Oh, yeah for the charging the 20v batteries i still go through the inverter too. I havent approached charging them from 12v to 20v yet.
Now that i think of it, it wouldnt take much more amperage than a laptop, so one of those 12v-20v Converters should work, but i haven't tried it out yet with the 20v batteries... https://steemit.com/off-grid/@jackdub/tech-talk-get-more-power-out-of-your-off-grid-system-with-single-voltage-conversion