time2roll wrote:
Only reason to go 200 would be the 300 does not fit.  I believe it is best to have a single unit when possible with lithium.  Although if you have a large inverter you may need multiple to have sufficient continuous amp rating.
Foe dimensions:  (shop around) 
https://www.lithiumion-batteries.com/products/rv-lithium-batteries/12v-300ah-lithium-ion-battery.php
Based on the dimensions, I think that would fit, but I don’t want to spend three grand on a battery.  The 200ah are in the 12 to 1400 range.  I think that will do what I need.  I just need to something to keep the fridge running for the day if we’re away from the motorhome.  If I’m there I can run the generator.