[Paul] recently purchased an inexpensive USB ... circuit using a Teensy microcontroller and determined that a 20ms pulse every 1.4 seconds was enough to keep it on — any less and it would ...

However, installing a kill switch on the negative battery circuit leaves the positive side of the electrical system energized. Machines have caught fire because mice, rats and varmints gnawed ...

thanks to everyone’s great feedback, i’ve now got a usb battery that’s much more efficient and capable of delivering more current to a portable device. like i promised, i put together a ...