Been noticing something similar with my setup in the van conversion. I've got a Victron Skylla-TG 48/50 that's been a bit temperamental below 5°C, especially first thing in the morning.
The charging voltage seems to drop quite a bit when it's cold, which makes sense chemically I suppose, but it's more pronounced than I'd have expected. The manual mentions a temperature coefficient of around -20mV/°C per cell, which adds up across 48V, but I'm seeing drops beyond that on my actual readings.
I'm wondering if it's worth fitting one of those battery heater mats under the batteries themselves? Seems like it might be the quickest fix. The shepherd's hut gets pretty chilly through winter and the batteries are in an unheated box, so that's probably not helping matters.
A few questions for anyone with experience here:
- Are you seeing actual charge current drop, or is it more of a voltage plateau issue?
- Has anyone retrofitted battery heating and found it actually makes a difference to charging?
- Are there chargers specifically rated better for cold climates, or is this just a universal battery chemistry thing?
I'm also considering moving the battery box into the insulated living space temporarily over winter, though that's more of a hassle than I'd like.
Would be good to hear if others are dealing with this. Curious whether it's a charger limitation, battery limitation, or just part of off-grid life in the UK winter.