April 19, 2022

TT# 130 Battery Replacement: Solving the “Which Cable Goes Where Questions”

By: Rob Lowe

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A frequent question from Motorhome owners is: "How do I replace the coach batteries in my RV and keep the cables organized and properly connected?”

This question arises since most larger coaches have four (4) six-volt batteries connected in what is known as a series-parallel format. What this means is that positive terminal of one pair of batteries is connected to the negative terminal on another six-volt battery, so the battery voltage is added together. Measuring the voltage from the open positive battery terminal to the remaining open negative terminal will result in a voltage reading of that pair of batteries of 12 volts (6V+6V=12V). If a second pair of similarly connected 6V batteries are added in a similar fashion with the two open positive terminals interconnected and the two negative terminals are also connected together, then you have what is known as a series-parallel battery connection. In this type of arrangement, it is critical to have each battery connection properly connected, to ensure that the RV coach system receives 12 volts and that there is the battery storage capacity to power the coach for a reasonable length of time. Replacing batteries becomes a chore since misplacing       even one connecting cable will result in potential problems.


Marking Each Battery CableI found a handy way to permanently label the battery cables is to buy a bag of small wire ties with four bunches of them in at least or four colors (say as an example red, yellow, green and blue). I recommend using the red and yellow on the positive terminals and the green and blue on the negative terminal connections. Start by labelling each battery by using an indelible marker with the number ‘1’ and increase as you move across the bank, ending at ‘4’ (see the circled numbers written on batteries in the photo). For the first positive terminal choose a (say) yellow tie and wrap it around the cable near the connection. Follow that cable to where it terminates and attach the same color (yellow) tie to the other end and add one of the same (yellow) color. On the negative terminal of the first battery select a (say) green tire and wrap it around the cable connected to that terminal then follow it to the other end and if it is on another battery wrap another tie of the same color then add another identical colored tie. For all the cables on a single terminal attach a wire tie to each wire using the same color wire tie. As you proceed from battery one to four change the color and increase the number so that there are more ties as you move (say left to right). Take a photo and prepare a written 'map' of the batteries showing the orientation of each battery and include any factory applied labels on your map to make it easy to trace and helpful to match up with any schematics or factory supplied documents relating to the batteries and connections.  Battery 'Map'

The wire ties stay attached and (unless you are color-blind) this approach makes it easy to document where the cables go, and which cable attaches where in the big scheme of things.



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