I plan on having a lithium battery bank sufficient for a few days of boondocking. In the event that the Sun stays hidden for several days and I need to top off my batteries, which is more advisable for the job? A DC to DC charger ($200-ish) where I just turn on my truck and I'm charging or a small inverter generator ($600-ish) that I'd need to unload, hook up, and get started (to say nothing of having to carry additional fuel and starting it every once and a while, and other routine maintenance.) OPINIONS ON ONE OVER THE OTHER.