Try this, I have 2 of these now. Their older one without the over/under charge circuits lasted 6-7 years before crapping out. These come with the Tender cord with the reset button built in. It gives you two ways to hook up a charger if you already have the BMW outlet. They weigh next to nothing & I simply use my standard Tenders with no problems. They come with a pile of stick on foam pads to fit them in your battery box. I highly recommend them.
www.ebay.com/itm/202968319079
cured!