Is the 6000mAh battery SKU: CE04381 suitable for the PowerBoost 1000C i.e. is that a single cell battery?
The Polymer Lithium Ion Battery (LiPo) 3.7V 6000mAh SKU: CE04381 is a single cell battery as it’s got a nominal voltage of 3.7 Volts.
LiPo batteries are normally described by series and parallel cell combinations. This battery likely has more than one cell in parallel to increase the current delivery capacity but the powerboost charger is primarily concerned with the number of cells in series which would give a higher voltage rating and usually require a LiPo compatible balance charger to ensure each series cell has the same voltage across it.
I’m no expert but that concerns me as other batteries I have include a cable connection for balance charging individual cells. Maybe I would be better off purchasing 2 of SKU: CE04379 2400 mAh batteries, wiring via jst plugs, in parallel to give me 3.7V and the ability to balance charge or is my thinking wrong?
A balance lead is only required for cells that are in series as it is used to maintain the same voltage across the banks of parallel cells.
There is a good guide to LiPo charging and LiPo safety I’ll link below: