If you want a portable jump pack, why do you need cables? (the jump pack comes with clamps and cables to attach to the main unit)
Here is a quick summary of your options for jump packs. Someone can chime in if I misstated anything or they have more thoughts to add. With the portable units, you have 2 choices. A lead acid or AGM battery like the JNC unit mentioned above. These are rock solid and work well in cold weather. For $100-120 you can get one that will start most cars and some light trucks (JNC660). They are rated in CCA so you can easily size to your intended application. They hold a charge for well over 3 months (mine was down to 12V after one year). But, they are a little on the heavy side (20-25lbs) and are somewhat sizable compared to the new lithium units. Longevity is pretty good on these (6-7 yrs) and you can get the battery replaced in them when it's time. But with the shipping cost back to the manufacturer, it's arguably not economical vs. going on Amazon and getting a new one shipped to your door for $100.
The second option are the lithium units. Quality is all over the map and there are lots of unheard of brands peddling their latest lithium jump packs. Even with a known good brand it seems like there are some duds. Cold weather performance is poor in the sense, if you leave it in a cold car parked outside, it's going to have a reduced capacity initially. But, if you make a few attempts to jump the car and it fails, 3-4 discharge cycles will warm up the battery quickly, which will help performance. Sizing to your application is more difficult as well, since they all rate their packs using more obscure marketing numbers rather than CCA. Some will give you some upper limits on the size and type of engine it can jump, but this almost always assumes there is some charge left on your battery. I would expect these units to lose charge faster than the first option above (but I haven't been able to verify how often they should be recharged). They are obviously smaller. Price can vary from just under $100 up to $200. It does seem like the lithium packs are maturing into a useful product now (I finally switched to them this year). Initially when they were released, they were largely not capable of starting a car unless the battery was just a little shy of what the starter needed. Longevity of these units are an unknown I think. I would speculate 5 years give or take.
There is one more option called a supercapacitor. They are around the $300 price point. They use a cap to gather the energy in your existing battery and they can release a very short burst of energy to your car to get it started. But if the battery is completely dead, this won't help you, where the other two options above will likely get the car with a dead battery started (assuming you sized the jump pack correctly).
