cyntur jump pak mini ?

[Midnitewarrior4]

so i need a battery bank and found the cyntur jump pk mini which i a small enough jump pak that has a 12,000 mah li-on battery with 2 2.1 amp usb ports for phones and such, i plan to ue it for charging my gopro batteries while riding my dirt bike/snowmahine cause if you own a gopro you now they die really fast and even quicker in -20 degree weather, not only does it hve an insane amount of power which should be good for about 10 gorpo charges, its water resistant which is perfect for in the snow, and rain and such in the summer. not to mention if i even get stuck in the middle of no where with no power in my bettery i can jump start whatever im on or be able to have light from the built in led and be able to keep my phone charged for a long time. so do you think that it would be worth the 140$ for this or is it overpriced ? idk whether to buy it or if theres another similar product for cheaper, let me know what you guys think about it

 

http://www.cyntur.com/Store/Product-Viewer/lithium-ionjumpstarter

[thekeemo]

I feel like you can make your own very cheaply compared to this. Though it will be bulkier.

[Midnitewarrior4]

I feel like you can make your own very cheaply compared to this. Though it will be bulkier.

how would i do this ?

[thekeemo]

how would i do this ?

hook a bunch of lithium batteries together. And buy a chap charging circuit.

[Midnitewarrior4]

hook a bunch of lithium batteries together.

oh lol, ya i dont trust doing that, plus black friday is coming might be able to get  deal on the pak ill have to see