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Independent power supply in the apartment or house step by step

UPS with an external car battery

What is being described here:

1. Why do you need independent lightening system

1.1 What are the options for the apartment and house

2. Autonomous lighting on uninterrupted power supply

2.1 Choosing UPS – why not a computer one

2.2 Choosing external battery packs or accumulators

2.3 Connect batteries to uninterruptible

3. Connection of uninterrupted power supply to electrical wiring

4. Summarizing the results of the system of autonomous lighting

1. Why do you need independent lightening system

Everyone who lives in private houses or, especially, in the cottages, is well aware that sometimes electricity «likes» to disappear at the most inopportune moment. Such intermittent blackouts prior to the 2022 war had various causes. Therefore, even then, many owners thought about how you can budget autonomous lighting in the house.

Since it was relatively uncommon to turn off the lights, few people have actually realized this idea. However, the situation has changed dramatically since the autumn of 2022. When a significant amount of Ukrainian energy infrastructure was damaged during the hostilities. And disconnection became permanent planned, and often additionally emergency.

In this article, a autonomous lighting system means a system of independent power supply of a low power house or apartment. It is possible to connect not only lamps, but also refrigerator, computers, router, mobile gadgets and other low-power consumers.

Will the wired Internet work if there is a power outage in the region?

In most private houses, it is enough to supply electricity to the router, so that you have the Internet even when scheduled power outages. When the entire area is left without normal mobile coverage, the Internet is an essential tool for communication (Viber, Telegram) and receiving news.

It was during the war in 2022 that the issue of the organization of autonomous lighting in the house was particularly acute. Our appraiser (who is also the author of the article) independently made such a system in his home and is ready to share the experience. By the way, the principles and systems described are also quite suitable for implementation in city apartments.

1.1 What are the options for the apartment and house

The main options for the self-sustainment system are only three:

  1. Generator. Many homes have petrol, diesel or gas generators with or without ATS. ATS – Automatic Reserve Input System – starts and switches the house to a generator in case the main power source does not work. After restoration of the regular power supply, the generator is deactivated.
  2. Uninterruptible power supply. Its operating principle is the same as that of the well-known computer UPS. As soon as the electricity in the network is lost, the uninterrupted system automatically switches to battery operation. When power is restored, the UPS charges and maintains the battery. And this is the difference from the inverter, which simply increases the voltage of the 12V battery to 220V. UPS combines voltage inverter and battery charger.
  3. A solar or wind power plant. Numerous calculations show that today, unfortunately, it is not worth it. The cost of establishing and maintaining such systems is considerable and does not make much sense for their owners. Unless only, if the house is not connected to the power grid at all. And the task is to organize a fully autonomous power supply.

Many articles have been written about the standalone power supply system from the generator. This technology has been known for a long time, is well-developed and does not raise questions.

Petrol generator in the basement

It is enough to choose a generator of the appropriate power and on the type of fuel you prefer. The generator is connected to the network of the house either through the ATS (automatic reserve input system), or through the manual switch of the power source: from the power grid or from the generator.

Despite the fact that the ATS seems to be a great option, many home owners prefer manual switches. Given that outages in 2022 occur quite often, it is unlikely for a regular home there is a need to start a generator at each such outage. Nor does it seem appropriate to keep him «in pairs» during a standard four-hour shutdown.

Practice shows that manual switching to a generator operates reliable automation and allows you to save on fuel and increase the life of the generator.

The system of autonomous power supply on the generator has its advantages. As a rule, the power of the generator allows you to connect most electrical appliances in the house. Including such powerful consumers as water pump and electric stove. However, there are disadvantages:

  • Noise. At night, use a generator in the house next to the neighbors or, moreover, in the apartment is unlikely to work without regular scandals.
  • Exhaust. The problem of exhaust exhaust is seemingly insignificant. However, people face challenges in implementing such a system. There are special corrugated metal gas hoses, but they are also not so simple as it looks like. The length of such hoses for normal operation should be small, and the number of turns is minimal. The hose is strongly heated from hot gases. It is often not easy to secure a hose to the generator exhaust pipe. There are also difficulties with street access, especially in city apartments.
  • Fuel reserves. In a private house, this problem is not very large. However, to store and replenish the reserves of gasoline or diesel fuel in the apartment – this is an occupation, as they say, «on the fan».

Generator exhaust venting to window

From this context, it is possible to reach the following conclusions:

  1. In a private houses, the generator is needed as an alternative source of energy for powerful consumers.
  2. In the apartment you will not be able to use generator.
  3. In the conditions of frequent and long power outages it makes sense to refuse (also to save well) from the ATS system. And connect the generator manually only if necessary.

2. Autonomous lighting on uninterrupted power supply

After discussing the strengths and weaknesses of the generator, we come to the following conclusion.

For autonomous backup lighting and maintenance of the fridge, computer, TV and router in case of frequent and long power outages, the use of a generator is not feasible.

The perfect option would be a system similar to the usual ups for a computer. When there is electricity, work from the network. When the light goes out, we automatically switch to the battery and continue usual life. How to organize such a system in the house or in the apartment? Would a simple computer circuit breaker also work, at least for emergency lighting?

We will handle it step by step!

2.1 Choosing UPS – why not a computer one

The most common question is: Will a conventional computer uninterruptible system be suitable for the organization of an autonomous power supply at home?

The conventional computer UPS is not suitable for the off-grid power supply at home for two reasons. Firstly, most UPS computers have too little power and battery capacity. Secondly, most often UPS have an output voltage in the form of e.g. approximated sine wave, which will not work at all or quickly break down LED lamps, any pumps and even the weakest electric motors.

If you plan to use a computer uninterruptible for lighting, it is necessary to make sure that it emits a so-called clean or correct sine wave. Often these UPSs write that they are suitable for heating boilers. Or just plug in the LED lights and try to power them from the battery. It is much better to make sure in advance that the offline lighting system is working correctly with a specific uninterrupted system than to know about it after all installation work.

battery backup for computer

Choosing a source of uninterrupted power supply for autonomous power supply of the house should pay attention to the following characteristics:

  1. Output signal type. Clean (correct) or approximated sine wave. If the UPS output signal is an approximate sine wave, it will not be able to function properly in the offline lighting system with LED lamps and boiler pumps.
  2. Inverter power. The inverter is the part of the UPS that converts the 12V battery voltage into the 220V we are used to. To calculate the required inverter power it is necessary to calculate the amount consumed (not rated) power each device, which you plan to connect to. These indicators are indicated in the instructions, operating manuals and technical passports for household appliances. Note that UPS power is often indicated in V (volt amperes) and consumers power consumption in W (watts). To transfer V to W you need to multiply UPS by 0,8. In such way, real power of UPS on 1000 V is going to be 800 V.
  3. Type of battery. Whether the UPS uses an external or internal battery (built-in). When creating an independent power supply, a significant storage capacity of the battery is required. Therefore, the preferred option is an external battery uninterrupted power supply.
  4. Maximum battery capacity. If the UPS supports the use of external batteries, pay attention to their recommended capacity. Of course, the bigger the better. The supported capacity is affected by the minimum and maximum current that the UPS can charge the battery.
  5. Battery voltage. Voltage of standard battery pack for car or uninterruptible power supply is 12 V. Therefore, if the UPS performance indicates a different voltage, you should understand that you will need several batteries. For example, if the UPS is powered by 36 volt batteries, you will need to buy 3 batteries, 12 volt each battery, and connect them in series. Of course, the fewer batteries in the system, the cheaper and more reliable. On the other hand, high power inverters require a voltage higher than 12 V. From here the requirement for multiple batteries with a cumulative higher voltage.

It is also important to pay attention to the type of UPS architecture:

  • Line-interactive. This UPS has an integrated stabilizer. If you have a stabilizer installed in your house or apartment, and the UPS is connected to the power grid through it, then you should not buy a linear-interactive safety switch. Due to the presence of two stabilizers in the system, false switching to the battery can be observed. On the other hand, linear interactive UPS are the most common on the market and the cheapest options.
  • Online. In this type of uninterruption, the load is always connected via an inverter, so switching to the battery is not really happening. Such UPSs are the most expensive, but their use is justified only for specific equipment, such as special medical equipment or «really-cool» servers.
  • Offline or backup. It is the best option to organize independent power supply in the house, especially if you have a stabilizer installed. The UPS does not have a built-in stabilizer, and the switch to the battery is automatic when the power in the network is gone.

The best UPS option for the home emergency power table is offline ups with pure sine wave, which runs on an external battery voltage 12V. But pay attention on whether for your tasks the power of this uninterrupted and time of its offline operation!

For our needs we have selected 1kW UPS Pendant from Ukrainian Elex manufacturer. Of course, I would like to be more powerful, but unfortunately, in this manufacturer’s line-up this UPS is the most powerful. All other parameters are perfect: offline, external battery for 12V capacity from 50 to 400 Ah, can withstand an extra power of 1,5 times 15 seconds (important for refrigerators with conventional non-inverter compressors). In addition, the type of battery recommended by the manufacturer is a hermetically sealed lead acid, which is many times cheaper than similar gels. But about this below…

This article is not advertising and we do not promote a certain manufacturer. Just on the example of our system show how we did. And what were the reasons for the choice. I didn’t want to buy a Chinese UPS of unknown quality. In addition, I have for a long time perfectly working stabilizer of the same manufacturer, so the choice was obvious.

2.2 Choosing external battery packs or accumulators

If the uninterrupted power supply has a built-in battery, its parameters are «not playable». But such UPSs are bad-suited to the organization of a autonomous power supply system at home due to the small capacity of the battery and low power inverter. So we will focus on how to choose the right external battery for the UPS.

Let’s start with the most obvious – battery voltage. UPS can operate from 12, 24, 36 and 48 volts. The higher the voltage, the higher the load can be connected to the battery backup.

To get the right voltage you need to buy several batteries of 12 volts. There are batteries at the right voltage, but it is usually just the same set of standard batteries of 12 volts interconnected. It is usually more profitable to buy and connect several batteries by yourself.

Now about the type of battery. Most UPS write that work with special gel batteries for UPS. Such batteries unlike automobiles are not afraid of frequent deep discharges. Oops, which we have chosen – Elex Kulon 1000 – is designed to work with sealed lead-acid car batteries. These batteries are about 3 times cheaper than the gel batteries, which most UPS use!

On the forums write that car batteries are afraid of full discharge. And in the case of frequent such failures battery will not live for long. But, first of all, it is not certain that it is really gonna last. And secondly, it is better to take a battery with a storage capacity and thus not plant it completely, than to overpay for a gel battery three times with an unknown result in terms of efficiency.

Be sure to use hermetically sealed maintenance-free batteries, especially if they will be installed in enclosed rooms. Such construccia eliminates the appearance in the air of electrolyte vapours that harm health. In addition, these vapors are explosive!

We were looking for a sealed lead-acid car battery with the largest capacity. It was Bosch T5 080 на 225Ah, which we ordered and bought in Epicenter.

Table. Operating time of UPS depending on load capacity and battery capacity

Operating time of UPS depending on load capacity and battery capacity

Looking ahead, we have come to realize over time that we lack the capacity to run the system properly. Rather, with our consumption the system «back to back» works for 4 hours. However, the battery for the next 4 hours simply does not have time to charge, so that the next shutdown to fully work.

Two car batteries whihch included in the UPS

We said above that when the batteries are connected consecutively (plus one by minus the other) you can increase the voltage. In the same way, you can increase the capacity if you connect the batteries in parallel (plus one for plus one, minus by minus).

If you are using multiple batteries in a UPS system, make sure that they are all the same (same model), same age and preferably from the same batch. This applies to both sequential (to increase voltage) and parallel (to increase capacity) battery connection.

Here is why two batteries will charge faster than one. And why, by buying a second accu, we will solve the problem with insufficient recovery time. It is the charging current. There is a rule that the charging current should not exceed 10% of the battery capacity. On our UPS Kulon charge current can be selected from such values: 5, 10, 15, 20, 25, 30A. Accordingly, having one 225Ah battery in the system, the current should be selected 20A. After installing the second battery, the total capacity will be 450Ah. For this capacitance we choose the maximum possible current of 30A. This way, at the same discharge in our case, the two-battery system will recover 1.5 times faster.

Display UPS Kulon

The storage capacity, in addition to its direct function of increasing system life, has a positive effect on battery life. And allows the system to function normally even if it has not had time to fully charge.

2.3 Connect batteries to uninterruptible

If your 12V battery is running and you do not need more capacity, connection is not very difficult. You simply connect the UPS wires to the corresponding battery terminals.

If the 24V or higher voltage circuit breaker works, you need to connect several twelve volt batteries in series. Sequentially, that means plus one to minus the other. And the inverter connects to the extreme free terminals: plus one battery, minus the other.

When the capacity of one accum is not enough, and the UPS runs from 12 volts, as in our example, the batteries must be connected in parallel. So one man’s plus one, one man’s minus the other. UPS wires are connected to different batteries: plus one, minus another battery.

There are situations when the voltage of the inverter operation exceeds 12 volts, but the capacity of the batteries is not enough. In this case, a combined connection is used. That is, some of the batteries are connected in parallel, some are connected in series. For example, there are batteries with a capacity of 200Ah, the inverter works with a voltage of 24V, and a capacity of 400Ah. In this case, you will need 4 accum. Each of the two pairs is connected in series, with two blocks 12V per 400 Ah. After that, these two units are connected to each other in parallel (through the extreme free terminals). We get a block of 4 batteries on 400 Ah and 24V. Connect an inverter to it, also using the terminal terminals, so that between the UPS wires in the chain have all the batteries.

Terminals are required to connect the wires to the batteries. If you use car accumulations, you can buy by and terminals to them in any auto shop. Written many articles about how to choose terminals. But, as they say, there are many letters 🙂 , that is why we are going to share our own real experience. In stores, the choice is usually limited to three types of terminals for the material: zinc, brass, lead. It is believed that the worst are zinc terminals, so do not choose them. The choice of brass or lead – it is only your preferences.

Lead terminals are softer, tighter tightened, in case of spark melt faster, breaking contact. Brass conducts the current better, but it breaks easily if you overdo the tightening.

In our system there are 4 terminals: a pair of brass and a pair of lead. First, the first battery was bought brass. And already under the second took lead, because the alternative was only zinc. My personal feelings, lead is more pleasant in editing. But I wouldn’t really focus on that. Both brass and lead are great choices.

Car battery terminals for UPS

And the last thing you need to write about in the section about the connection of batteries, these are connecting wires – jumpers. Let’s start with their cross-section area. On the Internet there are tables of dependence of cross section of wires from the power of inverter. In practice, however, we have seen that the information in them raises certain doubts. Firstly, it is obvious that the cross-section areas are indicated with a large margin. Secondly, most stores do not have many copper wires with a large cross-section to pick it up perfectly under load.

We went the other way. In our UPS Pendant of 1 kW standard wires have a cross section of 20 mm2. Correctly on plus and on minus goes two wires with a 10 mm cross section2. Based on sound logic, we decided that the standard 1×25 PV3 wire (copper flexible single core 25 mm2) will be pretty enough. This wire is common, we bought it in Epicenter.

There is immediately for him to buy terminals for a bolt. Squeeze such terminals ideally need a special manual press, but we coped with the usual pliers.

3. Connection of uninterrupted power supply to electrical wiring

Now it is necessary to connect the uninterrupted power supply to the electrical wiring of the house or apartment. We connected the UPS itself via an automatic switch to an electrical input wire. In our case, given the small power of the inverter in 1kW, an automaton for 10 or even 6 amps is suitable. We installed one circuit breaker to connect the UPS power supply to the mains, and the second one to the consumers.

Automatic switches when connecting UPS

Now we have to choose the lines that we want our customers on. The most obvious and important for connecting with UPS devices are:

  • Lighting.
  • Router.
  • Fridge.
  • Sockets for charging phones and possibly computers work.
  • If you have a gas or solid fuel boiler, connect the heating pumps.
  • If the inverter power allows, connect the pump in the well or pump station. It is important to note here that pump starting currents are usually many times higher than nominal. Therefore, the inverter protection can be activated at the start, and such a system will not work. To solve such problems, there is a variant of the use of soft start devices. However, in order not to complicate the system, we decided to abandon the idea of connecting the pump to the fail-safe. Instead, an additional we have purchased a hydrobattery on 300 L, which allows you to have a significant water supply without having to turn on the pump. Well, if that is used up, the generator will come to help you with it.

To connect consumers you need not only to find the right phases on the circuit breakers. Also for each such line it is necessary to find and power from UPS and zero wires.

It often happens that on the line with the consumer, which needs to be connected via a fail-safe, there is another device. For example, the boiler, which through the UPS do not need to connect. In this case, you will need to run separate wires from the UPS or the electrical panel to each such consumer.

If you have a generator, it is necessary to connect the UPS so that when you start the generator it not only provides power to consumers, but also charges batteries. If you have chosen the offline uninterruptible architecture, it is better to power it through a stabilizer. If you have a linear-interactive or online UPS with a built-in stabilizer, its power needs to be passed by the stabilizer, directly from the input electrical cable.

4. Summarizing the results of the system of autonomous lighting

Installing a back-up lighting and power supply system on the uninterrupted power supply in the house or apartment can solve several important tasks:

  1. Autonomous lighting.
  2. Internet (communication).
  3. Fridge. Inverter models will work better with UPS. They have reduced power consumption and no power surges when starting the compressor.
  4. Phone charging.
  5. Work on the computer.
  6. Heating system pumps.

If you live in a private house, the main question that arises when choosing a UPS is: «Is it possible to connect a pumping station or a downhole pump via an uninterrupted power supply?»

Yes, you can connect the pump. But you need to consider the following. The UPS should have an output voltage of «proper sine wave». The UPS must be significantly higher than the nominal power of the pump to handle high starting currents. You might have to use a smooth start for the pump to get the inverter to handle with the load.

Several accumulators in the water supply system at house

In most cases, it is easier, cheaper and more reliable not to connect the pump to the uninterruptible, but to buy additional hydraulic accumulators of the desired tank. First, it will give a large supply of water, which in the extreme can be replenished with a generator. Second, it will in any case have a positive impact on the life of the pump, because the more capacity of hydraulic accumulators in the system, the less it will have to turn on.

If this article seems useful to you, share it on social networks! This material is not commercial. And it can help people get through a difficult winter 2022-2023.