These so called High Power jump starters are popular on online marketplaces since these are labelled with high capacities like 40,000 mAh, 50,000 mAh, 60,000 mAh, 90,000 mAh or even 100,000 mAh and people purchase these looking at the fancy jump starters and reading false claims of sellers. These jump starters usually weigh between 300 – 500 mg and the actual capacity could be between 3000 – 6000 mAh depending upon the honestly level of seller. If you purchased one, you can check its capacity yourself by charging your cellphone (note the battery capacity of your phone) and seeing how many times you could charge it.
There is no way a 50,000+ mAh jump starter could weigh between 300 – 500 mg. The plastic case, the circuit board these also have got their weight included in that. I have got a 20,000 mAh power bank from a renowned manufacturer and even that weighs 470 mg. Batteries used in all these jump starter power banks are lithium ion or lithium polymer. And no matter how much high quality lithium batteries are used, they got their weight and weight increases with capacity. A real 50,000 mAh capacity jump starter should weigh over 1.1 kg and larger jump starters should be heavier than that.
The features offered in these fancy but scam jump starters are worth praising. You can not only jump starter your car if its battery is dead (twice or thrice) but also charge your phone and laptop. I have personally tested one of these. These do start the car if car does not require very long self. Although peak current claims are not true but these are still capable of powering starter motor with enough current to crank the engine and start the car. I also charged my phone and laptop too and these charged fine. I charged my laptop that contains 2600 mAh battery and the battery was hardly charged up to 70% and jump starter drained completely. I assume that that “High Power” jump starter with the label of 50,800 mAh had got actual battery capacity of less than 3000 mAh. (Some power is lost as heat and some in electronic circuits. So that was considered too while taking this estimate.)