Proposal: Smarter Backup Systems with Dual-Inverter Architecture
This #DesignTheNextBLUETTI idea came to us while testing the existing portable segment to find the best UPS for our servers.
Our criteria / needs:
- Advanced UPS modes, expandability and 145V MPPT input from large units.
- Low inverter idle consumption from small portable units (AC2A, AC50B, AC60)
Current large-scale power stations, like the AC500 and AC300, are powerhouses with inverters capable of handling up to 5000W. They’re perfect for heavy loads and scalable solar setups, but they come with a glaring inefficiency: they burn 40–60W idling, just to stay online. That’s over 1kWh wasted daily—worse if solar harvest is limited. For setups running small loads 24/7, like servers, networking gear, fridges, CCTV & alarm system, etc. this inefficiency is a problem.
Our solution proposal? A dual-inverter architecture.
The lineup could reuse existing designs (AC200, AC240, AC300, AC500) and include the Twin inverter architecture:
- Primary inverter: A high-capacity (e.g., 5000W from AC500) inverter for heavy loads and full-scale operation.
- Secondary inverter: A low-power (e.g., 300W similar to that from AC2A) inverter dedicated to 24/7 small loads with minimal overhead.
This design means small, critical loads run all day without wasting energy, while heavy loads activate only when needed. Here’s where it gets smarter:
- Custom UPS Mode: In grid-down scenarios, suspend heavy loads automatically to conserve battery.
- Threshold Activation: Heavy loads restart when a set battery level is reached.
- Solar Optimization: Keep the small inverter powered by efficient solar input even in low-harvest conditions.
This isn’t just about saving watts—it’s about smarter resource management. Why waste energy on an oversized inverter for a 250W load? Instead, let the small inverter handle it efficiently, and use the big guns only when required. It also reduces decision fatigue, and rather than considering, for instance, an AC500 for heavy loads AND an AC2A or AC50B for 24/7 UPS, both needs would benefit from the advanced UPS configurability, vast capacity, expandability, and massive solar input that small units don’t have as only large units embark those, without the taxing idle consumption of those units.
Last but not least, the suggestion capitalizes on two existing design families, and the hardware components are mostly available off-the-shelf from the existing supply lines. An early prototype could even be a “Frankenstation” housing an Elite 200 inverter together with an AC2A inverter, probably sacrificing some LFP cells to house that extra organ. Increase the DoD to offset that and we’re in business. The control board would obviously require some refactoring, as well as the firmware - but without the cost & logistics hit of setting up the assembly/supply chain.
Where the idea comes from
For the record, we’ve tried each small to medium portable station for this scenario. We’re running 6 servers (1 is a dual ETH firewall / proxmox node) and an internet router (dual DSL / starlink).
That’s at most 300W of continuous power.
See our testbed below.
We tried daisy chaining the DC output of B210 and B300 into the DC input of those small units, but noticed a significant overhead (probably due to internal 48V architecture, stepping down to 12V, being converted again by the receiving unit), and similarly to embarking the B80 in a Multicooler versus relying on an external battery to power a portable cooler, the built-in approach is a clear winner as we have energy efficiency in mind.
Excel sheet to track AC ON idle power consumption in AC2A, EB3A, AC50B, AC60, AC70 and AC180. Meet Dr Hexane on the left, from our next video game title in the Arborea series.
Next up, right before adding a 4th and 5th server, and clearing up the wires… notice AC50B serving as UPS for now, but again, it lacks the advanced UPS customization. This leads to keeping the battery pack at 100%, which means higher cell voltage, no cycles, thus lower battery lifespan:
Adding B210 to the testbed:
Last but not least
See this super-mini PC, it costs less than 180€ and has 4 cores, 16GB ram, 2x ETH and 512SSD. We’re running a few containers in Proxmox on it, including a firewall and ensuring some lightweight server duty.
The interesting reason to bring it up here is that it has 4 E cores (“efficiency”) cores, the intel N100’s 4 E-cores are the exact same ones you’d find in a high end i9 14900K. Same specs, stats and design, and the per-core performance rating of one of the E cores is that of a 2016 highend i7 laptop CPU.
So this little guy illustrates the parallel we want to suggest between CPU design, and transportable power stations. It would be the equivalent of the AC2A’s inverter in a larger unit, like an AC500 that would be comparable to the P(erf)-cores of a 14900K CPU.
