GOOLOO GT4000S Jump Starter 4000 Amp Car Starter 100W Two-Way Fast-Charging Portable Car Battery Charger Booster Pack for 10L Diesel and 12L Gas Engines, SuperSafe Lithium Jump Box for 12V Vehicles

I've been researching these compact jumper units for about a year, and they look pretty impressive - some better than others. But the price points - Oy vey! As sales went up the cost came down, Amazon offered this unit for 150 bucks. I jumped on it (pun intended). I was hopeful, but skeptical, this little box would deliver on the promise. But so far it appears to be everything the seller claims - and more. I've only had it for about a month and have yet to use it in an emergeny situation - but it seems capable.Was a little disappointed no hard case was included. However, the factory box it came in is built like a brick s***house. For long-term storage this container will work just fine. I'll be keeping mine primarily in the door well of my truck, though. The unit with the cables was heavier than I expected, which I think is a good thing. The main case seems quite rugged and possibly waterproof as well. The display is excellent - very easy to read. A blessing for my tired old eyes. All functions are easy to access, and operation is quite intuitive. No one should have any trouble making it work. There are a couple things you need to know beforehand, so I'd suggest you [gasp!] parse the manual before going into combat. No worries - the instructions are short and sweet.My unit came 80% charged. This sounds about right for a Lithium Ion array (safety first). Tried the 5V USB port to charge it up - it worked, but it was waaay slow. Still, it's nice to have that option in a pinch. But for fast charging, the included cigarette adaptor kicks butt (again, pun intended). As the photos show, I started at 80% when I plugged it into my truck (engine off). Charge rate showed 125 Watts - wow! Higher than Gooloo advertises. Charging really took off, and within 15 minutes was up to 90%. Another 10 minutes or so and it hit 99%. Not too shabby. at 99%, things slowed down quite a bit. That last 1% took about 12 minutes.Now for the real test - starting my truck with the battery disconnected. This is not recommended, except as a last resort. Some vehicle computers can go spastic doing this, and operating a running engine with the box connected can damage your alternator. BTW, this can also happen using standard jumper cables. I know my vehicle pretty well (2012 Chevy Colorado), and have previously tested the computer's resilience by disabling the battery while running. But again, be careful. Many newer PCMs/ECMs are quite unforgiving. A word to the wise.The result: Started my cold engine (48 degrees ambient) in 2 seconds flat. Also fired up my yard tractor without the battery in 6 seconds. The tractor's V-Twin engine is notoriously hard to start, even with a fully-charged battery. I'm looking forward to trying this on bigger engines, especially diesels, but for the time being this is all the testing I could do. The no-load potential of the Gooloo measured 16.2 Volts, which seems to be typical for these boxes according to the Project Farm guy and a few others. Doubtful that this voltage level will cause any problems with your computer or alternator.Only complaint I have is a minor one, nothing I can't live with. The side input/output ports are grouped together and covered with a long, hinged rubber weathershield. Nothing wrong with that, except that when the jumper leads are plugged in the hinge stays open and all the ports are exposed to the elements. This could *potentially* allow moisture, rain, snow, beer, etc to infiltrate. Sure, in most cases this won't be an issue, but for an otherwise well-engineered product this seems kinda cheesy. Maybe the next generation will address this.There you have it. So far, I haven't unearthed a single major flaw in this device. Of course, durability can only be measured over time. Normally I wouldn't award 5 stars to something still under warranty, but I'll stick my neck out on this one. If it tanks, rest assured I'll be back to let y'all know.

These GooLoo lithium battery packs work great to start a car with a weak battery. Very low maintenance, great shelf life and compact. It is impressive.I had a smaller one for a couple years, got it for a gift. I charged it and then left it for over a year. A friend called, his car wouldn't start due to a weak battery. I plugged the GooLoo in to give it a charge for a few hours, after a year it showed 16%. On the drive over to his place I continued to charge it from the 12V outlet in the car. It was at 82% charge, jumped his car, engine started easy. I was impressed and so was he. I gave him that lithium pack and bought this more powerful one, never know when I might need it.

At work I move cars around at an auction yard with a wrecker. Sometimes I need to be able get the car into neutral to be towed and most of the ones that I deal with have dead batteries. This unit is very handy, it’s lightweight, and I can charge it from the cigarette lighter or the usb port in my truck if I need to. Clamps are smaller than on larger boxes but they are strong and I am able to get into tighter spaces with them because of their size. Very pleased with this purchase. Already saved me enough time to be worth the money spent.

Keep it in my emergency kit, it was worked great being stored throughout its first new England winter so far. Has allowed me to extremely rapid start my dead car. I keep it in an emergency kit and I can have this thing out and my car started in 2-3 minutes. WAY better than jumper cables. After start my 2.1L 4 cylinder car from complete dead, It read 97-98% battery typically. It has consistently held its charge so far, if the % reported is accurate after using it.

Works great so far.

I bought one after someone started my car with a similar device when my car battery went dead. It is much easier to use than a pair of jumping cables because you don't need a second car (which can be difficult to get close enough depending on where you are parked).I haven't had a need to use these yet, but am confident that they will work as well as the one the other person used to start my car for me. It has a USB-C output and a flashlight built in. The flashlight is handy to see why you are doing if you have to start the car in the dark. The USB-C output makes it a massive power bank that will allow you to recharge many cell phones and other devices if you do not need to start your car at the same time. It thus would be very handy during a power outage.

Among the very best compact emergency vehicle starting devices available. Very strong, Very well designed and constructed and makes for an excellent battery bank for many other electrical devices as well.

I have used this to jump start my vehicle along with my neighbors vehicle on several occasions. He has a Silverado that had been sitting out for a little while. He attempted to start it and use a different battery pack. I was able to set this up within a minute and start this truck without issue with this still having a decent charge. Like that it gives you a digits display of how much percentage is left. It is slightly heavy but well worth carrying just in case. The bag it comes in is very convenient and holds all of the extra items that come with it and is easier to carry it around. I don't imagine I would need to purchase another one but if I did I would definitely get another one. Great product at a great price.