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Tip 2a Off-Grid Battery Bank Topic: Battery Cables

Battery cables


Tip #2 Design your own Cable scheme

You won't likely be accomplishing this with a pair of scissors, so break out your sharpest blade, grinder, or precision cut-off saw and let's get to work!




If you are working with a 48v Battery Bank, arrange the battery bank in a manner that will facilitate all cuts to be as short and direct as possible. There are no long connections in a 48v Battery Bank.

In a 12v Battery Bank, it is preferable to have the negatives and positives connected in a solitary un-cut cable.

The same goes for a 12v battery bank that is comprised of 6v Batteries (the series connections would be the only short cuts, i.e. 2 x 6v = 12v, your series cut would be located between the two 6v batteries with the longer non-cut cables comprising your parallel cable cuts.


After having chopped the connectors specified in Tip #1 clean off both ends and get a measurement leaving a slight allowance for movement on the parallel connections (none for the series connections).



Be careful while assessing your Battery Cable-cuts.


It's true, 12v electricity is eons safer than the grid electricity.

However handling batteries unsafely can hurt or kill you. I would love to divulge a couple of true-life examples here, but fear of our present economic system (codes, judiciary, etc.) keep me mute (despite the fact that a true-blue history of just how dangerous some batteries can be would be advantageous for an evolving world).




Photo of Deep Cycle Battery BankPhoto of Battery Bank





Onward!



One template cut for your SERIES battery connections and one template cut for your PARALLEL.


A.) When cutting for series connections, make the cables as short and direct as possible.


The series connections are generally clear from the service cell-caps so having slack in the series connection would be of little practical use.



B.) When cutting for parallel connections, keep the cables as long as possible to catch through as many terminals as possible.

Make the cables start from the first connector, T H R O U G H to the farthest battery connector your cable will reach, stripping off the protective jacket to allow for any intermediary terminals that your cable will contact.


Less cuts on the parallel cables equates to less energy loss, and minimizes other potentially detrimental variables.




These batteries are actually made by Dekka.



The argument for custom-cut cables isn't just an argument for safety's sake,

or that it looks neater,

or that the result are a more-efficient battery bank.



You are also gaining the least cost per lifetime by making your own cables.




Off-Grid Use


The photo above shows two 48v batteries each comprised of 8 x 6v batteries. The orienation of the batteries is not optimal, but allows for the wind turbine and solar inputs to be located at a central end. In the optimal orientation the 48v battery bank would be 8 batteries in a straight line. In the orientation seen in the photo above, notice that there is one series cable that is not congruent with the size of all the other series cables (seen near the purple Trojan batteries).



When these 16 batteries were setup to comprise a massive 12v battery bank, the longest cable that could be located here was only long enough to span 3 of the 4 parallel batteries, then hopped to another 8 6v batteries which were also connected in series to 12v.

In the 12v scenario, a stretch of cable was required to be doubled-up on the final terminal, and resume for yet another unadulterated stretch (just to hop over to the last remaining 12v battery.


The problem arises when the available cables are too short. If this happens to be the case, make absolutely certain to always keep the cuts to the back of the battery bank (away from the power-inputs and away from the power outputs or inverter connections). This will be your weakest link.


In other words, the end that receives the solar or wind-generated power should be connected to the longest continuous stretch of cable at terminal 1, then through terminal 2, then (in my case) terminating at battery terminal 3.



For instance, terminal 3 jumping to terminal 4 could become a hotpoint if the energy coming into the battery bank is located at terminal 4 instead of terminal 1. Terminal 4 in this scenario is the end of the battery bank, which is where any deviation from an otherwise perfect battery cable-length ought to be placed.

By doing so diminishes any possibililty of great heat building up due to shrinking of wire, unnaturally loosening of bolts, and other supernatural occurrences, etc.



As a final note, if you see burned (odd-bright colors), blackened, or greasy wire, these are signs of damage and the cable should not be relied upon.

Find another purpose for the damaged cable.

The reason you might find burned or blackened wire is due to overcharging, or a short-circuit, or some other problem and a permanent remedy should be sought.







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