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diy solar

Need Help with Seplos V3 BMS on Luxpower Inverter - Charging Issue

SwwilsSolarMan

New Member
Joined
Sep 17, 2024
Messages
8
Location
UK
Hi everyone,

First off, a big thank you to all the contributors here! The advice and insights on this forum have been invaluable to me over the past two years. You’ve helped me get this far, and I’m hoping you can lend a hand once more.

I’ve been running a Luxpower 3.6k setup for the last two years and recently upgraded to a Luxpower 6K inverter. My current system includes 6.9kWp of solar and 4 original Pylontech US2000s. Now, I’m moving on to a DIY project with the Mason 280L battery from Fogstar, looking to replace the Pylontechs. Assembly went smoothly, top balancing is done, and the cells and NTCs look good with no errors. The active balancer appears to be functioning, though it hasn’t kicked in yet, not that it would do much anyway, it's the only thing I don't like.

My Mason build includes 16 x 305Ah cells paired with a Seplos V3 BMS “10”. The issue I’m facing seems to be a communication or inverter-related problem when I swap in the Seplos.

The Seplos discharges just fine, but when I try to charge—whether through excess solar or forced charge—the charge ramps up briefly (around 5A), then BMS switches back to standby within a few seconds, repeating this cycle without errors on either the inverter or the BMS.

I’ve read that the V3 doesn’t have the typical “PN-GDLT” option, so I’m using BMSstudio for V3. Setting the inverter battery to “PYLON” and Seplos to “Pylon CAN” results in no errors but only shows 50Ah of capacity, which I’ve seen mentioned as common. If I change the inverter to “STD” and the Seplos to “SMA CAN,” it seems to read the full capacity fine.

I believe my wiring is correct—on the newer Luxpower 6K hybrid, P4 is CANH and P5 is CANL, which I’ve triple-checked. My existing CAN cable between the inverter and battery works fine. However, having the Seplos oriented differently has been a bit confusing (and I say that working in a school of EE!). If I wire it wrong, the inverter throws a communication error, so that seems fine.

Here’s where I’m scratching my head: connecting the Pylontechs works perfectly, so I’m wondering if I should try using 485 mode with the V3? Despite me using CAN normally.

Could this be a bug, or is there something else I’m missing? It almost feels like the inverter doesn’t want to push over 50V, but it’s definitely capable.

I’d greatly appreciate any advice or ideas! I’m happy to share more details or images if that helps.

Thanks in advance for your time and expertise!
 
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