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Bluetti D40 reverse engineering

Andrewr05

[Replicant 42069]
Joined
Nov 29, 2023
Messages
712
Location
New Hampshire, USA
I don't have the general electrical know-how to actually reverse engineer or anything, but I guess I don't know unless I try.

The Bluetti AC200L has a "48 volt" output port (it's speculated that it's just an output at its internal battery voltage) that can only be used by connecting their proprietary output box.

The Bluetti D40 converts the output to "12v".
It allows you to directly connect to your "house battery" to keep it topped off or it allows you to connect to a 12 volt fuse box/bus bar system and power all of your loads off it.

The box also contains its own MPPT controller as well to directly charge your house batteries through the D40 via solar.
It does not backfeed into the main unit to top off the AC200L.

I have seen threads where other people haveu sed a voltmeter and have gotten voltage directly out of the 48V port, but as soon as a load is put onto it it shuts off.
It is likely that the third pin on the connector has some sort of communication with the D40 box.

I wonder how hard it would be to reverse engineer that and be able to just pull a straight 48V out of that port for connecting your own devices?

Has anyone thought of this now that Bluetti is finally shipping the D40 unit?

Surely it wouldn't be too difficult to spoof whatever signal it is sending and get it to think the D40 is connected.

Anything is bound to be cheaper than the $200 Bluetti wants for the BLUETTI D40 DC-DC Battery Charger
 
So as somebody who’s messed around with reverse engineering the communications protocol with the B300 batteries, the first step would be to buy all these things, open up the AC200L to see what pins on that port connect to what things (on the AC300 for example two of the pins are marked H and L, which was a sign that it’s using CAN), double check the voltages, and then cut open the cable and attach a logic analyzer to the signaling cables. This is all doable, but isn’t cheap.

If I had different skills, I might take apart the AC200L and dump its firmware, but that’s not yet something I’ve learned how to do. No clue if that would be any less time consuming than the route I proposed, although with the firmware you could probably skip buying a D40… except then you’d still need to fabricate a connector somehow since it doesn’t seem like it’s sold separately? That’s the real struggle for me - these custom connectors.
 
People have found the type of connector they're using, so that's the easy part.

But tracing the wires to be the hardest part. Taking apart the D40 and seeing how that's connected and what it's sending back to the main unit would probably be the easiest route, though I admit I've never done anything like that before.
 
I'm wondering if adding a Y cable or Y adapter in between the D40 and the AC200L would work.

It's likely the D40 is communicating with the power station and signaling the unit to allow unfettered access to the batteries on that cable, so theoretically the power station would not know what was drawing that power.
It just knows it got the all clear because the D40 cable is present.

And that's just a speculation as well, it could very well be smart enough to know how much power the D40 is drawing and report it back to the AC200L, which would mean that piggybacking off of the connector wouldn't work because there would be a discrepancy between what the D40 was reporting and what was actually being drawn from the power stations main battery.

Either of these methods of communication to the main power station seem likely.
 
Really hoping someone can figure out how to either replace this port with something useful or hack the comms pin to get the 48v output working with a load. I just bought one of these ac200L units because I got it for a ridiculous price so can't complain overall but goddam it I hate when companies do this stuff.
 

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