I've had a Tacklife jumper for years. Only have had to charge it twice. It claims to be capable of starting up to a 7L diesel. Don't plan on puting it to the test. It's started my Jeep, my wife's, and my kid's car several times each before it even dropped to half charge.
My mower has a completely dead battery. When I try to use the jumper, it tries for one crank, but then stops and light flash on the charger. This makes me think that there's a problem inside of the battery. But if hook up cables to the mower from my Jeep, it starts right up.
My only complaint on the jump boxes is that the clamps are so big. Yes, I understand that they need to be. But the actual box is so small and easy to store, the clamps are kinda a pain.