The proposed charger (charger) intended to charge the battery voltage up to 28 V and a capacity of not more than 20 Ah and recharge batteries with a capacity of up to 3000 Ah.
Charge the battery (the compensation charge) is required in cases where the battery is not in operation for a long time. As a result, the self-discharge batteries will discharge by about 1% per day (for different types of battery self-discharge rate of its own). Compensation charging current can be calculated from the approximate formula 1md 0.5P * (C — battery, A h), on the basis of the said self-discharge rate of 1% per day and charge 20% more than the self-discharge. For example, for a battery capacity of 60 Ah compensation charge current of 30 mA. It should be noted that high temperature self-discharge the battery longer due to the increased density of the electrolyte.
The operating instructions for the lead starter batteries if they are not operated for a long time, we recommend charging them once a month 1 or hold on float charge. Better — the second option, since in this case the battery is always ready for use. The enterprises that use standby diesel generators for starter batteries, use the second option.
In the developed memory charge produced a stable current. Stabilization of the current is due to the inclusion of ballast capacitors in the circuit of the rectifier bridge. The idea of using a capacitor as a ballast resistance is not new, however, usually capacitors include the primary winding of the power transformer, and this leads to the fact that the device can not be operated without load (at breakage in the load circuit occurring transients on the power transformer there is a high voltage that leads to failure of his or ballast capacitors).
The secondary windings (two windings connected in series) power transformer T1 alternating current through one or more connected in parallel with the capacitors C1 … C11 is fed to a bridge rectifier diode VD6 VD9 …, and output through the thyristor rectifier VS2, ammeter PA1 and fuse FU2 — on the «+» terminal of the battery. Battery terminals connected to the bridge circuit itself.
Control voltage for opening thyristor rectifier formed VS2 ditransformatora. In «manual» mode, the thyristor VS1 closed and a positive voltage across the resistors R3 and R6 is supplied to the control electrode of the thyristor VS2. Thyristor opens and allows the charging current to the battery. The necessary given the current switching switches SA2 … SA11. For example, to obtain a charging current of 140 mA, short-circuit SA4 and SA6.
In the «Machine» closes SA12. The voltage from the battery through the series-connected LED HL3 and zener diode VD10 is supplied to the control electrode of the thyristor VS1. When charging and the battery voltage increases to 14.5 V «breaks» zener diode VD10, LED lights HL3 and opens the thyristor VS1, which is more open, bypassing the control circuit of the thyristor VS2. Thyristor VS2 is also closed at the end of the next half-wave of the mains voltage and the voltage drops to zero at the anode. Charge the battery stops.
The LED signals HL2 memory for inclusion in the network, the LED HL1 — the presence of the charging current (the compensation charge), a HL3 — to terminate the charge.
The work of memory, you can check in «manual» mode, without a battery, circuit connecting the output terminals and the ammeter reading on diodes VD1 … VD4 from a separate winding estimate the charge current. Setting the memory is reduced to verifying voltmeter connected to the battery. At the time of automatic shutdown charging 12V battery it should be voltage of about 14.5 V.
If there is a need to increase the threshold, then the series with an LED HL3 included germanium diode (D7G) or silicon (D226B). The voltage drop across the germanium diode is 0.5 V, and 0.7 … 1 kremnievom- V. The polarity switching diode such as LED and HL3. To reduce the threshold necessary to replace zener diode VD10 (D814D on D814G).
As the power transformer T1 transformer used TS90-1. The primary windings are included in full (two windings 127 in the series). Thus, the transformer can be freely withstand voltage of 254 V and completely heated, even with clock work at a voltage of 220 V. You can use the same standardized type transformer TPP295 which provides an output voltage of 40.4 V (two windings of 20.2 in connected in series) with a current of 1.84 A and 20 B (four windings of 5 in series) with a current of 1.84 A. This transformer can also be included in the lite mode, the primary windings are connected in series to 127 V. The output voltage in this case will go down 36 and 18, respectively.
Excluding the auto-off circuit to limit the capacity of the battery and rechargeable batteries to 4 Ah with voltage up to 28 V, the memory circuit is considerably simplified. This memory can also be used to recharge batteries with a capacity up to 360 Ah. Ammeter in this scheme is almost not needed, because the current charge (the charge of the compensation) is determined by a closed switch SA2 … SA7. LED indication of charge made HL1.
For the simplified scheme to choose a power transformer is even easier. Here, any suitable step-down transformer to supply low voltage electrosolderers 36 V or 42 V may also be used standardized type transformers TAN2, TAN14 which have two winding 40V and provide current 0.2 A. These windings can be connected in parallel for high-power . In these transformers it is also possible to include primary windings in series, but not in the normal way (110 + 110), while the «full» (127V + 127V). The output voltage drops to 36 V.
The proposed schemes storage safe in operation, have a high reliability and efficiency due to the fact that the ballast capacitors active power is not consumed.