[RE-wrenches] Sunny Island Battery Disconnects

[August Goers]

Hi William,



You might try reaching out to Roy Dyngen of SMA - he is a good contact for
these types of general questions. Email me off list if you would like his
contact info.



Is the SMA BATFUSE available in the US? Anyway, SMA has always recommended
connecting the negative of the batteries to ground when I called their tech
support line. As always, you would not fuse a grounded conductor so the
negatives wouldn't be fused. We've been using fuse blocks and fuses to fuse
our DC lines per one of my recent posts. It is certainly not the cleanest
way to provide over current protection but gets the job done and I think is
perfectly adequate. I typically fuse each string of batteries with a 175 A
fuse and use 2/0 wire. I think 3/0 is the largest that the terminal blocks
in the Sunny Island can handle -buried in the manual section 6.2.2 you'll
find that. A 175 A fuse allows for 6720 Watts of power (175 A x 48 v /
1.25) on the DC side or 8400 Watts before the fuse will blow and it
protects the 2/0. You will want to fuse each string of batteries before
combining them and running to the Sunny Islands.



I'll check out the products you've listed below and consider using them for
our next project as well.



Best,



August



*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *
william at millersolar.com
*Sent:* Friday, February 07, 2014 5:29 PM
*To:* 'RE-wrenches'
*Subject:* [RE-wrenches] Sunny Island Battery Disconnects



Friends:



I am reworking an installation with 3 Sunny Island inverters.  The battery
leads have no disconnecting means or OCP.  I have been looking for sensible
hardware to provide this and I have found some options.  I am interested in
any input on these or ideas I have not discovered.



1.       SMA BATFUSE.  I am having trouble deciding which one is right for
a 3 SI install.

a.       The B.003 appears to have fuse positions for the positive and the
negative leads.  I am fairly darn certain I don't want fuses in the
negative leads of a negative bonded system, and although this is my first
SI install, I am pretty sure this is negative bonded.  Am I missing
something here?

b.      The B.001 has only positions for two fuses as far as I can see from
the manual.

c.       So it looks like neither will work for me.  Does anyone have any
experience and/or wisdom here?

2.       Midnite Solar E-panels:

a.       The regular panel has DC and AC components.  I want to control the
AC elsewhere so I could order three slave units.  The Midnite unit mounts
right under the inverter but I would prefer to have the OCP closer to the
batteries.

3.       Outback:

a.       We could purchase an Outback FX1000 and install three breakers in
it.

4.       Breaker Size:

a.       I have started to read the manual but I have yet to find out what
size breaker fuse is recommended.  Have I just not found it yet?

b.      Also, I have not found a specification for battery cable size.  Am
I blind?



Thanks in advance.  I really appreciate the help I receive here.  I try to
give as well as receive.



William
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