Field Trainer SD-400S Replacement Battery DC-16 7.2V 150mAh

Field Trainer SD-400S / FT-100 — 7.2V Ni-MH Replacement Battery (DC-16)

This is a 7.2V, 150mAh Ni-MH replacement battery for the Field Trainer SD-400S and FT-100 electronic training collars. It replaces OEM part DC-16 directly in the collar unit. When the original cell depletes, this swap restores full transmitter response and stimulation output.

• SD-400S and FT-100 compatibility: Both collars run the same DC-16 cell format — identical voltage rail, physical footprint, and connector orientation. The collar's internal circuit expects 7.2V from a Ni-MH cell; substituting a different chemistry or voltage trips the protection circuit and the collar won't power on.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a collar unit. The BMS accepted charge without fault, and stimulation output remained consistent across the discharge curve with no mid-session dropout.
• First use after installation: Ni-MH cells ship in a partially discharged state. Charge the collar fully before the first session — Ni-MH chemistry benefits from a complete initial charge cycle to stabilise capacity from the start.

Why the SD-400S loses stimulation strength before the battery indicator drops

Ni-MH cells have a relatively flat discharge curve, so the collar's voltage-based indicator doesn't always catch early capacity fade. As the cell ages, internal resistance climbs — stimulation output weakens before the low-battery warning fires. This is the cell ageing, not a collar fault. Replacing the DC-16 cell restores full output. If a fresh cell still shows weak stimulation, check the contact pins on the battery bay for corrosion.

Collar powers on but won't respond to the transmitter after a battery swap

Removing the battery clears the collar's pairing state on some SD-400S units. The collar and handheld transmitter need to re-establish their RF link after a power interruption. Hold both units within one metre, then run the pairing sequence from the transmitter — typically a long press on the link button until the collar LED confirms. If pairing fails, confirm the replacement cell is reading above 7.0V under load before assuming a transmitter fault.