While I've received the SBMS0 and 3 DSSR20's (& yes, they are indeed very nicely designed pieces of kit) and my panels, I'm still waiting on my cells so I've not had the opportunity to assemble everything and put it through its paces, but let me try to explain (as a non-engineer) how it works. I've posted a detailed schematic of my system (see link in my sig) that I'll refer to and that may help you "see" better than Dacian's schematic how it's designed to work.
His SBMS40 and 120 are all-in-one SCC's. In other words, you make battery, panel and load connections directly to the SBMS40 and 120, ergo they're rated ("40" and "120") for how much current that passes through them since the SBMS sits "inside" the charge and load circuit (much like the BMS's that Will reviews). Dacian's SBMS0 sits "outside" that circuit and relies on multiple DSSR20's (or any other charging devices that allow remote on/off switching) to manage charging (more on that in a bit), which has the advantage that the SBMS0 can be used to build or upgrade to
any size system simply by adding as many DSSR20's (or other charging devices) you might need to accommodate your needs. You can add
up to 30 DSSR20s for a whopping
600A of "incoming" - all w.o. need of a heat sync (as the 40 and 120 and most other BMS's need, again, because they're "inline"). He's also got logic in his SBMS0 to configure/split your array into 2 differently sized sub-arrays the SBMS0 mixes and matches to optimize charging given the amount of sun hitting your panels (more on that in a bit also).
So, how does the SBMS0 manage all this? First and foremost, it manages the health of your battery by monitoring and balancing (during both charging and discharging cycles) your pack's cells just like all the BMS's Will reviews. You can see it do this with the aid of the SBMS's very nicely designed and user friendly graphical UI on the display (and on a PC if you purchased the USB/WiFi option).
Second, it will cutoff loads (via EXTIO3 ... see my schematic) if the battery or a cell reach their respective LVC values. Ditto, charging via EXTIO4 if battery or cell reach their respective HVC values. These values are all automatically configured when you set up your SBMS for the first time after selecting battery chemistry, cell capacity, number of series-connected cells, etc. Dacian's pre-configured profiles for your selections can be tweaked if you want to set specific values but he recommends using his unless you know what you're doing.
Next up, SOC monitoring and the wonderful world of Shunts. Probably the biggest thing I think most people (well, non-engineers like me at least) get confused about. He's got two and they MUST be connected the way they are in my schematic. Why? In my diagram, the 100A shunt only has current passing through it in one direction (panels to battery &/or loads), hence it will measure my Charge Current. The 200A shunt, however (because of how and where it's connected to the 100A shunt and loads) sees that Charge Current on its way to the battery, but also sees Load Current on it's way OUT of the battery. The measured current at this shunt is the sum of Load Current - Charge Current (notice the polarity of of the PV and ADC1 wires from the SBMS0 that accomplish this). The SBMS simply adds the measurements at both shunts to get the Load Current [Charge Current + (Load Current - Charge Current) = Load Current]. So now you have a way of measuring capacity and SOC. Because, of course, LFP batteries charge curve is so flat, SBMS won't know where you sit on this curve until you've charged your pack to HVC the first time. It'll set that as 100% and be able to report accurate SOC once that's achieved (pretty sure I've got that right). I've got breakers on each of my DSSRs so I can, conceivably, observe the Charge Current coming in from each individual source.
Back to managing charging and loads. My schematic relies on his DSSRs to connect/disconnect my panels to manage charging but you can insert any other kind of charger so long as it can take the EXTIO4 to turn it on/off (e.g. an MPPT or any other charger w a remote on/off switch). Ditto on the load side via EXTIO3 (FYI, I've even inserted a Sonoff switch in this circuit to be able to disconnect my inverter/AC loads remotely or on a timer in addition to having the SBMS0 automatically disconnect them when it detects LVC).
But WAIT, THERE'S MORE! (ha), There's an additional EXTIO5 that can be used in conjunction w EXTIO4 to build 2 differently-sized arrays if you've got room for a lot of panels. Dacian's user guide section "Dual PV array functionality and SOC charge limiting" does a nice job of explaining how his SBMS0 will select and combine these differently-sized arrays to optimize your battery's charge current as the amount of sun hitting your panels changes. I don't need this 'cuz my system is vehicle-mounted so my panel real estate is limited, but if you've got the space for lots of panels, this is a really nice feature!
Some final notes: Why am I relying on his DSSRs instead of going w an MPPT charge controller?
This is why. [5/10 EDIT: Confirmed
here by some RW side-by-side testing.] Also, I think he's discontinuing SBMS40 and 120
because of this.
Hope that helps and I've not gotten anything wrong. As I mentioned, this is all still "theoretical" for me 'cuz I haven't been able to set it up yet and see it in action, except vicariously through others who already have. Well, at least all his other SBMSs, which have been out a while. There are some good YT resources for reviews and seeing them in action. Haven't actually seen any SBMS0 installs yet, but pretty confident it will work as well. Dacian's reputation is unparalleled and he provides excellent support.
