If you add a 12V battery in parallel with one segment of your 24V system, you will not get more run-time because the system will be dependent on the 12V battery that doesn't have anything in parallel with it and the solution would be to get two 12V batteries so you can parallel the whole thing and get more run-time.How do I add a 12 Volt battery to a 24 volt series connection?No. It will actually create a hazard. Connecting a 12 V battery that is the same size as the original battery to each of the original batteries (parrellel) would be OK. Best bet is to replace original 2 bateries with larger 12 volt (higher amp hour rating) batteries.How do I add a 12 Volt battery to a 24 volt series connection?No,the battery shouldn't add back up time of the Inverter..
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