A123 ALM 12V7 Batteries now charging

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A123 ALM 12V7 Batteries now charging

Mark Hanson-2

Thanks Bill,
 
The Phoenix Contact "QUINT-UPS" UPS charges the A123 batteries to a fixed 13.5V per battery (27V total float charge).  The A123 manual I found online for the ALM 12V7 shows 13.6V flaot charge.  Hopefully that's not a significant difference to matter.  I'll check and see if the circuit is tweakable.
 
I don't have much luck getting hold of engineers at A123.  If you know someone there, please tell them to put a *label* or note on the batteries so other folk's don't go through this and reject their stock when they see 0V.  Mouser had all these batteries (came in from Phoenix Contact), boxed up and ready to ship back since they all read 0V, some are already in transit.  I told them about your findings (that they should be on the evdl.org) and that the manual said to hold at 14.4V for 4 hours with a separate supply to fully charge them initially (something the Phoenix Contact UPS *does not* do, just blinks red dead battery).  I need to let Phoenix Contact know too.
 
I thought if a LiFePO4 cell goes below 2.6V that it's toast? (why I have all those pesky BMS balancers/monitors on my EV).  I don't think you mean the cells themselves, but the internal *circuitry* which disconnects the outside terminals if a cell gets <2.6V.  
 
Best Regards,
Mark
www.REEVA.info
 
Date: Thu, 28 Jun 2012 18:00:28 -0600
From: Bill Dube <[hidden email]>
Subject: Re: [EVDL] A123 12V ALM 12V7 Batteries now charging, were 0V
now 13.2V
To: Electric Vehicle Discussion List <[hidden email]>
Message-ID: <[hidden email]>
Content-Type: text/plain; charset="us-ascii"; format=flowed
 
I also should emphasize that the cells themselves really are not
damaged by discharging to zero volts. In a pack, you should not ever
do this because of the risk of going _below_ zero volts, and this
will seriously damage the cells.
 
 
At 02:04 PM 6/28/2012, you wrote:
 

>http://www.endrich.com.tw/html/ezcatfiles/i-web17/img/img/25755/A123_ALM.pdf
>
>My Bad, the A123 12V ALM 12V7 batteries that read 0V are now being
>charged per the manual I found above and Bill Dube's
>recommendations. I've always seen batteries that read 0V as toast
>but these have internal disconnect circuitry that would appear dead
>but is really not. They were sold with Phoenix Contact new UPS
>QUINT-UPS/1AC/500VA which also confused it flashing the red dead
>battery indicator. It only charges to 13.5V per battery and the
>A123 manual says on page 5-4 #1 to hold at 14.4V for 4 hours for
>100% SOC so I'll check with them on modifying their UPS to work with
>these batteries/internal electronics uP. I'll also get back with
>Mouser to not send back their entire stock as they thought they were
>all bad as I did.
>
>Have a charged day,
>mark
>www.REEVA.info
     
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Re: A123 ALM 12V7 Batteries now charging

Elithion
Note: I am not a Li-ion cell chemist; (all I know if from the research I did for the "Battery Management Systems for Large Lithium-Ion Battery Packs" book).

In general, Li-ion cells suffer irreversible chemical damage if their OCV drops below a give threshold (1.9 V for  LiFePO4). (Note that a cell can be below that limit under heavy load, as long as it then snaps back to an OCV above 1.9 V.)

However, A123 M1 (26650) cells are different and have been shown to not only survive being discharged to 0, but actually have a lower internal resistance afterward. I have no knowledge on how that affects their lifetime and capacity.

Regardless, all cells will be very badly damaged by reverse voltage.
 
There is a significant difference depending on how cells are discharged:
1) If cells are discharged by a load across them (a balancer with a high stand-by current), they will be discharged to 0 V and stop.
2) But is the complete battery is discharged by an external load, the first cells to reach zero volts will then start charging in the reverse direction (powered by the cells that still have some voltage), and will be very badly damaged.

I believe that in your case (ALM 12V7 batteries) it is situation #1.

Again, just because a cell appears to recover, doesn't mean that its life or its capacity won't have been reduced.

Please ask Bill Dube' for more insights on this.
Davide Andrea
Elithion
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Re: A123 ALM 12V7 Batteries now charging

Lee Hart
On 6/29/2012 9:26 AM, Elithion wrote:
> In general, Li-ion cells suffer irreversible chemical damage if their OCV
> drops below a give threshold (1.9 V for  LiFePO4)... However, A123 M1 (26650) cells are different and have been shown to not only
> survive being discharged to 0, but actually have a lower internal resistance
> afterward. I have no knowledge on how that affects their lifetime and
> capacity.
>
> Please ask Bill Dube' for more insights on this.

Yes; I too would like more information about this. Is it a marketing
claim, or is there test data on it? And, what effect does it have on
life and capacity?

I can imagine a single cell not being harmed by 0 volts; a few other
types of cells can survive this. But it is much harder to imagine a pack
of series cells surviving it. For example, individual nicad cells will
being run down to 0 volts. But a series string of nicads can't be run
dead without a significant chance that one or more cells will get
reversed, and short out.

The pack Mark Hanson has *is* a series string.

--
Never doubt that the work of a small group of thoughtful, committed
citizens can change the world. Indeed, it's the only thing that ever
has!    -- Margaret Mead
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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Re: A123 ALM 12V7 Batteries now charging

Roger Stockton
Lee Hart wrote:

> I can imagine a single cell not being harmed by 0 volts; a few other
> types of cells can survive this. But it is much harder to imagine a pack
> of series cells surviving it. For example, individual nicad cells will
> being run down to 0 volts. But a series string of nicads can't be run
> dead without a significant chance that one or more cells will get
> reversed, and short out.
>
> The pack Mark Hanson has *is* a series string.

Bill can clarify if I have this correct or not, but from what he has said, my understanding is that the *cells* in Mark's pack were *NOT* at 0V.

The *terminal* voltage read 0V because the internal BMS had disconnected the cells from the terminals due to their voltage being below some non-zero threshold.

Either the BMS provides a path for charge current to flow into the cells, or reconnects the cells to the external terminals when it detects an external source of power (charger); either way, connecting a charger to the apparently 0V module allows the cells to be charged from their non-zero but low state back into a normal operating range.

Mark did not open the module to check individual cell voltages, and the module is not a simple series string of cells connected directly between the external module temrinals.

Cheers,

Roger.


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Re: A123 ALM 12V7 Batteries now charging

Bill Dube
On the ALM 12V7, the BMS is set to turn off the output terminals if
any cell goes below something around 2 volts. Since there is
virtually no capacity left below 2 volts (at any "sane" discharge
rate) is as good a place as any to switch off the output.

One or more of the cells inside could easily be at zero volts, and
you would never know the difference. After the output shut-off, cells
will continue to self-discharge. They may go to zero volts
eventually. You don't care if they do or not.

As I said in my earlier post, "I also should emphasize that the cells
themselves really are not damaged by discharging to zero volts. In a
pack, you should not ever do this because of the risk of going
_below_ zero volts, and this will seriously damage the cells."

Bill D.


At 08:48 PM 6/29/2012, you wrote:

>Lee Hart wrote:
>
> > I can imagine a single cell not being harmed by 0 volts; a few other
> > types of cells can survive this. But it is much harder to imagine a pack
> > of series cells surviving it. For example, individual nicad cells will
> > being run down to 0 volts. But a series string of nicads can't be run
> > dead without a significant chance that one or more cells will get
> > reversed, and short out.
> >
> > The pack Mark Hanson has *is* a series string.

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Re: A123 ALM 12V7 Batteries now charging

Lee Hart
Bill Dube wrote:
> On the ALM 12V7, the BMS is set to turn off the output terminals if
> any cell goes below something around 2 volts...After the output shut-off, cells
> will continue to self-discharge. They may go to zero volts
> eventually. You don't care if they do or not.

The internal BMS may turn off the output, but won't it continue to load
the cells itself? These cells have a very slow self-discharge rate; I
have A123 cells that have sat for over 3 years and are still above 3v.

If these *new* batteries have shut down because of a low cell, their BMS
must draw a lot of power. And it may continue to draw power even after
it has turned off the external terminals. That worries me. All the BMS
chips I've seen draw power from all cells, and aren't smart enough to
stop if one cell is totally dead. In other words, the BMS itself can
reverse a cell.

The description of Phoenix Contact's design so far does not inspire
confidence. The pack was delivered dead. Their charger won't recharge a
dead pack. The float voltage appears to be too low.

> I also should emphasize that the cells themselves really are not
> damaged by discharging to zero volts.

Do you have any test data on this? I would like to know what effect on
capacity, cycle life, etc. going to 0 volts will have.

--
An engineer can do for a nickel what any damn fool can do for a dollar.
        -- Henry Ford
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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Zero voltage = Zero damage on LiFePO4 (was: A123 ALM 12V7 Batteries now charging)

Bill Dube
Look in the archives of the EVDL. Folks on this list have done the
experiment on other brands. A123Systems has done extensive testing as well.

The result, discharging LiFePO4 to zero volts and leaving the cell
there for many days actually reduces the internal resistance and has
no detrimental effect whatsoever. True fact, even though it is
completely counter-intuitive.

Bill D.


> > I also should emphasize that the cells themselves really are not
> > damaged by discharging to zero volts.
>
>Do you have any test data on this? I would like to know what effect on
>capacity, cycle life, etc. going to 0 volts will have.

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Re: A123 ALM 12V7 Batteries now charging

Bill Dube
In reply to this post by Lee Hart
Lee, you are applying you many years of battery experience from other
chemistries mistakenly to LiFePO4. The LiFePO4 chemistry behaves in a
_completely_ different manner than any other battery chemistry. Completely.

For LiFePO4, the OCV only changes very near the end points of the SOC
curve. Voltage is pretty much flat for most of the SOC curve.
Completely unlike any other battery chemistry. Thus, the cells will
read over 3 volts for years. The voltage only goes low at the very
end of the SOC.

There is darn close to zero remaining capacity below 2 volts OCV.
Even a tiny BMS load or simply self discharge will bring a 2 volt
cell down to zero volts much more quickly than this might occur in
other battery chemistries.

I have no clue about the details of the ALM 12V7 BMS. Perhaps it
loads the cells after output shut-off. Perhaps it doesn't. It really
doesn't matter because the cells are unharmed by going to zero volts.

 >>>> personal anecdote <<<

I have personally discharged a 12 volt LiFePO4 battery to zero volts.
(Glove box light left on.) The battery was at zero volts for about
two weeks. Since the goal of building that 12v battery was to test it
under typical consumer use, I jump started the car with a
fully-charged 12 volt lead-acid battery, just like a consumer might
do. The jumper cables became noticeably warm from the large current
flow into the zero-volt LiFePO4 battery. Started the engine and
quickly disconnected the jumper cables, allowing the full 100 amps
from the alternator into the LiFePO4 battery. This  would have been
certain battery death, likely an explosion, and surely a fire with
LiPo.  Five years and 60,000 miles later, that 12v LiFePO4 battery
still working perfectly.

Going to zero volts (but not below!) with LiFePO4 does not harm the
cells in any way. It is a fact.

Bill D.


> > On the ALM 12V7, the BMS is set to turn off the output terminals if
> > any cell goes below something around 2 volts...After the output
> shut-off, cells
> > will continue to self-discharge. They may go to zero volts
> > eventually. You don't care if they do or not.
>
>The internal BMS may turn off the output, but won't it continue to load
>the cells itself? These cells have a very slow self-discharge rate; I
>have A123 cells that have sat for over 3 years and are still above 3v.

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Re: Zero voltage = Zero damage on LiFePO4 (was: A123 ALM 12V7 Batteries now charging)

David Dymaxion
In reply to this post by Bill Dube
Bill would you advocate a bottom balance with by drawing each cell individually down to 0 Volts?



________________________________
 From: Bill Dube <[hidden email]>
To: Electric Vehicle Discussion List <[hidden email]>
Sent: Saturday, June 30, 2012 11:26 AM
Subject: [EVDL] Zero voltage = Zero damage on LiFePO4 (was: A123 ALM 12V7 Batteries now charging)
 
Look in the archives of the EVDL. Folks on this list have done the
experiment on other brands. A123Systems has done extensive testing as well.

The result, discharging LiFePO4 to zero volts and leaving the cell
there for many days actually reduces the internal resistance and has
no detrimental effect whatsoever. True fact, even though it is
completely counter-intuitive.

Bill D.


> > I also should emphasize that the cells themselves really are not
> > damaged by discharging to zero volts.
>
>Do you have any test data on this? I would like to know what effect on
>capacity, cycle life, etc. going to 0 volts will have.

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Re: A123 ALM 12V7 Batteries now charging

Elithion
In reply to this post by Lee Hart
Lee Hart wrote
All the BMS chips I've seen draw power from all cells
In general, you're right. However, the Linear Technology LTC6803 may be powered separately, or you can place a switch between the battery voltage and the IC's power input pin, which can be opened when the battery is not in use or empty.

And don't forget that not all BMSs use an off-the-shelf BMS IC.

Lee Hart wrote
the BMS itself can reverse a cell.
Not with a distributed BMS (MiniBMS, Elektromotus, EV power, Elite, Elithion, Pacific EV, Tritium...), because each cell board gets power from its own cell, not from the series string.

Now, yes, a DC-DC converter that powers the BMS could reverse a cell, but I can't see a way that the distributed BMS itself can do so.


Davide Andrea
Elithion
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Re: A123 ALM 12V7 Batteries now charging

Lee Hart
Elithion wrote:
Lee Hart wrote
>> All the BMS chips I've seen draw power from all cells

> In general, you're right. However, the Linear Technology LTC6803 may be
> powered separately, or you can place a switch between the battery voltage
> and the IC's power input pin, which can be opened when the battery is not in
> use or empty.

The Manzanita Micro BMS uses this chip. It is powered exclusively from
the series string of cells it is monitoring. If one cell goes dead, the
BMS knows; but it also continues drawing its supply current from the
whole series string.

> And don't forget that not all BMSs use an off-the-shelf BMS IC.

No; that's true. Some use a microcomputer, or various digital or analog
hardware circuitry.

Even so, the "obvious" way to power the BMS is from the pack itself.
You're more familiar with these than I am, Davide. Do *you* know of any
BMS that does not draw its operating power from the pack itself?

>> the BMS itself can reverse a cell.

> Not with a distributed BMS... because each cell board gets power from
> its own cell, not from the series string.

That's correct. This type of BMS just runs one cell totally dead with
its own supply current.

But the BMS being talked about here (in the ALM 12V7) almost certainly
isn't this type. It will have *one* BMS, powered by 12v from the series
string of cells.

This problem could be fixed if the design had a low-voltage shutdown
that removes *all* the load, including the BMS itself. But I'll bet you
99 out of 100 BMS designs won't bother. Their designers won't even
*think* about it!

> Now, yes, a DC-DC converter that powers the BMS could reverse a cell

It doesn't even require that it have a DC/DC. Just any design that uses
power from a series string of cells to power the BMS.

Yeah, I know... I may seem paranoid about this. But I've seen too many
Pollyanna BMS designs that only work when nothing goes wrong. When
something *does* go wrong, the BMS fails to report it, or even
contributes to the problem!

--
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, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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BMS Power WAS: A123 ALM 12V7...

Bill Dennis
When I was playing with the LTC6803 chip, I had a 1 amp-turn reed switch in series with the chip's supply.  My theory was that it was mostly during charging and discharging that I wanted the BMS to be active, and I didn't care if it was monitoring/balancing cells when the car was parked or sitting at a red light or coasting.  

Bill

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Re: A123 ALM 12V7 Batteries now charging

Lee Hart
In reply to this post by Bill Dube
On 6/30/2012 1:36 PM, Bill Dube wrote:
> Lee, you are applying you many years of battery experience from
> other chemistries mistakenly to LiFePO4. The LiFePO4 chemistry
> behaves in a _completely_ different manner than any other battery
> chemistry. Completely.

Bill, don't give me marketing; give me facts. :-)

I have the deepest respect for your EV accomplishments, both on the
street and on the track. It is great work, and you have earned my
respect and trust! But that does not mean I blindly accept statements
from Authority without considering their basis in fact. You are after
all sponsored by A123.

I know A123 cylindrical cells are great! I believe it not because of
their marketing; but because I have a couple dozen of them, and have
tested them myself.

> For LiFePO4, the OCV only changes very near the end points of the
> SOC curve. Voltage is pretty much flat for most of the SOC curve.

That's fact; confirmed by the data.

> Completely unlike any other battery chemistry.

That's marketing.

Many other chemistries also do this. Most lithium chemistries, and in
fact most chemistries where the electrolyte is not directly involved
like it is for lead-acid. Remember the old mercury cells? Their voltage
vs. SOC curve was even flatter than A123 cells!

> Thus, the cells will read over 3 volts for years. The voltage only
> goes low at the very end of the SOC.

I agree; but it's only true if there is *no load* on the cells. My
concern is with designs that *permanently* connect a BMS or some other
load to the cells. And let's face it -- *most* designs do this! It's
cheap, it's easy, it's obvious, and the seller doesn't care if it
murders your cells. He assumes you'll just buy more from him!

> I have no clue about the details of the ALM 12V7 BMS. Perhaps it
> loads the cells after output shut-off. Perhaps it doesn't.

That's an important question, which we don't have the answer to.

I want to know why a new battery arrived dead. Did its BMS kill the
cells? That shouldn't happen. If it did, it's a crappy design.

Or, is the battery shipped in an "off" state, where the cells are in
fact still charged but the BMS and output is off? I could see this being
the case, so it could sit in a warehouse for years and only gets turned
"on" the first time you charge it. But that doesn't seem to be the case,
because Phoenix Contact's own charger doesn't turn it on.

> It really doesn't matter because the cells are unharmed by going to
> zero volts.

That is the point of my question. Don't just say it (that's marketing).
What are the facts? Where is the data?

I have never deliberately ran an A123 cell dead; but I have to other
types of lithium cells. They are seriously damaged and even destroyed by
the experience! So, I don't want to purposely run any A123 cells dead
without evidence that this is harmless.

>>> personal anecdote <<<
> I have personally discharged a 12 volt LiFePO4 battery to zero
> volts. (Glove box light left on.) The battery was at zero volts for
> about two weeks. Since the goal of building that 12v battery was to
> test it under typical consumer use, I jump started the car with a
> fully-charged 12 volt lead-acid battery, just like a consumer might
> do. The jumper cables became noticeably warm from the large current
> flow into the zero-volt LiFePO4 battery. Started the engine and
> quickly disconnected the jumper cables, allowing the full 100 amps
> from the alternator into the LiFePO4 battery. This  would have been
> certain battery death, likely an explosion, and surely a fire with
> LiPo.  Five years and 60,000 miles later, that 12v LiFePO4 battery
> still working perfectly.

That's pretty impressive! But, it raises some questions.

1. Was there a BMS on that battery? Did it detect a low cell, and
    disconnect the load, resulting in 0 volts on the terminals while
    the cells inside were still at some positive voltage?

2. If there was no BMS, was it just 4 cells in series, connected
    in place of the car's 12v battery? If so, why didn't the first
    cell that went dead get *reversed* by the current continuing
    to flow due to the other cells in series that still had charge?

3. This was an ICE vehicle? It only takes is a second or two of
    high current to start an ICE. The actual amphours needed is
    trivial; 2 seconds at 400 amps is only 0.22 amphours; less than
    10% of a single A123 cell's capacity. The cells could have lost
    90% of the amphour capacity and *still* start the ICE.

    Lead-acid ICE batteries are often almost totally shot, with
    almost no capacity left, and yet will *still* start the car.
    This is an old huckster's trick that's been used to sell "magic
    battery rejuvenators" for decades.

4. Did you have an ammeter in the battery? Do you know what the
    current was in or out of the battery? A "100 amp" alternator
    rarely (if ever) supplies 100 amps.

> Going to zero volts (but not below!) with LiFePO4 does not harm the
> cells in any way. It is a fact.

I'll ask again, because all I have are anecdotes with no measurements.
Where is the test data to show that cells were run down to 0 volts, and
then tested for capacity, internal resistance, and cycle life?

If you don't know, just say so. If there is no test data, maybe I have
to sacrifice some A123 cells to science. :-)

--
Opportunity is missed by most people because it is dressed in overalls
and looks like work. -- Thomas A. Edison
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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Re: BMS Power WAS: A123 ALM 12V7...

Lee Hart
In reply to this post by Bill Dennis
On 7/2/2012 12:58 PM, Bill Dennis wrote:
> When I was playing with the LTC6803 chip, I had a 1 amp-turn reed switch in series with the chip's supply.  My theory was that it was mostly during charging and discharging that I wanted the BMS to be active, and I didn't care if it was monitoring/balancing cells when the car was parked or sitting at a red light or coasting.

That's a clever way to do it. :-)

Presumably the current flow in/out of the battery itself is what pulled
in the reed?

--
Opportunity is missed by most people because it is dressed in overalls
and looks like work. -- Thomas A. Edison
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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Re: BMS Power WAS: A123 ALM 12V7...

Bill Dennis
Yes, current flowing through one of the traction pack cables.

Bill

----- Original Message -----
From: Lee Hart <[hidden email]>
To: Electric Vehicle Discussion List <[hidden email]>
Sent: Mon, 02 Jul 2012 14:55:50 -0400 (EDT)
Subject: Re: [EVDL] BMS Power WAS: A123 ALM 12V7...

On 7/2/2012 12:58 PM, Bill Dennis wrote:
> When I was playing with the LTC6803 chip, I had a 1 amp-turn reed switch in series with the chip's supply.  My theory was that it was mostly during charging and discharging that I wanted the BMS to be active, and I didn't care if it was monitoring/balancing cells when the car was parked or sitting at a red light or coasting.

That's a clever way to do it. :-)

Presumably the current flow in/out of the battery itself is what pulled
in the reed?

--
Opportunity is missed by most people because it is dressed in overalls
and looks like work. -- Thomas A. Edison
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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Re: A123 ALM 12V7 Batteries now charging

Bill Dube
In reply to this post by Lee Hart

>
> > Thus, the cells will read over 3 volts for years. The voltage only
> > goes low at the very end of the SOC.
>
>I agree; but it's only true if there is *no load* on the cells.

Again, you are making the incorrect assumption that the internal
resistance is a strong function of the SOC. In LiFePO4, the internal
resistance is only a very weak function of SOC. Over 90% of the SOC,
the load produces pretty much the identical voltage drop. Very little
increase in internal resistance over the bulk of the discharge.

The fact that there is little change in OCV or internal resistance
with SOC makes it quite vexing to determine the SOC by the typical
means of sensing voltage and/or internal resistance. This chemistry
really _is_ completely different. No marketing. Fact. Name another
chemistry that has _all_ of these features:

1) Little change in specific power with SOC.
2) Cycle life (to half remaining capacity) of over 10,000 cycles.
(100% discharge each cycle.)
3) Can be left at zero volts without damage.
4) Has specific power over 3000 W/kg in consumer production. (20,000
W/kg in specialty production.)

>My
>concern is with designs that *permanently* connect a BMS or some other
>load to the cells. And let's face it -- *most* designs do this! It's
>cheap, it's easy, it's obvious, and the seller doesn't care if it
>murders your cells. He assumes you'll just buy more from him!

There are _awful_ BMS designs out there. The worst of them
continuously draw large currents unequally from the cells.

         The typical BMS in a well-designed commercial product has
very low continuos operating currents. (Not always, but typically.)
While it is not all that good for the 26650 M1 cells, they are not
severely damaged by _tiny_ reversals. Also, the quality control on
the very mature 26650 M1 cell results in very close capacity and
thus, they run flat at pretty much the same time in a 12 volt pack,
generally shutting down the BMS by voltage starvation before cell reversal.

> > It really doesn't matter because the cells are unharmed by going to
> > zero volts.
>
>That is the point of my question. Don't just say it (that's marketing).
>What are the facts? Where is the data?

         I have done it myself. Others have done it. They have
written about it repeatedly on this list. The results are all the
same. No damage. Many folks have done capacity and internal
resistance tests before and after running them to zero. (Several on
this list.) All confirm _exactly_ what I am writing.

         The reason you are having such a hard time believing it, and
saying "This couldn't possibly be so!" is; "This chemistry is
COMPLETELY different" than any other you have dealt with before." No
marketing hype. Just a fact.


>I have never deliberately ran an A123 cell dead; but I have to other
>types of lithium cells. They are seriously damaged and even destroyed by
>the experience! So, I don't want to purposely run any A123 cells dead
>without evidence that this is harmless.

         See above. LiFePO4 is completely different.


> >>> personal anecdote <<<
> > I have personally discharged a 12 volt LiFePO4 battery to zero
> > volts. (Glove box light left on.) The battery was at zero volts for
> > about two weeks. Since the goal of building that 12v battery was to
> > test it under typical consumer use, I jump started the car with a
> > fully-charged 12 volt lead-acid battery, just like a consumer might
> > do. The jumper cables became noticeably warm from the large current
> > flow into the zero-volt LiFePO4 battery. Started the engine and
> > quickly disconnected the jumper cables, allowing the full 100 amps
> > from the alternator into the LiFePO4 battery. This  would have been
> > certain battery death, likely an explosion, and surely a fire with
> > LiPo.  Five years and 60,000 miles later, that 12v LiFePO4 battery
> > still working perfectly.
>
>That's pretty impressive! But, it raises some questions.
>
>1. Was there a BMS on that battery?

Yes. A  primitive one. Only balancing at full charge.

>Did it detect a low cell, and
>     disconnect the load, resulting in 0 volts on the terminals while
>     the cells inside were still at some positive voltage?

No.


>2. If there was no BMS, was it just 4 cells in series, connected
>     in place of the car's 12v battery? If so, why didn't the first
>     cell that went dead get *reversed* by the current continuing
>     to flow due to the other cells in series that still had charge?

The 26650 cells are quite well capacity matched as delivered. There
were six cells in parallel, helping with the statistics, no doubt.
The current draw from the glove box light was likely tiny at the end
of the discharge. Tiny reverse voltage makes tiny damage.


>3. This was an ICE vehicle? It only takes is a second or two of
>     high current to start an ICE. The actual amphours needed is
>     trivial; 2 seconds at 400 amps is only 0.22 amphours; less than
>     10% of a single A123 cell's capacity. The cells could have lost
>     90% of the amphour capacity and *still* start the ICE.

Zero volts. With a voltmeter. Zero. Nada. 100% dead.

>4. Did you have an ammeter in the battery? Do you know what the
>     current was in or out of the battery? A "100 amp" alternator
>     rarely (if ever) supplies 100 amps.

No ammeter. Warm alternator wire is a sure indication of high current
flow. No accessories on other than the engine.


> > Going to zero volts (but not below!) with LiFePO4 does not harm the
> > cells in any way. It is a fact.
>
>I'll ask again, because all I have are anecdotes with no measurements.
>Where is the test data to show that cells were run down to 0 volts, and
>then tested for capacity, internal resistance, and cycle life?

Look in the EVDL archives. Or do the test yourself.


>If you don't know, just say so. If there is no test data, maybe I have
>to sacrifice some A123 cells to science. :-)

There will be no sacrifice. They will be just fine.
See above. This chemistry is completely different.


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Re: A123 ALM 12V7 Batteries now charging

Hoegberg .
In reply to this post by Lee Hart


 > Date: Mon, 2 Jul 2012 12:02:16 -0500

> From: [hidden email]
> To: [hidden email]
> Subject: Re: [EVDL] A123 ALM 12V7 Batteries now charging
>
> Elithion wrote:
> Lee Hart wrote
> >> All the BMS chips I've seen draw power from all cells
>
> > In general, you're right. However, the Linear Technology LTC6803 may be
> > powered separately, or you can place a switch between the battery voltage
> > and the IC's power input pin, which can be opened when the battery is not in
> > use or empty.
>
> The Manzanita Micro BMS uses this chip. It is powered exclusively from
> the series string of cells it is monitoring. If one cell goes dead, the
> BMS knows; but it also continues drawing its supply current from the
>> whole series string.  >This problem could be fixed if the design had a low-voltage shutdown
that removes *all* the load, including the BMS itself. But I'll bet you
99 out of 100 BMS designs won't bother. Their designers won't even
*think* about it!
 
>> Now, yes, a DC-DC converter that powers the BMS could reverse a cell
 
It doesn't even require that it have a DC/DC. Just any design that uses
power from a series string of cells to power the BMS. --
> Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net
-------------------------------------------------------------------------------------------------- " ..including the BMS itself. But I'll bet you
99 out of 100 BMS designs won't bother. Their designers won't even
*think* about it! "
 -Well..  I  do!  ;-) Thanx for your thoughts Lee.   From datasheet:http://cds.linear.com/docs/Datasheet/680313f.pdf"The LTC6803 provides a standby mode to reduce supply
current to 12μA. Furthermore, the LTC6803 can be powered
from an isolated supply, providing a technique to reduce
battery stack current draw to zero. "   They also show a swich to disconnect.( in fig 25.)----------------------------------"HARDWARE SHUTDONTo completely shut down the LTC6803 a PMOS switch canbe connected to V+
,or V+ can be driven from an isolated
power supply. Figure 25 shows an example of a switched
V+. The breakdown voltage of DZ4 is about 1.8V. If SHDN <
1.8V, no current will flow through the stacked MMBTA42s
and the 1M resistors. TP0610Ks will be completely shut
off. If SHDN > 2.5V, M7 will be turned on and all TP0610Ks
will be turned on.
----------------------- Figure 26 is an example of isolated power supply. This
circuit provides power for two LTC6803s used to monitor
24 series connected battery cells. When 5V is removed, the
LTC6803s will draw 1nA from the battery cells. Note that...... "          
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Re: A123 ALM 12V7 Batteries now charging

Lee Hart
In reply to this post by Bill Dube
Bill Dube wrote:
>>> The cells will read over 3 volts for years. The voltage only
>>> goes low at the very end of the SOC.

Lee Hart wrote:
>> I agree; but it's only true if there is *no load* on the cells.

Bill Dube wrote:
> Again, you are making the incorrect assumption that the internal
> resistance is a strong function of the SOC.

Not at all; I'm only poionting out that there will only be voltage after
3 years if the load on the cell for that entire time is essentially
zero! 3 years is 26280 hours. Even a 0.1 milliamp load for 3 years will
totally empty a 2.3ah A123 cell.

> The fact that there is little change in OCV or internal resistance
> with SOC makes it quite vexing to determine the SOC by the typical
> means of sensing voltage and/or internal resistance.

I agree; but that's irrelevant to the current discussion.

> The typical BMS in a well-designed commercial product has very
> low continuous operating currents. (Not always, but typically.)

You must have had better luck finding such products than I have.
Essentially everything seems to have high-drain BMS systems.

I "collect" packs from various products to dissect and learn from. As an
example, essentially all laptop packs have fairly high standby drains. I
have to get the pack fairly soon after it was taken out of service, so
at least some cells are still good. If it has sat in a drawer for even 6
months, *all* the cells will be dead. And since these packs normally use
LiCr cells, they are destroyed.

The packs are designed to assume that they will never be left idle for
more than a few months at a time, without being charged.

>> What are the facts? Where is the data?

> I have done it myself. Others have done it. They have
> written about it repeatedly on this list.

These are anecdotes, Bill. Essentially storytelling; you know what I
mean! They are not repeatable, scientific tests. They are guys doing
uncontrolled experiments, with no documentation, and simply saying what
seemed to happen by memory. They provide interesting *hints*, but don't
really tell us what is going on.

An anecdote: "I connected a light bulb to a cell until it didn't light
any more. Then I charged it up, and it worked fine." No numbers, no
measurements, no way we can draw any meaningful conclusions from it.

A test: "I bought eight A123 ANR26650 LiFeO4 cylindrical lithium cells.
Each was fully charged, then discharged with a (model#) charger/load
tester with a 1 amp load to 2.0v, and its amphour capacity recorded. 4
cells (the test group) were then completely discharged to 0 volts with a
1 ohm resistor connected for 24 hours. The other 4 cells (the control
group) was left sitting with no load or charging after the discharge
test. After 24 hours, all 8 cells were recharged, then discharged again
with the same tester and same load. Here are the amphour capacities of
each cell after the test"...

The latter has real numbers, and sufficient information so one could
duplicate the test to verify the results. It would also be the basis for
further tests. For example, one could put the cells on a cycle life
test, to see if there was any change in the cycle life as a result of
being run dead.

> Many folks have done capacity and internal
> resistance tests before and after running them to zero. (Several on
> this list.) All confirm _exactly_ what I am writing.

Well, I looked in the EVDL archives when this thread started. I couldn't
find anything. Now maybe it's there; the EVDL search capabilities stink.
Do *you* have any links to any of these test that you can point to?

Are any of the people that made any of these posts reading this thread?
What tests did you do, what was the data, and what were your conclusions?

> The reason you are having such a hard time believing it, and
> saying "This couldn't possibly be so!" is; "This chemistry is
> COMPLETELY different" than any other you have dealt with before." No
> marketing hype. Just a fact.

No, no, no. You keep resorting to marketing claims as a way to dodge any
discussion of real test data or facts. *OF COURSE* I know the chemistry
is different! We all do!

I'm having a hard time believing it because I haven't seen any test data
to support it! All I'm getting are anecdotal stories.

If you don't have the data; say so. We'll have to get it elsewhere. Stop
pretending that anyone who asks for evidence automatically knows nothing.

>>>>> personal anecdote<<<
>>> I have personally discharged a 12 volt LiFePO4 battery to zero
>>> volts...  (Glove box light left on.)

>> That's pretty impressive! But, it raises some questions.
>> 1. Was there a BMS on that battery?
> Yes. A  primitive one. Only balancing at full charge.

>> Did it detect a low cell, and disconnect the load
> No.

>> 2. why didn't the first cell that went dead get *reversed*
> The 26650 cells are quite well capacity matched as delivered. There
> were six cells in parallel, helping with the statistics, no doubt.

OK; that would help.

> The current draw from the glove box light was likely tiny at the end
> of the discharge. Tiny reverse voltage makes tiny damage.

A glove box light draws about 250ma at 12v. The nature of a light bulb
is that it would still draw about 100ma even at 1 volt. That is not a
"tiny" load.

The A123 cells I have are indeed pretty well matched. But they came out
of DeWalt packs, which were probably already tested and/or matched up.

If the cells are well matched, it is reasonable that they would all go
dead about the same time, so no cell would get reversed by such a
discharge. But we really don't know if that was the case or not.

>> 3. This was an ICE vehicle? It only takes is a second or two of
>>      high current to start an ICE. The actual amphours needed is
>>      trivial; 2 seconds at 400 amps is only 0.22 amphours; less than
>>      10% of a single A123 cell's capacity. The cells could have lost
>>      90% of the amphour capacity and *still* start the ICE.
>
> Zero volts. With a voltmeter. Zero. Nada. 100% dead.

The point of my comment was that just because the pack recharged and
could start an ICE doesn't mean it still has normal amphour capacity. It
could have had 10% of its original capacity and still start the engine.

>> 4. Did you have an ammeter in the battery?
> No ammeter. Warm alternator wire is a sure indication of high current
> flow. No accessories on other than the engine.

OK; the warm wire meant the current was "high". But that doesn't mean it
was the 100 amps you specified.

>> If you don't know, just say so. If there is no test data, maybe I have
>> to sacrifice some A123 cells to science. :-)

> There will be no sacrifice. They will be just fine.
> See above. This chemistry is completely different.

(Sigh) It looks like I'll have to try it myself. No one seems to have
any real data; just marketing and stories.
--
If we knew what we were doing, it wouldn't be called research, would it?
        -- Albert Einstein
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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"Zero volts = OK for LiFePO4" (was: A123 ALM 12V7 Batteries now charging)

Bill Dube
The "zero volts" data was presented on this list many years ago. I
remember it well, but a brief search of the archives did not turn it
up. Very well documented tests were performed and results presented
on this list showing that LiFePO4 cells were not only unharmed by
discharging them to zero volts, the internal resistance actually went
down after discharging to zero volts, improving the specific power.

I know that A123Systems did extensive internal testing (unpublished)
on this effect and was on the verge of patenting the "discharge to
zero" process, but then found out that this was already in the public
domain. (I was the one that told them about the results presented on
the EVDL.)

If you don't want to take my word for the facts, and absolutely must
see the data yourself, do the search of the EVDL archives and find
the thread on the subject. Maybe 7 years ago?

Bill D.

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Re: "Zero volts = OK for LiFePO4"

Lee Hart
On 7/4/2012 7:08 PM, Bill Dube wrote:
> The "zero volts" data was presented on this list many years ago. I
> remember it well, but a brief search of the archives did not turn it
> up.

Yeah, the archives are a pain to use. Unless you know the exact wording
of the post you are looking for, you can't find it. It also isn't good
for really old posts.

> If you don't want to take my word for the facts...

It's not a matter of trust, Bill. I know you believe it, based on data
you have seen. But I haven't seen the data. Until then, it flies in the
face of my experience with other lithium cells (including LiFePO4). As
Carl Sagan said, "extraordinary claims require extraordinary evidence."

--
For every complex problem, there is a solution that is simple, obvious,
and wrong. -- H.L. Mencken
--
Lee A. Hart http://www.sunrise-ev.com/LeesEVs [hidden email]

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