Are Electric Bike Batteries Interchangeable. Upp battery bike

Are Electric Bike Batteries Interchangeable?

The electric bike battery is arguably one of the most important features of your e-bike. It provides your electric bike with extra power, assists handling, frame design, and weight, and determines the range.

Even though the manufacturer designs an electric bike battery to help you travel thousands of miles effortlessly, like everything else on your e-bike’s frame, the battery faces wear and tear, and so it has to be replaced eventually.

Whether your electric bike has recently been in an accident that has damaged its battery, or, you are looking for a new electric bike battery that provides a better charge range, or the old battery doesn’t hold its charge anymore, the only viable solution is to get your e-bike’s battery replaced.

One common mistake that e-bikers make at this point is that they believe that they can throw out the old battery and replace it with any type of battery that seemingly fits.

However, little do they know that every electric bike battery has different requirements and specifications. So until and unless you are swapping the battery with the right one, there’s a high chance that the wrong battery might end up deteriorating the e-bike’s overall performance. Read on to find the answer to the question “Are electric bike batteries interchangeable” or not!

Why Doesn’t Your Electric Bike Battery Work Like It Used To?

The use of a rechargeable electric bike battery is a brilliant idea. They hold a charge for a long time and don’t need to be replaced as frequently as disposable batteries. Rechargeable batteries are primarily made possible using a lithium-based design, which is simple to manufacture while cost-effective.

However, one disadvantage of lithium-ion batteries is that their overall charge capacity diminishes after each charge cycle.

Understanding this link is vital to know how to charge your electric bike battery properly. The energy capacity of your e-bike’s battery decreases with each charge cycle, even if you use optimal charging practices.

The good news is that lithium-ion batteries are built to minimize capacity loss, so you may charge your battery 800 to 1,000 times and still have 80 to 90% of its original capacity.

For the average electric bike rider, this means that an electric bike battery will last two to three years, or perhaps longer before it needs to be replaced. However, eventually, you’ll need to replace your batteries at some point, especially if you’ve exceeded the manufacturer’s recommended cycle limit.

Are Electric Bike Batteries Interchangeable?

The one-word answer to the question “Are electric bike batteries interchangeable” is “No.” Different types of lithium-ion e-bike batteries comprise unique specifications. This means that they might differ in energy/watt-hours (Wh), capacity (Ah), voltage (V), weight, and size.

Another important thing here is to understand that Total Watt-hours = Amp-hours x Voltage, meaning that an electric bike battery with a different amount of amps or volts will produce completely different Watt-hours.

over, the amp-hours and volts shouldn’t only match the total wattage of the electric bike but should be compatible with the battery’s charger.

For instance, a 36V lithium-ion battery might be slightly smaller and lighter than a 48V one. But even if both have the same amp-hours, ultimately, the Watt-hours produced will be totally different. This can cause the electric bike battery to overload and might also damage the hub motor.

According to the e-bike manufacturers and experts, you should only replace the old electric bike battery with the one that has the exact specifications and comes from the same manufacturer.

The primary reason here is that the manufacturer kit has the responsibility to make sure that the charger, electric bike battery pack, and the e-bike all work together cohesively. On the other hand, using a non-original electric bike battery will introduce uncontrollable risks and increase the chances of malfunction.

Another thing to remember here is that you should always try to use the charger from the original manufacturer. It will ensure fast charging but will perfectly sync up with the electric bike battery without overloading it.

Can You Use Any Electric Bike Battery for an E-Bike?

While you might believe that all-electric bike batteries are the same and that you can incorporate any battery in your electric bike if it fits, do not make that mistake.

In order to be compatible, an electric bike battery requires a specific amps/capacity (Ah), voltage (V), weight, and size. In simpler words, you cannot put a 36-Volt battery on an electric bike built for a 48-Volt one.

Failure to install the right e-bike battery can result in causing permanent damage to the battery itself, the electric bike’s ride quality and performance, and even the rider.

Therefore, when planning to interchange the electric bike battery, the first thing that you should do is check for its compatibility. To help you understand better, here is a list of reasons why e-bike batteries aren’t universal:

E-Bikes Have Different Battery Management Systems

When it comes to electric bikes, BMS (Battery Management System) is a complicated subject. The function of the battery management system is to control the energy output from the electric bike battery to the e-bike’s system.

Even if the electric bike battery has the same watt output as your e-bike, there’s a high chance that the BMS might cause the energy to follow differently because of the difference in electric bike design.

Therefore, it is recommended to stick with the same electric bike battery brand when replacing or upgrading your e-bike’s original battery. This is the only way to ensure that the electric bike battery you are investing in is compatible with the e-bike’s BMS.

The Electric Bike Battery Doesn’t Fit as You’d Expect

In case the interchangeable electric bike battery does not fit the battery holder or mount of the e-bike’s frame, it’s an obvious indicator that the two aren’t compatible.

But did you know that despite the awareness, even today, many bikers try to force the battery by making modifications to the frame of their electric bike? Even though most of them somehow manage to get the electric bike battery attached to the frame, if it is not the right one, it won’t function as expected.

Therefore, regardless of what the situation demands, never force-fit an electric bike battery into the e-bike’s frame.

The Electric Bike Battery Overwhelms the Motor

This is what gets e-bikers into problems most of the time. Many electric bike owners will purchase a compatible electric bike battery that might fit their e-bike, only to discover that the battery is too powerful for the electrical system.

This is usually due to the installation of a battery with a higher energy capacity than what the electric bike was designed for. As a result, the excess power overwhelms the e-bike’s motor and other electrical components.

While many electric bike models will operate with a larger battery, be sure you pick one that the manufacturer has tested to work with your e-bike’s model, so you don’t risk damaging the frame or the electric bike battery.

Note that installing an interchangeable electric bike battery that doesn’t come from the original manufacturer might void the warranty of your e-bike.

Therefore, before making a decision, always check with the electric bike company to understand their policy regarding the aftermath of using replacement e-bike batteries.

Where Should You Go to Get an Interchangeable Electric Bike Battery?

Are you looking for a new electric bike battery? Here are three case scenarios to help you out in finding the right interchangeable electric bike battery for your e-bike:

Contact the Original Retailer

Is your e-bike battery malfunctioning? The best and safest decision is to purchase the new interchangeable electric bike battery from the manufacturer (original retailer).

In case you have bought your electric bike from a local dealer, contacting them should be the first thing that you do. If the dealer doesn’t answer, take out the owner’s manual and get in touch with the manufacturers as soon as possible.

What If the Original E-Bike Batteries Are No Longer Available?

In case the original brand electric bike battery isn’t available, instead of deciding for yourself, try contacting the dealer to find a reliable and compatible replacement.

Make sure that it belongs to a reputable company and has the exact specifications of your old electric bike battery.

What If the Original Manufacturer Is No Longer in Business?

In such a case, visit the electric bike’s manufacturer’s website or give them a call to find an identical source of interchangeable e-bike batteries.

If you are unable to get in touch with the original manufacturer, visit a reliable dealer and ask them for their suggestion.

In short, regardless of what the situation is when buying an interchangeable electric bike battery, never take the decision until you are fully sure of it.

How Would You Know If You Have a Compatible Electric Bike Battery?

Once you’ve chosen and purchased an electric bike from a manufacturer or brand, don’t assume your connection with them is over.

Mostly, we’ve had excellent experiences with dozens of e-bike manufacturers, all working hard to promote their brand and encourage bikers all over the world to go all-electric.

As a result, most electric bike manufacturers have support teams who are eager to assist consumers in better understanding the needs of their e-bikes, including which batteries are compatible with specific models.

Recognizing that customers would ultimately need to change their batteries, several electric bike manufacturers provide official battery replacements and upgrades that have been tested to work with their models. In case you have any doubts, the first thing you should do is contact the electric bike manufacturer.

Wrapping It Up!

Being the sole source of power, traveling far and fast on your electric bike is greatly dependent upon the performance of the electric bike battery. Investing in an interchangeable e-bike battery can make or break your bike riding experience.

Upgrading your electric bike’s battery will be one of the most important decisions that you make. By choosing the right e-bike battery, you can expect a better traveling range, and it can help you travel farther at a higher speed without having to recharge every now and then.

Furthermore, if your original electric bike battery is in good condition, do not throw it out. Instead, keep it as a backup when going on longer trips. As long as you are swapping with the proper replacement battery, your electric bike will be good to go for years to come.

Electric Bike Battery | Frequently Asked Questions (FAQs)

Q1: How much does it cost to replace an electric bike battery?

Ans: Replacing a standard electric bike battery will cost you somewhere between 200 and 1000, depending on the specifications, capacity, and type. A high-quality lithium-ion electric bike battery will cost you a minimum of 500. Comparatively, low-brand batteries can cost you as low as 200.

Q2: Are e-bike batteries interchangeable between electric bikes?

Ans: You can only interchange e-bike batteries if they belong to the same make and model of the electric bike. Even though some e-bike motor systems can be swapped with smaller or larger capacity e-bike batteries, the style of the battery (integrated or external) must be the same.

Q3: What is the warranty of an electric bike battery?

Ans: Every electric bike battery comes with a different warranty. For example, Yamaha and Bosch’s e-bikes feature a 2-year warranty.

Q4: How long does an electric bike battery last?

Ans: A standard electric bike battery will last up to 2 to 5 years. Note that the modern Li-ion batteries are rated by 400-1000 charge cycles which means that the greater the number of charge cycles, the longer your electric bike battery can last without affecting the Watt-hour rating.

Q5: Can an electric bike battery be recovered if it’s dead?

Ans: Yes, it is possible. In order to recover a dead electric bike battery, all you need to do is either press and hold the power button on the battery or plug it into the charger as soon as possible.

You may like the following electric bike articles:

My name is Matthew, staying in Seattle, Washington. Electric Vehicles (Electric Cars Electric bikes) caught my attention for the last few years and my love for electric cars and bikes is everlasting. I spend many of my weekends traveling to various places all over various cities with my electric vehicle (e-bike and electric car). Here I am sharing my expertise, experience, and invaluable information about electric cars and electric bikes. Check out more.

E-bike Battery Not Charging – What To Do

E-bikes are still bikes without a working battery, but they’re heavy and clunky. If your battery isn’t charging, you’ll be forced to pedal a big bike on your own, pushing your weight, the weight of the motor, and the weight of the extra-thick frame and larger tires. Let’s take a look at how you can fix this issue!

If your e-bike battery isn’t charging, it can be due to electricity not flowing to the battery, a switch on the charger, a faulty charger or charging port, or an issue with the battery itself. Many issues can be corrected, but some may require you to replace your charger or battery.

In this post, we will go into some of the more common issues that can affect your battery’s ability to charge. In many cases, following a set of basic troubleshooting tasks can save you a lot of money and restore your battery to working order, fast.

Possible Problem #1: Electricity From The Outlet

If you’ve got your bike plugged into an outlet that’s not supplying electricity, it won’t charge. Most modern battery chargers have LEDs in them that let you know that they’re plugged in properly, but it’s easy to forget to check these.

Before you do anything else, take a few seconds and verify that your wall socket is delivering normal power. Does the charger’s light turn on when it’s plugged in? When you plug in a light, vacuum cleaner, or another electrical device, does it work normally? Is the outlet on a switch?

This issue seems basic, but you might be surprised how many technical issues are caused by simple human forgetfulness. It’s definitely worth the time to verify that your outlet works with other devices before you move forward.

If your outlet is causing problems, switch to a different one and enjoy your working battery.

Possible Problem #2: Switches

Many batteries and some chargers have switches built into them that perform different things. In some cases, having one of these in the wrong position will stop your battery from charging.

The most common cause of this issue is that you’ve got a charger that was built for use in different countries. These chargers usually have a switch that allows them to toggle between US electricity and rest-of-the-world electricity. If this toggle is on the wrong mode, your charger won’t work properly.

Be sure to take a moment to check that this is accurate before you move too far into your troubleshooting process.

Some batteries also have built-in switches. Consult the manual for your battery to determine if your battery should be on or off when it’s being charged. If it’s not working in one position, it’s probably worth plugging it in for a few seconds in the other position and seeing if your charger’s status flips to ‘charging.’

Finally, check any power strips or extension cords in between the wall and your charger to make sure they are receiving electricity. Again, this seems like a very basic check, but it’s definitely one that will fix charging issues for a surprisingly large number of people.

Possible Problem #3: Bad Charging Port

Almost every e-bike has a battery that can be charged while it’s still plugged into the bike. This time-saving feature is great, but it also adds an additional point of failure. Sometimes, the wiring between your bike’s charging port and your battery develops an issue that prevents your battery from charging.

If your battery won’t charge, remove it from the bike and try charging it again. If it starts charging, there’s a good chance that your charging port is the cause of your trouble. Either charge the battery outside of the bike from now on or take your bike into a specialist shop and have them look at your charging port.

Possible Problem #4: Bad Charger

Chargers are fairly complicated bits of electronics that have internal sensors and logic gates that detect when your battery is fully charged, allowing them to shut off before they damage your battery. They also tend to get very hot when they’re in use, which can lead to problems.

In some cases, your charger might think your battery is full, even if it’s almost out of power. In other cases, the internal wiring might be damaged in a way that prevents power from flowing to your battery.

electric, bike, batteries, interchangeable

If your charger turns out to be the issue, replacing it is your best bet. It’s almost never worth the effort to repair a charger instead of just buying a new one.

There are a couple of ways to test your charger, but the simplest is to try your battery with a different charger. Try borrowing a charger from a friend, from a similar appliance (be sure to check the voltage), or take your battery and charger to a speciality shop and have them test these critical components.

If you can’t do this, you can use a multimeter to read the voltage coming out of your charger. In general, having a number that’s a bit higher than the nominal voltage of your battery suggests that things are working correctly.

If you get a number that’s in the right ballpark but low, your battery isn’t currently charged, meaning that the issue you’re having might stem from another component. If you get a number that’s very close to zero, your battery has failed, either by being fully discharged or as a result of another issue.

If you get a number that doesn’t make any sense, take a moment to check what mode you have your multimeter on. There’s a very good chance that it’s not voltage.

If your charger turns out to be the issue, replacing it is your best bet. It’s almost never worth the effort to repair a charger instead of just buying a new one.

Possible Problem #5: Fully Discharged Battery

Lithium batteries are designed to hold a small amount of power at all times. Your battery will stop working if it runs all the way down to zero power. The bad news is that it’s tough to get a battery working again after it hits this fully discharged state.

There are a number of resources on the internet that suggest that you can “jump-start” a fully discharged battery by briefly charging it with a high voltage charger (like one for a bigger battery) or through the discharge port.

Before you blindly jump into this sort of thing, remember that lithium batteries can and will light on fire if they’re used improperly. Battery fires are very dangerous and difficult to put out.

If you’re very confident that your battery is fully discharged (you drained the power and let it sit for a couple of weeks in the cold, for example), you have a voltmeter a high voltage charger you can use already, and you’re sure that you know what you’re doing, it might be worth investigating these methods.

If there’s any doubt, however, you should definitely err on the side of caution and leave this sort of thing to a professional.

Possible Problem #6: Failing Battery

Batteries are made up of banks of individual cells. These cells are managed by a small circuit board called a BMS, or battery management system. In some cases, the BMS in your battery will cause unwanted behavior or prevent it from charging altogether.

The good news is that this is the BMS’ job. It’s usually doing what the manufacturer set it up to do. The individual cells in your battery will fail at different rates, and when one of them fails, the BMS will have to prevent power from going in and out of that failing cell.

If enough of your battery’s cells experience enough problems, the BMS will stop your battery from working altogether. This is exactly what it’s designed to do, as it keeps you and your bike safe.

If enough of your battery’s cells experience enough problems, the BMS will stop your battery from working altogether. This is exactly what it’s designed to do, as it keeps you and your bike safe.

Your BMS isn’t perfect, however, and it’s not unheard of for these devices to fail even when the cells in your battery are totally fine. Your BMS might be malfunctioning in a number of ways as a result of damage from heat, faulty wiring, or an unfortunate short.

Batteries aren’t meant to be disassembled, especially by consumers. Even if you opened up your battery and tested the components with electrical equipment, replacing a component like a BMS or a bad cell is currently difficult and expensive. It’s not easy or cheap to get your hands on replacement parts.

On top of that, batteries are dangerous. Without the proper expertise and training, it’s all too easy to start an electrical fire that’s dangerous and difficult to put out. Because of that, it’s best to simply replace a failing battery or give it to a professional to fix rather than trying to fix it yourself.

Currently, most professionals currently suggest just buying a new battery instead of trying to repair things at all. If your battery isn’t charging and you’ve tested the charger and the charging port, the battery is probably the issue.

If your battery was stored at a fairly high level of power and you don’t think you fully drained it, it’s likely that a cell or the BMS is the issue. This means you should probably look at replacing your battery.


In summary, if your battery isn’t charging properly, it can be worth doing a small bit of troubleshooting before replacing it. Sometimes it can be an issue with the power outlet or the charger rather than the battery, but there are times when, unfortunately, it is the battery, in which case you may have to replace it.

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How to charge your Ebike Battery to increase its Duration

Scientists and users agree: the way you charge your battery can affect its lifespan, albeit not its performance. From our point of view, the following tips have proven useful to extend battery duration on a daily application.

Avoid discharging your battery under 30%

This precaution is recommended for all lithium-ion batteries, be it for cell phones, electric cars or bikes. It seems that discharging battery cells too much causes a certain stress. I´d rather spare you the complicated scientific explanation of this phenomenon. Just use any lithium ion battery, and you will notice that this rule of thumb is well worth following.

It should be beneficial to discharge it all the way down to 5-10%, riding, every two months.

Never charge a hot battery

This is a rule followed by many users and manufacturers. Indeed, a prolonged usage can considerably increase the internal temperature of your battery. A kilometer on a steep climbing road with your ebike would be enough, especially if you use more your assistance than your muscles. As the cunning website states, it is natural for lithium batteries found in electric bicycles to heat up as they work. This is normal for any lithium battery. For instance, the battery of the electric car Nissan Leaf would refuse being charged when it’s too warm after usage. Typically, you would stop on the motorway after having driven continuously for a couple hundred kilometers, you plug in the charger and you have to wait about 15 minutes to let the battery cool down. Just consult the renowned auto-magazine Green car reports to find out more. On my electric car, there’s a big and powerful fan that cools down the battery for roughly a minute as soon as you start charging it. My recommendation: after you’ve used your ebike, wait at least 20 minutes before charging it. The hotter the external temperature, the longer you should wait, up to 35 minutes.

Faster charging could affect your battery duration

Here experts are not unanimous. Some say it doesn’t matter, other base their mistrust of fast charging on the fact that it heats up the battery more than normal charging. Indeed, there are few ebike battery chargers exceeding 6 Ah, what should strengthen the argument against fast charging. Again, Green car reports states this clearly. I think it would be better if chargers could give us a choice: slower charging when we got time to charge, faster charging when we need to charge our battery as soon as possible. For instance, the battery charger of the Mitsubishi electric car, shown in the photo below, gives the user a choice between 10 and 16 Ah. Unfortunately, no ebike charger offers this option. In my opinion, fast charging does damage batteries, although only slightly. Therefore, choose a more expensive fast charger only if you need to spare time on charges.

Never charge your battery beyond 90%

Some experts suggest even to avoid exceeding 80%. It’s difficult to provide scientific evidence for this argument. Nevertheless, there are some empirical, practical considerations that support it:

  • Practically all lithium ion batteries need much more time to charge once the battery has reached 80% of charge. In most cases, it takes an hour to reach 80% of the capacity, and at least 50 minutes for the remaining 20%.
  • The longer you charge your battery, the more its temperature increases. Just touch it if you want to verify.
  • Common sense suggests that, since all materials are wearable, even battery cells suffer when you stress them to their extreme limits. It’s a sort of physical principle that applies to our muscles, our internal combustion engines, our psychological endurance, etc.

In order to easily charge it without exceeding 80-90%, I suggest using a plug-in clock like the one in the picture below.

It’s better not to charge it and leave it idle

Ideally, even for just a day, store it with 30-40% charge, and charge it at 90% just before riding it.

Never leave a li-ion battery idle for months

I would avoid letting a li-ion battery idle for more than a couple of weeks without charging and possibly using it a bit.

Batteries are not alive, nevertheless they require care, almost as if they were plants. Leaving a battery untouched for months can considerably damage it. You should recharge it up to 50%, once a month.

Many experts suggest also to use it shortly once a month, in order to avoid software components and nasty surprises when you need it again.

Battery preservation is paramount

Should you think that applying all these suggestions would be too complicated, just reckon the increasing role that batteries play in our lives, especially since the advent of lithium-ion batteries and its derivatives. Battery preservation has become essential to the sound management of our economies, be it for companies or for individuals.

How to Replace a BMS in an e-Bike Battery

How to replace the BMS of an eBike battery — how to test, buy a replacement, and replace it.

Dana Hooshmand

I’m an entrepreneur and adventure traveller. I build software, immerse myself in other cultures and languages @ Discover Discomfort and make fun of the business world @ The Vanity Metric. posts by Dana Hooshmand.

Dana Hooshmand

Recently (as in a few months ago) I had a problem with my e-Bike where my battery wouldn’t hold a charge, and wouldn’t accept a charge from the charger.

Normally, when I plug my eBike’s battery in, the charger’s cooling fan whirls to life and one of the lights changes colour, indicating it’s charging. This stopped happening!

I did a suite of tests, tried a few techniques recommended on forums and by the lead tech at Luna Cycle, and eventually confirmed my BMS was broken and needed to be replaced.

So in this guide I want to outline

  • A bit about my bike (as background)
  • How to test your BMS to confirm it needs replacing (or whether it’s something else)
  • Tests to do on a BMS and battery before you replace it
  • Why a BMS might fail
  • Where to get a BMS to replace it with — what to look for, and what to pay; and
  • How to change the BMS over

About my electric bike

My electric bike is semi-custom. It is built like a custom, but by Luna Cycle in the USA. It has a Bafang (八方电气, “Eight Sides Electrical Appliances”) motor with a 50A controller that Luna Cycle calls their “Ludicrous” controller, though I have it set to operate in 25A mode.

Because this was a crazy year, it ended up being stored fully charged, and allowed to fully deplete, while in storage. This isn’t good for an eBike battery, it turns out, and so a few things needed to be done to get it back on the road.

The BMS — or Battery Management System — of a battery pack is the part that regulates both input (charging) and output (discharge) voltage and current from the cells.

Even though this might appear to be a guide for one kind of electric bike battery, it’s generally applicable to all e-Bike batteries, and even batteries on other devices like scooters and mobility devices.

Why? Because many of these batteries are built with the same underlying technology — a pack of lithium 18650 cells.

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

When the charging system of an electric bike fails, it means one of a few things:

  • Supply failure: The charger might be broken (not delivering voltage or current necessary to charge)
  • Mechanical failure: A connector wiring inside the battery might be broken,
  • Cell failure: Some of the cells inside the battery may have failed, or
  • BMS failure: The battery management system may not be operating
electric, bike, batteries, interchangeable

To get to the core of the problem, you have to test everything one by one.

The first (and easiest) thing to test is the charger. You measure the output voltage. For a 52V battery like mine, it should be supplying about 58V. For a 48V battery it should supply around 54V.

After you measure the output voltage, you do what’s called the “light bulb test” — where you use an incandescent bulb hooked up to the outlet. This is easier in America (or Japan I guess) where the voltage supply is 110V, but it still works with 220V bulbs.

You could also test it with an automotive bulb if you have one. But it might blow!

Second, test for mechanical failures. Probe around with a multimeter and make sure you read operating voltage in the places where you should.

Also, open up your e-bike battery and check all the wires are intact, and that none of the solder joints have broken. Bikes get beaten up and it’s possible — likely — that a joint will fail at some point, especially if your battery has gone flying across the road because you forget to lock it (guilty! Actually I lost the key for a while. )

Finally, you have to test the internals of the battery.

I did a suite of tests that Luna Cycle said I should do

  • Opened it up and tested all the wires and connections
  • Did a BMS battery reset
  • Tested voltages across the pins — making sure every individual cell was operating correctly

One trick for testing voltage across the pins of the BMS is that they’re often coated with silicon. You should scrape it away gently before checking the voltage.

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

A BMS is a delicate issue. There are actually people who believe in charging batteries without a BMS, like this guy on YouTube:

If “jumping” your BMS is unsucessful, you can do more extensive testing on your battery pack and on your BMS.

Watch the video below. The core of it is to check individual cell voltage (confirming they’re in the 3.6-3.8V range), making sure no cell is dead. If it’s dead, you can replace it, probably for about 15-20 of parts (and. a spot welder and some nickel strips).

Look at the number of pins and the style of connector at the top of the BMS.

It seems a lot of BMS manufacturers have an informal agreement as to what the connector should look like. This is good news!

The second rating to look for is the current rating. My bike is rated for 50A peak, so I found a controller that promised to get to that spec.

I would treat current ratings on eBay with a grain of salt. It’s possible they might be truthful, but it’s possible they’re wildly exaggerating. Given they’re so cheap, get the biggest spec one you can reasonably afford, assuming it’ll be a weak point.

Installing the new BMS

There are three steps to installing the new BMS.

Firstly, remove the connector at the top. Mine is a 14-pin connector; you might have 10 or 12 pins or some other number. This should be a plug-and-play replacement for your current BMS.

Secondly, use a low-power soldering iron to de-solder the three connectors at the bottom.

Finally, use the soldering iron to connect the wires to your new BMS.

You should now be ready to power up and give your repaired battery a go. If you’re lucky, like I was, then your charger will whirr to life and your battery will take a full charge.

Optional — I realised, as I was writing this, that there was a chance I could have destroyed the BMS again! The battery was discharged, and a surge might have fried it.

Luckily, this didn’t happen. But you should consider perhaps directly recharging each cell of the battery pack if you have a 3.6V battery charger available.

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