I use mine with great luck and today converted one to USB power. Open it up, Find a space to melt a hole for the USB cable. Run your prepared USB cable through and solder the red and black wires to the red and blacks posts on the underside/inside of the battery tray - secure it & DONE! (secure your wire so it can't pull out!) This will work with most battery banks too for long time use at a campsite or on the go! Just not the auto setting
- of course this all depends on whether or not you get a dud!
You can also install a TP4065 module by soldering that to the same posts inside as the USB cable version. Then you can use 1.5 V 2800 mah AA lithium ion rechargeable batteries and then USB power/recharge it by simply plugging in a micro USB cable to any 5v phone charger.