Originally Posted by MikeInColo
Just trying to get my head around why your switch enables you to use the first *or* second battery? I understand off/on but why would you want to only use one or the other battery singularly when using with an RV?
This will be required if you have two batteries that were not bought and placed in service at exactly the same time.
This way you can charge each battery individually and when in use get all that each is able to give.
When pairing batteries that are different in age, internal resistance, cycle life (place in service date and number of actual charge discharge cycles)) , or manufacture, one battery will be the "stronger" battery and one will be the "weaker" battery. The batteries will not charge properly; one will work much harder than the other; and both will operate at reduced capacity. Eventually both will fail much earlier than if they were used individually.
Battery pairs must be changed out at the same time. When you want two batteries in your camper, they need to be as identical as possible.
IF you can't do that for some reason, using a selector switch to use them one after the other is your only choice to get maximum life from your house batteries.
Practical considerations : BATTERIES AND POWER SYSTEMS
Deep Cycle Battery FAQ
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