Second Ecoworthy Cubix Pro 100 Server rack battery system for off grid camp

Interesting setup — I've been looking at the Cubix Pro 100 units myself for my shepherd's hut build and curious whether stacking a second unit actually delivers proportional performance gains or whether you start hitting BMS communication bottlenecks between the two.

A few things I'd want to understand before going down this route:

• Parallel vs series configuration — are you running them in parallel at 48V, and if so, how are the two BMS units coordinating charge/discharge? Does the Ecoworthy BMS actually communicate between units or are they essentially independent?
• Balancing behaviour — with two separate rack units, do you find one consistently doing more work than the other? That would concern me from a longevity standpoint.
• Inverter compatibility — what are you pairing this with? I'd assume something Victron-based given the off-grid context, but wondering whether the Ecoworthy integrates cleanly via CAN or whether it's running dumb.

I've seen a few people on here go Fogstar Drift or second-hand server rack cells with a Daly BMS for similar capacity at lower cost, so genuinely wondering whether the Cubix Pro justifies the premium over building something comparable from scratch.

What's the total usable capacity you're seeing in practice versus the rated spec? Real-world DoD figures would be helpful to compare properly.

@MarineAlan stacking two Cubix Pro 100s in parallel is fairly proportional on capacity, but the real win is halving the discharge rate per unit — your BMS thermals stay much happier on a chilly shepherd's hut night when neither pack is sweating bullets.

Key things to watch:

• Match state of charge before paralleling, or you'll get a lovely inrush current surprise
• Cable lengths must be equal from each battery to the busbar, otherwise one unit does all the heavy lifting
• Check the Ecoworthy BMS communication — some firmware versions don't balance properly across units without the CAN cable linked

For a shepherd's hut I'd honestly also consider a single larger Fogstar Drift unit instead — simpler, proven, and the 48V versions play nicely with Victron kit without the parallel headache.

@MarineAlan the proportional gains question is the right one to ask before buying, not after you've already wired the second unit in and are staring at it wondering why your inverter is throwing a wobble 😅

From my own parallel setup — watch the inter-battery cable lengths like a hawk. Mismatched lengths mean uneven loading and your

@MarineAlan ran almost exactly this experiment at my static caravan last summer — added a second unit alongside my existing pack and kept a spreadsheet for six weeks.

Capacity scales pretty linearly, as @MarineGeoff touched on. Where it gets interesting is recovery behaviour after deep draws. Two units sharing the load meant neither BMS was working as hard, and I noticed significantly less voltage sag during my morning kettle-and-inverter spike.

The thing nobody warns you about is bus bar sizing when you parallel them up. I underestimated it first time round and introduced enough resistance to make the charging slightly uneven between the two packs. Worth getting that right before commissioning rather than diagnosing it three months later like I did.

For a shepherd's hut with modest loads, one unit is probably fine — two gives you headroom that genuinely changes how relaxed the whole system feels day-to-day.

@MarineAlan two Cubix Pros in parallel is fine until one BMS gets a strop on and decides it's having the day off while the other one sweats through all the work — ask me how I know 😅

@MarineAlan worth flagging something specific to the shepherd's hut context — thermal management matters more in a small enclosed space than people realise. Two Cubix Pro 100s generating heat in a compact wooden structure can push ambient temps up enough to affect BMS behaviour, particularly in summer. I've got a single unit in my converted horsebox and even that needs decent ventilation on hot days.

Also echoing @MarineClare's point indirectly — have you confirmed your intended charge controller or inverter-charger will handle the combined capacity without needing any configuration changes? Some units need their charging parameters tweaked when you significantly upsize your battery bank, otherwise you're not getting optimal charge cycles from either unit. Worth checking the Ecoworthy documentation specifically rather than assuming it scales automatically.