Electric bike battery


Your electric bike battery

Batteries are arguably the most important component of any electric bike.  Without a good electric bike battery, you won’t get very far! Lately we’ve been noticing some incomplete information floating around on the subject of electric bike batteries. So much so, that we felt it was time to publish an article focused on electric bike batteries, the technologies available and the benefits and/or shortcomings of each. At Unconquered Custom Electric Cycle we are committed to gathering the most important and up to date information for our customers then distilling it in a way which is understandable for our readers to digest. Batteries are going to affect your range, power, your ability to climb hills, your charging time and the overall weight of your bike. 
Battery technology is evolving rapidly. In fact this is one of the reasons for the recent substantial bump in electric bike sales, and one of the main reasons electric bikes are now viewed as a viable alternative to the automobile. However, with so many battery technologies available, it’s hard to know which is best. So grab your pen and paper, ease into the tub with a glass of red - and let's dive in!
To help we’ve compiled a complete guide to the main battery types found on electric bikes and included our tips on how you can get the most out of your battery in terms of battery life and performance.

Electric bike battery types

Lead-acid electric bike batteries (SLA)lead acid electric bike battery

Ok, first off the old contemptables - Lead-acid electric bike batteries.. Old school may be the best school, just not in the case of these batteries. They are cheap and easy to recycle. However, they are extremely sensitive to poor battery management, and they don’t last very long. Lead-acid batteries are cheap for several reasons: they weigh twice as much as NiMh batteries, and three times as much as Lithium batteries. They are very heavy (hello lead?) so much so that this technology creates diminishing returns in terms of range efficiencies. Another way to put this is that lead-acid batteries are not as "power dense", meaning that for a given weight and volume, they have much less usable capacity than NiMh batteries or Lithium batteries. This is the same type of battery that you would find in most gasoline powered cars and because of this reason, they are widely available. However, they are not the ideal choice for an electric bike. Despite this, they are still frequently used in many Asian countries for electric bike applications.  Another point to note with Lead Acid batteries is that they "sag" significantly under load.  In other words, if you suddenly nail the throttle the battery voltage is will momentarily experience a significant drop. . To top it off, they only last for half as long as nickel or Lithium batteries. So, ultimately not a good choice if you’re using your bike to commute.
**Great time for a warning - if a cheap electric bike is advertised and the advert does not state what kind of battery it has, you can pretty much bet that it comes with a lead-acid battery. It might be cheap, but it’s not a bargain. If you are in the market for a serious electric bike, it is best to avoid lead acid batteries altogether.

 

Nickel-cadmium (NiCd) electric bike batteries
electric bike battery recycling

Often abbreviated as NiCad. Pound for pound, nickel-cadmium (NiCad) batteries have more capacity than lead-acid batteries, and capacity is an important consideration on an electric bike. However, these batteries really aren’t well suited for electric bike applications as their chemistry does not allow for rapid discharge.  Also, you may have heard the phrase “memory effect". This phrase describes the situation in which nickel-cadmium batteries gradually lose their energy capacity if they are repeatedly recharged after being only partially discharged. The rider would want to fully discharge, then fully recharge these batteries each cycle, which really isn’t ideal for an electric bike application. Also, nickel- cadmium is expensive. Not to mention for you environmentalists (preaching to the choir if you are in the market for an electric bike) - cadmium is a nasty pollutant and very difficult to recycle. On the other hand, NiCd batteries will undoubtedly last far longer than lead-acid batteries. But the reality is that because they are so hard to recycle or get rid of safely, NiCd batteries are going away fast and are becoming difficult to source or replace. The nail in the coffin for these batteries is that they are pretty toxic at the end of their lifecycle and most landfills won't even take them.  Bottom line - you don't want to use them. If you are a recycle conscious consumer, these are not a good choice of battery type, regardless of price.

Nickel-metal hydride (NiMh) electric bike batteries

Similarly to Nickel Cadmium, though they are not burdened by the same negative "memory" characteristics. NiMh batteries are somewhat more efficient overall than NiCd batteries, but they are also more expensive. Most riders report that NiMh offers a little improvement in range over NiCd though at the time of this article we could not find credible or definitive studies on the subject. On the other hand, there is plenty of evidence to support the fact that they will last longer (able to receive and endure more charge cycles) and are easier to dispose of correctly. Nonetheless, NiMH batteries are also becoming a rarity, mostly because the market place has quickly become dominated by Lithium-ion (Li-ion) batteries. And given the available choices of Lithium alternatives, you are most likely better off going the route of a more power dense Lithium battery.

Lithium-ion (Li-ion) electric bike batteries
electric bike battery

These have become the default battery when it comes to electric bikes, capturing over 90% of the market. On the plus side, Li-ion batteries last longer and generate more power for their weight than other batteries. On the negative side, they do require intelligent chargers and battery management circuitry to properly charge and balance. Of course, you needn’t worry about the latter, as Unconquered Custom Electric Cycles has already sorted the battery management conundrum out for you. But like all good things in life, Lithium-ion comes at a price: this battery type is very expensive, and shows little signs of becoming cheaper. Lastly, Lithium-ion is a general term for a battery which uses Lithium within its chemistry. The chemical composition of the cathode, can be further broken down into three main chemistries commonly found in electric bike battery applications.

Commonly used Lithium-ion electric bike battery chemistries

Lithium Cobalt (Li-cobalt)

The big boys! Lithium cobalt delivers the highest specific energy of any battery chemistry - but at a cost. They are the most dangerous li-ion batteries out there. This can be a problem for high-current discharging, as you can't safely discharge them at a higher current than their Ah rating. Though they offer optimum power in a light, compact package they are not the most ideal for an electric bike application (especially for those who like to twist the throttle) due to safety concerns.

 

Lithium Manganese (Li-manganese)

The same battery technology used in the Nissan Leaf hybrid car. Some claim it is the best of all. Lithium manganese provides a higher cell voltage than Cobalt based chemistries but the energy density is about 20% less. It also provides additional benefits including lower cost and higher temperature performance. This chemistry is more stable than Lithium Cobalt technology and thus inherently safer but the trade-off is lower energy density. Lithium Manganese cells are also widely available but they are not yet as common as Lithium Cobalt cells. Manganese, unlike Cobalt, is a safe and more environmentally benign cathode material. Manganese is also pound for pound, much cheaper than Cobalt.

Lithium Ion Polymer

Ok so this is the best Li-ion electric bike battery chemistry in terms of range, weight, and eventually price, (we hope!) Often abbreviated as LiPo (pronounced "lie-poh").  This is the most power dense Lithium combo available, and due to its polymer properties it can be molded into interesting shapes. Because of these two characteristics LiPo batteries can be found in almost every cell phone, laptop etc. They are not the least expensive, but because of the positives listed above they are our chemistry of choice and the only type of cells we use at Unconquered Custom Electric Cycles within our packs. LiPo batteries contain no liquid, so they do not require the heavy protective cases which other batteries need. Also, the absence of free liquid within these batteries means that they are more stable and less vulnerable to problems caused by overcharge, damage or abuse. In general, they seem to be ideal for use in high capacity, low power applications like electric bikes. Since these batteries can be molded into different geometric shapes Unconquered Customs has some radical design ideas in the que this spring for field performance evaluation.
electric bike battery chemistry
Obviously the best choice for electric bike applications is some type of Lithium-ion battery, but which specific chemistry may ultimately be subjective. For instance while Lithium cobalt offers higher energy density, Lithium manganese batteries are somewhat safer, and are more environmentally friendly. Unconquered Custom Electric Cycles uses a Lithium-ion Polymer chemistry at the cell level within our packs as we feel Lithium polymer is best for range, weight and stability. A good rule of thumb - If the electric bike you are considering comes with any kind of Lithium ion battery, you are off to a good start. Beyond that, you need to weigh the characteristics of each specific chemistry described above and decide which are the most important to you. For the remainder of this article all subjects will be in the context of Lithium-ion Polymer or LiPo battery packs as they are the battery of choice here at Unconquered Customs.

Quality is King!

In the electric bike industry, it's more likely that a limited battery lifespan is not due to cell chemistry, but instead due to poor quality control within the manufacturing process. If you purchase an Unconquered Custom Electric Cycle you can be assured that you are getting the best Lithium ion battery pack incorporated into your build that money can buy. Unconquered Customs is quickly gaining a reputation for our superior electric bike battery packs. This is because we use only authentic name-brand Lithium Ion cells (Panasonic or Samsung) and choose only the very best models from these brands made with the best polymer ingredients. 

Why not buy a battery pack from China?

China does not make a quality Lithium ion cell, and many “name brand” cell packs coming from China are actually made up of clone cells or re-wraps.  Chinese rewrapped batteries not only have bad performance and do not last long...they are also potential fire hazards.

What is a BMS?

Unconquered Customs also builds a proprietary battery management system or (BMS) into each pack. This is the circuit board that makes your electric bike battery “smart” including a temperature control loop to keep your battery as cool as possible. All of our packs incorporate our state of the art BMS to keep your pack safe. We are also hazmat certified and goods certified to ship our Lithium battery packs anywhere - and all our packs are tested and certified to (UN38.3) safety standards.

Chargers?

A quick word. Make sure you select a charger designed for the appropriate voltage and chemistry of your pack. Remember chargers for Lithium-ion packs need to have special logic installed to properly balance all of the interconnected Li-ion cells. At Unconquered Customs, we include intelligent chargers engineered to work with our specific Li-Po battery chemistry with each electric bike purchase.

Electric bike battery capacity 

If you are shopping for an electric bike then battery capacity is your new best friend.  Battery capacity more than anything is going to determine the range you can travel and ultimately how much you enjoy your new bike. Calculating battery capacity is simple, so long as you have one formula.  Here it is:
Wh = V x Ah  (Watt-hours = Volts multiplied by Amp-Hours)
Watt-hours will tell you how much energy your battery can store.  More watt hours means you can go further per charge. The battery you’ll find standard on an Unconquered Custom Electric Cycle for instance is a whopping 800Whrs! As your battery gets larger, it of course becomes heavier and more expensive. The goal of any electric vehicle manufacturer should be to maximize onboard energy (watt-hours) and minimize cost and weight.

Electric bike battery lifespan

An Electric Bike’s battery lifespan is rated in cycles.  One full cycle represents one complete discharge and one complete recharge of the battery.  First, it's important to note that if a battery is rated for 1000 cycles, it's not going to immediately die when it hits that 1000th cycle.  Most manufacturers rate their batteries to 80% of their initial capacity.  For instance, if the battery is rated for 1000 watt-hours when it's new, its total stored energy will slowly degrade over time, and on its 1000th cycle, it should have around 800 watt hours of capacity (80% of the energy it had when new).  It's still perfectly fine and safe to use the battery past the 1000th cycle, this rating just sets an expectation for the degradation with age of your battery.
Estimated cycles, however, are only part of the story.  Let's take a deeper look at how we can best estimate and maximize a battery's lifespan.

How to get the most out of your Lithium electric bike batteries

No matter what kind of Lithium battery you have, there is one Golden Rule for getting the most out of it: Keep it topped up! Overemphasis on the word cycles when it comes to battery life may cause you to worry that if top up your battery when you have only used a quarter of its storage, that you somehow are “wasting” an entire cycle. This is not the case at all – in fact, in most cases the opposite is true. A Lithium battery rated for 800 full cycles may very well get 2,000 half cycles. Proper maintenance is universal with any vehicle and it’s the same with your electric bike battery. Don’t wait till it’s totally discharged to give it more charge! Charge it up all the time!
So the best way to prolong the life of your battery is to charge it often. If you are driving your Unconquered Custom Electric Cycle daily, you just want to make it easy to charge fully. So do yourself and your battery a favor, and either have a spare battery charger at your work, the office, or else just pack a charger with you. Depending on the length of your commute, you may manage the journey on one charge. But you won’t be doing your Lithium battery any favors by almost completely discharging it. In fact, the best way to increase performance and lifetime on a Lithium battery is to reduce your amount of deep discharge cycles as much as possible. In fact, many people believe that you can double your battery’s life expectancy by discharging only 50% of capacity instead of 75% per cycle; and that you will get six times the battery life at 30% capacity usage per cycle!
Another way to prolong the life of your battery is to keep it fit during winter (or any other time when you are not using it). People can seriously degrade great Lithium-ion batteries by not using them for several months.
** A good battery maintenance tip: If you know you are entering a period of non-use of your electric bike, simply plug the connected charger into a digital timer, and program it to charge your battery for 30 minutes per week. This will work wonders to prolong the life of your battery. If you are driving your Unconquered Custom Electric Cycle daily, you just want to make it easy to charge it fully. So do yourself and your battery a favor, and either have a spare battery charger at your work, or office, or else just carry the charger with you.

In conclusion

Yes, Battery technology has become increasingly cutting edge thanks to consumer electronics such as phones and computers which demand lightweight and powerful batteries.  This has resulted in serious money being funneled into research and development to improve the technology and manufacturing process. Beware though, several times a year you may come across an article about the latest "breakthrough" in battery technology – take these claims with a grain of salt...  Don't get me wrong, Unconquered Custom Electric Cycles is all about innovation batteries included.. But you have to keep in mind that one off lab tests are not equivalent to real world testing, and that it takes time for any new technology to make it from prototype to trustworthy. 
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electric bike battery