Bendix King HH2500 Replacement Battery MA181 10.8V 1200mAh

My HH2500 drops to low TX power mid-shift even though the battery was fully charged at the start — what's happening?

Sustained RF output draws higher current than standby or receive mode, and Ni-MH cells show sharper voltage sag under that load as the pack ages or if cells are mismatched. On a new replacement pack, this can also happen in the first one or two cycles before the cells have balanced. Run two full charge-discharge cycles and check whether the sag continues — if it persists past that, the dock contacts may not be delivering full charge current, so clean the gold contact strip and re-charge to confirm cell voltage reaches 1.4V per cell before the next shift.

The charger dock blinks a fault LED and never clears after I install this battery — how do I fix it?

The Bendix King dock uses a voltage threshold to decide whether to accept a pack. A new Ni-MH battery shipped at storage voltage can sit below that threshold, causing the dock to reject the charge cycle entirely. Remove the pack, wipe both the battery contacts and dock contacts with a dry cloth to eliminate any resistance, then reseat the pack firmly and hold it in place for three seconds. If the fault LED clears and charging begins, the contact cycle completed the BMS handshake — if it does not, check that cell voltage across the pack reads at least 9.6V with a multimeter before re-inserting.

This battery sat unused in a drawer for several months and now the radio won't power on — is the pack dead?

Ni-MH cells self-discharge at roughly 1–2% per day, so a pack stored for several months can drop below the radio's minimum startup voltage. The pack is likely not dead — it is in a deeply discharged state. Place it in the charger dock and leave it for a full charge cycle of at least 12 hours; many Ni-MH chargers have a trickle-recovery mode that will slowly bring the cells back up from low voltage. If the dock accepts the pack and the charge LED cycles normally, check cell voltage after the cycle — it should read between 12.6V and 13.2V fully charged before you reinsert it into the radio.