So, if you want individual fusible cells, then a bus bar on both
terminals won't work. One side can be spot welded but the other side
needs the fuse wire - or something. Not sure how that could be done in
this model. Does Tesla really have each cell fused?
Part of my idea is to make each module easy to connect and swap out, if
needed. Also easy to pack into a tray.
Peri
------ Original Message ------
From: "Dennis Miles via EV" <ev@lists.evdl.org>
To: "Lee Hart" <leeah...@earthlink.net>; "Electric Vehicle Discussion
List" <ev@lists.evdl.org>
Sent: 19-Aug-14 5:29:00 PM
Subject: Re: [EVDL] CALB bolt terminals getting hot -
The cells in the TESLA pack are a group in parallel then the parallel
groups are wired in series for the desired voltage, The key to pack
survival when a cell fails is a fusible link (Correctly sized short
length
of wire) in series with each and every cell then any malfunctioning
cell is
isolated when the link opens. (Reducing pack capacity about 2%.)
Dennis Lee Miles
(*evprofes...@evprofessor.com <evprofes...@evprofessor.com>)*
* Founder: **EV Tech. Institute Inc.*
*Phone #* *(863) 944-9913 (12 noon to 12 midnight Eastern US Time)*
*Educating yourself, does not mean you were **stupid; it means, you are
intelligent enough, **to know, that there is plenty left to learn!*
* You Tube Video link: http://youtu.be/T-FVjMRVLss
<http://youtu.be/T-FVjMRVLss> *
* NEW You Tube Video link: *http://youtu. be/Pz9-TZtySh8
<http://youtu.%20be/Pz9-TZtySh8>
On Tue, Aug 19, 2014 at 7:32 PM, Lee Hart via EV <ev@lists.evdl.org>
wrote:
Peri Hartman via EV wrote:
To take this to a traction pack, I would want to try a similar
design
where strings of cells are spot welded in parallel for the desired
current load. As I understand it, you can put as many in parallel as
you
want and control them with a single BMS unit.
Well... There are those that believe this, and it is certainly done.
However, think about failure modes: Sooner or later, a cell will
fail.
What happens if one of the cells in parallel shorts? All the rest
will dump
all their stored energy into that one shorted cell. That is very
likely to
result in a burst cell or even a fire. And packed like this, once one
cell
starts burning, it can set the rest on fire.
When laptop manufacturers connected their cells directly in parallel,
there were some dramatic failures and fires. Since then, reputable
manufacturers are using cells with *internal* fuses and safety
devices.
Hobbyists and el-cheapo manufacturers aren't likely to use such
cells.
--
The principal defect in a storage battery is its modesty. It does not
spark, creak, groan, nor slow down under overload. It does not
rotate.
It works where it is, and will silently work up to the point of
destruction without making any audible or visible signs of distress.
-- Electrical Review, 1902
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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