Todd,
I have done it, a few times in my first years of doing this work.
Intermediate parallel interconnects went out of fashion because
they didn't seem to show any benefit. Yes, it gives you more paths
for current flow - but isn't that the problem to be avoided? A
single series string forces all cells to perform, given that the
string will be essentially only as strong as its weakest cell.
With several parallel strings, greater current flow and greater
work occurs in those strings with the least resistance to such
current flow. Intermediate interconnects allow current to more
readily select the path of least resistance, hastening the very
imbalance that the interconnects are trying to prevent.
Allan
Allan Sindelar
[email protected]
NABCEP Certified Photovoltaic
Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
On 4/29/2013 8:52 PM, [email protected] wrote:
this is probably a hair brained
question, but has anyone ever tried paralleling the
connections within the series strings?
yes, more cables, but might this
reduce the multiple parallel string unbalancing issues?
todd
On Monday, April 29, 2013 3:53pm,
"Wayne Irwin" <[email protected]> said:
The system is pre-existing. This is a battery
replacement only. I agree that fewer strings are best. The
8CS25 were the
most AH for the money.
However,
the 12 - 8CS 25's is a big step
up from the 32 - S530's (8
strings! and 96 holes to fill).
FYI. As
a case study, the S530 bank was 6yrs old
before showing signs of weakening
and could
probably keep
going at least
until
warranty exp.
Jan. 2014.
Cable's and terminals
were p retty clean, watered and eq'd regularly.
The 5 - CC design objective was to maximize efficiency and provide redundancy.
System seems to have worked
flawlessly for past 6 yrs. .
Supports a 3500sq'
Res/Farm with 1hp
well pump
for irrigation, AC
throughout home, pool, etc...
Wayne Irwin,
President
License
#CVC56695
State
Licensed Solar Contractor
Pure Energy
Solar International Inc.
[email protected]
http://PureEnergySolar.com
352 377-6527
Office
352
336-3299 Fax
352
316-1637 Cell
The content of this message is
Pure Energy Solar Confidential. If you are not the
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error, any use or distribution is prohibited. Please
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From: [email protected]
Date: Mon, 29 Apr 2013 14:37:50 -0700
To: [email protected]
Subject: Re: [RE-wrenches] 24V Rolls Charging Parameters?
Wayne,
In the first place, 4 parallel strings of anything is
a very bad idea. Micro resistances in cabling and
connections plus eddy currents and the like will, over
time, inherently unbalance the pack. Doing frequent EQ
charges will be required but will not overcome the
inherently bad design of too many parallel strings. If
you want to stay with Surrette, one string of 24
2-YS-31PS will give you about the same capacity in one
tasty, electrically happy string. Lots more money, I get
that, but that would be the ideal situation. As a
fallback, do yourself a favor and spec out 12 of the
4KS-21PS so that you have just two parallel strings.
Should even be a little less dough.
Jamie Surette ( [email protected]) is
usually pretty good at returning emails and calls. His
would be, without doubt, your best opinion as to a
proper charge regime for his batts. Good Luck. If you go with four strings, you'll need
it.
bob-O
On Apr 29, 2013, at 2:15 PM, Wayne Irwin wrote:
Hello
Wrenches,
Please provide
your opinions
on the proper charging voltages (e.g.
bulk,
float, eq,), and
recommended durations.
The
bank consists of 12 - Rolls
8CS25P (820AH @ 20hr rate)
(4 strings of 3). Design based
partly on budget
limitations.
FYI. The
system is
off grid and consists of an 8KW
array, 2 -
OB VFX 3524 Inv's. and 5 -
OB MX80
CC's.
I
have general parameters programmed
based on AH's but
would like to have
additional
opinions/suggestions
to compare
and/or see
if there is something
that I have
missed.
I have not yet received any
feedback from
Rolls tech
support .....
James?
Thanks
in advance for
your help,
Wayne
Irwin,
President
License
#CVC56695
State Licensed Solar Contractor
Pure
Energy Solar International Inc.
[email protected]
http://PureEnergySolar.com
352 377-6527 Office
352 336-3299 Fax
The
content of this message is Pure Energy
Solar Confidential. If you are not the
intended recipient and have received this
message in error, any use or distribution
is prohibited. Please notify me
immediately by reply e-mail and delete
this message from your computer system.
Thank you.
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