Li-Po Battery Charging and UPS
Check the battery manufacturers charging specification data sheet for the details on the chemistry / battery type you want to use. 

Letting the batteries discharge too quickly or letting them discharge to a low voltage can permanently damage them. Also the charging rate needs to be within the manufacturers specification or you will damage the chemistry / life.

The batteries tend to self balance themselves, however again most manufacturers don't recommend using multiple batteries in parallel.

That board looks cool, and it probably will save a lot of work, and end up costing about the same as diy.