DISCLAIMER: This item is a sophisticated electronic controller. You will need skill and knowledge to install it and use it. You will need to have done research, some available on YouTube - search "eBike School" and "Jehu Garcia" by example to find out what a bms is, what it does and especially how to install it. Wiring diagrams and how to use the bms are found on this listing. It will not be possible to return this item once opened and used, but most especially due to use or damge caused by negligence or lack of knowledge.