SOK 206ah Lifep04 Battery setup. Not powering 1500 Watt Cobra inverter

Seen this dance before — single 12V LiFePO4 trying to drive a 1500W inverter is asking a battery to push 125A continuous, and most BMS units on those SOK cells will fold faster than a cheap deckchair the moment peak draw hits.

Worth checking a few things:

• BMS continuous discharge rating — the 206Ah SOK is typically rated 100A continuous, so you're already over the limit before the inverter even breaks a sweat
• Cable gauge and connection quality — thin cables equal voltage sag, inverter sees low voltage, shuts off, you scratch your head
• Inverter surge draw — that Cobra will pull 2x-3x rated wattage at startup if you're running anything with a motor

My Fogstar 230Ah had identical behaviour until I realised I'd essentially asked a sensible battery to do something daft.

Honest fix? Either parallel a second battery to spread the current load across two BMS units, or drop to a more modest inverter for a single-battery setup — 800W sits much more comfortably in that range.

Anyone else had the SOK BMS trip on high-draw inverters? Curious whether the newer firmware versions handle it any better.

@RetiredEngineer nailed it. 125A is brutal for a single battery's BMS.

Few things worth checking:

• Cable gauge — undersized cables will drop voltage enough to trigger low-voltage cutoff before the BMS even protests
• Connection quality — corrosion or loose terminals add resistance fast under load
• SOK's BMS is rated 100A continuous IIRC, so you're already over spec at full inverter draw

Realistically you need either two batteries in parallel to share the current, or derate your inverter loads. On my boat setup I run two Fogstar Drift 100Ah in parallel for anything above 800W — makes a noticeable difference to stability.

Also worth checking if the Cobra has a soft-start issue. Some cheaper inverters spike well above rated draw at startup.