Electric Bike Batteries
The batteries are arguably the most important aspect of any electric bike. The kicker is that many electric bike manufacturers don't give you the full information you need to truly understand what you're purchasing. We're offering this information so that you can know what you're getting into before you buy because the batteries are going to affect your range, your power, your ability to climb hills and mountains, your charging time and the overall weight of the bike. Let's dive in!
Battery Capacity
If you're shopping for an electric bike, battery capacity is your new best friend. Truly, this is going to determine a TON about how much you enjoy your new ride. So grab that pen and paper, roll up your sleeves and get ready to be a battery capacity wizard.
Really, 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 tell the full story of how much energy your battery can store. More watt hours means you can go further per charge.
As your battery gets larger, it of course becomes heavier and more expensive. The goal for any electric vehicle is to maximize onboard energy (watt-hours) and minimize cost and weight.
Battery Lifespan
Lithium batteries have a significantly longer lifespan than older lead-acid and nickel-based batteries. In the state of the electric bike industry, it's more likely that a limited lithium battery lifespan is not due to a short cycle life, but is instead caused by a complete battery failure due to poor quality control in the manufacturing process. So, above all, be sure that you're buying a bike that's equipped with a high-quality battery. Just because it's lithium, doesn't mean it's high-quality.
The battery's lifespan is rated in cycles. One full cycle is a complete discharge and recharge of a battery. A half cycle is a half discharge and recharge. Cycles, however, only tell part of the story. Let's take a bit deeper look at how we can best estimate and maximize a battery's lifespan.
First, it's important to note that if a battery is rated for 1000 cycles, it's not going to fall dead on its face 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 aging of your battery.
As hinted at earlier, cycles only tell half of the story. The other important half is the overall range of your battery. Let's take a look at an example:
Bike A:
1000 cycles and 30 miles of range, expected miles to 80%: 30,000 miles
Bike B:
700 cycles and 100 miles of range, expected miles to 80%: 70,000 miles
As you can see from the example above, although Bike A has a battery that lasts for more cycles, Bike B will travel over twice the mileage before the battery begins showing its age. This is another reason why a larger battery is a big advantage on any electric vehicle.
The enemy of a long life for your battery is heat. Store your bike in a cool place whenever possible, and on lower performance batteries, it's a good practice to not charge immediately after your ride, but to let your batteries have a bit of time to cool down before charging.
Battery Types
Lithium Ion
Lithium Ion is a general term for a battery that uses lithium in its chemistry. The actual chemical composition, more specifically, can be broken into three categories in regard to its use in electric bikes.
Lithium Polymer
This is often abbreviated as LiPo (pronounced "lie-poh"). This is the most power dense battery, and also has the unique characteristic of being able to manipulate it's form. Because of these two characteristics it is found in almost every cell phone, laptop etc. This is the battery used in both the Alpha and Horizon.
Lithium Manganese
This is often abbreviated as Li-Mn.
Lithium Iron Phosphate
This is often abbreviated as LiFe or LiFePO4.
Nickel Metal Hydride
Similarly to Nickel Cadmium, they don't perform especially well in regard to rapid discharge. They don't carry the same "memory" characteristics as Nickel Cadmium, but given the lithium alternatives, you're most likely better off going for a more power dense lithium battery.
Nickel Cadmium
This is often abbreviated as NiCad. These guys aren't really well suited for electric bikes because their chemistry doesn't allow for rapid discharge. You've probably hear of battery "memory". That doesn't apply to most batteries, but it does apply to Nickel Cadmium, which means that you would want to fully charge and fully discharge them every time, which doesn't really make a ton of sense for an electric bike application. The last nail in the coffin for these guys is that they're pretty toxic at the end of their lifecycle and most landfills won't even take them. Bottom line - you pretty much don't want to use them.
Lead Acid
Lead acid batteries are comparatively heavy to the other batteries listed here. Another way to say this is that they are not as "power dense", meaning that for a given weight and volume, they have less power than batteries of other chemistry's. This is the same type of battery that you would find in most cars. Because of that, they are widely available, however they would not be the ideal choice for an electric bike. Despite this, they are still frequently used in many Asian countries for electric bikes. 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 voltage is going to momentarily drop significantly.
New Formulations
Battery technology is become increasingly wide-spread thanks to consumer electronics such as phones and computers that demand lightweight powerful batteries. This is resulting in serious amounts of cash being put into Research and Development to improve the technology, the manufacturing process, and also reduce the cost by increasing the quantity. Several times a year we'll hear about the latest "breakthrough" in battery technology. Be discerning if you come across articles that claim things like this. Don't get me wrong, we're all about innovation in regard to batteries, but you have to keep in mind that lab tests are not equivalent to real world testing, and that it takes time for any new technology to make it from a prototype to a consumer. We keep a close eye on this industry constantly, and we'll update this page with any new applicable battery as it becomes available.
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