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Old 03-12-2012, 11:13 AM   #163
_cy_ OP
Beastly Adventurer
 
Joined: Sep 2011
Location: Tulsa, Oklahoma
Oddometer: 5,937
@joel... excellent raw data! collect enough and some pattern will show itself. sure is nice to see data generated that's lab grade.

there's sooo many different sources for Lithium battery information it's hard to ferret out which one is worth spending your brain cycles on. here's one worth a cruise..

Charge LiFePO4 to 3.65v per cell then terminate charge if using a regulated power supply. if your power supply has constant current triggered by volt termination feature. set to 14.4v then allow time to top off. Your battery will absorb decreasing amount of current, closer to fully charged condition. ramping up voltage up to 3.65v allows faster charge for last phase. higher the volts delivered by charger, higher the amp rate pushed into battery. this is especially true during final phase before LiFePO4 reaches 14.4v fully charged state.

intelligent chargers that support LiFePO4 will have custom algorithms to support that chemistry. best chargers will have balance options that charge different cells at different rates. others will charge all cells at same rate, then shunt off excess current.

when you pull a fully charged LiFePO4 battery off charger. voltage should read just under 14.4v depending on individual battery. then surface charge will quickly bleed off to 13.9v range. after sitting overnight with nothing hooked to battery. resting voltage should be about 13.7v range. each battery will be slightly different. then as battery ages resting charge retained after a full charge will go down. when battery reaches 80% DOD it's considered spent.


Charging
Because lithium-ion batteries can have a variety of vocathode and anode materials, the energy density and voltage vary accordingly. Lithium-ion batteries with a lithium iron phosphate cathode and graphite anode have a nominal open circuit voltage of 3.2 volts and a typical charging voltage of 3.65 volts. The charging procedure is performed at constant voltage with current-limiting circuitry (i.e., charging with constant current which should be 30% of the battery ampere hour rating until a voltage of 3.65 volts is reached in the cell and continuing with a constant voltage applied until the current drops close to zero). Typically, the charge is terminated at 7% of the initial charge current. In the past, lithium-ion batteries could not be fast-charged and typically needed at least two hours to fully charge. Current-generation cells can be fully charged in 45 minutes or less; some lithium-ion varieties can reach 90% in as little as 10 minutes.

http://lithiumstorage.com/index.php?...11233f8fcc52f3

_cy_ screwed with this post 03-12-2012 at 11:31 AM
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