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Battery Bank Wiring


mz-Blue

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Hi 
 
I would like to know what the optimum configuration would be for both 6 and 8 batteries would be for a solar 12 v battery bank. The batteries are all 12 volt  and 75 Amp hour each and the output should be 12 volt. Below is the setup from your site indicating how to wire 4 batteries.  
 
Also what size wires should I use for this setup and where should I place the fuses and what size is optimal
 
 
 
Also using your method 4 could you please provide me with a wiring diagram for the above mentioned 12 volt batteries that are 75 ah each.. Also what gauge should the wires be for joining them. Should there be a fuse in the system? this would hook up to a 1500W inverter and I asssume that I should have an fuse both before and after the batteries. The Solar panel is 480 watts at 24 V. The Charge Controller converts this to 12 volts so it would produce 40 amps as a max when it reduces it to 12 volts. 
 
 
 
 
 
So, thanks to a colleague, we can also present another wiring method that achieves perfect battery balancing...............
batt_new_2.gif
Method 4
And here it is.
This looks odd but it's actually quite simple. What has been done here is to start with 2 pairs of batteries. Each wired in the proper "cross diagonal" method. Then each pair is wired together, again in the cross diagonal method.
Notice that for each individual battery, the current always goes through a total of one long link and one short link before reaching the loads.
This method also achieves perfect balance between all 4 batteries and may be easier to wire up in some installations. Many thanks to "smileypete" from www.canalworld.net/forums for this idea.


 

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The easiest way to wire a large bank such as 6 or more batteries would be to use busbars. At 75Ah each battery is fairly small so 25mm2 would be fine for the cabling from battery to busbars. Keep all the cables at about the same length and as short as practical  

Like method 3 on the SmartGauge site:

http://www.smartgauge.co.uk/batt_con.html

A 300A fuse wired to the output of the +ve busbar would work for a 1500W inverter.

Does that help?

Edited by WotEver
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Thank you for your quick reply.  Yes it does help. I have looked all over my town for a busbar and they are really hard to find. The best I can find is a busbar rated at 210 amps which has 4 terminals on it. I assume that I can join two batteries to each terminal and then use the 4th one to connect to the inverter.      

Below is the link to the specifications.

fetch.php

Given that the busbar is only 210 amp , will I have problems as you suggest an 300 amp fuse?  Do you know the formula to use to calculate the amperage that it will generate. Is it the batteries or the inverter who will generate the amperage?

I currently have 4 gauge wires that I had hoped to use they are in fact only 21 mm. am I at risk here?

Also before the battery bank in the feed from the charge control. I assume an 40 amp fuse will be appropriate?

 

Thank you kindly for taking the time to help me with my design.

 

Cheers

 

Mike

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Hi Mike. The maximum current drawn will be circa 150A, when the inverter is running flat out. Therefore your 210A busbar would be fine. Yes, you can double-up on those studs and in fact you'd need 3 connections to each: Batts 1,2,3 - Batts 4,5,6 - Batts 7&8+Inverter. The solar controller could connect to the smaller post and should be fused at something like 60A (or as mandated in the user guide). 

21mm2 will be fine. 

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