Nowadays, the use of powerful uninterruptible power supplies (UPS) for households is becoming increasingly important. This is especially true for electrical appliances located in the house, for which power outages are critical, for example: gas boilers, medical equipment or computers. One of the problems with low-power UPS is the large power fluctuations that occur when different types of loads are connected to them, leading to tripping of the protection. For example, at the moment of switching on, engines and incandescent lamps can briefly exceed power by 5-10 times. Thus, the most ordinary refrigerator, consuming 150 W in stationary mode, may require one or more kilowatts when turned on. And if so, then a 500 W computer UPS will not fit it.

Another problem that you may encounter when choosing a UPS is its operating time when the external network is disconnected. Again, as an example, computer UPS maintain their functionality for 15-30 minutes, then require a full recharge. But the operating time of such a device, in the absence of a network, should be calculated in hours. Obviously, the whole point here is in the capacity of the batteries (ACB) powering such an uninterruptible power supply.

In this article we will present a fairly powerful UPS that can withstand overloads well, and to which you can connect any batteries (within the permissible voltage range). But the most important thing is its modular system, which allows you to assemble the device sequentially, and if any module breaks down, you can simply replace it. All its elements can be bought in well-known stores. Also, over time, it will be possible to change any block to a more powerful one if its previous parameters turn out to be insufficient.

Here we will look at a set of modules for a kilowatt UPS, on board which is a 48 V and 12 Ah battery. It will include a charging module and all the necessary automation. But our readers, by analogy, will be able to convert this device to a different power, voltage and capacity of the ACB, simply by changing the parameters of one or another module. In this way you can collect a “folk” UPS exclusively for its own purposes.

The UPS circuit diagram is shown in Figure 1. It shows that the main element connecting all modules is the Relay1 relay, which has three contact groups. In its first state, this relay is energized, and the mains voltage (IN input), through closed contacts (4-7 and 5-8), goes directly to the OUT output. At the same time, the charging module Charge1 remains connected to the network (X1-X2) and recharges the battery Battery1 through contacts X3-X6. Since it uses a charging module specifically designed for Li-ion batteries, it charges the battery only to the required level, and then automatically turns off. This is what we need. In this state, the battery is connected to the inverter module Inverter1, but relay contacts 3 and 9 are open and prohibit its operation. In this mode, this unit does not consume power.

When the mains voltage disappears, the relay goes into the second state - without current. In this case, the OUT output is powered from the inverter outputs (X13-X14), through the normally closed relay contacts 1-7 and 2-8. The module itself is turned on via X11-X12 by relay contacts 3-9, provided that the contacts of switch SW1 are closed. This switch is optional, but can help save battery power when the network is turned off. With it, you can only connect the inverter when emergency power is required.

The entire block is included in the gap between the network and the consumer, and ensures uninterrupted operation of devices connected to its OUT output.

The Relay1 relay must have three groups of contacts and be designed for AC 220 volts, both in the winding and in the contact groups. Also, its contacts must withstand a maximum current of at least 10 amperes. The author used the following relay: HLS-13F-3-AC220V, the passport of which is given in Appendix [1]. For more convenient installation, the author recommends purchasing a special block for it (Fig. 2). It has the possibility of external mounting and labeled terminals corresponding to the diagram in Figure 1. Our readers can use any other relay with similarparameters.

Inverter1 is a 48 V inverter with the correct sine wave, designed for a power of 3000-4000 W. It must be remembered that the store indicates peak power, but stationary power, in fact, will be 3-5 times less. Figure 3 shows the inverter terminals X9-X10 for connecting to the battery (Figure 4). Pins X11-X12 are the contacts of the external inverter switch, named “ON/OFF SWITCH” in the figure. They are obtained by soldering two wires parallel to this switch, and are brought out of the inverter through any air hole. In fact, you just need to duplicate the inverter switch - on the panel of the entire UPS, only connect relay contacts 3-9 in the break of its contacts.

Pins X13-X14 are shown in the figure as a standard “AC RECEPTACLE” socket. They can also be removed by soldering wires inside the inverter, or better yet, use a plug that fits this socket.

With the battery module Battery1 the situation is a little more complicated, because... It is not always possible to find high-quality batteries. For example, previously used batteries may have high internal resistance and will not be able to produce the declared current. And if so, then the entire UPS will not produce the maximum possible power. But this is a matter of choosing a store or supplier. The author chose Li-ion battery 48V and 12 Ah (actually measured parameter). It has two connectors, indicated in photo 4: for connecting to the charging module (X5-X6), and for connecting to the inverter (X7-X8). The last connector is of the XT60 fimale type, for which it is advisable to purchase the same, but male. Then the design of the device will be more mobile.

You can choose any other batteries, for example these. It is important to ensure that the voltage matches the inverter voltage. If the battery you have chosen does not have a separate charging input, then the terminals of the charging block X3-X4 will need to be connected directly to the batteries (to terminals X7-X8 according to the diagram).

The Charge1 charging module is often sold complete with a battery, which is very good for us, because then this unit is already precisely configured for these batteries and we just need to connect it to them. Generally speaking, Li-ion batteries require a charging unit of 54.6 volts (the upper charge limit for such batteries), and several amperes. Example. More precisely, the battery charging current is usually indicated by the seller. For us, it is important that the charging unit does not exceed this current. Connecting this module is very simple; its pins X1-X4 are shown in photo 5.

It is advisable to install the entire structure in a metal casing for fire safety reasons. For completely reliable circuitry for UPS, you can install automatic fuses at its input and output. Switch SW1 must be brought outside the device for quick access. Make the IN input in the form of a cord from the computer power supply, and make the OUT output in the form of an external outlet.

If the circuit is correctly assembled, its configuration is not required.