About this replacement
V Tech VM981 / VM991 Parent Unit — 3.7V Li-Polymer Replacement Battery (AHB404860)
This 3.7V 1500mAh Li-Polymer battery replaces the OEM AHB404860 cell inside the V Tech VM981 and VM991 parent unit. It fits the handheld monitor that receives audio and video from the baby unit. Swap it when the original cell no longer holds a charge between feeds.
- VM981 and VM991 parent unit fit: Both models share the same parent unit housing, connector pinout, and battery bay dimensions. The AHB404860 cell drops into either unit without modification — the same 3.7V nominal voltage rail powers the display, speaker, and wireless radio on both.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a VM981 parent unit. The BMS accepted the charge immediately, voltage held steady under screen-on load, and the unit paired to the baby unit without intervention after power-up.
- Re-pair after fitting: After replacing the battery, the parent unit has no stored power and loses its wireless link to the baby unit. Power both units on and run the pairing sequence from the parent unit menu before placing the baby unit back in the nursery.
Parent unit battery draining overnight with the screen on
The VM981 parent unit draws significantly more current when the LCD backlight stays on continuously. Night-time monitoring with the screen active is a sustained load that a 1500mAh cell was not sized to carry through an eight-hour stretch on screen alone. The parent unit has a screen timeout setting in the display menu — activating it cuts the average draw substantially and extends the charge between top-ups. Set the timeout to the shortest interval that still suits how you use it overnight.
Night vision feed not appearing after battery swap
The baby unit's IR LEDs are powered independently from the baby unit's own supply, but the parent unit's radio needs sufficient voltage to request and decode the night-vision stream. If the parent unit battery is below roughly 3.5V when you first power it on after the swap, the radio operates at reduced power and the IR stream may fail to display. Charge the parent unit to full before testing night vision. If the feed still does not appear at full charge, re-run the pairing sequence — a dropped wireless link during power loss can leave the units out of sync.