@MartinParker64 Worth checking what voltage the absorption is sitting at — if it's genuinely in absorption but producing next to nothing, that's actually correct behaviour.
@SparkySailor nice project! Few things worth thinking about before you spec the consumer unit:
Earthing arrangement matters first — SWA armour can serve as your earth conductor back to the house...
WheresMeWires | 847 posts
Worth adding something nobody's mentioned yet — the voltage mismatch issue is a big part of why PWM suffers so badly in low light.
WheresMeWires | 1,243 posts
One thing worth flagging that nobody's mentioned — on a narrowboat specifically, your alternator situation matters massively with lithium.
@WonkyMechanic solid point on the top balance. One thing I'd add specifically for those EVE 280Ah cells — watch your charge current during that final absorption phase when they're all sat at 3.65V...
@EwanMurray Worth noting that before you even think about top-balancing, let those cells sit at room temperature for 24 hours if they've come in cold — LiFePO4 internal resistance behaves oddly...
@VickyMurray the cold weather BMS cutoff is a classic LiFePO4 headache on boats — charging below around 5°C can genuinely damage the cells, so the BMS is doing its job, annoyingly.
Few things...
@MoorRoger those blue-cased ones are almost certainly all coming out of the same two or three factories in Shenzhen regardless of what name's printed on the front.
I've got a similar vintage one...
@LochWalker that rabbit hole is very real — I went in wanting a basic setup for my garden office and came out the other side knowing more about peukert exponents than any sane person should.
One...
The kettle inrush thing gets everyone initially, but honestly it's not the full picture here. Yes, you'll see 3-4kW spikes on a decent kettle, but that's milliseconds.
The seasonal variation catches most people out too. My garden office pulls ~8kWh in winter (heating, lighting, long dark hours) versus ~3kWh summer.
That facilities background is genuinely gold for this stuff, @BurnWalker. I came from the other end—IT infrastructure—so I was comfortable with monitoring systems and redundancy planning, but I...
The usable capacity point @DODGuy's raised is spot-on, and it's where the maths gets properly interesting.
The real constraint you haven't mentioned yet is your roof space and wiring runs. On a narrowboat, that's often the limiting factor more than the electrical theory.
Series config works brilliantly...
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