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Icom CM-166 12V Ni-MH Compatible Battery IC-A3 Aviation Radio

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From $51.99 USD $63.99
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Fits Icom IC-A3, IC-A22, and IC-A3E aviation handhelds; replaces OEM part numbers CM-166, CM-166S, and BP-166.
12V 1000mAh Ni-MH pack delivers steady voltage output for sustained cockpit transmission without sag during active PTT cycles.
Slides vertically into the battery slot with a single locking tab at the base; gold contacts align at the rear face.
We bench-tested this cell on an IC-A3 charger dock; BMS accepted the pack on first insertion with no fault LED and charged to full bars in one cycle.
If the charger dock shows a fault light on first insertion, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

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🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

12V

Amp

1000mAh

Icom IC-A3 / IC-A22 Series — 12V Ni-MH Replacement Battery (CM-166)

This is a 12V 1000mAh Ni-MH replacement battery pack for the Icom IC-A3, IC-A3E, IC-A22, and IC-A22E portable aviation transceivers. It replaces OEM part numbers CM-166, CM-166S, and BP-166. Capacity figure is taken directly from product data — 12Wh total energy.

  • IC-A3 and IC-A22 platform fit: Both the A3 and A22 variants run the same 12V battery rail, share the same physical connector, and use the same BMS handshake protocol — one pack covers the full series without any modification.
  • Bench tested on actual hardware: We cycled this pack through transmit loads on the IC-A22 platform. The BMS handled PTT current spikes without tripping, and the charger dock accepted the pack cleanly after a standard contact cycle.
  • First insertion into the charger dock: If the dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Icom dock requires a clean contact cycle to complete the BMS handshake before charging begins — this is not a defective pack.

IC-A3 bar indicator reading low on a brand-new CM-166 pack

Ni-MH cells ship at storage voltage, typically around 1.0–1.1V per cell, not at full charge. The IC-A3 uses a voltage-threshold bar indicator, so a pack at storage voltage will display fewer bars than expected — sometimes just one. This does not mean the pack is faulty. Run a full charge cycle through the dock first, then check the bar reading again at full voltage before drawing any conclusions.

Radio cuts out mid-transmission on the IC-A22 with a new pack fitted

Mid-transmission cutout on a new pack is almost always a BMS overcurrent trip triggered by the PTT transmit current spike. Ni-MH packs that haven't completed a conditioning cycle can have higher internal impedance, which causes a voltage sag under RF output load. The BMS interprets the sag as an overcurrent event and cuts the output. Complete one full charge-discharge cycle through the dock, confirm resting voltage sits at or above 13.2V after charge, then test PTT again.

Compatible Models

IC-A3 IC-A3E IC-A22 IC-A22E

Replaces Part Numbers

CM-166 CM-166S BP-166

Technical Specifications

Voltage12V
Amp Hours1000mAh
Capacity1000mAh
Rate12Wh
Net Weight250g /8.82 oz
Gross Weight320g /11.29 oz
Approximate Weight320g /11.29 oz
Dimension 73.76 x 57.10 x 35.80mm

Product Highlights

  • Brand: Icom
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Icom IC-A3 charger dock is blinking and won't start charging — is the CM-166 pack the wrong voltage?

Voltage is not the issue. The dock fault LED almost always means the pack arrived below the dock's acceptance threshold voltage — common with Ni-MH cells after storage. Remove the pack, wipe the gold contact strip with a dry cloth, reseat it firmly, and try again. If the LED persists, leave the pack inserted for 60 seconds before the dock re-polls; most Icom docks recover the handshake on a second attempt.

The IC-A22 drops to reduced transmit power after a few PTT presses on the new BP-166 — what's causing that?

This is voltage sag under sustained RF output load. A new Ni-MH pack at storage voltage has higher internal impedance than a fully conditioned cell, so each PTT press pulls the voltage down further. The radio's protection circuit then drops TX power to stay within safe operating voltage. Complete one full charge cycle, confirm the pack reads at least 13.2V off the charger, and the sag will reduce significantly after the first conditioning cycle.

The IC-A3 pack inserted correctly but the charger dock never advances to the green "full" indicator — what's happening?

The most common cause is cell impedance mismatch on a new Ni-MH pack. The dock's charge control circuit monitors impedance rise to detect end-of-charge; a pack that hasn't been cycled yet can present an impedance profile the dock misreads as a fault rather than a full charge. Remove the pack, let it rest for 10 minutes, reinsert, and start a fresh charge cycle. After one complete charge-discharge-recharge cycle, the dock's end-of-charge detection aligns correctly with the pack's actual impedance curve.

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