Three methods/systems can be used to charge the lithium battery in your RV: solar power, a DC to DC charger, or a converter-charger, like those made by Progressive. So can you wire a 90 amp hour lithium battery with, say, a 160 amp hour lithium battery made by another manufacturer? You can, but not if they're different chemistries, meaning you can't connect a 12 volt LiFePO4 battery with a 24 volt LiMn2O4 battery. Going lithium is a very worthwhile investment, but only for those who camp extensively off-grid. If your truck camping experience involves hopping from one RV resort to another, then going lithium would be a total waste of money. You'll be better off getting a couple.