Bests & Worsts Reviews from Amazon

SEE UPDATES BELOW. Bought this to put in my wife's Subaru Outback for emergency jumps since it's small, light, easy to use and is nearly fool-proof. I haven't needed it to jump the Subaru but the battery in my Kubota tractor is getting old and weak...it cranks the starter but very, very slowly which is not enough to get the engine started. It's a 3 cyl 35hp diesel with a slightly smaller battery (490CCA) than the Subaru Outback (4cyl gas engine, 625CCA). The unit was fully charged but it didn't really help. After hooking it up to the tractor battery, the starter did speed up for the first revolution but after that the engine starter sounded just like it did before the Genius Boost was hooked up (I apply about 5 seconds of glow plugs prior to each start). I pulled out my Clore ES5000 'Booster PAC' 12V Portable Battery Booster (also bought on Amazon) and it allowed the tractor to start up right away. The Clore Booster PAC costs about the same as this Genius Boost but weighs 18lbs compared to the 2lbs of the Genius Boost and is a more traditional jump pack. So, I put the Genius Boost on a charger again and left it plugged in over night and it showed fully charged. Tried to start my tractor a couple of days later and the tractor battery cranked the starter very slowly on its own. Hooked up the Genius Boost and it cranked quickly for the first revolution and then back to barely turning the engine over after that...no start. Pulled out the Clore Booster PAC and it the tractor started right away. Both tests were done between 50-60F ambient temperature. So, either this product is incapable of starting a small diesel engine (with 5 seconds of glow) or the product is defective or maybe it just isn't a good product (although I suspect this isn't the case due to the numerous good reviews...which I believe to be true). I would like to try to jump start a gas engine to see if it can, but I don't really feel like purposely draining my battery to run an 'experiment'. I will contact NOCO to find out if I'm asking too much from this unit or if maybe it's defective before the warranty expires. Or maybe it has problems with the 5 seconds of glow plugs since they are a resistive load compared to a DC motor load of a starter. I am a former diesel engine mechanic and am a electronics technician so I know what I'm doing. In any event, I only bought this product after seeing good reviews which overcame my doubts over how such a lightweight product could produce enough cranking amperage to start an engine. I'll update this review if anything changes. Added on edit: I just went back to actually read all the good reviews. I think it's a little suspicious that the majority of the five star reviews are Vine reviews of free products and many of them never even test the product! I'm not saying anything unsavory is going on here as I don't have any evidence...I'm just finding it a bit suspicious that there are so many of them. On that note...I am off to drain my car battery as my curiosity has been piqued. UPDATE 11/30/14: I discharged the battery on Toyota Tacoma 4cyl 2.7L gas engine. Battery voltage got down to about 2VDC which is pretty much dead. It was 22F outside which is not unreasonable as that's a likely temperature to encounter battery/starting problems. Hooked up the Genius Boost. Cranked the engine but only got 3-4 clicks out of the starter solenoid and then nothing. The clicking is the starter solenoid engaging and then disengaging due to excessive voltage drop. I then engaged 'Boost' mode. The starter solenoid clicked more rapidly this time but still no crank. Did it about five times and then on the last time the starter engaged and the engine started. Success. So, the device does work but only in 'Boost' mode and even then it's a tenuous proposition. Would I trust that this will work every time? Especially after sitting around for months at a time? I don't know. I would much rather have my Clore ES5000 which I know works and hasn't let me down and starts the engine right away. Sure it's bigger, heavier and doesn't have protection features...but it works. So, it won't charge my phone...but it will start my car which can then charge my phone. And it only seems to work in 'Boost' mode. What if my wife forgets about 'Boost' mode or forgets how to turn it on? Or can't find the tiny manual with the tiny print? All of a sudden this thing is useless. I put the thing back on the charger, got the 100% green light and tried to start my tractor in 22F temperature. Used 'Boost' mode but still no start. It cranks once faster than usual (but still not fast enough to start) and then slows down. Still used 5 seconds of glow (which isn't enough at 22F but is a moot point as there isn't enough energy to crank the engine anyway). The Clore jump pack starter the tractor right up in one revolution after 10 seconds of glow. I'm going to send this back to Amazon because I bought this to serve as an emergency jump starter for my wife. But after some brief tests, I don't have the confidence in this device to work when I need it to. Sure, it started my Tacoma with a dead battery...but it barely did so. How will it perform after a year? I don't know...but I don't want to find out. I would prefer a larger safety margin and this device feels like it has none. It seems like a great idea but I think the laws of physics win here...larger, heavier battery will start engine...smaller, lighter battery maybe can start engine (but it can charge phone 3-4 times). This device may work for many but for me, I think it's more of a technological curiosity rather than a functional tool. Two stars.