I know this topic is almost a year old, but I'm going to post an answer in case others in the future have this question.
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I have one of those jump start packs, a BASSTOP 16800mah unit good for 800A, and it's amazing.
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It's strong enough to jump start the 5.7 liter V8 in my daily driver without blinking.
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It's also started my BMW 335i, and numerous stranger's cars and trucks over the past year I've been using it.
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It's nice being able to offer a jump start to a stranger with a dead battery without fear that I'll be stuck there for thirty minutes revving my engine while their feeble battery tries its best to recharge enough to do the job.
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Now, I hook the jumper pack to their battery, they immediately crank their engine, and I feel like a hero!
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Most of the packs have a built-in flashlight.
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That seemed pretty pointless until our power went out.
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I stood it on the living room table, shining up at the ceiling, where it served as the main source of illumination for a couple of days.
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It wasn't blindingly bright in there, but there was enough light get around without tripping over something.
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The USB charging ports came in handy to recharge our cell phones a couple of times, too.
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And did I mention that the lithium pack comes with a bunch of additional power adapter tips that will charge a number of different devices? I used it to recharge a handheld camera on a photo shoot, once.
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These things are tremendously handy, and are worth your money.
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In fact, they're so useful that I bought one for each of my siblings and cousins last year for Christmas.
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I've seen reviews on Youtube showing cheap packs swelling or even catching on fire, so buy the heaviest duty pack you can afford.
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It's worth the money!