With our cars and trucks parked during the quarantine period you need to keep checking on your your older models to make sure they still start. I had originally owned another product claiming to perform the same as this jump starter, but upon having a completely dead battery to the level that even the door locks would not open we used the previous battery pack jump starter and only got one start then it was requiring a recharge. This is dangerous situation if we had been traveling and could only get one start due to the battery being completely drained and having to require me to have that power supply hooked up for at least 20-30 minutes before I could attempt to start the vehicle. So using my time off I was able to perform a comparative study on these portable vehicle chargers and this model came in as my top pick for an 8L Gas or 6L Diesel Engine. We have a large transport truck that was built at the American General plant where the humvee was built and it needs a lot of starting cranking power. This unit was able to start the vehicle immediately and have plenty of charge remains.

Update 8/23/2023: Support reached out to me and corrected the matter to my complete satisfaction.

I attempted to get support at the supplied email, [email protected]. I did not get a reply. I never used this product to jump a vehicle. I removed from my vehicle for routine charging. The unit is completely dead. It will not take a charge or respond in any way.

On Lake pyramid, 22 miles out the engine would not start. Both batteries were dead.
This charger saved us and started the batteries right up. 4days ago 6/23

Like a dummy, I left the key in the ignition of my C50 for a couple of days and discharged the one-year-old battery BIG Time! Normally I have the bike on a Battery Tender but not all the time. So when I went out later to start the bike, nothing. I tried to put the bike back on the Battery Tender but there wasn't enough voltage there for it to work. I had read a review from a guy who said that he carries this product around because rides with a group of Harley riders and someone always does what I did and they end up with a dead battery in the morning. This little jewel no issue what to ever starting my bike. I let the bike run for a few minutes to get some charge in the battery. I connected the Battery Tender, left it overnight, and the battery was fully charged 24 hrs later. Cheap insurance if you ask me. Plus if I'm ever doing a remote FB live broadcast, I can use the USB ports for additional power... you know to make sure I use up all of my data. : )

I researched a large number of possible vehicle battery jump starters before settling on this one by Grepro.
The features, contents, and responsiveness of the seller to questions convinced me to purchase Grepro
vs the competition. So I purchased two of these units earlier this month.

Although I am not a fan of colder weather, it already provided me two occasions to need these for jump starting.

On one occasion, I jump started my father's car which has a 3.5L V6 gas engine.
The car battery was at 4.5 volts, nearly dead, not able to crank the engine, very weak headlights.
It was still dark outside and the built in LED light was helpful and bright enough.
I connected one of the Grepro units, did not need to wait any time, and the car cranked and started right away.
I turned the car off after a few seconds to try the other Grepro unit and had the same result.
I've jump started many vehicles in my life and this was very easy by far, since no long cables to untangle/re-pack.
There was no spark visible at all when I connected the Grepro clamps to the car battery.
So I think minimized chance of a car battery with hydrogen gas exploding since no spark.
Those sparks with traditional jumper cables always scare me.
The clamps themselves have shiny copper teeth and also plastic handles, which is an advantage in my opinion:
There is no chance of the plastic handles shorting the car battery to ground unlike metal handles.
This definitely beats calling and waiting for road service or asking a stranger for a jump.
It turned out that the car battery was defective and needed replacement after sitting a few days with the cold.

On the other occasion, I wanted to burn out the remaining gas in my Toro Wheelhorse riding lawn mower, but the battery slowly drained over the last few weeks to completely dead because I left the key on the on position.
So I also jump started that completely dead riding battery with similar success. I did need to press the boost
button on the clamp assembly box for that one.

I evaluated most of the other Grepro features and they work well.
I used the 12 volt output to power a car vacuum cleaner and a car seat heating pad.
I connected them both alternating between both Grepros for the same operating times.
During that load vs time testing, I checked the voltage decay for both packs
and found that they were both consistent in reducing
from 12.2 volts peak (fully charged 4 dots out of 4 dots)
till down to about 11.2 volts (about 2 out of 4 dots charged)
at the cigarette lighter socket.
I stopped test early since I did not want to drain Grepros excessively.

I also successfully charged an iphone by USB ports on both Grepros.

I charged the packs by using both the provided 110V transformer in my home
as well as the provided 12V cigarette lighter connector in my vehicle.
One trick I discovered: It is possible to charge the Grepro while it is still in the case!
Just flip / orient the Grepro in the storage case, keep the charging port connected to the end,
and zip the case around the protruding wiring.

*** Noteworthy PROS vs the competition (and it is hard to find all these features together in any given jump starter):
- High capacity and high current capable battery
- Both 12V (at 10 amps max) and 19V (at 3.5 amps max) output ports
- Included cigarette socket adapter charger
- Lots of types of connectors adapters for laptops etc
- Ability to charge battery by either included 12V cigarette socket connector or by included 110V transformer
- LED flashlight with solid, flashing, and SOS options
- Two USB output charge ports
- Metal outer shell for Grepro battery
- Cushioned case for storage
- Many safety features in the battery case and in the jumper cable / connector assembly per the listing

*** Noteworthy CONS:
- It is tight to fit everything back into the case
- This is a possible tradeoff of aesthetics vs function or price vs function, but for future re-design,
I recommend integrated rubber bumpers at each corner to make these units even nicer
to avoid damage if they were dropped. I would pay a few dollars extra just for that feature.
I prefer function over form.
- This is a common issue for most of the competition also as I have read, not just this one,
since they use the same type of jumper cable / connector assembly:
The boost button on the side of the jumper cable connector can only be pressed by using a pen tip
or similar tool which is included. That boost button need to be pressed if your battery is nearly dead or dead
(probably below about 4 volts). I wish this was designed to be pressable by my fingernail.
- Both 110V charger transformers did get warmer than I prefer.
I think they could be upgraded in the future.

Summary: This is a worthwhile purchase. Nice instruction booklet too. Yes I recommend Grepro.