Batteryless Jump Starter - Jumpstarts Vehicles Using Ultracapacitor Technology for Cars, Trucks, Boats, RVs, ATVs, and Other Gas Engines (RZ-550 (550A))

Super capacitors don't have to be maintained and pre charged like a battery that will lose its charge over time. You just connect it to the battery and if it has over about 8 volts (enough to turn lights on but not start the engine) it will charge the capacitor in about a minute or two and you can fire up your engine. These seem to have more instant power boost for the rating also. No more going to jump your car and finding out that your booster pack doesn't have a sufficient charge.

I've owned this jump starter for almost 2 years and liked it so much I purchased a 2nd for my wife's car. It's saved my as##$$ in more than 1 occasion. Imagine being on a fishing pier all by yourself ready to go home only to find our your car battery is dead. Or car stalling in the middle of the highway for a faulty fan and an overheated engine. Got the car safely to the side of the road and waited, battery dead also so nowhere to go. Waited until everything cooled down and used the Rezervo. I've found that it works even better if it's connected touching the battery posts. It does take around 5 minutes to recharge if your car battery is weak or if it's been stored for a long time. In my case I had it unused for months and it took around 10 minutes to fully charge. It usually takes less than 3 min. After that, it worked like new. Great product, there's another jump starter that has a similar technology but I haven't tried it yet (Autowitt) recommended by Scotty Kilmer. However, after 2 years of having the Rezervo I can definitely say this is a tool that drivers should have in their cars just as a precaution.

This item is garbage don't even waste your time

Bought in June 2020, as I have been shying away from lithium battery devices after having a lithium device burst into flames while charging. This super cap jump starter sat in my car for at least 8 months. Due to cold and snow, the battery went low. Trying to start the car, the headlights turned off, and just heard that dreaded "clicking" sound. What a better way to test any jump starter. Hooked it up as per instructions. Took less than 2 minutes before the LEDs showed ready (14v stopped blinking). Then tried to start the car. It started right up. Needless to say, I am VERY impressed. Never thought it would work, but bought it anyway. Glad I have them in both of my cars. I DEFINITELY recommend this, and I rarely write reviews.

I haven't actually used this one but have two of another well-known brand that perform amazingly well, much better than my professional grade battery powered jump box. I expect this one will work as well as the ones I already have, which look very similar in design.

This is the best thing since sliced bread! To know that I can get power from ANY battery through a cigarette lighter if needed, walk over 5 minutes later to assist someone without rigging cables between two vehicles - WOW! I'm amazed and under testing, the unit is doing exactly what it is expected to do! Love it!

Had high hopes but didn’t work the one time I needed it to. Bummer.

Gift for my son. He loves it and says it is easy to use and works like a charm!

Very good