Battery inter-connect sizing

[madlabs]

Hi All,

Getting close to switching over to 48V from 12V system. The new inverters are on the wall and I am starting to trudge through wiring the whole mess up.

Anyhoo, I will have 8 * 6V golf cart batts. Eventually there will be 3-4 similar banks in parallel. What size should I use for the battery inter-connects? Seems that 2/0 should be enough. Please don't tell me I need 4/0 like I ran to the inverter.

Jonathan

[thirteen]

Just wondering what are you going to use for a charging system?

[bart]

  Each battery cable is going to pull the same amps as going to the inverter. Until you get the other strings up. I went ahead and made up my interconnects the same as to the inverter, 4/0. Just that much less of different extra stuff to deal with and it is all the same.   Made the interconnects 2' long so that when I get rich and famous and can afford bigger batteries, they can be utilized on those.

[birdhouse]

i'd stick with the 2/0.  as of current, it will be undersized with just your eight batteries, but after another eight are added it will be perfect. 

do you plan on running the inverter full bore with just the eight batteries?  if so, that may cause issue with 2/0, but once you get 16 batts, the 2/0 will probably be a bit overkill. 

i ran 1/0 copper with 8 * 6v with a 24v system and an 1800w inverter, and the inverter has never tripped out due to not enough juice. 

what inverter are you running? 

adam

[madlabs]

I have two 4400W MagnaSine inverters. I don't plan on trying to use them at anything near full power, the batteries wouldn't do it regardless of cable size.

So, if I was to run one inverter at full capacity, that would be 91 amps. Over a run of 5 feet or so {less really, I can get the batteries closer) I would have a voltage drop of .15%. .30% if I did try to run at full power (although we all know the inverter's LVD would kick in if I tried).

So, I think 2/0 is ok. But then I thought it would be OK up to the inverter as well and was told I had to use 4/0.

Thanks!

Jonathan

[XeonPony]

you can devide the total amps by the number of strings you have.

For example, my battery bank at 12v was designed to have 4 parallel strings of 2 series running a 2Kw inverter (1800w cont)

(((So 2Kw*1.15) = 2300 / 12V) = 192A / 4) = 48 A per string now rarely I will ever draw 2 kw hell I rarely go much above a Kw so I can safely divide that 48 by 2 so 24A per string, 8 guage will handle that no issue.

So all my strings are don in 8 gauge, all wiring is exact down to the mm, I use collector boxes so every string used exactly 4 feet to the collector box, the collector box then goes 2 feet to the inverter via 2 gauge, and then from the collector box it goes all so 0/1 gauge to the charge controller and load.

this ensures equal charging and load sharing.  No your problem is unless you have all parallel strings ready to rock you got to size it for the battery strings you have now, plus side is your wiring will be way over sized!

So inverter to the main buss 0/4, each battery string to the main buss can be low as 2 gauge with the full compliment of batteries, with out the full compliment of batteries 0/2 will have to be used, and you need to keep all lengths exactly the same

Up to now I have run a full sized coffe pot/ Electric heater, vacuum cleaner, with my inverter and never an issue and no wire heating and all batteries where dead equal last hydrometer test which was yesterday!