I use the bolt power model. The $60-70 model is the one I recommend for most people it will start an 8-cyl car no problem. I have the $90 version it has a display that shows battery charge as % vs the cheaper one only has 4 LEDs.
The more expensive one has a fancy automatic cable clamp set that is the most likely failure point.
There is one brand that is higher rated but it's 50% more expensive.
Prices have come down a bit : Bolt Power D28-Ultimate 500 Peak Amps 12V Car Jump Starter for Cars & Trucks (up to 5 Liter V4, V6, V8 Engines) and 13600mAh Portable Battery Pack Phone Charger
https://www.amazon.com/dp/B073VZ9H7Q..._OeJZBb6EE287W
Bolt Power D29 900 Peak Amps 12-Volt Car Battery Jump Starter for Cars, SUV, Heavy Duty Trucks, Motorcycle (up to 6.5 Liter V4, V6, V8 Engines) & 18000mAh Power Bank Portable Pack Charger
https://www.amazon.com/dp/B01N3SEJIJ..._6fJZBbWNSD7NQ
I've started 6L diesel truck with my 900A model.
You need about 200-300A to start the X5 but most will come from the battery the little starter will pump some joules into the battery raising it's charge state then when you start current comes from both the battery and the jumper.