Might consider a solar charged power cell but 50,000 mili amp hours is a ton. A good 18650 is only putting out 3000 to 4000 mili amp hours so you need 16 cells at 5$ a piece, that’s 80$ for batteries and it will take a long time to recharge 16 batteries and the cost of the chargers. I see some power banks on ebay claiming to be 50,000 mili amp hours 9000000mAh 4 USB External Power Bank Portable LCD LED Charger for Cell Phone US | eBay this is listed for 15.99 there is no way this is 50,000 mili amps. Here is a video of a guy making one with 2,200 mili amp hour 18650,s and it is much bigger that that battery pack on ebay. How to Make a 50,000 mAh Power Bank from Scrap Laptop Battery - YouTube. Then this guy makes a 40,000 mili amp hour battery out of 3-6800 mah =20,400 + 3-1500 mah =4500 so 20,400 + 4500 =24,900 40000mAh power bank , Homemade a power bank - YouTube not even close to the 40,000 claim. A samsung S8+has a 3800 mah I phone s8+2,900 mah and a I pad air laptop battery is 7,150 mah. You are most likely getting a 20,000 mah battery and you will only be able to use to 2/3 of that avaible power not sure the phone and computer but that would help to determine the mah of the batteries in those devices to see what you really need my thought is with a 20000mah battery you could charge each phone and the laptop not sure the capacity of the camera battery but figure that information out first to determine your overall MAH then see what size you need . Here is a good video that explains the actual use you will get from various battery chargers Does a 3000 mAh portable power bank charge a 3000 mAh phone? - Gary explains - Android Authority. Hope some of this helps you can build a 50,000 mah battery but it will cost you a bit at least with a solar charger you can recharge your batteries on the go when you are not using your power bank.