Wiring to the DC7909 (8mm) input port

I’m trying to understand the wiring schema for the Bluetti AC50s DC7909 port. I’d like to create a custome MC4 to DC7909 that can accommodate my DC meter using Anderson PPs to the 8mm and create a another as a DC charge from my trailer (output) Anderson SB-50 to 8mm for flexibility and wiring backup. Please advise the wiring schema.

I did find this on diy solar forum:

"Bluetti uses a three-conductor 7.9mm barrel connector and solders the (+) cable to both the center pin and to the inner shell, soldering the (-) cable to the outer shell. This can be easily confirmed by CAREFULLY measuring the voltage coming from a Bluetti charger’s 8mm barrel connector, holding your voltmeter’s black (-) probe against the outershell of the 8mm connector, while using the red (+) probe to measure first the voltage at the inner shell (42V) and then at the center pin (again, 42V).

Now try that with an 8mm-terminated charging cable made for Jackery or one of the other products that accepts an 8mm plug - the center pin will be dead (0V), with only the inner shell of the barrel connector being hot.

If you look at some of Greely’s “8mm” cables on Amazon, for example, they provide a schematic of sorts that reveals the center pin is dead in their products. They don’t solder it to either conductor of the cable. They only solder (+) to the inner shell and (-) to the outer shell of the barrel connector.

I suspect that Bluetti’s charge controllers expect that center pin to be hot, in addition to the inner shell (both +)."

Now if the AC 50s does not use the center pin but relies on the inner shell, that would be useful info. I’d have to find a 8mm 3 wire for testing…


From what I understand, you want to charge the AC200 from your trailer via the 8mm charging port normally used by the AC Power Brick. If that is correct, you will need around 55 volts DC to charge through this port, Where would you be getting this source of high DC voltage from in your trailer to charge the AC200?

Hi. Thanks for your reply.
I’m new to the Bluetti Ac50s, I’m coming from a AGM battery with custom connections and a GZ extreme 350 customized with my own Anderson PP cable setups and cables to power our 52v ebikes and our Dometic 12v cFX. My goal is to backup all my cables — my Bluetti MC4 to 8mm and fabricate a MC4 to Anderson PP for the Bluetti for use with my solar panels. I will also supplement charging with my Bestec DC cig inverter that will be used in our truck for charging the AC50s (which may end up being the more efficient charging source). What has got me stymied is the wiring on the 8mm adapter. Some say it’s different than other 8mm devices. I’m still testing but I had run across the post I quoted as my first query into this issue.

I’m also looking to better understand the OEM stock 27.5v 3.45amp ac/dc charger with a smaller unit for travel and backup. The stock brick is pretty large l. I have other non OEM power supplies that work well in spec for other batteries and appliances - but this seems unique.

Thanks for any insight you can provide.



Hello Scott

I filled in some detail on my experience and my hardware ---- and where i’m coming from.
Igreely has 2 cables, one works with Jackery and my Goal Zero, its a 8mm to APP with the inside as power and the outside ground. They have another MC4 to 8mm/ 5.5mm adapter that they claim in their AMZ overview that is Maxoak/Bluetti compatible. I’ve havent found out yet how the center is wired. Again I think AC50S needs the center pin power. My tests I recall on the stock cables with the AC50S had inner shell and pin with power.

My next thing is to find from Bluetti a source for

  1. Extra pairs of 8mm to cig lighter cables and mc4 to 8mm cables
    Hopefully from either Bluetti or other 3rd parties as a source
  2. Looking for a smaller compact charger, that fits the 27.5v 3.25am 8mm spec.

Greely has an 8mm male to MC4 cable on amazon. I didnt see a cig plug to 8mm male but there are many cig plug to 5.5 that you could use an adapter to go from 5.5 to 8mm


Scott. thanks
I have a few spare cig cables from our Dometic CFx that i fabbed with Anderson PP to make them interchangeable, but my 8mm connectors don’t power the center pin which when I tested on the Bluetti with DC charge seemed not to work. So with my half dozen 8mm plugs (which all fabbed work on my GZ Extreme), i may need to find a 8mm plug that lets me ‘shunt’ the inner shell to the center pin when I solder. My plan calls for fabbing a 8mm to Anderson PP and a 8mm to MC4 for backup wire harnesses for travel.
I did ask Greely about one of their 8mm / 5.5mm APP cables, and have yet to hear back since they claim in the info that it works with Bluetti when my other iGreely 8mm to APP does not (so far)… thanks


MAXOAK DC7909 to MC4 Cable is back in stock on amazon now, see https://www.amazon.com/dp/B07NMNS2FG/ref=cm_sw_r_cp_apa_fabc_N5F2RRKH5GQ1XRR7WK05?pldnSite=1.