Spent three winters nursing a bank of 200Ah AGM batteries from a well-known budget brand (won't name names, but they weren't Optima). Constant desulfation cycles, never quite hitting the claimed capacity by year two, and that familiar sag when I ran the kettle at dusk. Fed up with babying them, I made the switch to a pair of Fogstar Drift 100Ah LiFePO4 units wired in parallel — so 200Ah nominal but genuinely usable.
The difference was almost embarrassing. I'm pulling a solid 180–190Ah before the Victron SmartShunt even blinks, compared to maybe 120Ah of actual usable juice from the AGMs at their best. Charging via a 400W panel array through a Victron SmartSolar MPPT 100/30 and the whole system just... talks to itself now. Victron-to-Victron comms via VE.Direct is one of those things you don't know you're missing until you have it.
The one thing I wasn't expecting: how much faster the lithiums charge. Same solar array, but the absorption phase is tiny compared to AGM. On a decent October day I'm back to 100% by early afternoon rather than limping in at 80% by sunset.
Has anyone else noticed their solar setup behaving differently after the AGM-to-lithium switch — particularly with a smaller array? Curious whether a 400W setup is genuinely sufficient for winter cabin use or whether I should be looking at adding another panel before the short days really bite.
