Mitel 600d Cordless Phone Compatible Battery 3.7V 800mAh

Mitel 600d / 612D — 3.7V Li-ion Replacement Battery

This 3.7V 800mAh Li-ion battery fits the Mitel 600d and 612D DECT cordless handsets. It replaces the original cell when the handset stops holding a charge or drops off calls unexpectedly. Slot it in and the handset powers up on the existing charging contacts — no tools needed.

• 600d and 612D platform fit: Both handsets share the same battery bay dimensions (55 × 34 × 4mm), connector orientation, and 3.7V supply rail, so a single cell covers either model without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 600d platform. The onboard protection circuit held cutoff correctly at low voltage and accepted charge current from the base station without triggering a fault state.
• First charge on the 600d base: Seat the handset in the base immediately after fitting and leave it for a full charge before making calls. Li-ion cells shipped in storage state can read as low as 3.0V — the 600d base needs to see sufficient voltage to begin a normal charge cycle rather than entering trickle mode.

Talk time shorter than the original battery after replacement

A new Li-ion cell often delivers noticeably less talk time for the first few cycles. This happens because the cell ships partially discharged and the battery management circuit hasn't yet calibrated to its actual capacity. Run two or three full charge-and-use cycles and talk time will stabilise close to rated capacity. If it stays short after five cycles, check that the handset contacts and base cradle contacts are clean — poor contact resistance causes the charger to terminate early.

Base station charge light not coming on after battery swap

If the base shows no charge indication after fitting the new cell, the battery voltage from storage may be below the base's charge-acceptance threshold. Remove the handset, wait 30 seconds, and reseat it firmly so all three contacts engage. If the light still doesn't appear, connect the base to a power cycle — unplug for 10 seconds and reconnect. The base should then detect the cell and begin charging from 3.0V upward.