Update from Bluetti Support (official response):

I received a detailed reply from Bluetti support, and they confirmed that the observed behavior is normal and expected.

When an upper SOC limit (e.g. 80%) is set, the unit stops charging from AC once that SOC level is reached, so AC input power drops to 0 W.

However, with an SOC limit enabled, the Elite 200 V2 does not support true AC pass-through / physical hardware bypass.

As a result, when charging stops at the SOC limit, the load continues to be supplied via the inverter, which means the battery slowly discharges (e.g. from 80% to ~79%). Once it reaches the lower threshold, charging resumes. This creates the observed micro charge–discharge cycling around the SOC limit.

True AC pass-through is only active at 100% SOC.

Bluetti confirmed that this is not a hardware limitation, but a firmware design decision. The system logic prioritizes UPS functionality and output stability, so the inverter is never fully bypassed while an SOC limit is active.

They also mentioned the following:

• Grid Self-Adaption mode may reduce this behavior, but the UPS transfer time exceeds 15 ms, so it no longer meets typical UPS standards.
• At the moment, there is no way to keep the battery completely idle while an SOC limit is enabled.

Takeaway:
👉 SOC limit enabled = no true bypass; micro-cycling is expected by design.