Application of lithium-ion batteries in single-phase UPS

    Lithium-ion batteries in single-phase UPS

    The past few years, lithium-ion batteries have gained popularity. According to Bloomberg New Energy Finance, by 2025 they will be used in 40% of data centers. They will account for 5.6 GWh of reserved capacity.

    So the use of lithium-ion batteries in industrial three-phase UPS is unlikely to surprise anyone. The relatively high price of such batteries is almost imperceptible against the background of the total cost of the energy infrastructure of a large facility, and is later compensated for at the expense of a lower total cost of ownership of the solution.

    It is quite another thing - single-phase UPS, the scope of which traditionally involves frugality. In the end, these are not infrastructure and image solutions. It should be in the corner of the box, which may be needed once a month, and even less. Such things are often acquired on a residual basis.

    So is it worth it to spend money on single-phase UPS operating on lithium-ion batteries or is it better to prefer the usual solution? In such an uncertain situation, it is best to quietly exhale and leave alone emotions to start counting the pros and cons. A decision to postpone until later.

    What is a lithium-ion battery?

    The principle of operation of lithium-ion batteries is based on the ability of lithium to integrate into the crystal lattices of silicon oxide, graphite, or other materials, which allows you to accumulate charge on one electrode. For example, when using graphite when charging at the anode, lithium graphite is formed. In the operating mode, the reverse process occurs - the excess charge goes to the cathode, and an electric current flows through the external circuit.

    As an electrolyte in lithium-ion batteries, polymers are used that are capable of incorporating lithium salts into their composition. This allows you to achieve a large inner surface and make products of almost any shape.

    The advantages of lithium-ion batteries

    The service life of a lithium-ion battery reaches 10 years, which is 2-3 times more than that of a traditional lead-acid battery. Even taking into account the difference in prices, savings over the entire period of operation can reach 35%, which is already a lot.

    Due to the lack of sulfation, lithium-ion batteries noticeably exceed lead-acid batteries in terms of discharge: 3-5% per month versus 10-15% per month. Thus, they can even be purchased in advance - under good storage conditions (temperature is about 15 degrees and 30-50% of charge), the battery will be fully operational even after several years.

    Charging a lithium-ion battery takes several times less time. This property can be decisive if it is necessary to provide uninterrupted power to remote objects, and where damage to the supply line often occurs. And also, with frequent disconnections, the lithium-ion battery will play a positive role: 400-600 versus 200 for lead-acid batteries. However, the decisive advantage of lithium-ion batteries when using them in the UPS is in two possible versions: power and energy-consuming . Thus, there is reason to talk about a universal source capable of protecting any equipment connected to it.

    The power version of the performance involves the return of high power in a short period of time. UPS on a lithium-ion battery can provide powerful equipment for 1-2 minutes, while discharging up to 20%.

    In energy-intensive mode, the battery will power the devices of low power connected to it for a relatively long period of time. Accordingly, at the same time, the consumption of capacity will be approximately 20%.

    Due to the chemical-technological properties of acid-alkaline batteries, they can work exclusively in an energy-intensive mode. Of course, it is he who in practice is the most sought-after, but the cases are different.

    The high energy consumption of lithium-ion batteries leads to the fact that all other things being equal, they will be smaller and lighter. Of course, in a home or office for 3-4 people, where the real need for a UPS is calculated in units of products, this is not particularly significant (although how to say?), But even for a small enterprise, the gain will be tangible.
    First, the extra space never happens. Secondly, both the size and weight is the cost of transportation.

    As for the working temperature, it is in the range from 0 ° C to 40 ° C. Thus, the use of these batteries in the UPS objectively does not require additional cooling, but do not forget that the more comfortable the temperature, the greater the life of the battery and the UPS itself, as well as the equipment that is powered by the UPS.

    The usual energy loss in lithium-ion batteries is half that in lead-acid. And this is without taking into account possible power cuts, during which the battery is discharged and then charged.

    For 10 years, the use of a lead-acid battery involves about two of its replacement. While for a lithium-ion battery, this figure may be zero. If we add to the cost of the equipment itself the inevitable organizational costs, then Li-Ion saves a lot of money.

    Lithium-ion battery features

    The highest performance of lithium-ion batteries is achieved under certain conditions. In particular, they do not have a "memory effect", so their discharge "to zero" is impractical and even undesirable - the optimal value for storage is approximately 40% of the charge. In practice, this means that the battery can be charged as needed without any damage to it.

    Over-charging of lithium-ion batteries should also not be allowed. The fact is that lithium ions introduced into crystal lattices of electrodes gradually change their composition. Thus, if the charge is too high (as well as when it is too low), too many lithium ions are in the anode or cathode, which leads to the degradation of the element and shortens its service life.

    The main issue is security. Indeed, at one time the Samsung Galaxy Note 7 made a lot of noise both in the direct and figurative sense. In addition, lithium burning even in water still confuses the average user, so you should thoroughly understand it here.

    First of all, lithium-ion batteries contain not metallic lithium, but its ions, which are less chemically active. Thus, the possible causes of spontaneous combustion of such batteries are not original: physical damage or overheating. Obviously, no lithium-ion specificity is observed here.

    However, due to the higher specific energy and temperature sensitivity under inappropriate operating conditions, lithium-ion batteries are potentially able to quickly reach a state of thermal instability. Thus, the problem of safety is solved through the use of reliable materials and an effective management system, which will be discussed below.

    In addition, it should be taken into account that today the number of lithium-ion batteries produced is estimated at millions, therefore there is always the likelihood of a technical defect or poor quality performance. When buying a UPS, you need to focus on well-known manufacturers with a proven reputation who carefully relate to testing their equipment and choosing component suppliers.

    As a solution, a lithium-ion battery for UPS is more expensive than lead acid. The reason for the most part is that a lithium-ion battery necessarily implies a complex control system, which is primarily responsible for the safety of using this battery, for instantaneous shutdown in case some of the parameters go out of the allowable range and secondarily for ensuring the best battery life conditions: how often and with what current to charge, how many percent of the capacity should remain at full discharge, prediction of the remaining service life and all this taking into account a large number of parameters. UPS with lead-acid batteries also have a battery management system,

    Thus, the main rule that ensures the safety of lithium-ion batteries is to prevent overheating from external heat sources and mechanical damage. And of course, do not disassemble. If the UPS is installed on a remote facility, it is useful to set up remote monitoring to quickly obtain information about UPS events.

    Even a superficial analysis of the properties of lithium-ion batteries leads us to conclude that their potential is very great, but this is precisely the potential. Single-phase UPS on lithium-ion batteries
    As an example, consider the uninterruptible power supply Smart-UPS Online on lithium-ion batteries with a capacity of 1 kVA and 1.5 kVA. They are available with or without a pre-installed network card. One external battery pack is included, and you can connect up to 5 blocks in total.

    The series consists of four models: SRTL1000RMXLI, SRTL1500RMXLI, SRTL1000RMXLI-NC and SRTL1500RMXLI-NC. The last two are equipped with a network card.

    The series models are designed for operation at temperatures from 0 ° C to 40 ° C, the operating mode of relative humidity is 0-95%. The UPS provides IP 20 protection class.

    One of the main guarantees of the source’s stable operation is timely preventive maintenance. The UPS of the series will inform the user in advance of the imminent expiration of the battery life so that the service personnel can replace it in time.

    A high level of efficiency is also ensured due to the possible setting of the “Green mode” mode, which means automatic transfer of the load to the bypass, if the mains supply does not need to be adjusted. This mode of operation will not affect the battery, it will continue to be under the control of the UPS.

    Efficiency of the battery, increase in the term of its service life and reliability increases the system of intellectual control. It allows you to continuously monitor the current state of the batteries and use the optimal mode of their charging, as well as continue to supply energy to the battery even when the device is turned off.

    When charging the battery, temperature compensation is applied. It allows you to adjust the charging voltage depending on the heating of the battery, which prolongs its service life and prevents the transition to a potentially dangerous state.

    There is an emergency power off via the EPO function. When it is activated, there is an instantaneous disconnection of both the load and all power converters, and the UPS itself automatically switches to the fault indication mode. EPO completely isolates the device from dangerous mains voltage, and the source is powered from extra-low voltage.

    The use of lithium-ion batteries in view of the high energy consumption allows to reduce the size of the UPS, as well as reduce the weight of the decision, which in some cases may come in handy. Since UPSs based on lithium-ion batteries belong to the premium segment, the equipment bundle is quite rich: an LCD display, two groups of controllable sockets, a SmartSlot socket for connecting additional controls, a serial port, a USB port. Sources SRTL1000RMXLI-NC and SRTL1500RMXLI-NC are additionally equipped with a pre-installed network card, with which the device can be integrated into a common power supply remote control system.

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