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Discussion Starter #1
Re: [EVDL] A123 Battery charging

I am contemplating to use the A123 cells in an application.
Does someone have a more detailed charge spec than the
datasheet on A123 website?
In particular, how much float charge is OK on these cells?
I could not find that on the website.


Cor van de Water
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Marty Hewes
Sent: Thursday, September 06, 2007 11:55 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] A123 Battery Feasibility

I think the capacitor bank for a shot of acceleration has merit, but would be significantly more difficult to implement because it is so different.

A cap loses voltage linearly with discharge. To use 80% of the charge in the caps, you need a controller that can still provide drive current when the caps have dropped to 20% voltage output. Either the cap voltage needs to start very high, or the controller needs to boost. I'm guessing that's a very different, and more expensive, controller.

Then the battery pack needs to recharge the caps which may need to charge to a significantly higher voltage than the batteries? I don't think that's a common or reasonably priced charger, although charging caps is probably a whole lot simpler than charging batteries. Just an inverter with current limiting?

----- Original Message -----
From: "Jack Murray" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, September 06, 2007 10:25 AM
Subject: Re: [EVDL] A123 Battery Feasibility


> Sure, but then what is the cost savings if you kill the power pack by
> charging and discharging it 100 times more than if it was a full pack?

Where does the 100 times more come from? I see two scenarios. Either the
power pack is made up of a small load of expensive batteries that can be
cycled many times, but don't carry enough charge to get sufficient range
(light but expensive solution). Or the power pack is made up of cheaper
higher capacity batteries but never discharged very deeply (cheaper but
heavy).

> Or the cost to replace the floodies from running them harder instead?

I'm guessing that since the acceleration current is primarily being supplied
by batteries designed to supply high current, the floodies shoud last longer
and not lose range due to Peukerts. I don't see how they would be run
harder?

> Or the extra weight being accelerated with a big heavy charge pack?

More weight than what? A combination of floodie and AGM should give you
more acceleration potential than an equivalent weight of all floodies, and
more range and life span than an equivalent load of AGM. I'm guessing that
since the hybrid would draw on each type to do what they were designed to
do, the result should be better than simply averaging all floodie and all
AGM numbers.

> My view is that a capacitor bank provides the biggest DIFFERENCE from
> batteries so it has a lot more potential to be exploited for some gains.
> But in any case, it is straightfoward (but still time consuming) to test
> any setup on a small scale to find out how it works, a computer model
> might be even easier.

A computer model would be great. But I don't see an inexpensive way to try
putting an advanced battery type in parallel with a floodie with a nominal
voltage maybe 10% higher. What is the cheapest deep cycle floodie
available? Maybe that and some power tool AA's? But mathematically I'd
think you could characterize charge and discharge curves of both, boost the
floodie curves 10%, and parallel them on paper so to speak.

Marty

> Jack


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Discussion Starter #3
Re: [EVDL] A123 Battery charging

Cor van de Water <[email protected]> wrote:
> I am contemplating to use the A123 cells in an application.
> Does someone have a more detailed charge spec than the
> datasheet on A123 website?
> In particular, how much float charge is OK on these cells?
> I could not find that on the website.
>

They don't have a "float" voltage. You charge them at constant current
until they reach the cut-off voltage, then you charge them at constant
voltage until they drop below a certain current, then you turn it off.

You choose where to put the cutoff voltage; there's a safe range. (4
to 4.2 for Li-Ion, I'm not sure for A123.) The lower the cutoff
voltage, the lower the capacity, but the longer the lifetime.

-Morgan

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Discussion Starter #4
Re: [EVDL] A123 Battery charging

Bill Dube wrote:

> The charge is as simple as the spec sheet says it is.
>
> Charge to 3.8 volts. You can stop the charge (after the
> current tapers down) anywhere from 3.45 volts up to 3.8 volts and
> there is not much difference in capacity.

3.8V is recommended for fast (10A/cell) charge; if charging at the
normal (non drag-racing ;^) rate of 3A/cell, in ambient temps of 0C to
60C, A123 recommends charging to 3.6V and holding until the current
drops to 0.05A (per paralleled cell) or 30min max. to get to 100%SOC.

Fast charging at 10A to 3.8V/cell for a maximum of 15min is said to
yield 96%SOC.

In ambients below 0C, A123 wants to see the normal charge voltage
elevated to 4.2V/cell and the charge rate dropped significantly.

> A "float" charge would be somewhere between 3.45 and
> 3.8 volts.

A123's recommended float charge voltage is 3.45V/cell (-20C to 60C
ambient).

Cheers,

Roger.

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Discussion Starter #5
Re: [EVDL] A123 Battery charging

Anyone have the full spec sheet and MSDS for the A123 cells?

- Tony

----- Original Message ----
From: Roger Stockton <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thursday, September 6, 2007 1:30:07 PM
Subject: Re: [EVDL] A123 Battery charging

Bill Dube wrote:

> The charge is as simple as the spec sheet says it is.
>
> Charge to 3.8 volts. You can stop the charge (after the
> current tapers down) anywhere from 3.45 volts up to 3.8 volts and
> there is not much difference in capacity.

3.8V is recommended for fast (10A/cell) charge; if charging at the
normal (non drag-racing ;^) rate of 3A/cell, in ambient temps of 0C to
60C, A123 recommends charging to 3.6V and holding until the current
drops to 0.05A (per paralleled cell) or 30min max. to get to 100%SOC.

Fast charging at 10A to 3.8V/cell for a maximum of 15min is said to
yield 96%SOC.

In ambients below 0C, A123 wants to see the normal charge voltage
elevated to 4.2V/cell and the charge rate dropped significantly.

> A "float" charge would be somewhere between 3.45 and
> 3.8 volts.

A123's recommended float charge voltage is 3.45V/cell (-20C to 60C
ambient).

Cheers,

Roger.

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Discussion Starter #6
Re: [EVDL] A123 Battery charging

Tony,

Grainger has the MSDS for the DeWalt lithium pack (using A123 cells)
here:
http://complyplus.grainger.com/grainger/msds.asp?sheetid=2829349

I hope this is what you are looking for.

Alan


-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Tony Hwang
Sent: Thursday, September 06, 2007 2:25 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] A123 Battery charging

Anyone have the full spec sheet and MSDS for the A123 cells?

- Tony

----- Original Message ----
From: Roger Stockton <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thursday, September 6, 2007 1:30:07 PM
Subject: Re: [EVDL] A123 Battery charging

Bill Dube wrote:

> The charge is as simple as the spec sheet says it is.
>
> Charge to 3.8 volts. You can stop the charge (after the
> current tapers down) anywhere from 3.45 volts up to 3.8 volts and
> there is not much difference in capacity.

3.8V is recommended for fast (10A/cell) charge; if charging at the
normal (non drag-racing ;^) rate of 3A/cell, in ambient temps of 0C to
60C, A123 recommends charging to 3.6V and holding until the current
drops to 0.05A (per paralleled cell) or 30min max. to get to 100%SOC.

Fast charging at 10A to 3.8V/cell for a maximum of 15min is said to
yield 96%SOC.

In ambients below 0C, A123 wants to see the normal charge voltage
elevated to 4.2V/cell and the charge rate dropped significantly.

> A "float" charge would be somewhere between 3.45 and
> 3.8 volts.

A123's recommended float charge voltage is 3.45V/cell (-20C to 60C
ambient).

Cheers,

Roger.

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