# [EVDL] A123 Battery Feasibility



## EVDL List (Jul 27, 2007)

An idea that I have had, along with many others, is to have a hybrid
battery pack. I've always thought it should work like this: Two
completely separate battery packs, with separate charging systems. Use
a switch to choose which pack you want.

So I've thought, why not just use a "cheap" golf cart battery pack for
range, then separately have a very light, very low amp-hour, A123 pack
for hard acceleration. Of course this raises questions like....

Do A123 batteries require using special balancers and chargers?

What is available in the market for balancing/charging A123 battery packs?

And....

If you had two battery packs and used a switch to choose which one you
are using, the controller will suddenly be receiving no power while
you are switching be the two battery packs.
Would suddenly taking away the power from the controller be harmful?

If it is, then you'd have to do turn off the whole car, then switch to
the other pack, and then turn on the car. But that sounds like it
would take too long if the whole point of the A123 pack is too
accelerate!

Is there some fancy capacitor thingy to solve this?

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## EVDL List (Jul 27, 2007)

Actually there is a discussion of using AGMs + Floodies in buddy pairs
for just the same idea. A veddy nice list member looks like he is
going to bench a pair and get some numbers on this scenario.

As far as using A123s as an 'acceleration pack', that's been discussed
as well. It's called a Hybrid pack, and such a thing has the potential
to be absolutely fraught with difficulties.

If order for this sort of thing to work -very- well, the pack control
would have to be based on amps demanded, and so it would have to be a
controller that had that smarts in it tp handle this scenario.

In order for it to work -reasonably- well (which is to say, it would
work, but not be elegant), you could spend a lot of time thinking
about balancing currents and battery voltages for unequal pairs, set
up faux 'buddy pairs' and go to town. The A123s would be a bit abused
by this treatment though.

All of this is predicated on the idea that the 'demand' battery (A123
in your case) has a lower internal resistance than the 'float' battery
and so would provide most of the current for short durations of high
demand. Once demand went down to below a certain threshold (depending
on your 'float' battery) then current would start to flow from the
float battery. If the demand were low enough, the float battery would
recharge the demand battery as well as supply current to the
controller.

I am actually working out a way to use NiCD floodies as a demand pack
myself. They are very resistant to abuse and have a pretty low
internal resistance.

What I've been learning is that you really have to think hard about
how you match up batteries, otherwise you'll end up with one or the
other cooked off by current runaway or overuse.

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## EVDL List (Jul 27, 2007)

yep, a capacitor thingy is a better approach than using A123, the caps 
can take the abuse of constant charge discharge. and while it would be 
complicated, it will also be very expensive, so if you consider how much 
lifespan it improves the cheap batteries, you might be better off to buy 
a few sets of batteries than pay for the caps and complications.
But if they are expensive batteries, e.g. some low-rate Lithium, it 
might be worthwhile to improve their lifetime by lowering their amp 
draws. If you are trying to go fast and don't care as much about cost, 
then it might be worthwhile approach in any case. I've been toying with 
some ideas, and might try them out on an R/C car.

Jack



> Timothy Balcer wrote:
> > Actually there is a discussion of using AGMs + Floodies in buddy pairs
> > for just the same idea. A veddy nice list member looks like he is
> > going to bench a pair and get some numbers on this scenario.
> ...


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## EVDL List (Jul 27, 2007)

> Joseph T. wrote:
> > An idea that I have had, along with many others, is to have a hybrid
> > battery pack. I've always thought it should work like this: Two
> > completely separate battery packs, with separate charging systems. Use
> ...


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## EVDL List (Jul 27, 2007)

For short burst of acceleration coupled to a 12 volt'ish battery system I
don't think you will be able to beat the competition stereo capacitors. 1-4
farads for a very affordable price. <note not nearly enough juice for the
quarter, but enough for quick response to pass someone, also will help
extend range of batteries>
The thing about a123 batteries are they are light for what you get. However
to have more umph than the lead acid / agm you need to buy enough of them
that you can probably run the vehicle on the a123 (figure 100 amps and 3
volt per cell at $10-20 each, a good lead acid will produce 500 amps, so
that means you need 10 times the system voltage divide by 3 or 3 times the
system voltage to get any benefit). I love them (using them in 2SSIC) but
they do not seem to be a way to save any money.

KD

-----Original Message-----
From: Jack Murray [mailto:[email protected]] 
Sent: Thursday, August 30, 2007 9:04 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] A123 Battery Feasibility

yep, a capacitor thingy is a better approach than using A123, the caps can
take the abuse of constant charge discharge. and while it would be
complicated, it will also be very expensive, so if you consider how much
lifespan it improves the cheap batteries, you might be better off to buy a
few sets of batteries than pay for the caps and complications.
But if they are expensive batteries, e.g. some low-rate Lithium, it might be
worthwhile to improve their lifetime by lowering their amp draws. If you
are trying to go fast and don't care as much about cost, then it might be
worthwhile approach in any case. I've been toying with some ideas, and
might try them out on an R/C car.

Jack



> Timothy Balcer wrote:
> > Actually there is a discussion of using AGMs + Floodies in buddy pairs
> > for just the same idea. A veddy nice list member looks like he is
> > going to bench a pair and get some numbers on this scenario.
> ...


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

If it were possible to load share both packs during acceleration, I don't 
see the point in switching out the floodies. Ideally, I'd like to be able 
to pull 500 amps from an AGM pack, and 250 from a floodie pack 
simultaneously. I suspect it would take a disconnect switch and two 
separate charging systems to fully charge them.

Now if the floodies were in a trailer, so you could disconnect it at the 
drag strip, then I could see accelerating with just the lightweight pack . 
The thousand pound weight reduction should make up for the lower available 
current, especially if you're limited by the controller anyway.

Marty
----- Original Message ----- 
From: "Joseph T. " <[email protected]>
To: <[email protected]>
Sent: Thursday, August 30, 2007 7:15 PM
Subject: [EVDL] A123 Battery Feasibility


> An idea that I have had, along with many others, is to have a hybrid
> battery pack. I've always thought it should work like this: Two
> completely separate battery packs, with separate charging systems. Use
> a switch to choose which pack you want.
>
> So I've thought, why not just use a "cheap" golf cart battery pack for
> range, then separately have a very light, very low amp-hour, A123 pack
> for hard acceleration. Of course this raises questions like....
>
> Do A123 batteries require using special balancers and chargers?
>
> What is available in the market for balancing/charging A123 battery packs?
>
> And....
>
> If you had two battery packs and used a switch to choose which one you
> are using, the controller will suddenly be receiving no power while
> you are switching be the two battery packs.
> Would suddenly taking away the power from the controller be harmful?
>
> If it is, then you'd have to do turn off the whole car, then switch to
> the other pack, and then turn on the car. But that sounds like it
> would take too long if the whole point of the A123 pack is too
> accelerate!
>
> Is there some fancy capacitor thingy to solve this?
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
> 


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

Is there any reason you couldn't use your charger as the "feed controller?"

----- Original Message ----
From: Bill Dube <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Friday, August 31, 2007 1:38:13 PM
Subject: Re: [EVDL] A123 Battery Feasibility

The hybrid pack concept has been discussed many times over the years.

 Once you think it through, the they way to do it is to have 
a higher voltage pack of flooded batteries, and a slightly lower 
voltage pack of high-power batteries (like A123 or perhaps peppy 
AGMs). You Connect the controller to the high-power pack in the 
normal manner. You then put a second, much smaller, PWM controller 
("feed" controller") from the floodie pack to the high-power pack.

You run the car with the high-power pack and then set the 
feed controller to keep it topped up at a current rate that is 
acceptable to the floodie pack.







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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

Is that significant for acceleration? My numbers suggest otherwise.

1 farad means that drawing 1 amp makes the voltage drop 1V/sec.

Series caps divide their capacitance. A 120V system with 10x 4 farad
caps in series is 0.4 farads. So under an acceleration where you try to
draw 100A from the cap, the voltage will drop 250V/sec. It sounds like
there will be only a delay of a few milliseconds before the batt+cap
voltage ends up at the voltage the batt would drop to anyways. 

In other words if the batt is 30V lower when loaded down, the 10x 4
farad caps in series can supplement all of 12 amp-seconds between the
higher and lower voltage states. 12 amps over 1 sec, 1 amp over 12 sec,
100 amps over 0.12 sec. 

It might help stiffen the battery against current ripple- but the total
capacitance is insignificant for acceleration.

Danny

----- Original Message -----
From: Michael T Kadie <[email protected]>
Date: Friday, August 31, 2007 12:51 pm
Subject: Re: [EVDL] A123 Battery Feasibility
To: 'Electric Vehicle Discussion List' <[email protected]>

> For short burst of acceleration coupled to a 12 volt'ish battery 
> system I
> don't think you will be able to beat the competition stereo 
> capacitors. 1-4
> farads for a very affordable price. <note not nearly enough juice 
> for the
> quarter, but enough for quick response to pass someone, also will help
> extend range of batteries>
> The thing about a123 batteries are they are light for what you get. 
> However
> to have more umph than the lead acid / agm you need to buy enough 
> of them
> that you can probably run the vehicle on the a123 (figure 100 amps 
> and 3
> volt per cell at $10-20 each, a good lead acid will produce 500 
> amps, so
> that means you need 10 times the system voltage divide by 3 or 3 
> times the
> system voltage to get any benefit). I love them (using them in 
> 2SSIC) but
> they do not seem to be a way to save any money.
> 
> KD
> 
> -----Original Message-----
> From: Jack Murray [mailto:[email protected]] 
> Sent: Thursday, August 30, 2007 9:04 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] A123 Battery Feasibility
> 
> yep, a capacitor thingy is a better approach than using A123, the 
> caps can
> take the abuse of constant charge discharge. and while it would be
> complicated, it will also be very expensive, so if you consider how 
> muchlifespan it improves the cheap batteries, you might be better 
> off to buy a
> few sets of batteries than pay for the caps and complications.
> But if they are expensive batteries, e.g. some low-rate Lithium, it 
> might be
> worthwhile to improve their lifetime by lowering their amp draws. 
> If you
> are trying to go fast and don't care as much about cost, then it 
> might be
> worthwhile approach in any case. I've been toying with some ideas, 
> andmight try them out on an R/C car.
> 
> Jack
> 


> > Timothy Balcer wrote:
> > > Actually there is a discussion of using AGMs + Floodies in buddy
> > pairs
> > > for just the same idea. A veddy nice list member looks like he is
> ...


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## EVDL List (Jul 27, 2007)

This thread is an ideal example of why we need to get all of this
wisdom onto a darned Wiki! 

Bill Dube offhandedly mentioned "Oh yeah, that problem was basically
solved a whole ago and the answer is this.." Wow! I mean, I would have
loved to have had that in a Wiki under 'Hybrid Battery Packs'
somewhere. It would have saved me a few hours of musing.

David, I suggest an EVDL approved Wiki, perhaps only accessible (for
edits and contributions) to EVDL/EAA/XXXorganization members. It's
free software, and instead of cobbled together FAQs it would be a
living repository where contributors could just post their musings
onto a community moderated board. The rate limiting factor would be
who you chose as editors. It would offload a lot of the repeat traffic
here, give us linkable material that is consistent, and allow for
collaboration way beyond what the EVDL allows.

I'd be happy to assist in setting it up and paying for it.. let me know!

--T

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

> To Morgan, super cool that you got the A123 and flooded batteries
> working together. How do they work together? Are the batteries still
> in good "health"?
>

I didn't say that I've done it; I'm saying that's how I *would* do it
to ensure that it works as well as possible and you don't have
problems switching over.

> "You end up trying to accelerate a vehicle that
> is carrying the weight of the floodies with just the small A123 pack. I'm
> just a clueless newbie, but that sounds like trouble to me. "
>
> I am also a newb! I don't think it'd be a problem though. The A123
> batteries are so light, and yet so powerful, that I think they can
> easily pull around an EV loaded with batteries.
>

The problem is that battery power is rated relative to battery
capacity. So if you make an A123 pack with half the capacity, it also
has half the power. I don't know whether A123 are powerful enough that
a small, cheap pack could still have enough power to help accelerate
well.

-Morgan

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## EVDL List (Jul 27, 2007)

Big misconception here. Battery power and battery capacity are NOT 
related directly if you are talking about different battery 
technologies (even differing topologies within the same battery technology)

"Specific Power" is given in Watts/kg and tells you how much HP 
(watts) you can draw from each kg of this type battery.

"Specific Energy" is given in Watt-hrs/kg and tells you how much 
energy (capacity) you have in each kg of this type battery.

You can alter the internal geometry (like the paste thickness, 
separator thickness, grid thickness) on any type of battery to 
increase the specific power to the detriment of specific energy. You 
can also do vice-versa. Basically, for a given battery technology, 
you pick how much power you are willing to give up to gain capacity, 
and you pick how much capacity to give up to gain power.

Bill Dube'

>The problem is that battery power is rated relative to battery
>capacity. So if you make an A123 pack with half the capacity, it also
>has half the power. I don't know whether A123 are powerful enough that
>a small, cheap pack could still have enough power to help accelerate
>well.
>
>-Morgan
>
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## EVDL List (Jul 27, 2007)

<<< The problem is that battery power is rated relative to battery
capacity. So if you make an A123 pack with half the capacity, it also
has half the power. I don't know whether A123 are powerful enough that
a small, cheap pack could still have enough power to help accelerate
well. >>>

The gurus may weigh in on this, but I think you are mistaken: 
different chemistries have different discharge rates based on capacity 
(C), and even within the same chemistry, design can be for power *or* 
energy.

T105s, 225Ah, can't handle much over 2-3C discharge or 100%DOD without 
risking damage and/or painfully short life-span.

A single Odyssey PC680, 17Ah, can handle more than 30C rates *and* 
survive many 100%DOD cycles (rated 400 to that depth, 500 to 80%DOD).

RC-type Li-poly can go 20C, some are even (optimistically) spec'd to 50C.

The A123 cells are only 2.3Ah each, but the Killacycle is pulling over 
200C...repeatedly...often without recharging! Don't know how many 
cycles he'll get, but with almost 1000 cells, I'm sure Mr Dube' does 
want to hunt down too many duds!

I'd say if any hybrid pack would work, it would be most likely with 
A123 cells feeding the high-power output.


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

<<<< If, as I suggested earlier, you connect the traction controller to
the high=power pack, and a low-power controller to the slightly-high
voltage floodie pack, you just need to charge the floodie pack and
let the low-power controller run the charge for the high-power pack.

While you are driving down the road, the floodie pack
charges the high=power pack through the low-power controller. That
low-power controller is a slave to the BMS on the high-power pack.
When you charge, just leave the low-power controller on, and let it
do exactly what it was doing while you were driving. >>>>

Could a boost converter be used to feed a high-power/high-voltage pack 
from a lower-voltage pack of floodies? Don't know how efficient it 
would be, but might be a nice way to have only 10 GC batteries feeding 
a Zilla a full 156V!

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## EVDL List (Jul 27, 2007)

It is very common however and I think easier to deal with it in relation
to capacity. Manufactures provide this info.

ie

A123 are 2.3Ah
so when they say good for 15seconds of 70C that is 15 seconds of 150Amps,
Don't You use 8 in parallel and 100 in series to give you 2000 amp pack
at 340V?

This is 680kw power and 6.256 kwh. (reguardless of the weight)

we can then create the aggregate 680kwh/56kg = 12kw/kg
and 111wh/kg.

I can see where you can say that Specific Power is not directly related
to Specific Energy for a cell.
But I think he was saying that within a pack made of like cells that the
power is related to the capacity. and I agree with that.

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## EVDL List (Jul 27, 2007)

> [email protected] wrote:
> > <<<< If, as I suggested earlier, you connect the traction controller to
> > the high=power pack, and a low-power controller to the slightly-high
> > voltage floodie pack, you just need to charge the floodie pack and
> ...


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

> Bill Dube wrote:
> 
> > The last part is where you are off-base. The floodies won't re-charge
> > the SLAa (or AGMs). The minimum charging voltage for a lead-acid
> ...


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## EVDL List (Jul 27, 2007)

> Roger Stockton <[email protected]> wrote:
> > I believe this is why Lee's suggestion was to use something like a 144V
> > string of floodies paralleled with a 132V string of AGMs rather than the
> > 1:1 floodie/AGM buddy pairs this poster proposed.
> ...


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## EVDL List (Jul 27, 2007)

> Morgan LaMoore wrote:
> 
> > But then you're keeping the AGMs on a constant float charge. That
> > would continuously waste power on the float current of the AGM.
> ...


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## EVDL List (Jul 27, 2007)

OK, another dumb newbie question:

If one were to try this, parallel strings with the deep cycle floodie string 
being somewhat higher voltage than the AGM string, what would be the impact 
on battery life and acceleration current capability of substituting floodie 
starting batteries for the AGM's with the floodie deep cycles holding up 
their charge?

Marty
----- Original Message ----- 
From: "Roger Stockton" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Wednesday, September 05, 2007 5:28 PM
Subject: Re: [EVDL] A123 Battery Feasibility




> > Morgan LaMoore wrote:
> >
> >> But then you're keeping the AGMs on a constant float charge. That
> >> would continuously waste power on the float current of the AGM.
> ...


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## EVDL List (Jul 27, 2007)

> Marty Hewes wrote:
> 
> > OK, another dumb newbie question:
> >
> ...


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

There is probabaly a very good reason EVs don't use hyrbid packs.
Try it and report some results. "it isn't hard", but one hell of a lot 
harder than typing a 2-minute email.

Jack



> Morgan LaMoore wrote:
> > Those aren't such big issues. Yes, it would need to know the state of
> > charge to keep the batteries safe, but no, it wouldn't need to know
> > the instantaneous current requirements from the drivetrain.
> ...


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## EVDL List (Jul 27, 2007)

What Morgan said 

Also, I was assuming you would want a BMS like a Rudman Reg on the
AGMs, which would handle the overcharge issue quite nicely.

--T

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

I believe the reason Bill suggested a small motor
controller between the two packs is that it's cheaper
and easier to get a 100A controller than a 100A
charger. If it were me, I'd just call up Rich Rudman
and order a PFC-xx and be done with it. What are the
continuous ratings of smaller motor controllers
anyway? While a Zilla 2K can put out 2,000 motor
amps, it only has to do it for a few seconds before
your car runs out of room 

- Steven Ciciora




> --- Morgan LaMoore <[email protected]> wrote:
> 
> > Those aren't such big issues. Yes, it would need to
> > know the state of
> ...


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## EVDL List (Jul 27, 2007)

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?
Or the cost to replace the floodies from running them harder instead?
Or the extra weight being accelerated with a big heavy charge pack?

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.

Jack




> Timothy Balcer wrote:
> > On 9/6/07, Jack Murray <[email protected]> wrote:
> >
> >>There is probabaly a very good reason EVs don't use hyrbid packs.
> ...


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## EVDL List (Jul 27, 2007)

Maybe I'm misunderstanding it, what was the purpose of that message, to 
repress innovation? Someone have a vested interest in supressing an 
inexpensive solution?

I have two comments in response:

Speculation is the doorway to invention. I never stop speculating because 
"There is probabaly a very good reason". To do so would stop all inovation. 
You could as easily say that "There is probably a very good reason" that 
there are very few electric cars (percentage wise) on the road today, so why 
bother? Maybe it hasn't been done because no individual organization has 
the brain power of all the people on this list, or because they aren't very 
interested in a less expensive solution because it's not their personal 
money they are spending on their more exotic solutions. Commercial 
development projects have their own limitations and agendas.

The fact that it is a lot harder (and more expensive) to try it than typing 
a 2 minute Email to try to draw on the experiences of the seasoned people on 
this list instead of each of us operating in the dark is the whole point of 
the list, isn't it? Am I mistaken here?


Some of us are newbies here. Personally I haven't gotten as far as 
installing batteries yet (far from it). I'm seeing that the current (no pun 
intended) choices are either slow (poor at supplying large current), short 
lived, or very expensive. I'd like to try to find a possible better solution 
before I build battery boxes. It looks like by combining technologies it 
may be possible to come up with a combination of inexpensive batteries that 
can provide acceleration and range. Load sharing resources with different 
characteristics to come up with a superior combination is commonplace in 
networking, power generation and hybrid drivetrains as well as many other 
disciplines. Why not here? It's kind of an interesting parallel between 
the gas/electric load share in a hybrid and the floodie/high current problem 
in a pure electric

So far we've had some very good contributions that seem to be getting us 
closer to a possible solution or two without anybody having to lay out a ton 
of cash on an ill fated approach. It looks to me like parallel strings of 
floodies and high current batteries (be they AGM, starting batteries or 
something more exotic) may be a real advantage.

Marty

----- Original Message ----- 
From: "Jack Murray" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, September 06, 2007 9:49 AM
Subject: Re: [EVDL] A123 Battery Feasibility


> There is probabaly a very good reason EVs don't use hyrbid packs.
> Try it and report some results. "it isn't hard", but one hell of a lot
> harder than typing a 2-minute email.
>
> Jack

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## EVDL List (Jul 27, 2007)

> Jack Murray wrote:
> 
> > There is probabaly a very good reason EVs don't use hyrbid packs.
> > Try it and report some results. "it isn't hard", but one
> ...


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## EVDL List (Jul 27, 2007)

> [email protected] wrote:
> > why not take a single sla and single flooded and try them in
> > parallel, measure [individually] currents into appropriate loads and
> > find discharge curves to foresee any problems. if they are 12V units
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> 
> > [email protected] wrote:
> > > why not take a single sla and single flooded and try them in
> ...


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## EVDL List (Jul 27, 2007)

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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## EVDL List (Jul 27, 2007)

So no one has heard of anybody (yet) buying 40 A123
(Dewalt) 36v packs for $5000 (yikes!) and running an
EV off of them....? (assuming 72v at about 50Ah for
around 1/2 hour of 100amp usage)

Imagine that. You look in the trunk and see a 5 by 10
array of the dewalts, upside down, plugged into a
panel of female receptacles, running the EV. BMS
indicates one went bad? No prob, just unplug the old
and plug in the new. Guess you'd have to have some
sort of retention so the buggers wouldn't pop out when
you hit a bump.

If the price ever comes down enough to around $50 per
pack, it'd be worth the money if you 1) had a good
BMS, 2) good charging system, and 3) got the expected
2000 cycles out of them. Even at current prices, it
is about a 7-fold life expectancy and ideally beats
out lead-acid for price-over-time and recharge time.

What say ye all?

Scott



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## EVDL List (Jul 27, 2007)

How about putting them all in a big fiberglass shell that looks like a big 
DeWalt power tool battery that plugs into a big socket in the trunk lid? 
That'd get some attention and get people thinking . Might get sponsorship 
from DeWalt .

----- Original Message ----- 
From: "S Collins" <[email protected]>
To: <[email protected]>
Sent: Thursday, September 06, 2007 2:15 PM
Subject: Re: [EVDL] A123 Battery Feasibility


> So no one has heard of anybody (yet) buying 40 A123
> (Dewalt) 36v packs for $5000 (yikes!) and running an
> EV off of them....? (assuming 72v at about 50Ah for
> around 1/2 hour of 100amp usage)
>
> Imagine that. You look in the trunk and see a 5 by 10
> array of the dewalts, upside down, plugged into a
> panel of female receptacles, running the EV. BMS
> indicates one went bad? No prob, just unplug the old
> and plug in the new. Guess you'd have to have some
> sort of retention so the buggers wouldn't pop out when
> you hit a bump.
>
> If the price ever comes down enough to around $50 per
> pack, it'd be worth the money if you 1) had a good
> BMS, 2) good charging system, and 3) got the expected
> 2000 cycles out of them. Even at current prices, it
> is about a 7-fold life expectancy and ideally beats
> out lead-acid for price-over-time and recharge time.
>
> What say ye all?
>
> Scott
>
>
>
> ____________________________________________________________________________________
> Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, 
> news, photos & more.
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>
> _______________________________________________
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> http://lists.sjsu.edu/mailman/listinfo/ev
>
> 


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## EVDL List (Jul 27, 2007)

> S Collins <[email protected]> wrote:
> > So no one has heard of anybody (yet) buying 40 A123
> > (Dewalt) 36v packs for $5000 (yikes!) and running an
> > EV off of them....? (assuming 72v at about 50Ah for
> ...


----------



## EVDL List (Jul 27, 2007)

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of S Collins
Sent: Thursday, September 06, 2007 12:15 PM
To: [email protected]
Subject: Re: [EVDL] A123 Battery Feasibility

So no one has heard of anybody (yet) buying 40 A123
(Dewalt) 36v packs for $5000 (yikes!) and running an
EV off of them....? (assuming 72v at about 50Ah for
around 1/2 hour of 100amp usage)

Imagine that. You look in the trunk and see a 5 by 10
array of the dewalts, upside down, plugged into a
panel of female receptacles, running the EV. BMS
indicates one went bad? No prob, just unplug the old
and plug in the new. Guess you'd have to have some
sort of retention so the buggers wouldn't pop out when
you hit a bump.

If the price ever comes down enough to around $50 per
pack, it'd be worth the money if you 1) had a good
BMS, 2) good charging system, and 3) got the expected
2000 cycles out of them. Even at current prices, it
is about a 7-fold life expectancy and ideally beats
out lead-acid for price-over-time and recharge time.

What say ye all?

Scott

Scott,

Michael T Kadie "KD" of this E-mail list has a website
http://ssi-racing.com that shows his 2SSIC DeWalt lithium powered kit
car, a 1965 Shelby Cobra Daytona Coupe. He replied the following to
this list when asked about his project:

"I'm using 96 torn down dewalt packs with custom balancers that engage
on every full charge. From testing <and on something smaller like a
motorcycle> it would be possible to keep them intact (you can't draw
more
than 50 amps per pack for sure) and then balance them using the dewalt
charger periodically. I would recommend that you check the voltage of
all your packs (I got between 2-3 bad dewalt packs out of approximately
110) and any that are off mark once balance with dewalt, put them
somewhere else charge discharge cycle maybe 10-20 times, measure again.
If one battery comes back high or low (say 1 volt above or below the
rest) 3 times I would probably look at changing it out. That should
give you a good feel for drift and an estimate for how often to balance
them. 
Note heat will change the voltage and charge dis-charge characteristics
of these batteries, so if you find one spot that is consistently high or
low it probably has something to do with temperature and you may need to
think about not having batteries there (simplest answer)."

KD puts the DeWalt packs in trays layered below the rear window in the
car. Check out his website and you can find pictures of the build, and
how he connects to the batteries.

For DeWalt powered bicycles, at least one builder uses the base of the
floodlight tool to attach to the frame, attach to the battery, and pick
up connections to the battery.

KD has taken the car to drag races, so you should be able to find
reports of how the car is progressing.

Alan



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## EVDL List (Jul 27, 2007)

Thanks so much for the responses!

Scott

p.s. Hopefully we'll be talking about using an UltraCapacitor in this group
one of these fine years.
-- 
View this message in context: http://www.nabble.com/A123-Battery-Feasibility-tf4357606s25542.html#a12534466
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

Would there be a way to stick an identical controller(at least in
topology) on each and set the current limit of the one on the floddies
to 200A and the AGMS to 600Amps. Would they actually have to be modifed
to make them parallelable?


Or a crude way, a curtis on the floodies and a shunt powering a
microswitch (reed switch attached to cable?) This in series with a
control relay that powers a contactor connecting the agm's directly to
the motor. It might be a rather abrupt boost.

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## EVDL List (Jul 27, 2007)

Making controllers parallelable sounds like a nightmare. What happens when 
the on periods overlap, and then don't? Although I'm sure two could be 
synchronized, for a price. Might be easier to use two controllers and two 
motors. I could see wiring the AGMs to the motor and using a controller on 
the floodies that feeds a couple hundred amps from the floodies to the AGM's 
during acceleration, maybe just a second pot on the pot box. 800 amps 
available during acceleration sounds like a good thing. Then use a separate 
battery charger to charge the AGM's off of the floodies, or maybe the same 
charger you charge them with anyway. That might reduce the need for a 
custom control box to manage it.

Personally, I'd still like to see what happens if a 156 volt string of 
floodies is simply paralleled with a 144 volt string of AGM's. The 
hysteresis between voltage under load and under charge of the AGM's might 
just straddle the floodie pack voltage. If I were at the point of buying 
batteries, I might just try it, but realistically I'm probably a year away 
from being there. Life, and ICE vehicle issues, keep interrupting the 
project. At the rate I'm going, I might be buying a Volt instead of 
batteries.

Marty

----- Original Message ----- 
From: "Jeff Shanab" <[email protected]>
To: <[email protected]>
Sent: Friday, September 07, 2007 8:09 AM
Subject: Re: [EVDL] A123 Battery Feasibility


> Would there be a way to stick an identical controller(at least in
> topology) on each and set the current limit of the one on the floddies
> to 200A and the AGMS to 600Amps. Would they actually have to be modifed
> to make them parallelable?
>
>
> Or a crude way, a curtis on the floodies and a shunt powering a
> microswitch (reed switch attached to cable?) This in series with a
> control relay that powers a contactor connecting the agm's directly to
> the motor. It might be a rather abrupt boost.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

> Marty Hewes wrote:
> > Making controllers parallelable sounds like a nightmare. What happens when
> > the on periods overlap, and then don't?
> 
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> > For the classic buck converter used for PWM EV controllers, the way to
> > parallel them is to use a separate inductor for each controller, and ten
> > run them *out* of phase so their on-times do *not* overlap. This does
> ...


----------



## EVDL List (Jul 27, 2007)

Making sure they do not overlap implies a combined duty cycle of 100% max 
though, right? So I'd think this would only make sense where you didn't 
want to pass a lot of power through both controllers at once, or if the 
battery pack voltage was so high that you'd never want to be on much over 
50% anyway?

Now if one controller was used to feed current from a deep cycle string into 
an AGM string, and another controller was used from the AGM string to the 
motor, interaction should be irrelevent, because the AGM string should be 
acting like a big cap (or accumulator)? But then the controller on the 
floodies is pretty much just being a battery charger? Might it make more 
sense to use one controller and one charger?

Marty

----- Original Message ----- 
From: "Morgan LaMoore" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, September 09, 2007 11:49 AM
Subject: Re: [EVDL] A123 Battery Feasibility




> > Lee Hart <[email protected]> wrote:
> >> For the classic buck converter used for PWM EV controllers, the way to
> >> parallel them is to use a separate inductor for each controller, and ten
> >> run them *out* of phase so their on-times do *not* overlap. This does
> ...


----------



## EVDL List (Jul 27, 2007)

> Morgan LaMoore wrote:
> > You don't *need* to make sure they run out of phase, though; it just
> > helps with noise. Two perfectly normal Curtis controllers should
> > parallel just fine if you put a big inductor between their output and
> ...


----------



## EVDL List (Jul 27, 2007)

Sorry for late response -- I just rescued my EVDL messages from my spam
folder  



> --- S Collins wrote:
> 
> > So no one has heard of anybody (yet) buying 40 A123
> > (Dewalt) 36v packs for $5000 (yikes!) and running an
> ...


----------



## EVDL List (Jul 27, 2007)

Wow! With silver at $0.373/Wh (w/o BMS), that's the cheapest LiIon
I've seen yet!

-Morgan

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## EVDL List (Jul 27, 2007)

> Wouldn't it be easier and cheaper to purchase the LionEV battery modules?
> 
> http://lionev.com/Battery_Orders.html


http://lionev.com/Battery_Charts.html

is a copy of Kokam's 200Ah datasheet.

I guess that's all about their product quality if they are not confident
enough to publish own data.


Marcin

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## EVDL List (Jul 27, 2007)

> http://lionev.com/Battery_Charts.html
>
> is a copy of Kokam's 200Ah datasheet.
>
> I guess that's all about their product quality if they are not confident
> enough to publish own data.

If Kokam is the supplier of their batteries that they assemble into
modules, then it seems perfectly reasonable to use Kokam's datasheets.

I wouldn't expect DeWalt to come up with their own datasheet for their
A123-based packs; I'd expect them to use A123's (with some
verification, of course).

-Morgan

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## EVDL List (Jul 27, 2007)

Kokam is not their supplier. That's first.
On their website they constantly describing cells as LiFP and using 3.2V
value as a nominal voltage. Kokam produces NCM with 3.7V nominal
voltage.
And third reason is the price. Too low to be reseller.

Marcin





> Morgan LaMoore wrote:
> > > http://lionev.com/Battery_Charts.html
> > >
> > > is a copy of Kokam's 200Ah datasheet.
> ...


----------



## EVDL List (Jul 27, 2007)

[No message]


----------

