Introduction
It’s no secret that many Xiaomi e-scooter owners would like to increase their scooter range and top speed. This can be achieved in 2 ways: the first one is replacing the scooter internal battery to a new higher voltage one, and the second way is mounting an additional external battery.
In the following two videos I will show you how to equip the scooter with an additional external battery that can be detouched and connected back at any moment, without voltages equalizing. We can even use a higher voltage external battery, like 48V one.
The first video is long and full of theory:
The second video is focused on installation process and testing, so it is shorter and simpler:
The text below is a short text version for people who prefer reading rather than watch a video. But this text contains only like 30% of information, so I still highly recommend to watch the videos.
The parts we need
If you are going to install an external battery, you basically need 3-4 parts: battery itself, mounted bag, adapter to match batteries, and a new charger(optional).
Battery
Of course, this is the most important part. The bigger your battery, the greater range and speed improvement you get. “Bigger” means 2 battery characteristics:
-more capacity
-higher voltage
Increasing capacity, you extend range. Raising voltage, you improve top speed. For sure, you would like to get it all, so people usually install a battery with both increased capacity and voltage. But you have to be careful, since the maximum voltage is limited by the scooter hardware and must not exceed 55V for Xiaomi e-scooters. At the same time, the capacity is not limited, let it just fit into the bag.
My battery is 44V 10Ah, and since the original internal battery is 36V 7.8Ah, I expect about x1.2 speed boost and about x2.6 range increase.
Mounted bag
That’s really funny, but there are still no factory-made bags with a rigid mount on the scooter frame after 5 years since the scooter was released. Therefore, the solution is to get a cheap standard “WildMan 2L” Aliexpress bag and equip it with a 3d-printed mount. Above you can see the mount I designed. By the way, the design is opensource, so you can make it yourself, just get and print the model:
Higher voltage charger
This part is optional and needed if only we use a battery with increased voltage. My battery is 44V one, so I need the new charger.
Adapter to match batteries - "Rita"
Let me explain why we can’t simply join the batteries and need to use a special adapter. The thing is the battery voltage depends on its charge level:
So, if we join the batteries, current starts to flow from the more charged one to the less charged one, like water in communicating vessels:
Finally, the voltages will be equalized:
But the problem is the current between the batteries can reach significant values during the equalization process, exceeding the batteries, wires, and plugs current limit:
Therefore, we must block the current between the batteries: let’s try to use 2 diodes for this purpose:
But this simple solution is not acceptable for Xiaomi e-scooters, because its main controller not only drain current from the batteries, but also recovery energy back when the brake is pushed. Diodes block the energy recovery current, therefore voltage at the controller instantly rises up, and the controller burns out.
So, we need a smarter circuit that could distinguish energy recovery current and current between batteries. This circuit must analyze controller and batteries voltages, and decide which current should be passed, and which – blocked. And this circuit also must be connected to data lines of the scooter controller to provide information about the additional battery state:
I am proud to tell you that I have successfully designed this smart device, here it is:
I named it “Rita”. Why? Well, the answer can be found in the first video at the beginning of this article =)
Ok, finally, we have everything we need to install the external battery, let’s pass to the installation process.
Installation
The first step is securing the bag:
Use a wrench for the most secure fit:
After the bag is mounted, you can still put your feet under it and fold the scooter:
Now let’s put Rita inside the scooter and plug in all the wires:
Range and top speed improvement test
Conclusion
Now I am really happy with this external battery: I just go wherever I want and never worry about remaining charge. I highly recommend this mod to everyone who needs more range and speed for his electric scooter.
Here are the links to the parts I used:
-
44V 2A charger
39,00 € -
“Rita” adapter for Xiaomi
64,00 € -
Mounted 2L bag for Xiaomi M365 / 1S / Essential / Mi3 / PRO / PRO2
39,00 € -
44V 11Ah external battery
255,00 € -
Range+speed boost kit for Xiaomi M365 / 1S / Essential / Mi3 / PRO / PRO2
375,00 € -
Range boost kit for Xiaomi M365 / 1S / Essential / Mi3 / PRO / PRO2
340,00 €
Afterwords
If you like this post, please share it on your social networks and e-scooter communities you belong to. It will really help me to get more customers, grow my small business, and release new cool devices. =)
I also invite you to join my telegram group related to Xiaomi and Ninebot electric scooters, where I share the newest inventions and answer the questions:
https://t.me/m365_custom_electronics_en
Thanks for your attention!
