marcopolo57, keep in mind the cable that came with the Nexus 7 is designed to only work with the Nexus 7 and provide just enough power to charge it, on it's own. Now we've thrown an OTG cable in the mix, so you are probably loosing just enough amperage through that cable to no longer charge the Nexus. I had a similar issue and ended up fixing my problem by hard wiring something like this into my vehicle wiring: http://www.amazon.com/Photive-2-1Amp-Charger-Designed-Android-Devices/dp/B00DYYTO4M/ref=sr_1_7?ie=UTF8&qid=1417632199&sr=8-7&keywords=cigarette+lighter+dual+usb+2a so ACC line -> (above) adapter -> usb cable -> OTG adapter -> Nexus 7. This fixed my problem once and for all, now the Nexus charges every time the vehicle is turned on or ACC line is hot. Hope this helps.