Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

I don't think we can convince them to sell at $5 each at low volume.
However, we could get 10-20 people together to order at high quantities. In
a year or two, I'd be interested, and I'd expect that other people would be
interested now.

$7500 of batteries would be 11.5kWh with 96kW continuous power rating, and
it would only weigh 126kg.

Also, over the next few months, I'll be designing a Lithium-Polymer BMS for
school. I'll have to check whether it would be legal for me to release the
design or if it belongs to the school or something.

-Morgan
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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

< $7500 of batteries would be 11.5kWh with 96kW continuous power rating, and
it would only weigh 126kg. >

...but the specs don't show any welding tabs, so you'd have to add on
the price of creating connections, too. You can find Dewalt packs near
$100, and those 10 A123 cells will all have tabs (just not the kind
used in the Killacycle).

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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

That is getting close. I was expecting 5$ per by the end of the year.
(arn't these the M1 cells?)

So if I was ready with my BMS and was willing to put 5 packs on the
road, I could get the $5 per cell costs.

I really like the fact that the lifecycle chart shows 900 cycles to 80%
capacity At 100% DOD and at 20A. I realize this is because calender life
starts to come into play if they test slower and there hasn't yet been
enough years to give that data.

But I could imagine a group buy in the near future.

I was thinking 144 cells per module for 19.2V and 55ah, 17 modules per
vehicle for a 326V pack. This is 2448cells /vehicle.
They're cells are a lot heavier than A123's at 84 grams but that is 27
lbs of cells per module. figure at least 3-5 lbs for case and
interconnects and we are talking about 30-33 lbs/module, or about 561
lbs pack. figure $100 bms per module and $25 case and $25 interconnects
and we are talking a raw cost of $870/module or about 15K for such a
pack. Still a bit high to make a profit on, but getting closer.

The way I see it, since you get a true 55ah and can regularly go down to
20% SOC, and they weigh 1/2 the weight of the 50ah(c/20 rate) lead pack
this should about triple the range on any conversion. ie 3.2V2.4ah
-->2.5V.5ah scales to about a 290V avg across 48ah for about 14Kwh
(maximum) pack

@ 300wh/mile = 46miles
@ 250 wh/mile = 56miles

humm, Id like to get 100miles range.

reconfigure the modules to 12.8V 86ah and put in 24 modules. Now we are
talking about 870lbs and 21K pack with about 19kwh useable

@ 350wh/mile = 54
@ 300wh/mile = 63
@ 250wh/mile = 76

getting there.

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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

Dewalt packs are connected in series, not of much use for us. You can't
really cut them free and if you rotate them, the cell can be damaged.
But you could take say 24 such packs as is and interconnect each tab for
balancing and connect the + and _ for power to get a [email protected]

My plan is make 12 cell sub-modules (that can be replaced if necessary.)
12 of these submodules are in the battery module with bms and can be
interconnected either 6x2 or 4x3 for [email protected] [email protected] the
same electronics and case. (The case is re-useable, ie not permanently
sealed.)

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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

This welder will most likely damage A123 cells.

I did a tad of research and Bill Dube can definitely chime in here as he
actually has done welding but you need a short,controlled, and powerful
pulse thru the top of the battery to weld the tab on. A shorter pulse at
less power is actually more energy into the cell and it heats damageing
the active material or seal near the vent.

This is so critical with lifepo4 that the Miyachi ME35 is not
recommended as it uses the zero crossing detection of the provided 60hz
to be the minimum pulse which is like 16ms and 10ms is the upper limit,
mostly they are welded between 4 and 8ms.

the IP-217(need 3phase) is good end of life equipment and you want the
dual thinline head (positive and negative electrode side by side with
individual pressure control )

ebay 220148054354 is what the system looks like, but this is the
single head and ME-35

type in miyachi to get you going in ebay.
The transformers and controls ae easy to find, the heads are the
difficult part.


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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

What is the best way to make parallel-series packs out of Dewalt
packs? Does this very artistic sketch of mine make any sense?

http://www.havina.fi/dewalt.htm

What size the wire making parallel connections should be?
Any ideas how the packs should be physically placed to get as short,
safe and sensible connections as possible?

kiitoksin,
Osmo

P.S. Jeff, it would be easier to follow the threads if you keep the
messages you are replying to in your mails.




Jeff Shanab kirjoitti 12.9.2007 kello 15.01:

> Dewalt packs are connected in series, not of much use for us. You
> can't
> really cut them free and if you rotate them, the cell can be damaged.
> But you could take say 24 such packs as is and interconnect each
> tab for
> balancing and connect the + and _ for power to get a [email protected]
>
> My plan is make 12 cell sub-modules (that can be replaced if
> necessary.)
> 12 of these submodules are in the battery module with bms and can be
> interconnected either 6x2 or 4x3 for [email protected] [email protected] the
> same electronics and case. (The case is re-useable, ie not permanently
> sealed.)
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

I would expect that each DeWalt pack with its own BMS will do its
internal balancing, so I expect that you will get the best results
treating each pack as a black box - you would not even need to open
the original packs, so warranty is not even voided if you can find
a reasonable way to connect to the tabs of the complete pack.

With each pack as a module taking care of its internal balance, you
will only need to care for the total balance, like when having
multiple Lead-acid battery strings, you don't connect individual
cells (because you can't get at them) and even if you form high
power strings, it is advised to interconnect the strings with
thinner wires to allow a slight imbalance between strings to
accommodate differences in temperature and chemical mix and such.
The thinner parallelling wires will eventually balance the modules
without causing undue stresses on a particular module or its BMS.

In your drawing: keep all red wires, remove all blue wires and then
add a blue wire between the middle 3 red wires.

BTW, in order to reduce discharge differences between strings due
to different resistance from for example wire length differences,
you can best use the top left and the bottom right as places to
interconnect your 3 strings, not connect both sides in the middle
because then the middle string will suffer most deep discharges.

Hope this clarifies.

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Osmo S.
Sent: Thursday, September 13, 2007 8:56 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)


What is the best way to make parallel-series packs out of Dewalt packs? Does this very artistic sketch of mine make any sense?

http://www.havina.fi/dewalt.htm

What size the wire making parallel connections should be?
Any ideas how the packs should be physically placed to get as short, safe and sensible connections as possible?

kiitoksin,
Osmo

P.S. Jeff, it would be easier to follow the threads if you keep the messages you are replying to in your mails.




Jeff Shanab kirjoitti 12.9.2007 kello 15.01:

> Dewalt packs are connected in series, not of much use for us. You
> can't really cut them free and if you rotate them, the cell can be
> damaged.
> But you could take say 24 such packs as is and interconnect each tab
> for balancing and connect the + and _ for power to get a [email protected]
> module
>
> My plan is make 12 cell sub-modules (that can be replaced if
> necessary.)
> 12 of these submodules are in the battery module with bms and can be
> interconnected either 6x2 or 4x3 for [email protected] [email protected] the
> same electronics and case. (The case is re-useable, ie not permanently
> sealed.)
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

So it would be ten cells in series, three of those in parallel, and =

two of such SP-combinations in series? This way, parallel at Dewalt =

pack level and being able to use original BMS would certainly make =

things easier. But against Bill Dube=B4s advice to parallel at cell =

level though.

Osmo

Cor van de Water kirjoitti 13.9.2007 kello 21.56:

> In your drawing: keep all red wires, remove all blue wires and then
> add a blue wire between the middle 3 red wires.



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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

Where would be the fun in just buying them (actually, if I had the
money I would buy a set right now)
Just curious, Do you know how they balance them? pwm resistance shunt?

I think if I got to their production quantities, I can reach 1/2 their
cost at 8 to10 times the power level (read that again! 10xpower) This is
WAG
They would be heavier but also more usable on DC systems
They would allow for bigger cables.
They would be rebuildable and reconfigurable
They wouldn't have as much sag.
Just a different optimization point chosen.

I am hoping to have internal temperature control, full telemetry and a
isolated 12V/42V transfer buss between the modules during charge that
serves as a tapped pack with 12V avail for the legacy stuff and 42volts
that is becomeing the standard for the power steering.


Hey, Even if it does nothing but force valence to lower their costs it
would be a good thing.

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Re: [EVDL] Tesla batteries (maybe good news via Valence batteries)

> From the pictures those tabs look very similar to the ones on A123
> evaluation cells, which are rated for 100 A (continuous I think). But
> maybe those Dewalt tabs are thinner then, hard to say.
>
> Osmo

When I talked to A123 they said good for 70A continuous with 4 weld
spots. that you need double tabs to get over 100Amps

In my design, I was actually thinking of going smaller on the
interconnects. Here is the reasoning,

In each brick, I plan on 12 in parallel and the system will have either
3 submodules or 2 submodules in parallel

so at 24 cells in parallel and a 1000A discharge, we are talking only
40A/cell (2000A units avial as special order with signed waiver )
at 36 cells we are talking only 27A/cell.

It may be wise to notch the interconnect to blow at 75A for 1-2
seconds(fuses are this way) Maybe even make a fuse cover for when they
blow as part of a fuseable interconnect concept.

Any one shorted cell in danger of becoming a sub-ohm resistor across 23
highpower cells is taken out of the circuit in short order. The
telemetry would start showing a drop in capacity and you would be
entived to open it up where the problem would become quite obvious.


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