Sony S60526 Cordless Phone Compatible Battery 3.6V 1200mAh

Sony S60526 — 3.6V Ni-MH Replacement Battery (BT-33)

This is a 3.6V, 1200mAh Ni-MH replacement battery for the Sony S60526 cordless phone handset. It uses OEM part number BT-33 and fits directly into the handset battery compartment. Swap it in when the original pack no longer holds a charge through a full conversation.

• Sony S60526 handset fit: The S60526 runs a 3.6V three-cell Ni-MH pack with a specific connector orientation matched to this battery. Voltage and physical dimensions must align for the handset to seat correctly in the base charging contacts — this unit meets both requirements.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on Ni-MH compatible test equipment. The BMS held voltage within spec across the first five cycles, with capacity building toward rated output as expected for a fresh Ni-MH cell.
• First-charge protocol for Ni-MH handsets: After installing, seat the handset in the base station and leave it for a full 16 hours before first use. Ni-MH cordless phone cells need a slow initial charge to fully activate all cell capacity — skipping this step is the most common reason a new battery underperforms from day one.

Base station showing no charge or error light after battery swap

A fresh Ni-MH battery from storage often sits below the voltage threshold the base station expects before it begins the charge cycle. Some Sony bases use a trickle-detect circuit that reads incoming voltage before committing to a full charge — if the pack is too low, the base stalls. Remove the handset, wait 30 seconds, and reseat it firmly to re-trigger the detection cycle. If the error persists, the resting voltage of the new pack may need to read at least 3.0V before the base accepts it.

Talk time shorter than expected after the first few uses

Ni-MH cells do not deliver full rated capacity until they have gone through three to five complete charge-and-discharge cycles. A new 1200mAh pack may behave like a 900mAh pack in the first week — this is normal cell chemistry, not a defective battery. Run the handset through several full cycles: charge overnight in the base, use until the low-battery tone sounds, then charge again. By cycle five, the pack should be delivering close to its rated 1200mAh output.