Originally Posted by f150k
I have two 12 volt batteries in our 5th wheel. They are on either side of the front storage bay, each positive lead goes to a single post ( same post) on a 30 amp circuit breaker and than to a disconnect switch and than on into the camper system. Both batteries negative cables are grounded to the camper chassis, is this ok or should they have run the wiring some other way?
To ensure even charging and discharging, the total resistance (wires and internal resistance) from the charging source to the positive terminal of the battery bank; through the bank (or cell) to the negative terminal; to Frame Ground must be identical. Now, in your setup the split to the two batteries begins at the post of the 30 amp breaker (CB) and ends at the Frame.
In order to keep the current flow to the two batteries identical the wire lengths from the CB post to each battery must be equal and the length of the ground wires from the ground battery post to the frame must be equal.
Since your system has two different grounds, you must be very diligent to make sure the ground connections of both batteries are good. Rust can increase resistance at the ground connection and isolate one of the batteries without any indication to you (except decreased capacity). It will just work the "good ground" battery much harder while allowing the other to "loaf."
While all that may not seem like a big deal, remember that deep cycle battery life is determined by the number and depth of each charge/discharge cycle. If one battery is being discharged deeper than the other continuously, that battery will need replacement before the other one. Since they much be switched out in sets, you will not get full usage out of the "loafing" battery".
You might think you can rotate the batteries through the two "stations" but once they get "out of sync" the weaker battery will continue to be over worked and the stronger one will continue to loaf due to increased internal resistance in the weak battery.
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