not enough cash

[m gol]

Hello,

Looks like I'll have the funding to get the $5K battery welder.

But not sure I'll have enough money to make a 100ah 144v A123 pack.

If I do a 72volt 100ah pack made up of A123 cells and connect it to a 72volt
pack made up of TS100's...

does anyone see any issues? Would I be better off make a 144volt 60ah (a123)
+ 144volt TS60's

Thanks,

Mike Golub
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[Mike Nickerson]

How are you planning on connecting the bank of A123 cells with the bank of
TS cells (72v of each)?

Are you thinking about connecting them serially to have a 144v string?  This
seems like it would be a problem because of the large differences in device
characteristics between the two types of cells.  The A123 cells can provide
way more current than the TS cells.  If they were connected in series, I
think you would severely stress the TS cells.

I'm assuming that the 144 volt strings of 60 ah batteries would be hooked in
parallel.  This seems like it might work better, but I still wonder if it
would have problems.  The string of batteries with the lowest internal
resistance (the A123s I think) would take the bulk of the load.  I don't
know how well the TS cells would provide backup to them.  I think this might
stress the A123 cells.

Please keep in mind that I have some basic electronics theory, but no
practical experience with any of these systems, yet.  However, all my
training says that life is MUCH easier when all the batteries are as close
to the same type / specs as possible.  It might be possible to get fancy,
but it's also possible for more stuff to go wrong when you do.

Mike


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of m gol
Sent: Monday, November 09, 2009 8:44 PM
To: Electric Vehicle Discussion List
Subject: [EVDL] not enough cash

Hello,

Looks like I'll have the funding to get the $5K battery welder.

But not sure I'll have enough money to make a 100ah 144v A123 pack.

If I do a 72volt 100ah pack made up of A123 cells and connect it to a 72volt
pack made up of TS100's...

does anyone see any issues? Would I be better off make a 144volt 60ah (a123)
+ 144volt TS60's

Thanks,

Mike Golub
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[Morgan LaMoore]

On Mon, Nov 9, 2009 at 9:43 PM, m gol <[hidden email]> wrote:
> ...
> If I do a 72volt 100ah pack made up of A123 cells and connect it to a 72volt
> pack made up of TS100's...
>
> does anyone see any issues? Would I be better off make a 144volt 60ah (a123)
> + 144volt TS60's

Hi,

72V TS in series with 72V A123 will only have the performance of
Thunder Sky (although slightly better voltage sag), and you'd need a
very good BMS to handle it.

You will be much better off with 144V A123 60Ah in parallel with 144V TS60.

Actually, I suggest Sky Energy over ThunderSky because Sky Energy has
the same charge/discharge voltages as A123, while TS is higher
voltage.

However, you will need a separate BMS for each battery pack. Also,
because A123 is more powerful, it will tend to provide more power at
first, so it will empty before the TS has a chance to be used much.
That means your car will be very powerful at first but will lose lots
of power part-way through the charge.

I've been thinking about such a pack, and I think it would work best
with separate contactors and amp-hour contactors for each pack. You
could use just ThunderSky for most of your driving and turn on the
A123 booster when necessary. I would probably write software to
automatically do this, but you could have a manually controlled
switch.

Where do you plan on getting the A123, just from the e-bay sellers?

-Morgan

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[m gol]

a123 supply looks like ebay,, any other suggestions?

the problem is that ts60 vs ts100 weigh more per watt.

On Tue, Nov 10, 2009 at 3:03 AM, Morgan LaMoore <[hidden email]> wrote:

> On Mon, Nov 9, 2009 at 9:43 PM, m gol <[hidden email]> wrote:
> > ...
> > If I do a 72volt 100ah pack made up of A123 cells and connect it to a
> 72volt
> > pack made up of TS100's...
> >
> > does anyone see any issues? Would I be better off make a 144volt 60ah
> (a123)
> > + 144volt TS60's
>
> Hi,
>
> 72V TS in series with 72V A123 will only have the performance of
> Thunder Sky (although slightly better voltage sag), and you'd need a
> very good BMS to handle it.
>
> You will be much better off with 144V A123 60Ah in parallel with 144V TS60.
>
> Actually, I suggest Sky Energy over ThunderSky because Sky Energy has
> the same charge/discharge voltages as A123, while TS is higher
> voltage.
>
> However, you will need a separate BMS for each battery pack. Also,
> because A123 is more powerful, it will tend to provide more power at
> first, so it will empty before the TS has a chance to be used much.
> That means your car will be very powerful at first but will lose lots
> of power part-way through the charge.
>
> I've been thinking about such a pack, and I think it would work best
> with separate contactors and amp-hour contactors for each pack. You
> could use just ThunderSky for most of your driving and turn on the
> A123 booster when necessary. I would probably write software to
> automatically do this, but you could have a manually controlled
> switch.
>
> Where do you plan on getting the A123, just from the e-bay sellers?
>
> -Morgan
>
> _______________________________________________
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>
>

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