Xiaoxiang 200A 8–24S BMS (BatteryHookup) – abnormal voltage on output (6.8V) despite full pack voltage

Seen this before with the Xiaoxiang units — that 6.8V on the output is a classic sign the BMS is sitting in a protection state and hasn't properly "woken up" after a connection sequence. The MOSFET discharge path is effectively open even though the pack itself is fine.

A few things worth checking:

• Did you connect load before charger? Some of these BMS boards need to see a charge source first to kick the discharge FETs into life
• Check your cell voltages individually — even one cell slightly out of range (overvoltage or undervoltage) will latch it into protection silently
• The app — are you using the Xiaoxiang Bluetooth module? If so, what's the protection status showing? It'll flag which fault triggered it

I've got a similar 8S unit on my static caravan setup (though mine's a JK, not Xiaoxiang) and the latching behaviour caught me out initially. These cheaper BMS boards from BatteryHookup aren't bad value but the documentation is essentially nonexistent, so you're piecing it together from forum posts like this one.

One more thing — that 6.8V reading, are you measuring across the output terminals with no load attached? Because some multimeters will show odd floating voltages on a high-impedance open circuit with MOSFETs involved. Slap a small resistive load on there and measure again, see if it drops to near zero or holds at 6.8V.

If you've already ruled all that out, it may be a duff board. Has anyone else here had dead-on-arrival Xiaoxiang units from that batch? I'm curious whether it's a one-off.

@DODGuy mine did exactly the same thing when I wired it up backwards for approximately three embarrassing minutes — try hitting the discharge enable via the Xiaoxiang app (Bluetooth), sometimes the MOSFETs just need a gentle nudge to come out of their sulk rather than a full reconnect cycle.

Had this exact issue with my static van setup last summer. Worth checking if the BMS needs a charge source connected first to wake the discharge FETs — some of the Xiaoxiang units won't enable the output until they see a charger on the charge port initially.

Stick a bench PSU or even just your solar controller on the charge terminals briefly. Mine came straight to life after that. If you're not seeing anything change, the Xiaoxiang app via Bluetooth is dead useful for reading exactly which protection state it's stuck in — saves a lot of guesswork.

Also double-check your cell group voltages in the app rather than relying on the pack total. Had one cell sitting low enough to keep the whole thing locked out even though overall pack voltage looked fine.

If the MOSFETs are stuck in protection mode, a 3.6V lithium cell briefly touched across the output terminals (positive to positive) sometimes gives it the "kick" it needs to wake the discharge side — done this twice on my narrowboat build when the Xiaoxiang threw a wobble after I botched the connection sequence at 11pm like a complete professional.

Worth grabbing the Xiaoxiang BMS app via Bluetooth too — if it's actually in short-circuit protection the app will tell you outright rather than leaving you guessing at 6.8V like it's some sort of cryptic crossword clue.

@ExPostie86 that's a new one on me — slightly nervous about poking cells at output terminals but I can see the logic if the MOSFETs just need a nudge!

Quick question though — does the Xiaoxiang app give any clues when it's in this state? I've got the BT module on my Fogstar cells setup and sometimes the app shows a protection flag that isn't obvious from the pack behaviour itself. Wondering if it would flag which protection mode it's actually stuck in before you start prodding things?

Also — is there a specific charge voltage threshold the BMS is looking for on that initial wake? Like does it need to see a proper CC/CV profile from a charger, or would even a cheap Renogy unit pushing the right voltage be enough to coax it out?