I want to stop an electric forklift from starting until a remote signal is sent to it. I currently have an Arduino Nano ESP32 that can receive a signal from a Windows form using Bluetooth. I have some experience with electronics, but I am unfamiliar with working on anything higher than 9v.
Current Issue: I am having trouble designing a system that can connect to someplace in the forklift to stop it from running. I am currently thinking of having a relay that would break the connection of the starting key, but I am unsure if that would be the best solution.
The forklift battery is an E125-12. It is 36V with 750 Ah.
Why not use a key? To disable the forklift safely talk to your mechanic. That person can tell you where to tap the starter circuit. Not knowing what you have you need to design for a lot more then 36V, why; A 36V battery should be charged at a voltage from 42 to 58 volts. The recommended charger for a 36V battery is one that can output at least 5 amps, with a maximum charge rate dependent on the battery. From this your electronics must withstand about 60V. You have not stated if this has a combustion engine or all electric.
Quick question: why?
The "requirements" are always very important when planning any project.
Any forklift has (should have) a stop button: are you worried that they might steal the forklift, so you just need something "hidden" to prevent anyone from starting it, or what else?
Anyway, in addition to what @gilshultz said, I don't know your local laws, but generally speaking, IMHO any "custom" change to an industrial item needs to be officially approved for safety and omologation reasons. But even if I strongly suggest you to check that, this is not our current topic.
This means you need to have you and your your laptop be near the forklift to activate it, it seems not so handy. Why not using WiFi connection?