Yes.... but...
I have 3 sets of 6v and 480w solar panels...
Right now, in Bend, OR yesterday and today I've had to run the Gen due to clouds/rain etc.
I'm sure others will chime in here, but adding another battery will basically just delay it a little bit...
I would recommend getting a Gen as a backup. Solar won't help much if in trees/snow/clouds etc.. and the extra battery might last another day or two, depending upon your use...
Hope that helps a little..
... and there are some who can probably use a flashlight battery and live off that for a week...
Depends on your usage...
good luck.