Recovery of AB radiotelephones. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Telephony

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The peak of popularity of "indoor" radiotelephones, designed for a small removal of the handset from the base unit connected to the city telephone network, in general. passed as cell phones became ubiquitous. But for many, they still "plow" in apartments, and questions about their reliable operation remain.

One of these topical issues is the premature (as it seems to the owners of radiotelephones) "wear and tear" (loss of capacity) of the storage battery (AB). It often happens that a new radiotelephone (RTA) bought in a store does not provide the normal operation stated in the passport even during the warranty period (20-30 minutes of continuous conversation with a charged battery) In my practice, the loss of battery capacity became noticeable at 3-4 months of operation RTA. What are the causes of loss of battery capacity? There are several.

Firstly, these are the operating conditions of the RTA. One owner has frequent conversations and. accordingly, often discharges and recharges the battery (when he puts the handset on the "base") The other rarely talks. and, as a rule, his tube is constantly on the "base", i.e. in recharge mode. Despite. that in most RTAs the recharging system is automated (battery charging occurs up to a certain point and stops when the battery is "saturated"), this does not save the situation, since the battery "trains" little with periodic discharge-charge cycles. PTA manufacturers focus on the first, active users of phones, in which battery training occurs by itself. Thus, the active owner of the PTA. without knowing it, it extends the life of the phone from a standard battery. Secondly, it is important what type of battery is used.

Nickel-cadmium (NiCd) (Fig. 1) batteries are cheaper, they are still produced, but they have the notorious "memory effect". This effect is manifested in the loss of battery capacity, if a battery that is not completely discharged is switched on in the charge mode (the handset is placed on the base). With constant use in this mode, the time of "active" "use of the handset gradually decreases, which creates inconvenience. People begin to scold manufacturers of RTA, regret the "thrown to the wind" money, although the situation is actually easy to fix.

First of all, it should be noted that NiMH batteries are more adapted to frequent mode changes (Fig. 2). They are devoid of the "memory effect", are able to gain capacity with partial discharge almost to the maximum, and, conversely, "do not like" when they are discharged to the end. It is easy to find out which type of battery is used in a particular case by opening the PTA battery cover and reading the designation on the battery case.

Both considered types of batteries are similar in appearance and, as a rule, have a nominal voltage of 3,6 V. In addition, they differ in capacitance, the value of which directly determines the duration of the conversation. For ordinary PTA users, I would not recommend buying batteries with a capacity below 600 mAh.

There are also Li-ion batteries (Fig. 3), which differ from those considered in manufacturing technology, long service life, appearance and scope (used in cell phones).

In addition to replacing a NiCd battery with NiMH, there is a simple and effective way to restore PTA batteries. To do this, a battery disconnected from the tube (capacity 300 ...

In parallel with the resistor, it is desirable to connect any DC voltmeter with a measurement limit of 5 ... 10 V to control the discharge of the battery. Without monitoring, we can assume that a 300 mAh battery will be completely discharged in an hour. The resistor may heat up a little during the discharge process. For batteries of a different capacity, a resistor of a different resistance is selected. In practice, it has been observed that the greater the resistance of the shunt resistor (of course, up to certain limits), the longer the battery will last.

The AB, discharged in this way, is installed in the handset, which is placed on the base, and recharged for 8 ... and charge at the base. The cycle of forced discharge and regular charge is repeated 10 5 times. As a result, the battery is restored to a state close to new. In principle, you can limit yourself to 7-2 cycles, the result of increasing the capacity will be noticeable after that.

In this way, I managed to restore more than five dozen NiCd and NiMH batteries for the PTA. The only exceptions were completely "lost" specimens that had been in complete inactivity for a long time. They usually manifest themselves as the absence of a noticeable effect after 1-2 discharge / charge cycles. Other miniature batteries with a different nominal voltage can also be restored using the recommended method.

Author: A.Kashkarov, St. Petersburg

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