After dong some reading, and Consumer Reports recommendation I bought s Bolt D28. I also gave one to my SIL. I have not needed mine, but My Daughters car needed a jump. They used it and it worked as advertised. Subsequently they have used it a couple of times and it did OK.
I gave mine to my son and bought a D29, but still have not used it.
https://www.amazon.com/Bolt-Power-D28-Ultimate-13600mAh-Portable/dp/B073VZ9H7Q/ref=sr_1_3?ie=UTF8&qid=1548008860&sr=8-3&keywords=bolt+d28+jump+starter

https://www.amazon.com/Bolt-Power-D29-Motorcycle-18000mAh/dp/B01N3SEJIJ/ref=sr_1_4?ie=UTF8&qid=1548008903&sr=8-4&keywords=bolt+d28+jump+starter

Jerry