How to replace a Varta V21 PX battery

The 4.5 volt Varta V21PX batteries are used in some 1970s PRAKTICA cameras and have been removed from the market years ago, due to their environmental cost. Apparently, they contained lead and mercury.

Addendum on 2003: The english Small Battery Company sells a replacement for Varta V21 PX.

Addendum on 2004: The german ABCD & Electronics company sells a replacement for Varta V21 PX.

However, using three LR44 batteries, which are easily found in most European and American coutries, it is possible to replace the V21PX battery, giving new life to the Praktica lightmeters.

The following material is required:

1. One square of thick paper (I used cardboard with 260 g/m² or 68 lbs/ream) with approx. 5cm (2in).
2. Three LR44 1.5 volt batteries.
3. One screw with flat-head and 3cm (1.2in) long and its bolt (I used a 5mm-diameter screw (aprox. 1/4 inch diameter) ).
4. One spring with 2cm (0.8in). The spring diameter should be larger than the scew diameter and smaller than the outer diameter of the bolt.
5. scotch tape.

To create the battery envelope, roll the paper (5cm long, 2in) around the three LR44 batteries, with a cylinder shape. The cylinder should be tightened with scotch tape.

The batteries ought to be stuck on one of the cylinder ends. A simple way of getting this result is to tight one of the ends a little shorter and insert the batteries through the other end.

The batteries are inserted in serial arrangement with the negative pole (-) first. Then the bolt is fastened around the screw and the spring is inserted around the screw end.

The position of the bolt should be adjusted according to the spring length., such as the rest length of the ensemble is greater than 6 cm (2.4 in) and the compressed size is shorter than 5 cm (2 in), which was the size of the original V21PX battery.

To insert the batteries inside the paper cilynder, you may use the screw or a pencil, pushing the LR44 batteries until the first negative pole (-) gets out of the other cylinder end. This should ensure a good electrical connection to the terminal. Then, you should insert the spring-screw set, which will connect to the positive (+) pole terminal.