Is there a way to charge deep cycle batteries with free energy besides solar?

I want to set up some rechargeable batteries to allow for lighting and a small refrigerator. I don't want to use solar to charge them. Is there another easy way to keep them charged with free energy?
Update: I don't mean free as in won't cost me anything at all or not cost me time and personal energy. I mean free as in no cost for being on the electric grid. For me it is not about saving money, I want to be able to generate power without visible proof that I am doing so. For example, no solar panels or wind... show more I don't mean free as in won't cost me anything at all or not cost me time and personal energy. I mean free as in no cost for being on the electric grid. For me it is not about saving money, I want to be able to generate power without visible proof that I am doing so. For example, no solar panels or wind turbines that people can see. Any other ideas?
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