[thrashh]

Someone already mentioned this but I want to clarify that mAh alone is not a full measure of capacity.

OP mentioned his mAh rating in 12 V but you’re comparing it to Ah ratings in 5 V. OP’s battery should be able to charge a full smartphone fine.

Also, most of those 10-20k battery packs won’t be able to jump start your car because they have greater capacity but cannot provide power quickly. There are high capacity battery packs that do jump start but they’re over $100 from the last time I looked.

[sasawpg]

I purchased a 20,000mAh “jump pack” for $120CAD two years ago to use with my boat. I’ve jump started it with no problems, and this was a Mercruiser 350. I’ve also boosted a car and a truck in -25C weather. They work great, are super portable and only weigh 2-3lbs.

Caveat - unlike a standard battery booster pack (lead acid), lithium battery does not take kindly to freezing temps, so it is useless to keep it in the car over winter. I wouldn’t expect to be able to start anything in the middle of winter up here unless it was kept indoors at room temp.

[B2B_human]

Spoiler, it works.

I use a lithium booster battery pack for an old car I use, and have used the battery pack to jump-start my car multiple times on a freezing-cold day (sub 10f) while trying to locate a store with a new car-battery in stock.

[colanderman]

Amp-hour ratings only should be adjusted for voltage if a DC-DC converter is used. If the jump starter uses a cheaper linear regulator, the amp-hour ratings remain the same. (The excess energy is discarded as heat.)

[fy20]

I had a cheap one 5 years ago that was able to jump start a car. The instructions said to leave it connected to the battery for 30 seconds before trying to start it, so I guess it's more a portable battery charger than a jump starter. For sure if you disconnected the 12V battery and only connected this it would not work.