More Power Save Power Bank Long Life 24 hours Working

In Day to Day Life Power bank is Need for in (offices,works,tours,etc..) even the Power banks have just
20000mah but since it is for only two phones can chargerd full ,So We devolped an new item
just 12 v 7.5 ah battery to 70000mah powerfull to charge 20 phones in 24 hours

Items is Need for Making

1. 12v 7.5 ah battery
2. Switch
3. A Car MobileCharger Board 

Just 3 items to get more Powerfull......