As necessity is the mother of invention I made some battery equalizers for
my Li-ion T-sky batteries using a simple PWM (1kHz) feedback technique to m=
odulate the power shunt resistor so the darlington transistor doesn't fry (=
like on other storebought versions). (Sent in circuit to post on EVDL) It'=
s designed for a 2A max shunt current and am using on T-Sky yellow batts se=
t to 3.8V. The charger is a standard dv/dt=3D0 charger so it shuts off whe=
n the voltage stops rising for an hour. I took a turn off the secondary to=
reduce the taper current to 1A which keeps the balancers from getting too =
hot. I also found that when discharging they stay fairly close in voltage =
since they were equalized on charge (solar boat 16 cells 52.8V at 3.3V per =
cell) final charge is 3.8 x 16 =3D 60.8V
Also on my www.evdl.org/lib/mh circuits is the battery scanner I use as wel
l to see each cell voltage AND the "DC Watt Hour" which is actually listed =
under the renewable energy products so I can see how empty/full my 11kWh pa=
ck is (the Curtis 900R guage always says "full" since the cells stay at 3.3=
V until the very end).
Remember to conformal coat your equalizers and gliptol (red finger nail pol
ish) the multiturn 10k pot. I emailed Dave the equalizer circuit so should=
be posted soon.
BTW, I'm amazed that the Li-Ion battery manufacturers don't show a recomend
ed balancing circuit on their websites since they require balancing. Most =
companies i'm used to in electronics do for things that are required to mak=
e their product last.
This month's issue of Circuit Cellar (Sept 09) showed a Ryobi drill with no
balancing that crapped out fairly new and an LT6802 chip to balance the ba=
tteries (Linear Tech), also has a nice PC display on the eval board.
have a renewable energy day,
Mark in Roanoke, VA
www.solectrol.com solar-wind home
www.evalbum.com/1273 & solar boat
Windows Live: Make it easier for your friends to see what you
92re up to on=
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