Feedback Input needs 250k Ohm equivalant to correctly bias diff pair of LT3652 feedback (Vfb) amplifier.
LiFePO4 becomes overcharged as it cools, but the full charge rated voltage is constant, 3.3V for each cell.
When the current in both legs of diff pair are matching then the network is at threshold voltage.
Charge to 7.3V (3.65V/cell 576kOhm switch closed) then float at 6.68V (switch open) which is 1.2% above the ideal rest voltage so the charger will keep the battery full but hopefully not over full.
Circuit board(s) I am working on with this:
http://epccs.org/indexes/Board/CC02/
