BATTERY, SECONDARY
No. 22

Battery, Secondary No. 22 is a red plastic cased battery pack that was used in some 700 type push button telephones.  Most of these batteries are now dead or failing and the instructions below advise on how to replace the battery.

The original battery comprises of two cells marked NCB 1572A - Made in Germany.
The battery supplies 4.8 volts - 150ma total output.

The lead is terminated in a Jack No. 37A (McMURDO socket connector assembly BMP 3523)

Hyperflight.co.uk a battery pack that has the same specification and the dimensions 31mm x 22mm x 11mm so it should fit inside the original casing.

Replacing the batteries
The lid is glued and difficult to prise open.  Drill a small hole just under the lid and then use a small screwdriver to prise the lid off.  Once the lid moves, it will come off quite easily.

Remove the old batteries - your have to prise these out - and then remove the lead.

Obtain cells or a battery that matches the voltage and current criteria and that will fit into the case.  Try to use NiMH batteries.

Ensure that the leads are connected correctly.

Safety
REMEMBER dispose of the old cells in a responsible fashion.  Most battery companies and council waste sites make provisions.  DO NOT put into general household waste...Please!

Hyperflight battery

Last revised: July 25, 2025