I'd like to take a moment to compare what I call a full-size jumpstarter to the smaller ones that seem so popular. The one I have in my car has the following manufacturer specs:

• 12 VDC
• 400 cold cranking Amps
• 1000 peak Amps
• 18 Ah capacity
• "Starts cars, trucks, recreational vehicles and boats..." (in the manual)
• 20 lbs weight
• Chemistry: Sealed Lead Acid Absorbed Glass Mat

Compared to the manufacturer specs of Big River's "Choice" in much smaller and lighter jumpstarter:

• 12 VDC
• not listed: cold cranking Amps (the manual claims 500 "cranking" Amps, which I think is telling)
• 1200 peak Amps
• 18000 mAh capacity (18 Ah)
• Different, contradictory labeling about what kind of vehicle it's suitable for. In one place it says "Works with cars, motorcycles, watercrafts, ATVs, UTVs, SUVs, lawn mowers, yachts, boat, pickup,snowmobiles, etc." In another place it says "ATV, UTV, Dirt Bike, Snowmobile, Adventure, Personal Watercraft".
• 1.16 lbs weight
• Chemistry: "Lithium Ion" (see below)

How can the one pound lithium ion jumpstarter provide the same vehicle starting capability as a 20 pound SLA AGM battery based unit? It can't, quite. If your vehicle's battery is not completely flat, many of the lithium ion devices are competent. For larger vehicles, completely flat vehicle batteries, and very cold weather, SLA AGM jumpstarters are substantially more likely to have the cold cranking amps you need to get the vehicle started.

To be sure, lithium ion devices self-discharge more slowly as well as take up less space, weight and money. Furthermore they can last longer, as they are rated for more charge cycles.

In terms of safety, traditional Lithium Ion batteries (sometimes called LiPo, Lithium-Cobalt or LiCo) may not be suitable to store in a car. These batteries can go into thermal runaway at about 140 deg F, which the trunk of your car might reach on a hot summer day. A newer battery chemistry (most commonly called LiFePO4, or Lithium Iron Phosphate) is safe to over 420 deg F. Which battery chemistry does the above Lithium Ion unit use? I don't know. That bothers me. I would avoid buying such a device unless I knew it used the safer LiFePO4 chemistry.

EDITED TO ADD: Please see downthread, it looks like I posted bad information regarding Lithium-Cobalt batteries and thermal runaway.