Battery Wiring

[Tarlak333]

Hello,

So I just got my Magnum Energy MS4448PAE Inverter/Charger and will be ordering 16 Crown CR430 batteries soon (2 strings of 8, 48V system). I don't think I will ever run this inverter to full capacity but I wanted to have some room to grow beyond my current needs. My question is what will be a good DC wiring setup for this system. I have looked into using copper plate and various types of wire between the batteries but I keep coming back to using 1/0 copper for each battery string, and 4/0 copper for the + & - trunk lines up to the inverter (all wire connections with 5/16" Bare Copper Terminal Lugs).

So I started second guessing my wire selection when I looked up a magnum 100A DC breaker (BR-DC100-BM) which states that it only accepts up to 6AWG wire. huh??? 6AWG is only rated for 37A on the American Wire Gauge chart. What is going on here?

Lastly I knew my 4/0 & 1/0 wire selection was overkill but I want to minimize losses...so in an effort to find the point of diminishing return on increasing the wire size I used the voltage drop calculator found at the link below. I seem to be happy with #2 for the battery strings and 2/0 for the trunk lines based upon the results.

Does this seem reasonable to you? ......and what the heck is up with only #6 on that 100A breaker...makes no sense to me based upon the American Wire Gauge chart.

Thanks

[Tarlak333]

Ok so I still have no idea where the amperage ratings for the various wire sizes on the American Wire Gauge chart come from but I ran my specs through a few different wire size calculators for battery banks. It looks like for a total length of ~20ft I should be at ~0.5% Voltage drop with 2 AWG on the main lines (~6ft) and 4 AWG (14pc @ ~8") for the battery connections.

Does this sound good with you guys?

Thx

[sensij]

The 100 A breaker can only be used on an 80 A circuit continuously, so 6 AWG isn't so far out of line. I think you might have been looking at an old data sheet though, I found one from 2010 that says 6 AWG, but one from 2013 says it is good to 0 AWG.

http://ressupply.com/documents/magnum/BR-DC75-100_Data_Sheet.pdf

2011 NEC wire ampacity (corrections and adjustments for temperature or more than three conductors in conduit not included here)

http://www.inw-training.com/joomla1/images/2008NEC/310.15B16.pdf

[solarix]

I use 2/0 wire (trunk and interconnect) for these inverters. You need to design for the surge rating of the inverter which can be way more than the continuous rating and you don't want the voltage drop in the wiring to cause the inverter to drop out during startup surges. 2/0 is rated at 175A ampacity at 75degC, a 4400W inverter may surge to double that which would be about that 175Amps.

[Tarlak333]

Thx for the info, I looked at the wire gauge specs again and as I had selected earlier I'm back to the #2 for the interconnect and 2/0 for the trunk lines and be within the 200% surge rating for the inverter. However if I can get a good price on the 2/0 and lugs I'll just run that throughout everything.

Also what size DC breaker should I go with since we're talking ~92A continuous and up to ~184A surge?

Thanks again.

[Amy@altE]

Read the manual for the inverter (page 18, Table 2-3). It recommends 2/0 wire and a 175A fuse or breaker.

[Tarlak333]

Thank you Amy@altE...I haven't opened the box yet and have been looking at the pdf manual, I must have skimmed over page 18. Because, yup, it's all there.

[Amy@altE]

The answer is usually RTFM