Lipo / LiFePO4 ebike battery information
There is a solution: dividing a battery into smaller packages. Grin Technologies sells e-bike batteries that are allowed in aircraft luggage.
Don’t charge to 100%
This article explains why, in order to extend battery life, you shouldn’t charge to 100%: How to make a lithium battery last, or…kill it, if you like.
Common battery types for ebikes
Batteries for e-bikes can be broadly divided into two types, lithium and LiFePO4. The latter is also lithium but has a lower cell voltage and a very long life. Batteries for e-bikes can be broadly divided into two types, lithium and LiFePO4. The latter is also lithium but has a lower cell voltage and a very long life. The voltage of lithium cells varies considerably during discharge and the nominal voltage is therefore stated with 3.6V or 3.7V.
|Lithium [V]||LiFePO4 [V]|
|Charge cut-off voltage||4.2||3.65|
|Number cells in series for “36V”||10||12|
|Battery charge cut-off voltage||42||43.8|
Commonly, e-bikes use lithium ion batteries which are available in different chemistries: LiCoO2, LiNiO2, Li-NiCoMn, LiFePO4 etc. LiFePO4 batteries have some advantages: longer cycle life and fast charge capability. The disadvantage is the lower energy density [Wh/kg], but note that the energy density of other lithium ion batteries degrade drastically after some years of usage.
Note that I built this battery in 2014 so higher capacity batteries are available in the meantime. I prefer LiFePO4 battery cells ANR26650 from manufacturer A123. This battery offer high charge rates of 15 minutes, which allow fast charging on the go. There are more LiFePO4 manufacturers, but they differ in quality. Not just the LiFePO4 technology is the key to success, but its patented method in nanotechnology. LiFePO4, like any other multi cell lithium battery needs a BMS, which protects cells from over discharge and over charge. Also a balancer is required which usually combined with the protection circuit.
A123 LiFePO4 battery cell ANR26650
Here are some figures of the A123 LiFePO4 battery cell ANR26650:
- Battery cells old: 3.3V, 2.3Ah, 7.6Wh, 70g, specific energy: 108Wh/kg
- Battery cells new: 3.3V, 2.5Ah, 8.3Wh, 76g, specific energy: 108Wh/kg
- Recommended fast charge current 10A to 3.6V CCCV, 15 min
- Cycle life at 10C discharge 1000 cycles
- Self-discharge 2% / month
LiFePO4 A123 battery 12s2p 4.6Ah 180Wh 43.2Vmax
Chinese LiFePO4 battery 36V / 10Ah
Note that I built this battery in 2014 so higher capacity batteries are available in the meantime.
|Charge cut-off voltage|
|Discharge cut-off voltage|
|Measured battery capacity at 5.5A||398Wh|
|Measured specific energy at 5.5A|
|Battery cells weight|
|Battery holder weight||0.36kg|
LiFePO4 battery discharge graph
Panasonic CGR18650CG Li-NiCoMn battery 36V / 9Ah
|Rated capacity||3.6V / 2.25Ah|
|Rated specific energy||184Wh/kg|
|Max. charge current||1C|
|Cycle life at 1C discharge||600 cycles|
|Charge cut-off voltage||42.5V|
|Discharge cut-off voltage||30V|
|Measured battery capacity at 5.5A||308Wh / 7.7Wh per cell|
|Measured specific energy at 5.5A||175Wh/kg|
|Battery cells weight||1.76kg|
|Battery holder weight||0.31kg|
Li-NiCoMn battery discharge graph
LiNiCoAl Lithium Nickel Cobalt Aluminum
This information is out of date, who can make an update? The highest specific energy of 265Wh/kg can be obtained with the new lithium ion battery chemistry LiNiCoAl from Panasonic and Samsung
|Rated capacity||3.6V / 3.4Ah|
|Rated specific energy||265Wh/kg|
|Max. charge current||0.7C|
|Cycle life at 1C discharge|
|Charge cut-off voltage|
|Discharge cut-off voltage|
|Measured battery capacity at 5.5A|
|Measured specific energy at 5.5A||224Wh/kg|
|Battery cells weight||1.38kg|
Fast charge Lipo batteries
Standard Lipo batteries have a low maximum charge current of about 0.2C, but Lipo batteries for model aircraft allow higher charge and discharge currents. Some Lipo batteries have a maximum charge rate of 10C. ZIPPY Compact 5000mAh 10S 25C Lipo Pack Specific energy: 5A 37V / 1.161kg = 160Wh/kgMax. charge rate 5C.Note that Lipo batteries are not intrinsically safe, there is a risk of explosion or fire.
Lipo battery, charge rate 5C, specific energy 160Wh/kg
Hybrid supercapacitor battery
A hybrid battery contains batteries of different technologies. In this way, the hybrid battery can have better properties than the individual batteries. An example is the combination of ultracapacitors and lithium-ion batteries. The ultracapacitor withstands high peak current in contrast to the lithium-ion battery, so the combination has a higher lifetime.
LiFePO4 battery energy storage efficiency versus voltage
When the battery efficiency is 100%, the stored energy is U I t. The battery efficiency however varies as function of the voltage. Between 3.0V and 3.4V the efficiency is high; here most of the energy is stored. At the end of the charging cycle, not only the voltage rises rapidly but the battery efficiency is very low too. In other words, there is less energy stored in the battery between 3.6V and 4V.
The evidence of the limited energy storage above 3.6V is that after charging, the voltage drops quickly without load. See the charge curve.
LiFePO4 batteries overcharge tolerance
Usually it is recommended that LiFePO4 batteries should be charged until the voltage reaches 3.6V. They can however be overcharged to about 4V without degradation or safety issues. To store more energy it doesn’t make sense to overcharge a LiFePO4 battery.
How to store lithium-ion batteries
Batteries will age, even at storage. In order to extend the lifetime when stored for a longer time, treat the battery as follows:
- Try to keep the battery temperature between 15°C and 25°C.
- Discharge the battery and then charge the battery to 40% of the capacity. For instance, a 10Ah battery should be charged 2 hours at 2A.
Determining the number battery cells
As an example we take the LiFePO4 battery A123 ANR26650.
At 5A the average cell voltage is 3.15V:
LiFePO4 discharge characteristics
For a motor voltage of 36V the number of cells in series is 12. To get a capacity of for instance 180Wh, we need 24 batteries.
Battery internal resistance loss
As an example we take the LiFePO4 battery A123 ANR26650.
As we can see below, the internal resistance of the 12s2p battery pack is 110mΩ. Assume the motor input power is 200W:
Measuring battery internal resistance
As an example we take the LiFePO4 battery A123 ANR26650.
Battery nickel solder tabs
The A123 solder tabs are not made of copper but of nickel 200/201, which has a high electrical resistivity ρ compared with copper.
The dimensions of the solder tab between two battery cells are 9mm x 0,25mm x 35mm. The resistance is thus 9.6 10.8 35 10.3 / (9 10.3 0.25 10.3 ) = 1.5mΩ.
Battery DC load test
There’s a lot to talk about how to measure the impedance of batteries, if you google on “battery impedance testing” you’ll find a lot. Determining the internal battery resistance can be done by using a DC load and measuring the discharge current and voltage drop. The load is simply created with a power MOSFET and three 12V/100W halogen lamps which give a load current of 8.4A
Measuring internal battery resistance
I have connected and disconnected the load several times and measured the battery voltage with a digital storage oscilloscope built with an Arduino.
12s2p LiFePO4 A123 ANR26650 load test 60sec
12s2p LiFePO4 A123 ANR26650 load test 10sec
The negative voltage spikes occurs because the lamps have a positive temperature coefficient. As we can see in the chart, after the voltage jump, the voltage decreases exponentially during more than 60 seconds. Also there is a recovery period after disconnecting the load.
The resistance is measured at the value of the voltage jumps, which average value is ~ 0.8V. This gives a battery pack resistance of 95mΩ (0.8V / 8.4A). It is clear that measuring the Rapid voltage jumps with a multi meter is not possible; by the slowness of the measurement we get too large resistance values.
The internal resistance per cell is about 16mΩ which is far more than the value of 10mΩ according to the manufacturer. A123 uses a pulse load test to measure the internal resistance but that gives the AC resistance instead of the DC resistance.
Battery pulse load test
The pulse load is simply created with a 50Hz square wave generator connected to the gate. Use an oscilloscope to measure the battery voltage change.
Battery pulse load measurement
- T battery = 34°C
- VDC = 40V
- I average = 4.95A, I = 9.9A
- Δ Ubat = 0.6V, see scope:
A123/ANR26650 34°C VDC=40V scope 200mV 5ms. Internal resistance = 8.6mΩ
Calculation battery internal resistance
- The battery has 12 cells in series and 2 cells parallel (12s2p)
- The A123 ANR26650 internal resistance = 60.6mΩ / 6.1.5mΩ = 8.6mΩ
At 25°C the internal resistance is about 10mΩ which is equal to the value in the ANR26650 datasheet. However, this value is too optimistic and practically unusable.
Internal resistance temperature dependence
As the LiFePO4 temperature increases, the internal resistance decreases. See here the results of the measurements that I have done. Note that the chart is measured with the pulse load test.
A123 ANR26650 LiFePO4 internal resistance versus temperature. VDC=40V
Li-ion, like other battery types, performs better at high temperatures than at low ones. But heat also stresses the battery.
Impedance characteristic temperature dependence
As we see here, the impedance characteristic changes with temperature too.
A123/ANR26650 17°C VDC=40V scope 200mV 5ms. Internal resistance = 12.5mΩ
Battery equivalent electrical circuit
I have created a LiFePO4 cell model that corresponds to the measurements at different temperatures. See more about the so called “randles circuit” here. Please note, it is just a rough approximation and the pulse load test is used. I still have to make a randles circuit with the DC load test.
A123 ANR26650 LiFePO4 battery simple cell model
Reviving over-discharged Li-ion batteries
One of my Li-ion batteries was fully discharged because a faulty battery fuel gauge pulled constantly 6mA out of the battery, outside of the BMS. Charging was not possible anymore. If the voltage of a one ore more battery cells comes below the cut-off voltage, the BMS comes into action and the battery will be switched off forever. I have done the following to awake the battery back to life:
Open the battery housing. Charge the battery manually with a current of 100mA, outside of the BMS, until the voltage of each cell is higher than the cut-off voltage. This normally just takes less than one minute. The BMS will reset the blockade and charging can be continued in the normal way with the battery charger. The cut-off voltage is 2V to 3V, depending on the battery type. Recovering a single battery cell works the same way. Beware, the procedure is not without risk: if a cell is defective, then the above may result in fire or explosion.
The energy required for climbing hills can be calculated roughly with the potential energy. The motor power loss is not included.
Eupen – Baraque Michel: E = 90 9.81 410 / 3600 = 101Wh.
The history of A123
2001: A123 was founded in the USA. 2012, The Chinese Wanxiang Group acquire 80% of A123 after A123 was bankrupted, the name changed to 123 Systems.2018: Battery manufacturer Lithium Werks in the USA took over 123 Systems from China.
Safe charging and storing lithium-ion batteries
Lithium-ion batteries can catch fire or explode during use and sometimes even when just stored. The safety depends entirely on built in fail-safe circuity electronics.
Charging lithium-ion batteries battery can cause fire. For safety, charge batteries in a fireproof container. But that is not enough, also use fire extinguishing granulate: This is the perfect solution for the safe storage and in the event of a fire, the extinguishing of lithium polymer batteries. When charging, place it over the battery and you have effective and good fire protection. When shipping LiPo batteries, simply pack them neatly around the battery and you don’t have to worry anymore.
Safer battery types are LiFePO4, Li-Mn and Lithium-titanate (LT).
Comprehensive lithium-ion battery test
Henrik K. Jensen from www.lygte-info.dk has tested many battery cells used for flashlights; these battery cells are used in e-bike batteries too. For instance HERE, 18650 size lithium-ion batteries are tested on capacity:
18650 size lithium-ion battery capacity comparison
The 18650 size li-ion battery with the highest capacity is the Panasonic NCR18650B (3400mAh).
- Elithion LLC BMS technology, Li-Ion manufacturers etc.
- Parameterization of a 14.5 Ah LiFePO4-battery cell. Peter Andersson, Olle Collin
- How to rebuild a Li-Ion battery pack
- Tesla Roadster battery technology
Tesla Roadster battery technology
A Deeper Dive into Running Out of Charge on Bosch Batteries
We’ve touched on battery topics a few times like special considerations for cold weather. and how to extend your range with dual battery setups. best practices for Bosch battery care can be found in the updated Battery Guide 2021.
A question we’ve gotten a lot lately though, is:
What actually happens when you run out of battery while riding your e-bike?
First, when you hit “no bars” on your battery indicator, the system will remain on but the assistance mode will switch off. The bike offers no pedal assistance to you even though the system is still on.
Why? The battery holds reserve power to run the lights for at least two hours. The amount of power held on reserve this way is dependent on the power required for the lights. If your system is configured for brighter lights, the system knows to save more power to keep them powered. If you have a Kiox or Nyon display, you might have noticed that this is around 2 or 3% on the battery indicator.
If your bicycle additionally has integrated e-shift, it also holds reserve power to power through at least 50 more shifts.
Then, If you keep riding the battery all the way down to 0% on the indicator, the entire bike will shut off. If this happens, it is important to reconnect your battery to a charger as soon as you have completed your ride and get it at least partially charged. Otherwise, your battery can reach what is called “deep discharge” where it will no longer take a charge and must be replaced. Lithium ion batteries, unlike lead acid batteries found in cars, cannot be “jumped” or re-awaken from this state. According to Bosch, fully discharging a battery into deep discharge is considered misuse and is not covered under warranty.
How does this deep discharge scenario actually happen?
The answer is complicated, and to be honest, I do not fully understand. Battery experts, drop me a line, I would love to hear! My understanding is basically that the battery is holding a teeny bit of charge left even when it is telling you it has no more power to give. That amount of charge is required for its internal processes, including the Battery Management System. Batteries very slowly lose charge over time even without use (commonly referred to as “trickle discharge”), so if you run your battery all the way down to its last teeny reserve, it will then trickle discharge that power, and there will be nothing left and become unusable. I reached out to Bosch and they summarised it,
“All modern lithium ion battery cells, whether they’re in a Bosch PowerPack or some other device, contain a protection circuit that, for safety reasons, renders the cell unusable if over-discharged.”
I also asked Bosch about exactly how bad for the battery it is to run it down to system power-down,
“I would definitely avoid doing this if possible. It’s not the worst thing for the battery, but it’s not great either. I recommend not making a habit of it, but also not worrying too much if it happens on occasion”
I would agree with trying to avoid running the battery down to system power-down if possible, but the important thing is to charge the battery as soon as possible after doing so. If you are regularly running out of battery on your route, consider checking out if there is a way to set your bicycle up for dual battery.
How fast does it trickle discharge?
The battery will lose charge slowly over time, but how slowly though? This is an important consideration for fair-weather riders who might be putting their bike away for nine months of the year.
According to Bosch, high-quality Lithium ion batteries lose charge at approximately 0.5%/month. This means if your battery had only 4% charge when you put it away, it would be into deep discharge by the time summer rolled around next year. Lithium ion batteries are also sensitive to temperature, so storage below 32 F (0 C) or above 86 F (30 C) can increase the rate of trickle discharge. This scenario should be avoided by bringing your battery up to a medium charge level before putting in storage.
So how should I store my batteries?
Bosch batteries (or any high quality Lithium ion e-bike batteries) should ideally be stored between 32 and 68 degrees F (0-20 C) and between 30 and 60% charge level. Avoid leaving the battery plugged in for a long time, and avoid leaving it for long storage at full charge.
So when winter comes and you’re putting your bike away for the season, charge the batteries up to 60%, put the bike somewhere at room temperature, and let it sit. If the bike lives somewhere that might be the outside temperature like a shed or uninsulated garage, consider removing your batteries and bringing them in the house for secure room-temperature storage during the winter.
If the whole summer passes by without a ride, while you theoretically have many years before it trickles out of the ideal range, we still recommend taking a moment to check the charge level again before starting another year of storage.
Bosch makes a special Battery Capacity Tester tool, that among other things, can be used to set the charge level to 60% when putting the battery into storage. Bosch recommends doing this if planning to leave the battery unused for three or more months. We are thrilled to say we now have one of these cool tools! Give us a call and we can arrange to do this for your batteries in advance of your planned storage.
What if my battery suddenly won’t respond?
Another consequence of trickle discharge and deep discharge being considered user fault is that if you are having a warranty issue on your battery that it suddenly becomes wholly unresponsive, the battery will continue to trickle discharge. This is especially a concern if it was at low charge before it finally died all the way. If the battery trickles all the way into deep discharge, we won’t be able to determine that it was a warranty.
So if your battery has suddenly become unresponsive, especially within the two year warranty timeline after purchase, please reach out to us right away so we can see if it can be revived, or if we can pull the error codes to make the warranty claim smoother.
What is the normal lifespan of the battery?
In a battery that does not experience a warranty shut-down or deep discharge, what life span can you expect from it? There is no single answer as it depends on use and storage conditions. Like our cell phone, as the battery ages, its capacity decreases over time, meaning we get less power per charge. Bosch cites that after 500 charge cycles (over 10,000 miles), the user can still expect the battery to have 60-70% of the original capacity.
The basic diagnostic report we run during tune-ups will show how many charge cycles your battery has been through. But the Battery Capacity Testing tool can also be used to assess the current capacity of your battery – you can request this extra diagnostic as well when your bike is in for service. It takes several hours to run so this is a service that must be done by appointment.
When your battery has reached its end of life, whether by unresponsiveness or the capacity having decreased to unusably low, we are an e-bike battery recycling collective site. Bosch batteries cannot be refurbished, but we can get them properly disposed of for you. on that coming in a future post.
Best Electric Bikes with the Bosch Intube Battery
The Bosch Intube battery is finally available in the United States! Electric bike enthusiasts have been waiting on this development basically since completely integrated batteries have been a thing. Read on to check out the best electric bikes with the Bosch Intube battery.
It has been a rather long road to get Bosch Intube batteries approved in the States. It was very important to Bosch that they had UL certification before bringing the batteries to the mass market. Now that they’ve been approved, these bikes are expected to have limited quantities initially, so ,if you want one, grab it quick! Bosch has always been a top of the line motor, and now they have created a battery to rival the integration of Brose electric bikes. You’ll now get the power and reliability of a Bosch motor, but with the sleek downtube of a traditional bicycle.
2018 Riese Muller Supercharger GT Touring HS
I’m starting with a Riese Muller Bosch intube bike because they are definitely the most versatile of the bunch. There are options for a mountain touring ebike (see the Supercharger Mountain) and also options for a geared hub making this line one of the most tech heavy bikes available. And, of course, Riese Muller has continued to offer a dual battery option for riders looking to ride for at least 150 miles.
I love the GT Touring HS model specifically because of its real cycling feel and its incredible comfort. A Suntour Aion fork and a Cane Creek Thudbuster suspension seatpost provide a full suspension feel. Plus sized Schwalbe Moto-X tires provide extra cushion when riding over bumpy terrain. I also like that Riese Muller have kept the integrity of the front triangle. You can see that the batteries load on the outside of the triangle so that you’ve got room for water bottle cages on the inner part of the triangle.
2018 Haibike XDURO AllMtn 9.0
Probably the most anticipated of the Bosch Intube bikes, the Haibike XDURO AllMtn 9.0 takes the always popular AllMtn line and amps it up a couple levels. The AllMtn line is a lot slacker in terms of the build this year, which is great for riders who want to ride a little more aggressively. The Intube battery improves the center of gravity so that riding feels even more like traditional mountain biking on the downhills. Another cool feature on the Haibike’s with Bosch’s intube battery is the Modular Rail System. This is allows riders to put bottle cages, frame bags, or pumps anywhere on the downtube.
Serious e-MTB riders will love the downhill capability of this bike, but it is also suited to intermediate and beginning riders who want a spec-heavy bike for fire roads and single-track trails. Check out the Fox 34 Elite suspension, Magic Mary tires, and Mavic wheelset for clues as to why this will be a top choice electric bike in 2018.
2018 Bulls Six50 EVO AM 4
On the other hand, you could go with the Bulls high-end option with the Six50 EVO AM 4. In my opinion, this is the best eMTB available this year with a Bosch motor. I love that Bulls has set you up Fox Factory fork with Kashima coating. That fork also comes with 36 mm stanchions whereas many of the other eMTBs come with 34mm. There is pretty much no expense spared in terms of components. KS-Lev dropper seatpost, Magic Mary tires, DT Swiss wheelset, and of course the Bosch Performance CX motor with the new intube battery make this a solid option for those riders looking for some high-end action.
2018 Haibike SDURO Trekking 9.0
If you’re looking for less of a trail rider and more something that is going to get you from point A to point B, check out the SDURO Trekking 9.0. This would be a great option for commuters and those interested in bike touring. All the components on this bike are top of the line. Haibike sets you up with a Shimano Deore XT drivetrain and brakes. It’s crucial to have top components for shifting and braking on a commuting bike. You also have a carrier that can hold up to 55 pounds of gear–another necessity.
In terms of the build, this ebike really is a complete commuter. The geometry keeps you upright. Haibike includes fenders and integrated lights. You also get Schwalbe Super Moto-X tires which are the top tire for street riding. There’s even a low-step option.
Riese Muller New Charger GT Nuvinci HS
Another of the incredible hand-build options from Riese Muller, the New Charger series are a sleek looking bunch with a wide variety of options. I chose the GT Nuvinci HS because I love 28 mph bikes and I think the Nuvinci hub gear is one of the best drivetrains on the market. There is no maintenance with this system. Ever. It also is one of the smoothest drivetrains available. There are not set speeds as it is a CVT. As with most hub gears, you also don’t have to pedaling when you shift.
There are loads of options within the New Charger family. They are all built with this same sleek design and are incredibly comfortable to ride. Check out the New Charger Mountain for a trail-ready bike. As with all Riese Muller bikes, there are upgrades to please even the pickiest rider.
Of course, these are just a few of the options available with the new Bosch Intube battery. To check out a full lineup, go to the collection on our website. We do expect these bikes to sell very quickly initially, but they will probably become the norm long term. Be one of the first to snag these brand new eBikes!
Everything you need to know about e-bike batteries [from a battery engineer]
Would you be the person taking the stairs or the escalator?
I’ll be honest. barring the one-off day that I’m feeling particularly sprightly, I would just hop on the escalator with those 30 people on the right. And I’m willing to guess that most of you would too.
What we can gauge from this picture is that most people would rather do as little work as possible to get from point A to point B. This is especially true when it comes to commuting on a bike. The picture above is analogous to the difference between a regular bike and an e-bike.
Even if we address all the concerns when it comes to biking in a city (like safe biking infrastructure), we can’t expect to change fundamental human behavior. when given the option between less work or more work to achieve the same outcome, people will more likely choose to do less work.
Since getting my e-bike, I can comfortably bike from my home in Somerville to the Seaport district in Boston. a roughly 5-mile trip. in just about 20-minutes. All of a sudden, biking 5-miles is a piece of cake. I also don’t have to spend time sitting in traffic, waiting for public transit, or worry about showing up to a meeting looking like I swam across the Charles river to get there.
The beauty of an e-bike is that it makes cycling an inclusive mode of transportation because it doesn’t discriminate by age or physical ability.
When it comes to purchasing an e-bike though, there are a plethora of options for both the bike and battery. So how do you decide which one is best for your needs? As a battery engineer who has built hundreds of batteries and logged way too many hours soldering battery packs, here are my thoughts on the most commonly asked questions when it comes to e-bike batteries.
If you’re new to battery terminology, you might want to start here: Battery terms that every e-bike owner should know.
In this post, we’ll cover the following questions:
What is the best e-bike battery?
This is one of the hardest questions to answer. There are so many variables that go into what makes a good battery and what’s best for you, may not be the best for me. Even then, a good battery can perform poorly if it’s not cared for properly.
Battery packs are made up of individual battery “cells”. Cells are classified into cylindrical cells (like your AA and AAA) and prismatic cells (like the one in your phone). Each class of battery is manufactured in a variety of form-factors (in the battery world we use this term to mean size). The most commonly used form-factor of cells in an e-bike battery pack is the 18650.
A battery pack is only as good as it’s weakest cell.
When it comes to batteries, in my experience, there is a strong correlation between price and quality. I don’t follow this rule when it comes to most things like for example, box wine (I’m just saying, there are plenty of really good box wine options these days!). When it comes to batteries though, you really don’t want to be compromising on quality because you’ll eventually end up having to pay the price.
Here are some things to keep in mind when purchasing an e-bike:
Cell Manufacturers: Panasonic, LG, and Samsung have a good reputation in the battery industry for their high quality cells, so paying a premium for these cells is certainly worth it. If the e-bike you’re trying to buy doesn’t have or provide cell manufacturer information, they’re likely not going to be a reliable source anyway.
Cell Chemistry: Lithium-ion (li-ion) batteries are the best option for e-bikes. Although lead-acid batteries are significantly cheaper, they’re three times as heavy as their li-ion equivalents.
Li-ion has several variants of cell chemistry. The most popular ones for e-bikes are Nickel Manganese Cobalt (NMC), Lithium Cobalt Oxide (LCO), and Lithium Iron Phosphate (LFP). The metrics to look for when selecting a cell chemistry are:
- Specific Energy: has an impact on the range of your battery.
- Specific Power: how the battery handles high load scenarios like going up
- a hill.
- Safety: does the chemistry have a history of high in-field failures.
There are trade-offs when choosing one chemistry over another, but as we’ve shown in the image below, NMC and LFP are both great options that both offer the best value in terms of performance, price, and safety.
Picking the right battery chemistry has to do with figuring out what matters most to you. Do you want a battery that has a longer range (higher specific energy) but doesn’t have as much power? Or do you want a battery that has a more power (higher specific power) but may not last as long?
In my opinion, the best e-bike batteries are likely going to be made from cells manufactured by Panasonic, LG, or Samsung with either LFP or NMC cell chemistry.
What is the range of an e-bike battery?
The range of a battery pack depends on the amount of energy packed inside of it and is measured in Watt-Hours (Wh). Watt?
Watt-hours are calculated by multiplying the battery capacity, in Amp-hours, by the battery Voltage, in Volts.
Let’s assume that, on average, 1-mile requires about 25Wh of energy. So a 14Ah, 36V battery should get you about 25-miles per charge.
Keep in mind that the weight of the rider, outside temperature conditions, and the amount of pedaling will make a significant difference in range.
A word of caution: the range that e-bike manufacturers provide should be taken with a grain of salt. That number is generated from tests that are run in perfectly tailored lab conditions. Do you charge any of your electronics in an incubation chamber set at 28° C with a lab-grade charger that applies the perfect current while charging? Yeah, I don’t either. And so, We should assume that the manufacture-specified range is delivered only if the battery is charged and discharged under ideal conditions i.e. not real world conditions.
For a more realistic estimate, shave off 15% of the manufacturer specified range and assume this padded number to be your real range.
If you’re looking for a longer range, choose a battery that has higher capacity (Ah). If you’re looking for more power, choose a battery that has higher voltage (V). Learn more why voltage and capacity matter.
What is the lifespan of an e-bike battery?
There are several factors that affect the lifetime of a battery such as:
- environmental conditions: temperature during charging discharging
- charging rate: how fast or slow your battery is charged
- charging voltage: what voltage the battery is charged to
- depth of discharge (DoD): what voltage the battery is discharged to
The list above isn’t exhaustive but, in general, batteries decay as a function of time in the charged state. Period.
Day 1: You get your new e-bike and charge it up to 100% and go on a bike ride. When you come home, you charge the bike back up to 100% and you’re excited to ride it again soon.
Day 2. 364: Life get’s in the way and you still haven’t been out on your bike since that first ride.
Day 365: One year later, it’s the perfect day for a bike ride and you finally have some time on your hands. You head to your basement, unlock your bike, and excitedly turn it on. 80% charge. What? You clearly remember charging your bike to 100% last year before moving it to the basement!
The truth is, we can’t beat thermodynamics. I’ll say it again: batteries decay as a function of time in the charged state.
Now, because you left your battery at 100% for a whole year in a basement with no temperature control, you inadvertently caused your battery to lose a certain amount of irreversible capacity. Your range will be ~20% lower and you’ll likely have to replace your battery sooner than you expected. The table below shows you how much recoverable capacity exists in a battery after storing it at different temperatures and different charge states for 1-year.
This is why a lot of electronics come with batteries that are only partially charged. to help slow down this decay. That being said, it’s hard to track how long e-bikes and their batteries have been sitting in warehouses before being delivered to your door so you could get a battery that has been decaying for a year or two.
Manufacturers also tend to overrate their batteries and will make claims about certain batteries having a lifetime of at least 1,000 cycles. Show.me.the.data.
The lifetime of a lithium-ion battery is described as the number of cycles until the capacity (Ah) drops below 80% of it’s initial capacity. In general, this is roughly 250-400 cycles (depending on battery chemistry and other factors) which amounts to roughly 1.5 to 2 years if you charge discharge daily and care for your battery properly.
How to charge your e-bike battery to make it last longer
- The thing that will kill your battery faster than anything else is leaving it charged at elevated temperatures. If it’s 80 degrees outside and you have your e-bike fully charged, move it indoors where it’s cooler and try to drain the battery as soon as possible.
- Charge your battery at room temperature as often as possible.
- When sourcing an e-bike battery charger, the slower the charge rate the better. For example, if you have a 2-Amp charger, and your battery is a 14 Ah battery pack, you are charging at 14 Ah / 2-Amps = 7-hours. This is a nice, slow charge which will certainly improve the longevity of your battery pack. Avoid charging at rates that are faster than 2-hours for a full charge.
There’s a lot that goes into choosing the best battery for you e-bike, and there certainly isn’t a one-size-fits-all approach. But if I were buying an e-bike battery today, here’s what I’d do: LFP or NMC, slow charge, avoid storing or charging in hotter temperatures, and leave the battery at around 30% charge if you don’t plan on using it for a while.
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How Much Does an Electric Bike Battery Cost?
Most of an electric bike’s worth lies in its battery. the priciest component. It is typically worth around 30% to 40% of the bike’s value, which means that it makes the biggest price difference as well. However, just like any other part, it’s not immune from the effects of wear and tear.
Eventually, you will be compelled to replace the power source because it will either be damaged or too old. keep in mind that these things have a shelf life.
If it ever comes to this, it is important that you find a new model that fits your budget, as well as your e-bike. So, what is the cost of an electric bike battery? What can you expect?
Generally speaking, a premium e-bike battery retails for around 500-900, but this is obviously determined by many factors, including the brand, the quality, the capacity, etc. The before mentioned price would is typical for a battery with parameters between 400wh and 700wh.
Note that batteries manufactured by big brands usually cost more than off-brand models, so keep that in mind as you consider the cost/Wh.
Comparing the Cost of E-bike Batteries Between Brands
When searching for the right battery to power your electric bike, you may find yourself overwhelmed with a wide range of brands offering quality levels tailored to different budgets.
It’s important to research and decide what fits best in regards to cost as well as performance.
Bosch might be one of the priciest manufacturers on the list, and one of the most famous ones as well. at least when it comes to electric bike batteries. A pack from Bosch retails for a price anywhere between 675 and 1000. This translates to a rate that stands around 1.72 per Wh.
For instance, the Bosch Powertube 625, which is rated at 625 Wh capacity, costs over 900 on Amazon.
Shimano is another popular brand in the market selling e-bike batteries. Their stand anywhere between 500 to 750, which ends up costing approximately 1.42/Wh.
The SHIMANO Steps BT-E8014 with a 418wh capacity, costs 500 on Amazon.
Finally, if you are not looking to spend too much on your brand new battery, there is always the option of looking for something more price-friendly. We suggest you look for an off-brand battery, but don’t compromise the cell quality. That’s why you should look for brands such as Samsung, Panasonic, or LG that will rate at about 0.82 per Wh.
These will serve as a great alternative to the more expensive Bosch power pack. Below is a list of some e-bike battery brands and their price range on major online retailers:
Shimano STEPS BT-E8020 Battery, Integrated Downtube, 504 Wh
Yamaha E-Bike Battery, 500Wh
However, you should note that the lower the price of an e-bike battery, the lower expectations you should have. there is a strong link between the two.
Most of these budget-friendly batteries are manufactured in China and you can find them by contacting the sellers directly. Unlike the cells from Korea and Japan, China doesn’t have a reputation for producing quality 18650 cells.
Also, keep in mind that these battery packs from China sometimes don’t have the high production value that “legit brands have”. the could be made out clone cells or reused materials. This generally results in underwhelming performance and a relatively shorter battery life expectancy.
Not to mention, these kinds of batteries are truly problematic sometimes and they can be a real problem when it comes to flammability. So, before you decide to go for the cheapest model you can find, keep the above mentioned facts in mind.
What’s Inside the E-bike Battery?
Most modern electric bikes have lithium-ion batteries built into them, and these consist of lithium-ion cells and a Battery Management System that takes care of the battery health.
The default e-bike battery pack consists out of smaller source cells that are typically arranged in the 18650 format. Each of these cells is only a little bit bigger than a regular AA battery. They also usually have a 1.5V charge. Meanwhile, their capacity is anything between 3200 and 350OmAh.
The small cells are usually arranged in either series or parallel to make up a large battery. The actual number of cells arranged might be different than expected because we need to take into account the capacity and the voltage. The type of arrangmenet is also very relevant.
For Bosch power packs, the number of individual cells is between 40 and 50.
What is a Battery Management System (BMS) in E-bike Batteries?
Some of these electronic bike batterie brands also use an integrated BMS, which is essentially the “control panel” for the battery. All of this serves to maintain balance as well as safety for all parts of the battery, each cell inside it, as well as the wiring. Performance obviously depends on battery health.
This system is quite important as it regulates the current that travels through the battery while it is charging, but also while it is being used. Some Battery Management Systems have the ability to monitor the temperature of the battery because this can prevent damage to the that happens when the system is overheated.
Some BMSs have the ability of Bluetooth connection, which gives you a great overview of your battery status through your smartphone.
How Costly is E-bike Battery Charging?
Many forget that aside from the initial investment you make when you’re getting the actual product, you need to cover additional costs related to battery charging. Most bikes have a battery rated between 300-500W, which means you will have to get a 2-Amp or 4-Amp charger.
If you have a battery with more capacity, you will have to give it more time to fully recharge. A standard e-bike battery takes about 4-6 hours for a single full charging, and it can provide anywhere between 25-80km depending on the level of pedalling assistence you decide to go for.
You will basically need to recharge the battery after every 4-6 hours if you were to use the bike at all times. Keep in mind that the cost of battery charging varies depending on each country. Typically, the rates can range from 5-dollar cents per KWh to 35-dollar cents per KW/h for those in the United States.
Another important thing worth noting is that you’ll have to charge your bike as much as you use it with the assistance set to max. Basically, if you are almost always in throttle mode, you can expect a shorter shelf life for your battery, as well as more charging per week.
How Long Does an Electric Bike Battery Last?
The lifetime of a battery is usually determined in charge cycles. This means that you can count how many complete charge cycles you can go through before the battery isn’t effective anymore. Note that a full charge cycle isn’t just “any charging” but the full movement from 0-100%.
Generally, an e-bike battery can go through several hundreds of charge cycles. However, the actual number will depend on the nature of the battery you’re using, as well as the overall maintenance of the battery.
For instance, if you tend to store your battery pack in a dry area that is well shielded against temperature fluctuations, then you will enjoy longer service from it. On average, the battery becomes less and less efficient after 3-5 years of use.
An e-bike’s battery shelf life is mainly influenced by the type of battery it is. Usually, the most common types you’ll find in the market include:
- Lithium batteries- These are the most widespread and can last up to 1000 full charge cycles or even more for the latest Lithium Iron Phosphate designs
- Nickel batteries- You can expect around 500 cycles
- Lead batteries- These can go up to around 300 cycles
How To Extend the Life of an Electric Bike Battery?
There are a couple of e-bike battery maintenance practices that you should adhere to if you want a long life for your battery. These will come in handy whenever you’re charging, storing, as well as cleaning the battery. In short, you should do the following:
During charging, you want to make sure that you’re using the charger and adapter that came together with the e-bike battery. This will save you any problems arising from overcharging, as well as damage as a result of short-circuiting.
Before charging the battery, allow it some time to cool, and avoid using it immediately after recharging. Don’t wait for the battery to be fully drained before charging and when you charge your battery, make sure it gets to 100%.
Lastly, if you won’t be riding the e-bike for a long while, try to partially charge the battery pack every few months.
During storage, it is advised that you find a cool and dry place for this. Ideally, find an area with temperatures between 0 and 20 degrees Celsius to maintain the battery’s capacity. Also, avoid exposing the battery to direct sunlight or placing it close to heat sources.
The first thing to take note of is that water and electricity don’t mix, so you don’t want to use steam pressure when cleaning the battery. Instead, find a damp cloth and wipe any dirt, grime, and dust off the battery.
Whether you are planning to replace the battery you already have or motorize your regular bike using an e-bike conversion kit, you should have a good idea of the type of battery to invest in.
Remember that the battery is the bike component that will cost you the most, and that you will need to replace it eventually. This article lets you know how much money you need to set aside for the battery, and how often you have to make this investment.
Last update on 2023-06-14 / Affiliate links / Images from Amazon Product Advertising API