Introduction: DIY Cordless Phone Batteries

My home telephone is now over 1.5 yrs old, I have three cordless receivers. The upstairs phone (shown in the pics) was the most frequently used receiver. Recently, despite being on the charger all day, the receiver would only hold a charge for about 5-7 minutes. It was time to replace the batteries or get a new phone set.

Cost of a new phone set with three headsets (receivers): $50
Cost of a new 500mah 2.4V battery (branded): $34
Cost of rechargeable (low drain) battery (2000mah 2.4V) (set of 8): $13.16

The cheapest and best solution was to make my own rechargeable cordless phone battery.

Items needed:
Soldering Iron + solder wire
Glue gun + glue sticks
1" of copper wire or small strip of metal
2 AA rechargeable batteries (NiMh or NiCd)

Step 1: Connect Batteries in Series

Sand all terminals of the batteries.
Solder a small wire to the positive and negative terminals of the rechargeable batteries to connect them in series (1.2V + 1.2V = 2.4V).

Check the voltage output using a Voltmeter. Once the desired voltage is achieved, glue the wire and batteries in place using a hot glue gun.

Step 2: Connection Plug

Cut off the connection plug and wires off of the old battery.

Strip the open ends of the wires.

Solder them correctly onto the open ends of the batteries (red wire - positive terminal, black wire - negative terminal).

Check the voltage again using the voltmeter. Once the desired voltage is achieved, glue the terminals and wires to the battery using a hot glue gun.

Place electrical tape on all exposed wires.

Step 3: Summary and Final Product

The diagram summarizes all the steps.

Finally connect the connection plug to the receiver and check that it works. Install the battery cap and place the phone receiver in the phone cradle for charging.

From past experience NiMh and NiCd batteries can be charged using the same charger. (please verify this for your self). Do not mix new and old batteries. Do not mix NiMh and NiCd batteries in the same circuit.

With the original phone battery: talk time ~ 200 minutes
With new DIY battery: talk time ~ +700 minutes
I still have 6 low drain batteries left over for other use.
Total cost of new replacement battery $3.29 (assuming I have use for the other 6 batteries).