First let me say, two 6 volt batteries in series will not have more energy than one 12 volt battery with the same amphour rating. Wiring batteries in series still gives the same amphour rating as a single battery since the same current flows through both batteries. Energy (in watthours) = amphour rating × voltage, and since both setups have the same amphours and same voltage, each has the same energy in watthours.
Therefore if you want to increase your battery energy and you have room for two batteries, your best bet is to wire two 12 volt batteries in parallel. That will double the amphour capacity and thus double the energy in your battery setup. One caveat is that since in this setup there will be two paths for charging current to flow, it's possible that over time, one battery could become undercharged compared to the other. There are two ways to detect if this is happening: one is to take and compare specific gravity readings of the acid in the two batteries. If they differ then one is undercharged or failing compared to the other. The other option is to disconnect the batteries from one another and read each one's voltage with a meter. If they're not close, one is undercharged or failing.
First let me say, two 6 volt batteries in series will not have more energy than one 12 volt battery with the same amphour rating. Wiring batteries in series still gives the same amphour rating as a single battery since the same current flows through both batteries. Energy (in watthours) = amphour rating × voltage, and since both setups have the same amphours and same voltage, each has the same energy in watthours.
Therefore if you want to increase your battery energy and you have room for two batteries, your best bet is to wire two 12 volt batteries in parallel. That will double the amphour capacity and thus double the energy in your battery setup. One caveat is that since in this setup there will be two paths for charging current to flow, it's possible that over time, one battery could become undercharged compared to the other. There are two ways to detect if this is happening: one is to take and compare specific gravity readings of the acid in the two batteries. If they differ then one is undercharged or failing compared to the other. The other option is to disconnect the batteries from one another and read each one's voltage with a meter. If they're not close, one is undercharged or failing.
Hope this helps.
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