The best thing I bought for my 2000 Blazer was a 12volt power adapter for all my devices, its round and fits in a drink holder, has 2 12v cigarette lighter ports and 2 USB ports. Now I can plug my NAV, Dash Cam and my cell phone in all at the same time. The unit plus into the dash cigarette lighter outlet. It has lights on the unit telling you if your car battery is fully charge is it's being drained. The unit was about $15. My other unit was a 12v splitter but would fall out of the lighter port when driving down a dirt road.