Hollyland HL-NP550 Mars 4K Replacement Battery 7.4V 2000mAh

Hollyland Mars 4K / Mars 400S Pro / Solidcom C1 Pro — 7.4V Li-ion Replacement Battery (HL-NP550)

This 7.4V 2000mAh (14.8Wh) Li-ion battery replaces the HL-NP550 cell used in Hollyland wireless video transmission systems including the Mars 4K, Mars 400S Pro, Mars 300 Pro, and Solidcom C1 Pro. It fits the transmitter and receiver units used in professional video production. Voltage and form factor match OEM spec at 70.80 × 38.50 × 21.00mm.

• Mars 4K and Mars 400S Pro shared platform: These units run the same 7.4V power rail and use the same battery bay connector, which is why one cell covers the full lineup. The BMS handshake across these models uses the same charge termination protocol — the replacement triggers charge complete at the same threshold as the factory cell.
• Bench tested on actual hardware: We cycled this battery through transmit-active load conditions on the Mars 4K. The BMS held voltage above the low-battery cutoff point without unexpected shutdowns, and the protection circuit responded correctly to overcurrent during peak DSP and RF transmit draw.
• Cold-weather transmit tip: Li-ion capacity drops noticeably below 5°C. On outdoor shoots in cold conditions, keep the spare battery in an inner pocket until the moment of swap — a cold cell can trigger the low-battery warning well before actual depletion, cutting transmission early.

Voltage sag under combined RF transmit and DSP load on the Mars 4K

The Mars 4K draws simultaneous current for its RF transmitter, video encoder, and DSP stack. This combined load creates brief current spikes that can push a degraded or counterfeit cell below the BMS cutoff threshold, causing sudden shutdowns mid-transmission. A correctly rated 2000mAh cell maintains enough internal capacity headroom to absorb those spikes without triggering protection. If the unit shuts off under full transmit load, check resting voltage first — a healthy cell should read 7.4–8.2V at rest before load is applied.

Receiver fails to sync after swapping the transmitter battery

When the transmitter loses power — even briefly during a battery swap — some Mars series receivers drop the paired link and do not automatically re-establish it. This is not a battery fault; it is the system's power-loss behaviour. After fitting the replacement battery and powering the transmitter back on, press the pairing button on both units to re-establish the link manually. Confirm the receiver's signal indicator is solid before rolling camera again.