FAQ: Initial charging information 

The above is the original offical ThunderSky instruction for the first charge of the LFP batteries. Please see more details here.

Note: This information (4.20V) was applied for the cells made in 2008 and 2009. For cell made in 2010 and after the initial charge voltage is max 4.00V.

UPDATE 
The initial charging voltage is between 3.70V to 4.00V based on the instruction form the manufacturer. For small capacity cells the initial charge voltage is usually smaller (i.e. 3.7V to 3.8V), for large capacity cells the initial charge voltage is usually higher (3.9V to 4.0V)

FAQ: Is there a difference between charging to 3.8V and 4.0V (previously up to 4.2V)?
Generally there is no signicicant difference. The voltage increase from 3.80V to 4.00V is very fast. If you charge to 4.00V it is 100% DOD cycle. If you charge up to 3.80V it is 98% and more  of the DOD cycle.