LiFePo4 battery charging for maximum cycle life with solar panels
I Have two LiFePO4 8s battery=packs (Headway 40152 - LiFePO4 cells) and I undercharge them with my charger. I bought my charger with a default 29,2 volt and re-set the voltage to 28,5 volts.

Per cell will this give: 
29,2 / 8 = 3,65 volt per cell  (Default for LiFePO4)

and after: 
28,5 / 8 = 3,56 volt per cell (Undercharging LiFePO4 for more cycle-life)

You can set the voltage with the blue block with copper screw closed to the Power out. Just connect multimeter to the charging plug and turn the screw until the multimeter gives 28,5 volts instead of 29,2 volts.

This undercharging will cost almost nothing of the total capacity, because of the voltage drop and climb characteristics of LiFePO4. I think it will cost only 1% or less of the capacity of the cell or battery. Check it in a discharge table of a LiFePO4 cell. Very easy to Google to find a discharge curve of a LiFePO4 cell. Example: 40125 discharge curve.

An other advantage for lowering the max. charging voltage is that It's more unlikely that you get damage through unbalance.