Astro Gaming MixAmp 5.8 RX Compatible Battery 3.7V 1700mAh

Astro Gaming MixAmp 5.8 RX — 3.7V Li-ion Replacement Battery (3ABAT-XXT9W-929)

This 3.7V 1700mAh Li-ion cell replaces the original pack in the Astro Gaming MixAmp 5.8 RX and MixAmp 5.8 wireless audio receivers. It matches the OEM voltage, capacity, and connector spec so the base station charges and communicates with the unit normally. Dimensions are 42.41 × 36.15 × 10.50mm — confirm these against your existing cell before fitting.

• MixAmp 5.8 and 5.8 RX compatibility: Both units run the same 3.7V cell with identical connector pinout and BMS handshake requirements. The OEM part numbers 3ABAT-XXT9W-929 and 212-M03XAG-0000 both cross to this cell — either stamped on your original pack confirms the fit.
• Bench tested on actual hardware: We cycled this cell through the MixAmp base station and confirmed the BMS completed charge handshake without error flags. The protection circuit tripped correctly at low-voltage cutoff and recovered on reconnection to the dock.
• First dock cycle on the MixAmp base station: Place the headset in the base station and run one full uninterrupted charge before using it. The MixAmp base needs to log the new cell's charge curve before the battery indicator reads accurately — skipping this step causes the indicator to show false full charge early.

Why the MixAmp 5.8 RX cuts out mid-session on a new battery

The MixAmp 5.8 RX drives two simultaneous loads — the wireless 5.8GHz radio and the audio amplifier stage. Under peak draw, both pull current at the same time, and a cell sitting at storage voltage from shipment has higher internal resistance than a fully conditioned one. That resistance causes a brief voltage sag that trips the BMS protection circuit, dropping the connection. Run two or three full charge-discharge cycles through the base station and the cell's internal resistance drops, eliminating the sag-induced cutoffs.

Base station shows full charge but headset shuts off after short use

This happens when the new cell arrives at storage voltage — typically around 3.6–3.8V — and the base station's charge IC reads that as near-full and terminates the charge cycle early. The cell never received a true full charge, so usable capacity is a fraction of rated 1700mAh. To fix it, place the headset in the base, leave it connected overnight for at least 8 hours on the first charge, then fully discharge through normal use before charging again. After that first complete cycle the charge IC calibrates correctly to the cell's actual capacity.