How To Do An Electric Bike Battery BMS Reset

Electric bikes are an improvement over traditional bikes as they are installed with a battery and a motor that will allow you to travel faster and longer distances without exerting much effort. The electric bike battery is the second most expensive part of any electric bike other than the motor; without them, your electric will become like any other regular bike.

Most electric bike batteries are made with lithium ion; inside your batteries also includes a microprocessor that controls anything from overcharge, discharge, and charging; these are called your battery management system. While lithium ion batteries can quickly resolve battery issues on their own, in some cases, resetting might be the best option to save your bike battery, so how do you do an electric bike battery management system reset?

There are different ways to perform a BMS reset; you can either do an internal battery reset by disconnecting the wiring harness from the battery’s BMS chip, or you can also do an external BMS reset, otherwise known as reverse charging.

This article will tackle why you should do an electric bike battery BMS reset, how to test an electric bike battery charging system, its importance, and many more.

Let’s get right into it.

Tell me the importance of battery management systems.

The BMS inside your e bike battery is a piece of essential equipment that controls how the battery charges and discharges. They are also tasked with maintaining the battery cells to be balanced and disconnecting the connection between the battery and motor (see also why ebike motor is cutting out) in the event of any electrical problem.

In many cases, your e bike battery will be able to resolve and recover issues on their own once they are discharged and fully charged, but if they can’t do this themselves, doing a BMS reset might do the job.

Here are some reasons why the BMS on your e bike battery might fail.

How does the BMS of an e-Bike battery fail?

The BMS on your battery pack might have failed because the voltage detection wire detected a poor connection, has a crimping process, or they are connected poorly. The BMS on your battery pack could also fail because of overcharging, which causes the electrolyte in your batteries to decompose and release gas.

Other ways to make your BMS fail are if too much current flows, which will trip the battery; this can result from the battery being charged from being completely flat or if the battery cells fail.

Lastly, a bad connector and a faulty solder can also result in your BMS failing.

How to test an electric bike’s BMS/charging system?

To test whether the BMS on your electric bike battery pack is doing its job, double check the voltage on your battery, and to do this, turn the battery off and remove the screws off the frame of the battery. Once you have done this successfully, you must wear electrical gloves for safety measures and then turn the battery on.

Then find a multimeter to measure the voltage of your battery by putting the negative side of the multimeter on the negative side of the battery. Conversely, put the multimeter‘s positive side to your battery’s positive terminal.

If the numbers are stable and only moving a little, then your ebike battery is working fine, and if the numbers are jumping up and down, then there is most likely a problem with your battery, and you might have to do a BMS reset.

Although, not all BMS issues are a direct reason because of the damaged internals of your battery pack because a supply, mechanical, and cell failure can also cause your BMS to fail.

You should first test your charger; it should output at least 6 volts higher than its specified voltage. You should then do the light bulb test by connecting an incandescent bulb to the outlet.

The second thing you should test for is mechanical failures; you can do this by opening up your electric bike battery pack and checking if all the wires are intact and there are no solder faults. After you’ve made sure that every individual cell is operating correctly and your battery still isn’t working properly, then you can conclude a BMS failure.

Why do I need to do an electric bike battery BMS reset?

You might have to perform a BMS reset for two different reasons. One reason might be that your bike battery is not working correctly when it comes to charging and discharging.

The second reason might be that you have tried troubleshooting your bike battery problem, and they’ve told you to perform a BMS reset. In either case, performing a BMS reset will likely solve your battery problems and save you tons of money from buying a new BMS.

How do I reset the battery on my bike?

There are two methods when resetting your BMS chip, specifically the external or internal BMS reset methods; you can choose any of the two methods as they will ultimately solve the issue with your battery cells. Here are the different BMS reset methods.

External method

If you prefer to use the external method of resetting your BMS, you must ensure that you have the appropriate tools. Ensure you have safety gloves since it involves resetting externally and requires you to work with live electricity, wire cutters, a soldering iron, a multimeter, a DC jack receptacle, and red and black wire.

This method is excellent if you don’t want to meddle with the internal components of your battery, as you only pass an electric current through the battery discharge port by utilizing a makeshift adapter.

Step-by-step procedure

The first step is to create the makeshift adapter. First, wear your safety gloves, as your adapter will most likely be composed of a DC barrel jack and two wires; use your soldering iron to connect the red wire to the positive terminal and the black wire to the negative terminal of the jack.

To keep them wired together, you can use electrical tape.

To test if your adapter works well, plug one end of your makeshift adapter into the battery charger and use a multimeter to check if the adapter is conducting electricity. Ensure that the two ends of the bare wires should not touch as this could close shut the circuit, which could be very dangerous.

The reading from your multimeter must be positive to indicate that your adapter is working fine.

The last step is to perform the BMS reset. The first is to connect the makeshift adapter to the battery’s discharge port and connect the red wire to the positive terminal and the black wire to the negative.

If both your battery and adapter are working, then the light on the charger will turn red, and to reset your BMS, hold the wires for 20 seconds. Once finished, turn the battery off and remove your adapter, and check if your battery management system is working well by connecting them to a charger.

While this method doesn’t require you to open your battery pack, this method is more costly as you must purchase wires and jacks. Also, if something is wrong with your battery’s internals, then this method won’t work.

Internal method

The internal method of resetting your BMS chip does not involve working with electricity, custom wiring, a makeshift adapter, and other complicated tools. Here’s how you can reset internally reset your BMS.

The first is to make sure that you have the appropriate tools to do so. Ensure that you have a flathead screwdriver and a plus screwdriver. After you’ve acquired the necessary tools, turn off the battery and use your screwdrivers to open the top cap of the battery. This will allow you to access the internals of your battery pack, such as the BMS, the battery cells, and all of the wires.

You can then inspect your BMS chip by gently sliding everything out; it’s also essential to remember that you shouldn’t forcibly pull any wirings inside the battery. To perform a BMS reset, disconnect the wire harness and then charge the battery. After this, reconnect the wiring harness.

To test whether your bike is working again, test its charging ability by plugging the battery into a charger and its discharging ability by putting it back on the bike. The voltage should now be stable, but if the number still isn’t, then visit your local bike repair shop, or you must buy a new BMS completely.

Where to find a new BMS?

If you weren’t able to fix your BMS directly, then it’s time to purchase a new BMS. You should never ride a bike with a faulty BMS, as charging and discharging them can ultimately be dangerous and might damage your bike.

You can easily purchase a replacement BMS online, and a great thing about them is that they are not expensive. To buy the appropriate BMS for your bike, always note the size of the battery pack it is rated for.

The most common battery sizes are 24V, 36V, 48V, and 52V, and the measures tell you how many cells are in the battery. If you have a 36V battery and each cell comprises 3.6V, you have ten cells inside your battery.

Another thing to look out for is the number of pins and the connector style that your BMS uses. Lastly, also check for the current rating that your battery uses.

How to install the new BMS

Installing a BMS can be quite hassling, and if you don’t want to go through the tedious process, you can bring it to your local bike repair shop. But if you prefer to install them yourself, here are some steps you can follow.

You need to install two types of wires, specifically the thin and thick wires. The thick wires are the charging/discharging wires, and the thin wires are the balance wires. The thick wires will most likely be comprised of three wires, namely the B, P, and C.

First, you have to install the B wire, and you can do this by connecting it to the wire clamps on your bike battery. Once you have done this step successfully, it’s best to mount your BMS on your battery and use hot glue or double-sided tape to hold the BMS intact.

Once the B wire is finished, install the thin balance wires. You can do this by starting with the thin black wire and connecting it to the negative end of the first cell group. When connecting the thin wires, remove the nut on one cell group and wrap the wires around the threaded post.

Continue with each balance wire and connect them to the positive terminal of every successive cell. The last balance wire should also be connected to the positive end of your last cell group.

Once finished, you can install the P wire, which takes care of the negative discharge connection that will plug into any device you are powering. Installing the P wire means you have to solder it to your BMS’s P wire pad.

After this, you can move on to the last thick wire, the C wire. You can do this by simply soldering the wire into your BMS’s C wire pad and then installing a charger connector that will be able to handle your loads.

To make them function properly, you will need to install the positive charge and discharge wires connected to the positive end of your last cell group. You might want to use the same thickness as the P and B wires for your discharge wire and a thinner wire for your charging wire to have enough space for the two wires.

Add your connectors and then install them before connecting the wires to your battery.

Conclusion

Bike management systems are essential to keep your battery performing at the top of its game. They are crucial components when it comes to charging, and discharging your battery’s power, so maintaining its health is vital if you want to ride safely. Although BMSs are relatively cheap and are readily available, you can fix the BMS issues on your battery by doing a simple reset.

We hope this informative article has helped you become more knowledgeable on how to do an electric bike battery BMS reset.