# [EVDL] Li-Ion Battery equalizer/balancer free circuit



## EVDL List (Jul 27, 2007)

Hi Folk's

=


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

_________________________________________________________________
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## EVDL List (Jul 27, 2007)

Now posted in the EVDL library - http://evdl.org/lib/

It's under battery managers.

David Roden - Akron, Ohio, USA
EVDL Administrator

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## EVDL List (Jul 27, 2007)

Ah, thanks. Excellent repository - I didn't know about it!

How do we submit items to post? I'd like to put up my AXEMON, Alltrax 
monitor for the Palm (and hopefully a few more items in the future).

- SteveS



> EVDL Administrator wrote:
> > Now posted in the EVDL library - http://evdl.org/lib/
> >
> > It's under battery managers.
> ...


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## EVDL List (Jul 27, 2007)

> On 11 Sep 2009 at 9:02, SteveS wrote:
> 
> > How do we submit items to post [in the EVDL library]?
> 
> ...


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