# [EVDL] A123 LiFePO4 balancing help



## EVDL List (Jul 27, 2007)

Hi,
=

I'm using A123 C size cell batteries ANR26650-M1 on a UPS I built for work =
float charging to 3.45V per cell X 14ea =3D 48.3V.
=

Something weird happenned, about half the batteries (after leaving on a 48.=
3V supply over the week-end) are at 4.6V and hot and the other random batts=
about half are at 2.3V. When I put them in they were *all* at 3.3V They=
are on an A123 100 ohm resistor divider balancer that puts a 100 ohm 1% re=
sistor across each battery with an opto coupler during float charge for bal=
ancing.
=

Does anyone know why they would be so far out of wack? I'll probably have =
to switch to NiMh if these are to be unreliable. I didn't get much help fr=
om A123.
=

Best Regards,
Mark
www.evalbum.com/1273 =

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Windows Live=99: E-mail. Chat. Share. Get more ways to connect. =

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12009
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## EVDL List (Jul 27, 2007)

Is the opto-coupler input in series with the 100 Ohm
(about 20-30mA through the Optocoupler LED) or is the
opto-coupler *output* connected to the battery side
to create a balancer?

I do not really understand how you are balancing.

Is it possible your balancer has crashed and sent
the cells into imbalance by enabling half the
balancers and disabling the other half?

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

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-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Mark Hanson
Sent: Tuesday, February 03, 2009 2:01 AM
To: [email protected]
Subject: [EVDL] A123 LiFePO4 balancing help


Hi,

I'm using A123 C size cell batteries ANR26650-M1 on a UPS I built for
work float charging to 3.45V per cell X 14ea = 48.3V.

Something weird happenned, about half the batteries (after leaving on a
48.3V supply over the week-end) are at 4.6V and hot and the other random
batts about half are at 2.3V. When I put them in they were *all* at
3.3V They are on an A123 100 ohm resistor divider balancer that puts a
100 ohm 1% resistor across each battery with an opto coupler during
float charge for balancing.

Does anyone know why they would be so far out of wack? I'll probably
have to switch to NiMh if these are to be unreliable. I didn't get much
help from A123.

Best Regards,
Mark
www.evalbum.com/1273 
_________________________________________________________________
Windows Live(tm): E-mail. Chat. Share. Get more ways to connect. 
http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_allup_howitworks_
012009
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## EVDL List (Jul 27, 2007)

Most likely your balancer unbalanced them due to software bug. Been
there done that! Did you verify that the correct load resistor turns
on when balancing? If not, turn them on one by one and measure that
the correct ones turn on. It is easy to get your signals mixed up
between software and battery.

Also, what is your float charge current limit?

The cells are not unreliable in my experience.

On Mon, Feb 2, 2009 at 12:31 PM, Mark Hanson <[email protected]> wro=
te:
>
> Hi,
>
> I'm using A123 C size cell batteries ANR26650-M1 on a UPS I built for wor=
k float charging to 3.45V per cell X 14ea =3D 48.3V.
>
> Something weird happenned, about half the batteries (after leaving on a 4=
8.3V supply over the week-end) are at 4.6V and hot and the other random bat=
ts about half are at 2.3V. When I put them in they were *all* at 3.3V Th=
ey are on an A123 100 ohm resistor divider balancer that puts a 100 ohm 1% =
resistor across each battery with an opto coupler during float charge for b=
alancing.
>
> Does anyone know why they would be so far out of wack? I'll probably hav=
e to switch to NiMh if these are to be unreliable. I didn't get much help =
from A123.
>
> Best Regards,
> Mark
> www.evalbum.com/1273
> _________________________________________________________________
> Windows Live=99: E-mail. Chat. Share. Get more ways to connect.
> http://windowslive.com/howitworks?ocid=3DTXT_TAGLM_WL_t2_allup_howitworks=
_012009
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>



-- =

www.electric-lemon.com

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## EVDL List (Jul 27, 2007)

I have worked with Li-ion phosphate packs and I would suggest that the bala=
ncer may just have not been on (not active) and the cells drifted apart jus=
t as a function of imbalance as the more charged cells reached the end of c=
harge - at 3.3V you can not tell if they are in balance or not, the curve i=
s too flat. -Chris




________________________________
From: Peter Gabrielsson <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Monday, February 2, 2009 4:14:21 PM
Subject: Re: [EVDL] A123 LiFePO4 balancing help

Most likely your balancer unbalanced them due to software bug. Been
there done that! Did you verify that the correct load resistor turns
on when balancing? If not, turn them on one by one and measure that
the correct ones turn on. It is easy to get your signals mixed up
between software and battery.

Also, what is your float charge current limit?

The cells are not unreliable in my experience.

On Mon, Feb 2, 2009 at 12:31 PM, Mark Hanson <[email protected]> wro=
te:
>
> Hi,
>
> I'm using A123 C size cell batteries ANR26650-M1 on a UPS I built for wor=
k float charging to 3.45V per cell X 14ea =3D 48.3V.
>
> Something weird happenned, about half the batteries (after leaving on a 4=
8.3V supply over the week-end) are at 4.6V and hot and the other random bat=
ts about half are at 2.3V. When I put them in they were *all* at 3.3V Th=
ey are on an A123 100 ohm resistor divider balancer that puts a 100 ohm 1% =
resistor across each battery with an opto coupler during float charge for b=
alancing.
>
> Does anyone know why they would be so far out of wack? I'll probably hav=
e to switch to NiMh if these are to be unreliable. I didn't get much help =
from A123.
>
.
> Best Regards,
> Mark
> www.evalbum.com/1273
> _________________________________________________________________
> Windows Live=99: E-mail. Chat. Share. Get more ways to connect.
> http://windowslive.com/howitworks?ocid=3DTXT_TAGLM_WL_t2_allup_howitworks=
_012009
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>



-- =

www.electric-lemon.com

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=

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