Common E-bike Battery Problems and How to Fix Them. Trek ebike battery

Common E-bike Battery Problems and How to Fix Them

There’s nothing worse than having to spend hundreds or thousands on an eBike only to have problems with its battery. Don’t get me wrong; e-bike batteries are built to last. but they’re still prone to failure if they aren’t adequately taken care of during their lifetime.

What happens if your battery fails?

Well, in this article, I’ve covered some most common eBike battery problems and how to fix them. So, if you’d like to know more. keep scrolling!

Ebike Battery Problems

When it comes to eBike troubleshooting, there are a couple of things that might be causing your battery problems, including:

  • eBike battery pack swelling
  • eBike battery not charging
  • eBike battery not running for very long
  • eBike battery pack not holding a charge
  • eBike not turning on
  • eBike not speeding up

Don’t worry, though. I’ll walk you through each one here!

eBike Battery Pack Swelling

If your eBike battery pack is swelling up, well, you likely have a pretty serious problem with one. or more. of the lithium-ion cells.

Some electric bike models use flat pack cells. and these are known to swell if they suffer some damage. On the other hand, the 18650 lithium-ion cells are far more resistant to swelling and, in turn, more reliable.

If you notice that your eBike’s battery pack has a bulge in it, be sure you turn off the power and carefully remove the battery from your eBike. It’s a good idea to recycle the battery; most cities have a place where you can do this.

Now, some eBike battery packs are positioned inside the bike’s frame. That makes it somewhat harder to notice if you have a swollen battery pack.

The only way to check if the battery is swollen is to drop the lower plate and take out the battery pack. Note that you’ll have to disconnect some cables before you do this.

eBike Battery Not Charging

If your battery isn’t charging, start by checking the following:

  • Is the power turned on at the outlet?
  • Is the charger working and outputting over 36 Volts?
  • Is the battery hot?
  • Is the battery charger port full of dirt?
  • Has the battery been left discharged for several months?
  • Has the fuse blown in either the eBike battery pack or the charger?
common, e-bike, battery, problems, them

eBike Battery Not Running For Very Long

Lithium-ion batteries generally have a life of 700 charge cycles. They usually tend to lose full charge capacity over this mark.

That is entirely normal. and will, unfortunately, only get worse as time goes on.

Still, if you’re charging your bike every few days, you should be able to get many years out of your electric bike before you begin to notice the capacity of your battery is starting to degrade.

If you notice your eBike battery isn’t running as long as it used to, check the following:

  • Is the battery pack being charged to 100%?
  • Do you have a dragging of a disc brake?
  • Is the terrain uphill?
  • Are you assisting your battery by peddling?
  • Are your eBike’s wheel bearings freely spinning?
  • Do you have a short circuit in the battery, wiring, or motor?

Any of the scenarios mentioned above could lead to your battery discharging rather quickly.

eBike Battery Pack Not Holding A Charge

Lithium-ion batteries are good at holding a charge. However, like any other type of battery, they will slowly discharge over time.

If your eBike hasn’t been charged for a more extended period, it would be a good idea to give it a top-up. and see how it goes.

If you notice that you’re charging your battery, but it still discharges quickly without being used, you might have a short circuit somewhere or a faulty battery at your hands.

Here’s a quick test that can detect the problem:

Remove the battery pack from your eBike and charge it up on a bench. Once it’s fully charged, test the battery by leaving it off the bike.

If it holds a charge, the issue will be your electric bike. most likely a short circuit in the bike’s wiring or the motor. However, if it doesn’t hold the charge, your lithium-ion cell is faulty.

How Do I Know If My Bike’s Battery Is Charged?

Your battery charger will probably feature a LED light indicator that changes states depending on the bike’s battery level. It’ll go from red to green when the battery is fully charged in most cases.

However, in some chargers, the LED light will turn off completely when the battery is charged.

Either way, the point remains the same. you’ll have a way to track the progress while charging the battery.

Remember not to leave the battery pack on the charger longer than 24 hours, though.

Lithium-ion batteries don’t prefer being left on the charger. In the short term, this won’t hurt. but after a while, the battery’s capacity will go down.

common, e-bike, battery, problems, them

You’ll also have an indicator of the battery’s current level on the battery pack itself or the speed controller. Some will use a 0-100% range, while others have a series of LED lights, depending on the model.

eBike Not Turning On

Let’s start with the obvious solution:

If your e-bike isn’t turning on, be sure to check if the main switch is in the “On” position.

Next, check the fuse for the battery pack. This fuse is usually located on the side and could blow up because of short circuits, vibrations, over-current, or old age.

If the fuse is in good condition and the battery pack is fully charged, check if the speed controller is in good condition, as well. The speed controller is the component that sends signals to turn on the battery pack.

These speed controllers could malfunction if damaged. either by dropping your bike or allowing water to get into them.

Hold the bike’s “On” button for about 10 seconds to force the speed controller to turn on. Some speed controllers are turned on by pressing the “M” button. Again, it depends on the e-bike model you have.

Be sure to check that your battery pack has at least two bars of power. An extremely low battery power level can lead to your electric bike not turning on, by the way.

Another thing to check here is that the electrical cables are correctly connected. Sometimes, the dirt roads can dislodge the cable connections; this is often the case with mountain electric bikes.

Water can find its way into these connections, too. Pull them apart and ensure the connection is tight.

eBike Not Speeding Up

There are numerous reasons why your electric bike isn’t speeding up.

often than not, the feedback magnets. positioned on the pedal crank or the rear wheel hub. for the proximity switch get dirty. Clean them with a rag, and you should be good to go.

This common eBike battery issue is often wrongly diagnosed.

Most quality electric bikes feature a switch on the back and front brakes to stop the drive motor. In some cases, these switches can get stuck. leading to their failure. Activate both brake levers a couple of times to try and free up the switch.

To check the limit switch, though, you might have to remove the whole rear or front brake lever. That’s another reason why you should avoid leaving your eBike out in the rain.

Also, while it might sound obvious, be sure to check if you’re in the proper mode. for example, pedal-assist, throttle-only, or pedal-only. I’ve sometimes found myself in the wrong mode, and I couldn’t figure out why my eBike isn’t speeding up.

There is typically a minimum speed that will activate the drive motor. That is just a safety feature. and it’s usually around 1.8 mph.

What Speed Are eBikes Limited To?

eBikes are limited to 25 km/h. or 15.5 mph. to conform to the majority of road rules around the globe. Once the motor reaches this speed limit, it will stop providing power further.

Of course, you can still pedal faster than 25 km/h, but you won’t get any assistance from the main motor.

Once the speed controller recognizes that you’re under 25 km/h, the battery management system will again supply power to the main motor. That is a standard component on most electric bikes. and, again, its role is to ensure that you conform to road rules.

Is 250Watts Enough For An eBike?

In most standard cases of use, 250W is more than enough power for you to ride your eBike on asphalt or dirt roads casually. A 250W drive motor is usually limited to 15 mph and can handle up to 240 pounds in rider weight.

If that doesn’t sound impressive, remember that you can always assist the main drive motor by pedaling.

You can always upgrade your bike with a Bafang conversion kit, though!

common, e-bike, battery, problems, them


We can agree that e-bikes have come a long way since their first appearance. Granted, battery problems can occasionally happen, but most can be solved easily and quickly.

Hopefully, the tips I’ve outlined above will help you keep your eBike running fast. and for a long time. And remember:

The most significant danger to batteries of eBikes is excessive heat and low voltage. Make sure you keep your eBike battery topped up. and it will last for a very long time.

E-Bike Batteries Are Causing Fires: Is Your E-Bike Safe?

Repeated fires have prompted the FDNY to release recommendations for the care and keeping of e-bike and other lithium-ion batteries.

  • A spate of fires caused by lithium-ion batteries throughout New York City on April 21 has prompted the FDNY to issue lithium-ion battery safety tips, including for e-bike batteries.
  • Similarly, a Florida bike shop burned down on April 9, after a refurbished e-bike battery was left on the charger overnight.
  • E-bike batteries can be fire hazards when used and stored incorrectly. Below, we discuss how to use an e-bike battery correctly.

Between New York City’s fire department (FDNY) issuing a warning about e-bike batteries and a Florida bike shop going up in flames after a battery was left unattended on a charger overnight, it’s been a worrisome week for e-bike owners. But don’t panic: Your e-bike is likely safe, but consider this a warning to check your e-bike battery charging and storage practices.

Because lithium ion batteries—commonly found in everything from cell phones and laptops, to e-bikes, scooters, and electric cars—can store a large amount of energy, improper care and keeping of the batteries can result in fires.

“If using a lithium-ion battery, follow the manufacturer’s instructions for charging and storage. Always use the manufacturer’s cord and power adapter made specifically for the device. If a battery overheats, discontinue use immediately,” the FDNY tweeted earlier this week.

From Bicycling

New York Daily News reports that the FDNY was called to the scene of four different fires caused by lithium-ion batteries, all on April 21. The batteries were used in an array of vehicles ranging between electric motorbikes and scooters. The vehicles pictured in the fire department’s tweets are all motorbikes, rather than e-bikes—but e-bike batteries have caused fires in the past.

The largest of the four fires reportedly happened due to several batteries stored on a work shelf. While no deaths were reported, 12 people were injured in the fires. And the FDNY issued the grim reminder that four people were killed last year in fires caused by these batteries.

How do you prevent charging incidents like this from happening to your e-bike? Avoid aftermarket and off-brand or bargain batteries for your bike, first of all. Stick to the manufacturer’s specifications and recommendations. Furthermore, e-bike batteries that are charging should never be left unattended. If you’re charging your e-bike in the garage, set a timer to remind yourself to unplug it when it’s done, and if you’re leaving the house, unplug it and finish charging it when you return.

Bike shop owners should be just as careful. Unfortunately, earlier this month, Andante Bike Shop in Cutler Bay, Florida, learned this the hard way. The shop was destroyed on April 9 when a rebuilt battery was left on a charger overnight. While a normal e-bike battery from a reputable brand shouldn’t set itself ablaze when left too long on the charger, a malfunctioning battery is a serious fire hazard. Inexpensive lithium-ion batteries also present a serious risk of malfunctioning. Regardless, it’s important to never leave any e-bike battery charging overnight or without supervision.

Related Stories

It may sound excessive, but considering the number of buildings destroyed just this month due to these batteries, it’s worth taking precautions. New York Daily News reported that in the U.S. alone, charging lithium-ion batteries caused 330 fires from 2015 to 2018.

Human Powered Solutions provided Bicycle Retailer a detailed set of instructions for bike shop e-bike charging protocol, and you may want to take some of their advice for your own at-home e-bike charging station.

Trek ebike battery

The battery for your electric bike is typically worth about a third of the value of the entire bicycle, so it’s important to find a good quality one and take care of it.

In the case of Pedego Canada, we offer a 5 Year Prorated Battery Warranty with all our electric bikes, which is one of the best in the business. Why we’re so confident in our batteries is the quality of the cells within them. If you take nothing else away from this post, remember this: do not buy an electric bike with anything less than a five year battery warranty and do your best to purchase a battery by one of the “big three” name-brand cells: Samsung, Panasonic or LG. Cheap electric bicycles like the kind you find at Costco do not have the quality of manufacturing or warranty that will ensure you can enjoy the bike for years. It’s our recommendation that you spend a bit more money up front to save you from headaches (or worse – the garbage dump or even a fire!) later.

No matter what electric bike you buy nowadays, chances are it runs on a lithium-based battery. Believe it or not lithium batteries have been around since 1912 but it’s only been in the last 15 years that they caught on and became economical in consumer applications. There are “lithium-ion” batteries and “lithium polymer” (aka “lithium-ion polymer”) batteries and the difference between them is the type of electrolyte used. Other than that, there isn’t a significant variance: Li-Polymer allows for a slight increase in energy density but is 10-30% more expensive and so manufacturers have yet to decide upon one over the other.

There is also a range of lithium chemistries available in different batteries and manufacturers might claim some are more robust than others but the single most important factor affecting the life of a battery is how well it is looked after. You should typically expect a battery to last between 3 and 5 years if it is well maintained. (A lithium-ion battery will slowly lose its capacity over time, even if it’s not used.) Below are three things you can do to ensure you get the longest usage out of your electric bike battery.

#1. Keep The Battery Cool

Environmental conditions are an important factor affecting lithium-ion batteries. For example, leaving one in your car in the hot sun will guarantee you lessen the life of your battery. In fact, that would be the worst situation: keeping a fully charged battery at elevated temperatures. It’s a good rule of thumb to store your bike out of the direct sunlight for long periods and when not in use, keep your battery in a cool place, preferably below 20°C (68°F). The chart below, provided by Battery University, shows the impacts of temperature upon recoverable capacity of a battery.

#2. Store A Battery Partially Charged – But Not Too Low!

You’ll also notice in the above chart that storing a fully-charged battery has an impact on the recoverable capacity. Even more important, storing a fully depleted battery may be disastrous because, as we mentioned above, a lithium-ion battery will slowly discharge over time even when you’re not using it. If the voltage drops below a certain point this may cause irreparable cell damage, depending on the time it’s left sitting. Ideally, when storing the battery for a long period, ensure it has a charge between about 80% and 40% of a full charge. Some chargers have a lower ‘storage’ voltage setting, so just switch to this before charging it for storage. An easy alternative is to take the bike for a ride after you’ve charged it fully and before storing.

Also, don’t leave your battery on the charger for long periods of time, as storing it at or close to 100% will reduce the life of the battery. You can also check your battery every couple of months over winter. If you notice that the battery indicator has dropped too low, you can give it a quick charge to bring it back to the ideal storage voltage (this is unlikely to be needed if the battery was at 40% or above). If you don’t have a battery indicator, it’s probably a good idea to charge the battery for half an hour every few months. Again, try not to put the battery away fully charged (but it won’t be the end of the world if this happens.)

#3. Don’t Regularly Fully Discharge Your Battery

It’s amazing that we still see tech sites advising regular full discharge of your battery, even when this has been proven as detrimental. The chart below, again provided by Battery University, proves that regularly discharging lithium-ion batteries to 0% is harmful and partial discharges with regular top-ups are recommended to extend the recharge-cycle lifespan of the batteries. The occasional full discharge on that extra long ride is no problem! It’s ok to top up lithium-ion batteries regularly and, as the chart below shows, it’s best to operate them in the top half of their discharge cycle; lithium-ion batteries don’t have a ‘memory effect’ that some other battery chemistries have. If you are doing short rides on a regular basis, it is slightly better to charge it every few rides rather than every ride (to avoid long periods at or close to 100% charge, as discussed above).

As an extra note for the winter season, make sure your battery is above freezing before charging, otherwise you could harm the cells. It is no problem to ride the bike in below-freezing conditions (it doesn’t harm the battery), just make sure you let the battery warm up before charging. When you are riding in very cold weather, you will notice a drop in power and range; this is normal and expected. You can help avoid this by bringing the battery inside whenever you aren’t riding to keep the temperature of the battery up. That way you will get that extra bit of power!

Correct maintenance and storage of your battery as detailed above will significantly increase its lifespan. A well-maintained lithium-ion battery will last between three to five years, whereas a poorly maintained battery can be badly damaged over just one season or sooner. For more detailed, scientific information on batteries and how to care for them, check out the excellent online resource at Battery University, where the above charts came from.

The Trex FX 2 is a great, simple electric bike but needs a bit more to live up to its high price tag

Tom’s Guide Verdict

The Trek FX 2 is an eBike that is easy to ride and feels like a bike, but the lack of certain features makes it tough to justify its 2,399 price.


  • Clean design
  • Responsive pedal assist
  • Comes with fenders and rack included


Why you can trust Tom’s Guide?

Our writers and editors spend hours analyzing and reviewing products, services, and apps to help find what’s best for you. Find out more about how we test, analyze, and rate.

The Trek FX 2 feels like a bike. Trek has definitely made an effort for this city-focused eBike to look and feel like a bike as much as possible and in that effort, it succeeded. The FX 2 felt like riding a traditional bicycle until you really turn on the pedal assist, and even then it still largely kept that feel. At around 40 pounds, it also is closer in weight to a traditional bicycle, at least compared to the competition. I was able to get it up and down stairs without breaking a sweat, which was convenient.

Weight: 40.13 pounds Max rider weight: 300 pounds Gearing: 9-speed Shimano Altus Battery: 250Wh Motor: 250W HyDrive motor Max assisted speed: 20 mph Max estimated range: 35 miles

For all these successes, the 2,399 FX2 is significantly more expensive than our best budget electric bike, the Aventon Soltera (1,399) or our best overall electric bike, the Rad Power RadCity 5 Plus (1,999). This despite the FX 2 having no throttle, no LCD display and no removable battery. As enjoyable as riding it may be — and it is — it’s tough to recommend it over the competition.

Trek FX 2 eBike review: Price and availability

The Trek FX 2 came out in May 2022 at a starting price of 2,200, but the version we reviewed came with a price tag of 2,399. Unfortunately, it looks like the price has gone up since launch, with the 2023 models of the FX 2 coming in at 2,499 on Trek’s website.

The good news is that you are not forced to buy the FX 2 from Trek. Trek offers its bikes through local retailers in addition to its website, and those retailers may offer lower (or higher) than Trek. So make sure to check with your local bike shop before adding the FX 2 to your cart.

Trek FX 2 eBike review: Design

Trek offers the FX 2 eBike in four sizes (S, M, L, XL) and three colors: Satin Trek Black, Viper Red and Satin Mulsanne Blue. The model I was provided with was a Satin Mulsanne blue in size L, which worked perfectly with my 6-foot 2-inch height and 32-inch inseam.

At first glance, the FX 2 looks like a traditional bicycle. That’s because Trek has intentionally designed it this way, with the cables and battery stored within the tubes of the bike. Unfortunately, that means the battery isn’t removable — at least by you. Trek says that the battery can be removed by a trained technician, so you’ll need to head to a shop if anything goes wrong.

That said, you can still add an external battery for extra range. There are two water bottle holders, one on the seat tube and one on the down tube, and the one on the downtube allows for a 250Wh plug-and-play Range Extender battery. This allows you to easily double your range if needed. That battery life comes at a price though; the Hyena Range Extender Battery costs 499.

Designed for commuters and city bikers, the FX 2 comes already equipped with some much-needed accessories. The eBike comes stock with a front fender, rear fender, headlight, taillight, kickstand, bell and rear bike rack — no need to buy one of the best bike lights separately. There’s also a chain guard to prevent clothes from getting caught in the chain.

Still, there are a couple of things missing in the design that would be nice to have. First, the Hyena pedal assist control system has an LED display for the battery status and pedal assist mode. It is easy to use and read, but many eBikes now have LCD displays, so this feels cheap by comparison. Additionally, the wheels are not quick-release, which means if something goes wrong you’ll need tools on you to get the wheels off.

But the biggest design flaw is the lack of any shock absorption in the bike. The FX 2 definitely feels every bump and pothole, especially at top speed. Even merely adding a seat post shock absorber would be a welcome addition.

Trek FX 2 eBike review: Performance

The performance of the Trek FX 2 was more than adequate. Between the three power modes (Eco, Normal and Turbo) and the nine-speed rear cassette, I was able to hit the top speed of 20 mph frequently, regularly averaging 13MPH while riding through the streets of Atlanta.

Hills were also not a problem once you get a feel for the bike. I could regularly keep my cadence going up hills by using the full range of the bike’s gears and the Turbo pedal assist mode. The pedal assist modes kicked in very smoothly and with almost no lag.

The only shortcoming the FX 2 really has in terms of performance is the lack of a throttle to give riders fully motor-assisted thrust (i.e. no using your pedals), which does come on some of the FX 2’s competitors like the Soltera and RadCity 5 Plus. However, I would be lying if I said I missed it. The bike is plenty quick and easy to ride without it.

Trek FX 2 eBike review: Battery life and range

Trek states that the FX 2’s 250Wh battery can provide riders with up to 35 minutes of range. This of course depends on a range of factors, from the pedal assist mode you typically use to how hilly your terrain is.

My commute to work was just over five and a half miles round trip and I would go through about a quarter of the battery. That puts my estimated range at closer to 22 miles. However, I almost always used the Turbo (highest) pedal assist and I do have a large hill each way. So had I been more conservative I could have probably got more range out of the FX 2.

Luckily if you do need to charge the bike, it only takes around two hours for a full charge and the charger can be plugged into any wall outlet.

Trek FX 2 eBike review: Competition

Unfortunately, the Trek FX 2 really struggles when compared to the competition, at least on paper. I have yet to ride the Aventon Soltera, but it is currently our best budget eBike and has a very similar feature set and design aesthetic compared to the FX 2. While the pedal-assist seems like it is not as smooth and responsive as the FX 2 and it lacks a 9-speed option, you can still get a 7-speed for 1,399. That’s 1,000 less than the FX 2 I reviewed, but you get more range, a throttle and an LCD display.

If you want something higher-end, the Rad Power RadCity5 Plus is our best budget bike and would still be my pick over the FX 2 based on the research I have done on the RadCity 5 Plus. The FX 2 is lighter, and significantly so (over 20 pounds!), but the RadCity 5 Plus has a feature set that really sets it apart. Yes, you only get a 7-speed rear cassette, but you also get a throttle, a removable battery and two LCD displays compared to the zero LCD displays on the FX 2.

Trek FX 2 eBike review: Bottom line

Ultimately, if the Trek FX 2 eBike was cheaper it would be a lot easier to recommend. It was a lot of fun to ride, easy to carry with its 40-pound weight and has a very clean design. If price weren’t a factor, I would say the quick pedal assist make it a great choice, and the fact that it comes with fenders and a rack standard is a nice touch.

But none of that can make me get past the fact that this bike is hundreds — if not a thousand — dollars more than its competition without providing a lot of reasons why. Yes, it’s lightweight, and it’s a Trek so the build quality is excellent, but it lacks the LCD displays, removable battery or throttle that so many of the best electric bikes have. If the FX 2 had even some of those features, I’d rate it significantly higher, even with the price.

Malcolm McMillan is a staff writer for Tom’s Guide, writing about the latest in tech, gaming and entertainment with a particular FOCUS on artificial intelligence (AI) and AI-based tools like ChatGPT. He has written up much of our coverage on the latest AI tools including ChatGPT, the new GPT-powered Bing and Google Bard. He also covers A/V tech such as televisions, soundbars and more, in addition to covering VR headsets from the Meta Quest 3 to the PS VR2.

Before writing for Tom’s Guide, Malcolm worked as a fantasy football analyst writing for several sites and also had a brief stint working for Microsoft selling laptops, Xbox products and even the ill-fated Windows phone. He is passionate about video games and sports, though both cause him to yell at the TV frequently. He proudly sports many tattoos, including an Arsenal tattoo, in honor of the team that causes him to yell at the TV the most.

Leave a Comment