Updated: May 12
What you need to know & what you can ignore (like this very simplified article if you are an ebike battery expert).
We all want the best from our ebike or emtb experience, right? The only problem is that these ebikes and batteries and configurations can get extremely complicated. Most of us just want to buy our conversion kit, be able to slap it on our bike frame, and not worry about all the mechanics or electronics behind it.
Although you can do this for a lot of motors, when it comes to batteries, you need to be able to make an informed decision. Why? Because if you don't, you are likely to end up in one of these scenarios:
- running out of battery in the middle of your trail
- carrying around a huge & unnecessary load or
- not getting anywhere close to the motor's rated power
The goal is to find balance between the distance and the power output you want to achieve... and think about the size & weight of the battery at the same time.
To find this balance, you will need to look at some of the specifications that your ebike battery supplier provides you with.
Your battery's specifications probably look like this (if not even more detailed):
52v 21ah 14s6p
1100 watt hours
50amp continuous BMS
There are 4 aspects that you need to consider here
- the voltage (52V)
- the capacity (21ah)
- the watt hour (1100)
- the continuous current drawn (50amp)
Don't worry about the "14s6p" for now.
It's important to have an idea of how each aspect will affect your ebike conversion kit's performance. So, let's have a look.
What's the mileage looking like?
Your range will mainly depend on 2 factors: the capacity (ah) and the watt hours (wh). But here's the tricky part, there is no fixed formula to calculate your range since no 2 riders are the same, no 2 bikes are the same, no 2 setups are the same, and no 2 trails are the same.
The rule of thumb >> higher capacity means longer range!
But what does "watt hour" have to do with anything then? When you multiply your voltage with your capacity, you get watt hours. Watt hours are what we use to determine your range. Since there is no fixed calculation here's an idea:
A 36V battery, for example, may or may not have a very long range. If this battery has a capacity of 8ah, then 36V x 8ah = 288wh. This is not much. On the other hand, if this battery had a capacity of 21ah, which gives you 756wh, then you're looking at decent mileage.
This only tells us how to read the numbers though. It doesn't give us any idea on how far we can go. Luckily, based on our experience and user feedback, you can expect the following from high powered motors:
15wh per mile or 9wh per km using pedal assist only 30wh per mile or 18wh per km using throttle only
It's obvious to assume that the less power you use, the more range you can expect. If you're riding according to your region's legal limits (usually 250W only) then you can expect at least double the range.
So in our example, if you are only using pedal assist, the 36V 8ah (288wh) battery will give us approx. 19 miles or 31km. Whereas the 36V 21ah (756wh) battery will give us approx. 50 miles or 81km.
Don't hold us to this number though. Like we said before, this will differ significantly for each rider. If your kit has a throttle or if you have a good relationship with that turbo button, then you might want to consider keeping a spare battery for those cross country rides. At least you can still pedal with a dead battery but that's not a point any of us wants to reach.
OK, so we got the distance down. What about the power?
Higher voltage means more POWER! Right? Not necessarily but it does mean a higher top end.
A higher battery voltage will give you a higher top speed because the higher the voltage, the higher the maximum motor RPM. The important thing to note here is that just because 2 batteries have the same voltage & can go up to the same speed, doesn't mean that they output the same power. It might take one 52V battery 5 seconds to reach 25km/h yet for another 52V, it might take 30 seconds to reach 25km/h.
To put this into perspective, you can have a 72V battery that can output only 2200W or you can have a 72V battery that can output 5800W. The difference? The continuous current rating. The former battery is rated at 30A continuous, while the latter is rated at 80A continuous. Note that your continuous current can be limited by your ebike kit's controller. It doesn't help you get a 80A continuous current battery when your kit's controller is limited to only 50A. This, in most cases, won't do any damage to your kit, but it means that your battery is bigger (& heavier) than it needs to be.
Our advice: Look at your kit's controller 1st. What is the continuous current rating? Then, look at the motor's rated power. Now, work out the specs you need by multiplying the continuous current with the voltage. Does it give you your motor's rated power?
Now what's the catch?
The catch is that there is usually a trade-off between these factors. This is where the size & weight of your battery comes in.
It's very important to consider how much physical space you have available to mount your battery as well as how much weight you want to add because the battery nowadays weighs more than the motor! Take the CYC X-52 battery for example. The X-52 has the following specifications:
52v 8ah 14s2p
416 watt hours
60amp continuous BMS
The X-52 get reach up to 3120W continuously which means it's very good for high powered motors like the CYC X1 Pro, but it only has 416wh which is good enough for most uses but it's not enough if you want to do a 80km trip. The reason for this is because if the capacity was higher, it would mean the physical size of the battery would be bigger, making it too big to fit inside the triangle of most full suspension bikes.
On the other hand, if we wanted to keep the physical size and increase the range, we would need to decrease the continuous current rating, ultimately giving the kit less power to accelerate. This is why it's a good idea to know how much power you need, how much range you want, and keep in mind how much space you have available on your frame.
There's a whole lot more to batteries than this but we are not going to dig into cell types, BMS, chargers or battery health here. You can read all about it in our other battery blogs.
So, there you have it! An idea of how to read the main numbers & get a ballpark of what battery specs you need for your brand new ebike conversion kit.