As long as your consumers don't share a common earth, then yes you can.
20 12V batteries is in the order of 240V, so it's a mystery as to what you are doing though.
I'll give you an example of why it might not be a great idea though :
When we got our boat, it had 2 24v banks comprised of 4 6V batteries. The 12V supply for the boats electronics was tapped from half way down the bank. What this did was make sure that the bottom half of each bank discharged faster and deeper than the top half of the banks. When charged with a 24V charger the batteries never properly charged or equalized, and so we used to go through a set of batteries every year or two. Batteries that don't last their rated lifespan generally don't die, they are killed.
By using a 24V to 12V dc to dc converter and removing the mid-bank taps, we've gone from 1-2 yearly battery replacements to 5-7 years. Battery strings don't like uneven charge/discharge, and using a 48V charger to charge banks you are going to pull 24V & 12V from is likely to cause you a world of hurt.