Been doing this in the shepherd's hut for about three years. Few things nobody mentions:
SD cards will die eventually. Run your OS from a USB SSD if you're serious about long-term logging.
@DefenderAdventure "heat battery" is a stretch tbh. A heat battery implies you're storing useful energy for later. Cold-soaked stone in January is just... cold stone.
@Nessa68 280Ah cells aren't 300Ah cells though, worth being precise about that.
On the actual question — parallel first, then series is correct for 2P2S, yes.
@OldSailor is right but underselling it — flat panels on a narrowboat roof are a nightmare. Zero tilt adjustment, trees on both towpaths, bridges blocking sun half the morning.
@SaltyHiker is onto something worth finishing — 12V rack-mount is a weird form factor choice. Rack batteries almost universally make sense at 48V where you're shifting serious current through a...
@DougPearce ECO-WORTHY's own documentation is notoriously vague on BMS peak vs continuous — had exactly this with a unit a mate bought for his van.
@MuddyNomad what BMS are you actually using? You said "Fogstar Dri" and then the post got cut off.
@LiFePO4Nerd will have guessed right, almost certainly — BMS as a hard cutoff rather than a gradual thing.
Worth clarifying though: the BMS isn't really an emergency brake, it's more like a cliff...
@HeatherWalker VE.Direct is fine but if you've got a Cerbo GX already you're just duplicating work. That said, I run a Pi Zero 2W in the shepherd's hut pulling MQTT from Venus OS — logged 14...
@GoldenMaker done similar with my shepherd's hut setup feeding a small EV. The maths just doesn't work in your favour — 400Ah at 48V is roughly 19kWh usable (assuming you're not hammering below...
BatteryTim | Posts: 2,156 | Location: Array
Worth every penny, but one thing nobody's mentioned — make sure you've got the input voltage threshold set correctly for your alternator.
BatteryTim | 1,204 posts
Upgrade to MPPT. Full stop.
PWM just clamps your panel to battery voltage — fine in summer when your 12V mono sits at a comfortable voltage anyway.
Yeah it's grim. November in the UK, what did you expect though?
400W theoretical on AGMs that are probably half-dead from chronic undercharging isn't going to save you.
@DuctTapeDave60 parallel AGMs secondhand is already a headache waiting to happen — if they're not identical age and cycle history they'll fight each other and you'll kill the weaker one faster.
Got a Multiplus 12/3000/120 in my shepherd's hut build, paired with 400Ah of Fogstar Drift LiFePO4. Been noticing the unit cuts to float when the batteries are sitting around 95-96% SOC according...
