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What is PMS inside GT40 and how it works?
10.09.2021 | John Ivy | GT40 Engineering


GT40 is a range modification that aims to extend the range on the onewheel pint, it feeds power from an external battery pack into your main power lead in the front compartment of your pint.


The original battery inside the pint is a pack made of 15 sony vtc5d cells, they have a capacity of 2.8Ah, adding an external battery pack that has 5Ah capacity will yield a 2.8X range improvement comparing to original board, but it can be dangerous if you dont know much about litium batteries, here are a few dangerous scenes and how PMS solves them.


1.  Voltage matching. when connecting two different battery pack together, you have to make sure they have very close voltage level, if you conncect two battery that has big difference in voltage , a surge of current will flow between the two packs and damaging your BMS in side the original battery. The PMS inside GT40 does voltage matching automatically by comparing the internal and external battery level 600 times per minute, and it decide wether it is safe to feed power into your board, if it is safe, the PMS will establish a connection between the external and internal battery pack by turning on a high speed switch inside, and showing a flashing green light on the indicator. If the voltage of your board is below safe limits, the PMS will show a blue light and you can connect your board to the charger until the PMS turns green. If the voltage of your board exceeds the safe limits, the PMS will show a red light, you can go out and ride your board with GT40 connected and the PMS will automatically establish the connection once the board is within safe limits. 


2.   Error code. Did you know you can trigger the error code on your board by connecting an external battery to it? In other external battery mods, you will have to connect the external battery after you turn on your board, if you connect the battery when the board is off, you will trigger an error code and your board will flash red to warn you. And if you forget to disconnect the external battery before the board turn off, you will also trigger the error code. In the GT40 mod, you can leave the GT40 connected to your board and you dont have to worry about any error code, due to the help of PMS, It detects the status of your board, when you turn on your board, the PMS wakes up and establish the connection automatically. When your board turns off, the PMS shuts down the connection immediately to prevent error code and red flash. Meanwhile in other external mods for example the VnR, which doesnt come with PMS, you will have to manually connect the battery everytime you turn on your board, and disconnect the battery everytime you turn off the board.


The PMS is the brain child of our team, it took 11 months to develop the hardware and code for it, and suddenly the IC shortage hit, we had to redesign several times and tune the code to behave right in every senario. We used parts and chips from reputable suppliers such as murata and Texas Instruments, It has many expensive MLCC cap on it to keep it stable in harsh evironment, and finally it is submerged into weather resistant coating gel, every surface is coverd in thick gel incase of any water damage.