Description Application :this BMS will work for 3S 4S li ion or Lifepo4 battery with 20A or 30A Constant current ,client can select suitable parameters in according to your battery specification  Function :This BMS has such basic functions : over-charge protection ,over-dicharge protection, over-current protection, short-circuit protection.with ON/OFF switch function .  Advantages :This BMS was build with high end Integrated electronic components (High End IC and MOSFET ) ,simple structure design will let it have more stable quality working performance . with aluminum substrate for better heating sink than normal BMS for large current . Specification reference: l Transaction terms : 1) Shipment time : once received your order ,we will proceed it quickly within 3~4 working days without problems .order can be cancled within these days ,otherwise we will reject to cancle the order ,because our items can not get back when in the process of shipment . we will inform our buyer if  there is a stock problems with the order and arrange a properly agreenment on the shipment schedule by email . 2) Shipment Methods : Client can choose suitable shipment methods based on your demand ,Post air parcel service or Express service , we will ship all orders strictly in according to the selected shipment methods by our customer . normally , Post parcel shipment time takes 7~60days depends on different countries serivce . and express takes 2~15days to the destination normally . 3) About Tracking number : Tracking number will be uploaded and will be informed by the registered email on each Friday ,please pay attention to your email later on for the tracking number update . 4) Quality Service : we will take a full responsibility for any defect product caused by our design and production problems ,warranty time is 12 months since the shipment date . but for any defect product caused by any wrong or slavery application from customers . we will not take the responsibility for that , because for this BMS product ,it do need some skills to make installation . please consult us in advance if you are not clearly with bms connection in the hope of avoid any mistakes of connection . if Buyer damaged the BMS , we can offer the free repairing service to our client , but client should take care of shipment cost .please know it kindly in advance . thanks Please send email to this address for any questions [email protected], we will give you reply within 12hours without problems .