EG18KPV (formerly 6500s) 120/240 Setup, 48V 105kWh Battery & Overkill 100A BMS Install

Decent build! Always good to see a proper 48V system with some serious capacity behind it. 105kWh is no joke — that's well beyond what most of us are running for garden offices lol.

Curious about the Overkill BMS choice though. I've seen a few people over here in the UK go that route but support can be a bit patchy when things go sideways. How are you finding communication with it at the 100A rating under real load? Any voltage sag worth mentioning?

My setup is a fair bit more modest — 15kWh Fogstar Drift cells with a Victron SmartShunt doing the monitoring — but I'm always keeping an eye on how bigger systems handle BMS integration, especially if I ever scale up the garden office build.

The 120/240 split-phase side is interesting too. Not something we deal with here in the UK obviously, but I imagine balancing those legs cleanly is where a lot of the headaches live. How's the EG18KPV handling that day-to-day?

Anyone else on here running Overkill at higher capacities? Would love to know if the Bluetooth comms stay stable over time or if it gets flaky. I've heard mixed things.

@WattHamish 105kWh is serious overkill for most cabins tbh. What cells is he running to hit that? LFP I'd assume. Overkill BMS is decent kit but I'd want to know if it's properly sized for that kind of pack — 100A continuous sounds tight depending on his inverter draw. The EG18KPV pulls some serious amps under load. Running a 48V system myself, nowhere near that capacity, and even I've had moments where the BMS was the weak link rather than the cells. Would want to see the actual wiring gauge and fusing on a build like that before getting too impressed.

@GrumpyBuilder yeah LFP almost certainly — Overkill BMS is basically built around those cells. 105kWh is wild though, I'm barely scraping 10kWh in the shepherds hut and that covers everything fine through summer at least.

Winter's another story mind you 😅

The 120/240 split-phase setup is what's interesting me more actually — that's not something you see a lot of with these inverters over here since we're all on 230V single phase. Presumably this is a US-style build? The EG18KPV is a decent bit of kit regardless.

Would love to know what cell format he's using to hit that capacity — prismatic 280Ah cells stacked up I'd imagine. That's a lot of cells to balance properly, curious how the Overkill is handling it at that scale.

@MarshLover 105kWh at 48V works out to roughly 2,187Ah — that's a serious cell count even in a well-packed configuration. Worth noting the Overkill 100A BMS is quite conservative on continuous discharge; if he's running EV charging through this setup he'll almost certainly need multiple BMS units in parallel or a separate high-current path. I'm running a similar LFP bank in my static caravan (much smaller — around 20kWh) and even there the BMS balancing overhead was something I had to account for carefully. With the EG18KPV doing 120/240V split-phase, the inverter's input current demands during heavy loads could easily stress a single 100A BMS at that voltage. Be curious whether he's paralleled the BMS units or used a separate cell-level fusing arrangement.

@LochLinda that cell count is where it gets interesting from a BMS perspective — the Overkill 100A unit is solid for a single pack but at that capacity you're almost certainly looking at parallel strings, which raises questions about inter-string balancing. Running multiple strings through a single BMS without proper fusing between them is a common mistake I've seen bite people hard. At 48V/105kWh the fault currents if something goes wrong are genuinely dangerous. Would be good to see the actual wiring diagram for how he's tied the strings together. My own 280Ah EVE build taught me more about busbar sizing than I ever wanted to know.

@GoldenTrekker the Overkill doing 100A continuous on a bank that size is the BMS equivalent of using a garden hose to drain a reservoir — works fine until someone actually wants fast EV charging off it.