect the battery and make sure that all the battery cells are balanced, and in the event of any problem, it disconnects the connection immediately

In order to do a BMS test, you should first know what you are going to test?
 
What we will test are the main connections of the BMS with the battery cell groups because BMS has two types of connections.
 
The first type: is the connection of the BMS with the battery cell groups & the cells themselves.
 
The second type is the connection to the motor through the controller, as the motor does not communicate directly with the battery cells, but is via the BMS chip.
 

How to test the battery BMS?

The first step is to double-check the voltage of the battery before opening it.

To do this, you must first turn on the battery and then, using a multimeter, measure the voltage by placing the negative side of the multimeter (most often black) on the negative side of the battery.

Then the positive side of the multimeter (red most of the time) is on the positive side of the battery.

If the numbers are unstable, jump higher or lower, this means that the battery has a problem, and you must find out if the problem is from the BMS or from the battery cells themselves.

Step for testing the BMS.

The second step is to make sure that the battery cells themselves are working fine without the BMS

Here are the steps to make sure of it

  • Turn off the battery
  • Remove the screws of the outer frame of the battery
  • Put the battery after opening it on a wooden table (very important for your safety)
  • Wear electrical gloves
  • Turn on the battery
  • Place the positive side of the multimeter on the positive side connected to the battery cell assembly
  • Place the negative side of the multimeter on the negative side connected to the cells assembly
Testing Battery BMS

Result: If you find the voltage measurements are stable and equal to the voltage of your battery, this indicates that the battery cells are working well.

The last step is to test the BMS chip itself.

Here are the steps to test it

  • Place the positive side of the multimeter on the positive side connected to the battery cells assembly
  • Place the negative side of the multimeter on the negative side of the BMS, which is directed to the controller and the motor.

Result: If you find the voltage numbers jump up or down, this indicates that the BMS chip has a problem and you can do rest or change it

How Do I Reset My Ebike BMS battery?

As a general rule, the BMS battery can be reset by disconnecting the BMS  wiring harness and then connecting it while charging the battery or by charging the battery from the discharge port using an external adapter for 20 seconds.

In order to make a BMS reset for your electric bike battery, you have two methods, the first is from the inside (the preferred one) and the outside method.

We will explain together each of the two methods in steps so that you can choose the right one for you.

Internal Battery BMS Reset.

Personally, I prefer this method because it is easy and does not require any complicated tools.
 
On the other hand, it comes in a natural sequence after the BMS test This method depends on charging the battery without connecting the BMS chip, then connecting the BMS chip during charging.
 
This method gives an order to the chip that it is connected to a new device, and then it does rest for itself.
 
Here are the steps for making the internal rest
 
  • Turn off the battery
  • Remove the screws of the outer frame of the battery
  • Put the battery after opening it on a wooden table (very important for your safety)
  • Wear electrical gloves
  • Disconnect the wiring harness from the BMS chip
wiring harness from the BMS chip 
  • Charge the battery
  • Reconnect the wiring harness

Note: you should use your hand while removing the wiring harness, instead use a small screwdriver and start from the right side and then the left. When re-delivery, make sure that the delivery was done well.

After doing the reset, measure the voltage again. If you find that the voltage readings are correct and stable, the problem has been resolved. But if the readings continue to jump, you must visit the nearest electric bike shop or change the BMS.

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The external BMS test (reverse charging)

This method depends on the reverse charging of the battery, in a more precise sense, which is to pass an electric current through the battery discharge port.

What happens is that the entry of electric current for at least 20 seconds to the battery through the discharging port gives a signal to the BMS chip to reset its settings again in order to receive the electric current.

In order to perform this test, an adapter should be prepared so that the electric current reaches the discharging port In order to prepare the adapter, you will need these tools.
 

1-DC Barral jack

2-Electricity wire (two different colors )

3-Electrical tape

To prepare the adapter

Connect one electrical wire to the positive side of the jack and tie it well.
Then connect the second wire to the negative side of the jack.

adapter jack

After that, plug the battery charger into the adapter (make sure that the two ends of the wire do not touch) and measure the voltage.

to be sure that you have done the adapter correctly, the reading of the multimeter must be positive.

After making sure that the adapter is working well, the last step is to connect the positive end of the adapter wire to the positive terminal of the battery discharging port, then connect the negative terminal of the adapter with the negative terminal of the battery discharging port of 20 seconds.

battery discharge port

After that charge the battery in the normal way and try the electric bike to see how long the battery is ranging.

Check this List out for all the Dc barrel jacks to choose what fits your battery from Amazon

What are the advantages and disadvantages of this method?

The advantage of this method is that it enables you to do the rest of the BMS without opening the battery or tampering with the internal wires.

Disadvantages of this method

  • Cost: This method is considered expensive to purchase tools such as wire or jack.
  • It is not possible to check the internal cells of the battery because you do not open the battery and check the internal cells.

Conclusion.

You can test the BMS battery by measuring the voltage between the positive terminal of the internal cells of the battery and the negative terminal of the internal cells connected to the BMS and making sure that the voltage reading is constant.
 
 
On the other hand, you can test the BMS by measuring the voltage between the positive and negative terminals of the BMS connected to the controller. If the reading is not stable, the problem is with the BMS.
 

You can rest the life of the BMS in the electric bike battery by making an internal rest by charging the battery directly without the BMS and then connecting the BMS during charging.

 

Or by charging the battery from the discharging port for 20 seconds.

Useful Resources.

 

Why Do Ebike Batteries Fail? (Explained)

What Happens When An Ebike Battery Dies?

How long Do Ebikes Batteries last? Charge & lifespan

Can I Leave my ebike On Charge Overnight? (Solved)

How to Charge An Ebike Battery For The First Time? (Explained)

How Do You Discharge An Ebike Battery For Storage? (Solved)

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