I ordered this, and then ended up not needing to jump a vehicle for quite a while. I charged my phone off the device as a power bank several times with no problem. I then left it sitting with a half full battery for a couple months.Then last weekend I was at my parents' house, and my dad's 15 passenger van which hadn't been driven in months had a completely dead battery - no glow at all in the interior lights, not even a click when trying to start it. He was about to connect a battery charger, and I stopped him so I could test this jump starter. When I pulled it out and hooked it up, he laughed and said there was no way it'd produce anywhere near enough power to get the van engine going, especially with the battery so dead.We tried to start it, and it fired up no problem! Not even slightly sluggish, it sounded just like starting the engine with a full battery. I left the jumper connected for a few seconds after the engine started, and the device properly detected the vehicle trying to push power back and disconnected with an appropriate indicator on the screen.The van was definitely having problems, and we ended up stalling it and having to jump it a few more times. After the second time, my dad said we better be careful, because "my little toy" probably wouldn't have enough power for much more. I wasn't sure myself how many starts we'd get, since I'd made the mistake of leaving it sit for months and it only had half a charge when we started. We ended up having to jump start the van 4 times - every time this little jumper provided enough power for a strong start, and only after the 4th start did the power indicator drop from 2 lights (out of 4) to 1.We were both very impressed with the performance, and as soon as we were done, my dad had me help him find this device on Amazon so he could order one for himself.While the jump starting capabilities are obviously the key feature of this device, it has a few other features which also worked very well:- When you connect the jumper cables to power bank, it gives a nice display of its output voltage. Once you connect to the vehicle's battery, the jumper will briefly switch every few seconds to show the vehicle battery's voltage. When you're starting the vehicle, the output voltage will drop a bit due to the load, but the display allows you to monitor and make sure the jumper can handle the load of the engine you're trying to start.- Once the engine is started, the alternator will begin charging the vehicle battery, and that would also push energy back into this jump starter, which it wouldn't be able to handle. It has the ability to detect this situation, and safely disconnect itself internally. This means you don't need a second person standing by the engine to disconnect the jumper immediately after the engine starts.- The jump starter will properly detect if you accidentally connect the cables together, and will safely prevent the short circuit from doing any damage.- The jumper cables plug in separately, so when you are using the device as a power bank, you don't have them knocking around- The power bank features also work well. I connected my phone to the USB 3 power port, and my phone detected quick charging capabilities and charged nicely.- In the photo with the cables hooked to a car battery, the display looks odd. This is just a problem with the camera on my phone. In person, the readout looks just fine, like it does in the close up photo.I initially had a bit of a problem with the jumper cables always falling out of the pouch when I opened the case, but after arranging them as shown in the photo, they have stayed put nicely.