LiFe charge with 3.2v supply and current limiting resistor?

[EternityForest]

Has anyone ever heard of charging a lithium battery with a constant voltage(equal to the cell target voltage) through a resistor? seems like the result would be the same as a(very slow) CC-CV cycle. This is for a standby backup power for a very low power circuit so even three weeks charge time is acceptable where I live(one or two power outages a year at most here almost never more than an hour or two). I also don't care if it never gets fully charged because I hear you get better life if you only go to 80% or so.

It seems to me this would work and not damage cells because they will just stop accepting current once they get to the supply voltage and the resistor will prevend charging too fast.

I have seen people charge LiPos from a bench supply by setting it to the desired voltage and setting the current for the standard 0.7C or so charge rate and it seems to work great, but are these techniques safe and will the battery have good life?

 

[Externet]

Your plan sounds right for your expectations. Safe, yes; good life, yes. But specify figures for cell capability and figures for circuit drain as "very low power" means nothing. Constant voltage is fine. Your expected "80%" may be more like 50%

 

[EternityForest]

Thanks for the confirmation that I'm not crazy!
very low power in this case is about 0.1 watt with occasional 10W or so peaks which should be no trouble for a 220AH cell(obviously I would pre-charge with a normal charger before connecting it to avoid waiting days to weeks)

Thanks a lot!