If you want to choose the right battery for your electric bike (also called an e-bike), learn about the following areas related to e-bike batteries. After reading this post, you can also browse battery-related products in our store.
1. Know the difference between battery styles
First, when you are buying an electric bike, I would look at battery style. Ask yourself these questions:
- Is it proprietary technology?
- If, and when, my e-bike battery dies, how easy is it going to be to replace it?
If you have a generic-style battery that mounts to the frame, you can likely find the battery from another vendor or source. If you had to, you could unbolt the cradle that comes with this battery and replace it with something entirely new and no one would know the difference.
I recently had a customer ask me for a new battery for his brand-name electric bike. The capacity was similar to the generic battery, but they wanted a whopping $1,400 USD for a relatively simple 48-volt battery. Instead, we were able to get him set up with something for half the price with much more capacity and a little more voltage for his bike.
I have seen a few instances where the e-bike battery has a special BMS (that's a circuit in the battery that helps protect it from low voltage or over-current), but it has one that talks to the controller on the e-bike, so you can't replace the battery with one of a different brand, even if the voltage and specifications are the same. There's an electrical communication that has to happen for the bike to operate.
So, be aware of the type of battery that will be required for the type of bike you're going to purchase.
2. Compare battery capacities
Many manufacturers of electric bikes make voltage claims, but you also will see claims about amp hours and watt hours. It can be difficult to understand how e-bike batteries compare when they are described with different units. Let me share a simple formula to help you with your e-bike battery purchase.
v * ah = watt hours
(voltage times amp hours equals watt hours)
In the image below, you'll see the label for one of my batteries. It has 48 volts, 12.8 amp hours, and 614.4 watt hours. If I multiply 48 by 12.8, I get 614.4.
How can you use this formula? Take these examples.
Example 1: Comparing two e-bike batteries with the same amp hours
You want to compare two e-bike batteries: one with 36 volts and 10 amp hours, and the other with 48 volts and 10 amp hours.
If we take a battery with 36 volts and 10 amp hours, that equals 360 watt hours (36v * 10ah = 360 watt hours).
If you wanted to compare the capacity of that e-bike battery with a battery that has 48 volts instead of 36, you would replace the variable and the formula would read:
48v * 10ah = 480 watt hours
You can always stretch your algebra muscles and solve for a missing variable. If the e-bike battery has a watt hour rating, and they don't give you the amp rating, but you do have the voltage, you can solve for the voltage in that formula. This way, you can accurately compare the total capacity, which is the watt hours, of any given battery.
Example 2: Comparing two e-bike batteries with information in different units
You want to compare two e-bike batteries: one with 36 volts and 10 amp hours, and the other with 600 watt hours. Which one is better? Plug your numbers into the formula.
36v * 10ah = 360 watt hours
Compared with the 600 watt hours of the second battery, the first battery has a lower capacity at 360 watt hours.
Why does this matter? This goes to the next point.
3. Don't trust what the manufacturer claims about range
Manufacturers will claim a range for how far their e-bikes will go and how long the e-bike battery will last (in miles, usually). I've noticed that in two different bikes with the same battery capacity, that the claims are wildly different: one might claim the battery will last 20-40 miles, while the other will claim 80-100 miles. How is this possible that two manufacturers can be so different in their claims when all else is equal between the products
Let's take a real e-bike example: imagine a 48-volt, 12-amp hour battery. We do the math (48v x 12ah =576 watt hours) to determine the capacity. Now, if we take this battery and put it into a 750-watt hub motor, how far will it go? Well, we can't really answer that question unless we have more information.
Is it going uphill or downhill? How fast is the electric bike going? How much does the rider weigh? There are so many variables, that the range could be anywhere between 10 miles (full throttle, uphill, with a heavy load, killing the battery as quickly as possible) and 50 miles (if you're riding it like a bicycle on a low pedal-assist setting and using the motor a small amount).
Could you go further than 30 miles on your electric bike? Absolutely, but there are some requirements to make that happen, and that's not what most people do. And could you drain it faster than that, also yes, but that's also not the typical scenario.
So, rather than believing the range claims by various e-bike manufacturers, I would ignore them altogether and use the new knowledge you have about battery capacity, the quality, and the types of motors to determine which bike is going to be best for you.
No one size fits all
There's no best e-bike battery to buy when you're looking for a new e-bike. It depends on your preferences, who you are, how you will be using your e-bike, and so on. Leave a comment to let me know what battery you decided on and why!
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