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:* [email protected] [mailto: [email protected]] *On Behalf Of * [email protected] *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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