Been running a similar parallel AGM setup on my static caravan for a couple of years now, so this caught my attention.
Two Victron AGM 110Ah batteries in parallel is a solid foundation, but I've learned the hard way that parallel AGM banks are surprisingly fussy about how you charge them. A few things worth checking:
Equalisation of charge current — are your cables from each battery to the busbar genuinely the same length and cross-section? Even a small resistance imbalance means one battery works harder than the other. Over months this creates a mismatch you can't easily recover from.
The 25A Victron charger — depending on which profile you've got selected, it might be undersized for a 220Ah effective bank. Victron generally recommend around 10–20% of capacity for AGM, so ideally you'd want 22–44A minimum. At 25A you're at the very bottom of that window, meaning bulk stage takes ages and the batteries may never fully saturate, especially in winter.
Mixed charging sources — if you're combining a solar controller (sounds like a Sunwind unit?) with the mains charger simultaneously, you need to make sure both are configured to the same absorption voltage. Conflicting charge voltages confuse AGM batteries badly and accelerate sulphation.
What symptoms are you actually seeing — low capacity, slow charging, voltage dropping under load? That would help narrow it down considerably. I went through two sets of decent AGMs before I sorted my charge regime properly, so definitely worth diagnosing before throwing money at replacements.
Anyone else on here running parallel AGM banks long-term? Curious whether others have found Victron's Smart Battery Sense made a meaningful difference with temperature compensation.
