On 2/19/2013 1:36 PM, Bill Dube wrote:
By the way, I've been running a LiFePO4 "12 volt" battery in my GMC van,
(and when I sold the van last year, in my Prius) since 2005. Since
neither of these cars have any (other) modifications to the charging
system, then you would have to conclude that 13.8 volts float charge is
just fine.
"Float" implies leaving the voltage on the battery continuously; 24
hours a day, 7 days a week.
A normal car alternator (or the DC/DC converter in a Prius) isn't a
float voltage charger. It applies a higher voltage like 13.8v nominal
(which in fact varies quite a bit). But it works, because the car is
only "on" for maybe an hour a day.
So, it sounds like your experiment shows that LiFePO4 cells can survive
occasional charging to 13.8v. But it doesn't indicate whether they would
survive if left continuously at that value.
BTW: What kind of cells did you use? Were they matched, or did you have
a BMS? I'm concerned that without such precautions, a damaged or dead
cell is virtually certain if you ever "hit" either full charge (driving
a very long time), or dead (left a dome light or something on too long).
--
Ring the bells that still can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in.
-- Leonard Cohen, from "Anthem"
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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