3.Battery Ah calculation. "name": "Home" So, the battery charger will have a minimum output rating of 40 amps. The main reason is that Li-ion batteries have higher specific energy [Wh/kg] and specific power [W/kg] compared with other types [2]. thanks. The high voltage battery pack ofMitsubishi i-MiEV consists of 22 modules made up from 88 cells connected in series. How to Calculate the Battery Charging Time & Battery Charging Current? the equations are not readable. Finally, total up two of the columns. Spam Comments Will Be Deleted. UPS back-up time information is based on estimation. @ @ l!! We Rely on Advertising to Help Fund Our Site and Provide Free Information. Download UPS Sizing Calculation Excel Sheet Take the power produced by the solar panels and divide by the voltage of the batteries. Thus, youneed your engineer on record to review the existing chargers compatibility. On the other hand, a high voltage limit can improve performance, but it can also cause grid corrosion to form on the positive battery plate. . Unlike solar panels, A moderate temperature is needed for proper operation of the batteries. All about Electrical & Electronics Engineering & Technology. The values on our Solar Sizing Worksheet assumes typical power output is based on 6 hours charging per day and will vary at different times of the year, by location, and with varying weather conditions. The volume can be also calculated function of number of strings and number of cells in a string. The equations should be readable. In short, the deeper discharge will shorten the life of the battery. 6) Charging voltage: To maintain optimal battery performance, its important to use the correct charging voltage limits. UPS sizing information is provided for reference only. Step 1: Collect the total connected loads that the battery requires to supply Step 2: Develop a load profile and further compute design energy Step 3: Choose the type of battery and determine the cell characteristics Step 4: Choose the battery cells required to be linked in series fashion hbbd``b`$^ Fv $AN Your comment highlights how the post needs some added clarity with the percentage though. Use the correct battery rating (100-Hr), or a battery rating that approximates the actual autonomy hours for the system load. The continuous load is at 3.8 A. thank you. In most off-grid PV systems, you have a battery that stores the solar-generated electricity. @ @ l! 301-325. The calculations performed are based on Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications and Recommended Practice for Sizing Nickel-Cadmium Batteries for Stationary Applications IEEE standards. It seems that a single powerwall will handle both the maximum power (3.5 kW) and energy (running on solar during the day, charging the battery for use overnight. TV, Fridge, Lights, etc..). Add an optional factor of safety (20% or more) to determine the final battery-set size. People usually share this information in their build threads. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); document.getElementById( "ak_js_2" ).setAttribute( "value", ( new Date() ).getTime() ); please share download link for your solar pv design software. For automotive applications there are different types of cells used [1]: Image: Different shapes of Lithium-ion battery cellsCredit: [1]. Select Type of Connection of Batteries in Battery Bank Select Rating of Each Battery in Battery Bank Size of Inverter Size/Type/Tripping setting of Main MCCB. Get Free Android App | Download Electrical Technology App Now! Step 1: Calculate Your Load. Over 100 Powerful Engineering Resume Buzzwords, Homeowners Guide For a Structural Engineer Inspection, 12 Essential Portable Generator Maintenance Tips. |@ @ l! Thank you for this very informative article. The battery size calculator will show the required size of battery bank and number of. The UPS battery bus voltage is 480 V. The typical table is for 12 V batteries (six cells of 2 V each). Battery recharge time = battery capacity or size in watt-hours / power input in watts This MS Excel spreadsheet calculates the following: Total Demand Load Size of Solar Panel Select Type of Connection of Solar Panel Select Rating of Each Solar Panel Energy from Solar Panel as per Daily Sun lights Size Battery Bank Select Type of connection of Batteries in Battery Bank Size of Inverter Although the 12V system is more common, you may use a 24V or 48V system for solar panel installation systems depending on the system configuration requirement. 1  A r i a l 1  A r i a l 1  A r i a l 1  A r i a l 1  A r i a l 1  A r i a l 1 A r i a l 1 *  C i t y B l u e p r i n t 1  A r i a l 1 A r i a l 1 A r i a l 1 $ A r i a l "$"#,##0_);\("$"#,##0\)! Battery Sizing The battery capacity for a PV system can be calculated using the following formula: 3) Battery room temperature: Optimum temperature is normally between 68-77 Fahrenheit. ${{V}_{\text{eodv}}}$, Represents end of discharge voltage (Vdc)if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[300,250],'electricalacademia_com-large-leaderboard-2','ezslot_4',111,'0','0'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-large-leaderboard-2-0'); ${{V}_{\text{charging}}}$, charging voltage of cell (Vdc). We assumed the following values in order to compute the battery capacity: Using the above mentioned parameters, we can compute the minimum battery capacity as: \[{{C}_{\text{minimum}}}=\frac{3245\times \left( 1.30\times 0.96\times 1.12 \right)}{120\times 0.75}=50.4\text{ Ah}\], Did you find apk for android? Find your perfect solar solution! Example: A solar array is producing 1 kw and charging a battery bank of 24V. You can see how the 120V AC power supply feeds the 21kV switchgear protection loads. This is your suggested battery size in amp-hours if using 80% of the capacity ==> Electric Skillet 2 LED reading lights. In our example, the depth of discharge is 50%. In this example we are going to caclulate the volume of the battery pack considering only the battery cells. It is provided without warranty of any kind. Also, the electric motor and driveline have some losses which we need to consider. This needs to be considered as well. I was wondering if the 8 hour rate of discharge is discussed in IEEE standards as a typical rate to use in substations or this is just an industry practice? Notify me of follow-up comments by email. Elsevier Butterworth-Heinemann, 2004, page 129. Battery Bank Sizing Calculator Let's determine the size of the battery bank for your system. Its an industry standard, but youll come across various requirements from customer to customer. You may find the latest data from weather forecast resources or state meteorological department for average sunshine and estimated cloudy days in specific areas. "item": @ @ l!! driving cycle taken from spreadsheet calculation are as follows: total time is 196s, total distance < - . Important Note: All batteries have internal resistance, which causes the cell voltage to decrease as it depletes. Select highest battery capacities per unit to reduce the number of battery strings in parallel for better charge balance. 6 Reasons It Is! 06 v difference. For lead-acid type batteries, an EODV is principally based on an EODV value that prohibits cell damage by over-discharge. If your items are not listed on the form, select the nearest item available from the list. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. The total number of cells of the battery pack Ncb [-] is calculated as the product between the number of stringsNsb [-] and the number of cells in a stringNcs [-]. ups battery sizing calculation excel sheet. But why, you ask? IEEE recommends you use the lowest voltage of your battery to calculate all your loads and during sizing. The battery sizing can be initiated once we have the following information:if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[320,50],'electricalacademia_com-medrectangle-3','ezslot_2',106,'0','0'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-medrectangle-3-0');if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[320,50],'electricalacademia_com-medrectangle-3','ezslot_3',106,'0','1'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-medrectangle-3-0_1'); .medrectangle-3-multi-106{border:none !important;display:block !important;float:none !important;line-height:0px;margin-bottom:7px !important;margin-left:auto !important;margin-right:auto !important;margin-top:7px !important;max-width:100% !important;min-height:50px;padding:0;text-align:center !important;}. Just do it and click on the calculate button. VDC. Lead-acid or nickel-cadmium). You will have to connect 10 batteries each of 100Ah in parallel to run a 900Wh load (minimum for 3 hours) per day with 2 autonomy days. Direct usage of renewable energy like wind and solar power is not that much efficient if we dont store them for later use. Other than storage purposes, batteries are extensively utilized in order to provide voltage support for weaker electric power systems such as very long transmission lines.if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[320,50],'electricalacademia_com-box-3','ezslot_8',141,'0','0'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-box-3-0'); Battery sizing is crucial in order to ascertain that it can supply power to the connected loads for the time period it is designed. ${{k}_{af}}$, Battery Aging Factor (%)if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[250,250],'electricalacademia_com-leader-1','ezslot_6',112,'0','0'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-leader-1-0'); ${{k}_{tcf}}$, Temperature Correction Factor (%), ${{k}_{crt}}$, Capacity Rating Factor (%), ${{k}_{mdod}}$, Maximum depth of Discharge (%). Battery Capacity in Ah = (Energy Demand in Wh x Autonomy Days x Backup Hours) / DoD in % x DC Voltage, Battery Capacity in Ah = (900Wh x 2 Days x 3 Hours) / (50% x 12 Volts), Required Size of Battery Capacity Bank = 999 Ah (Almost 1000Ah). (a) 1 x 100 % Battery and 2 x 100 % Battery Charger are considered for 220V DC system. The battery is always on standby, ready to power your system. 5. Size of Invertor. Generally, the Autonomy Method is utilized to establish a load profile for batteries. Yes, all batteries have an internal resistance, and the cell voltage decreases as it depletes. not just cells. Additionally, specify the battery discharge rate, also known as the C rating. How to Find the Number of Outlets on a Single Circuit Breaker? All we have to do is find the current through the controller by using power = voltage x current. Ive updated the XLS link above, please check. x@ @ Temperature correction factor:if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[300,250],'electricalacademia_com-large-mobile-banner-2','ezslot_12',114,'0','0'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-large-mobile-banner-2-0'); The battery cells capacity is generally provided for a standardized temperature which is 25oC and if it varies somewhere with the installation temperature, a correction factor is needed to implement. Cathodic Protection - DnV RP-B401 (aluminium & zinc anodes). The first step is the determination of the total connected loads that the battery needs to supply. It actually captures the reduction in battery performance because of the age factor. @ @ " x! Cloudflare Ray ID: 7a1638403ecb3f64 If it is home based, you may easily get annual power usage data from the energy meter or, Keep in mind that if the number of days of autonomy increases, you will have to add more batteries, even more power sources like, This is the rating of DC voltage of the battery (generally, 12V, 24V, 36V, 48V, 72V etc). 14. %PDF-1.5 % The battery acts as a backup power source if the AC power supply fails, so it must always be fully charged and ready to go. When you login first time using a Social Login button, we collect your account public profile information shared by Social Login provider, based on your privacy settings. For two level charging typically 1.47 to 1.7V/cell. Hello Sir, I find your article very useful and relevant to my work as a maintenance personnel in a distribution Utilities. The number of cells required for a particular voltage rating is presented below:if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[250,250],'electricalacademia_com-banner-1','ezslot_7',143,'0','0'])};__ez_fad_position('div-gpt-ad-electricalacademia_com-banner-1-0'); Nevertheless, the number of cells required can be determined more precisely in order to match with the load tolerance more accurately. But now, the battery charger feeds a 125V DC panel, which in turn powers allthe critical DC loads. In order to chose what battery cells our pack will have, well analyse several battery cells models available on the market. How to Find the Proper Size of Circuit Breaker? x@ @ l! To use this spreadsheet enter your data in the shaded cells. IF I HAVE 620 volts lithium ion battery pack, how much HP motor is required to generate 1450 RPM?. Unsuitable sizing of the battery can pose many serious problems such as permanent battery damage because of over-discharge, low voltages to the load, insufficient backup times. This website is using a security service to protect itself from online attacks. In other words, the number of days without charging the batteries (mostly in cloudy weather). @ @ l! There have been several developments in substation equipment technology that can have an impact on battery size requirements. The high voltage battery it is one of the most important component of a battery electric vehicle (BEV). Maximum, minimum and nominal temperatures pertain to site ambient/installation conditions. The voltage of each cell is 3.7 V and the total voltage of the battery pack 330 V. Image: Battery pack (modules and cells)Credit: Mitsubishi. Stuck in the Battery Pack Formulation?Watch this video exclusively on Battery Pack Calculation!#electric #vehicle #batterypackHere are some informational res. How to Determine the Right Size Capacity of a Subpanel? ) _(* #,##0_);_(* \(#,##0\);_(* "-"_);_(@_)? Select your backup times and click Step 2. The string continuous current Iscc [A] is the product between the continuous C-rate of the battery cell C-ratebcc[h-1] and the battery cell capacity Cbc [Ah]. Author: Shrikant Kajale. I added a note. Did you manage to work it out? The battery cell energy densityis calculated as: The energy density for each cells are summarised in the table below. Step 4: For each appliance, determine . Please read and accept our website Terms and Privacy Policy to post a comment. The following step is the selection of the type of battery (e.g. Add and modify positions, e. g. for accessories Attach price lists how have you implemented battery depth of discharge and solar efficiency. Based on the calculated data and conclusions, we can choose which battery cells are suitable for our electric vehicle battery pack. This is the rating of DC voltage of the battery (generally, 12V, 24V, 36V, 48V, 72V etc). Think about it, every critical component in a machine needs a backup plan, right? In terms of mass and volume there is no clear distinction between cylindrical and pouch cells. "@id": "https://electricalacademia.com/category/batteries/", Please Whitelist Our Website by Allowing Ads, How to Calculate the Right Size Battery? The comment form collects your name, email and content to allow us keep track of the comments placed on the website. Home Batteries Battery Sizing Calculation | Solved Example { Instead, IEEE standard Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications provides certain guidelines for autonomy (backup or discharge) times. How to Calculate the Right Size of Solar Charge Controller? A battery cell consists of five major components: electrodes anodeand cathode, separators, terminals, electrolyte and a caseor enclosure. Im going to go over a typical substation battery sizing calculation. This sheet is gold. He studied Electronics and Physics and enjoys everything that has moving electrons and fun. Battery Buss Voltage. thank you in advance! Nevertheless by looking only at cell based volume and mass, we can estimate which model willbe better compared to the other. Battery life will shorten if the temperature goes too much higher. [3]Tom Denton,Automobile Electrical and Electronic Systems, Third edition. Footnote on Tesla Powerwall: I placed a deposit a year ago with Tesla for Powerwalls. 1000ma = 1A b. hUoLe^8k{=NaHXeY5K]Q6l-~(e5OJq~$o l>@4`UD_Zoa}+l@h6yi%_%b7gYPM!NRGLc}Y a\pEtWAsWr@5SI#[#Vn>y{op}u1VGR$9SeW. why does it extracts from 2? x @ Check your inbox now to confirm your subscription. ?_);_(@_)6 + 1 _(* #,##0.00_);_(* \(#,##0.00\);_(* "-"? If you are getting the solar panel for TV and fridge. Professional Installer Support: 1-800-468-1502 Monday through Friday 9:00AM - 5:30PM CT . Important Note: The substation battery sizing calculation well be using is per IEEE Standard 485. 5 minutes = .083 hour c. To add a 20% safety factor, multiply the required battery-set size by 1.2 (120%). %%EOF How to find C-rate for each cell? Insert all figures in decimal, eg 2 or 1.5. The input parameters of the battery cells are summarised in table below. In short, you want ample backup power allowance for operators to restore AC power or make any necessary control decisions. "@type": "BreadcrumbList", Total: 50VA + 110VA + 90VA + 160VA + 1000VA = 1,410VA. I have a query sir. And inverter sizing consists of two parts, voltage and current sizing. In Summer. The following table shows the typical wattage rating of different home appliances. As for energy and capacity, the pouch type cells have higher peak (continuous) current and powerthan cylindrical cells. How Much Watts Solar Panel Do You Need for Home Appliances? Homeowner Support: 1-800-633-3991 Monday through Friday 9:00AM - 8:00PM CT Based on daily PV production: 20 kWh (PV per day) / 3.1 kWh (battery at 90% DoD) = 6.4 (3.5 kWh batteries) From this calculation, you can round up to 7 or round down to 6 batteries based on customer preference (such as mode of operation). = 13,950.8VAh. The direct current (DC) supplied by the battery is converted into alternated current (AC) by the inverter. & Load LoadDuration (Mins. @ @ " x! NOTICE ANN Annunciator Smoke Detector @ @ " " 8 There are several types of batteries (chemistry) used in hybrid and electric vehicle propulsion systems but we are going to consider only Lithium-ion cells. { Substitute I = Iav in the equation for battery capacity of lithium-ion. Watts Here. I have been using them and they have a very high C rate up to 20C which approximately equals 1000W. Solved Examples, How to Find Voltage & Ampere Rating of Switch, Plug, Outlet & Receptacle. Hi, I have the same question as you. 4) Slow charging: Lead-acid batteries charge slowly. The following calculations are going to be performed for each cell type. The battery pack capacity C bp [Ah] is calculated as the product between the number of strings N sb [-] and the capacity of the battery cell C bc [Ah]. "item": Breaker Calculator & Examples, How to Find The Suitable Size of Cable & Wire ? @ @ ! Even if Wh/km is not really energy but factorised energy, since its dived per unit of distance (km), for simplicity, we are going to refer to it as average energy. = (0.5 + 1.0) x 2 x 1.5. This is less important since the aim or the article is to explain how the calculation is done. You can find new, Battery Sizing Calculation | Solved Example. EE-Tools, Instruments, Devices, Components & Measurements, battery only store DC power instead of AC power. If you look at whats going on in the automotive industry most of the OEMs have 400V battery packs with 800V being the next generation. Battery sizing calculation Adjusted battery load calculation. This MS Excel spreadsheet calculates the following: Calculate Size of Solar Panel, Battery Bank and Inverter (MS Excel Spreadsheet) [XLS], Mike is the founder and editor of Electronics-Lab.com, an electronics engineering community/news and project sharing platform. . Keep in mind that battery only store DC power instead of AC power. Well, the same goes for a power substation, which is essentially a massive machine. This is mostly particular to the battery application like UPS system or solar PV system. } This calculator assumes and adds for inefficiencies in batteries, panels, and wiring. The battery pack which will be in the vehicle will have additional components (wires,electronic components, soldering, case, etc. These are the number of days where you can use the storage power of deep cycle batteries without charging them. This is why they need batteries to ensure all critical substation loads can operate at any time. The AC power supply powers the loads through the battery charger. For example, if you need a battery, which can discharge for 24 hours, use C24 in your battery call-out. Can you please tell me where the E_avg equation is coming from? Calculate size of battery bank and inverter This MS Excel spreadsheet calculates the following parameters: Total Demand Load Size of Battery Bank in Amp.Hr. Products specifications are subject to change without notice. If you know which batteries have been supplied, you can enter the battery size into the bottom box. For this particular example, a vented lead-acid battery has been chosen. Choose the required number of cells within these two limits (although choosing cell numbers in the middle of minimum and maximum values would be most suited). and Excel sheets. The controller size is then 1000/24 = 41.67 amps. Performance & security by Cloudflare. This particular factor accounts for voltage reduction during the discharge of the battery. "url": "https://electricalacademia.com/category/batteries/", Voltage per cell,12,V Amp-hou. (See example below). VDC. If you see more generator run events in the months and locations you will camp or be at your cabin, you will. Sizing battery banks for switchgear and control applications is commonly performed using software designed specifically for that purpose. The Battery Sizing module determines the number of strings, number of cells, and cell size of a battery for a designated duty cycle and also compensates for real-life variables such as temperatures, aging, and initial capacity that apply to these type of critical electrical systems. the charger is rated at 25A, 48V output, and 240V input. Measured with Kill-a-watt Watts used while on: 6W Watt-hours over a 6 hour period: 18Whr Calculated: Average Watt-hours per hour = 18Whr/6hr = 3Whr/hr Watt-hours per day = 3Whr/hr * 24 Hr/day = 72Whr/day Time on per day = (72Whr/day)/6W = 12 hrs/day Edited to clarify run-time math Daily Sunshine Hours. Do you have any substation battery sizing tips? endstream endobj startxref x! How to Determine the Suitable Size of Inverter for Home Appliances? For this example we are going to consider that the battery pack is made up only from several strings connected in parallel. Do Not Promote Your Business or Your Website Here. and Battery voltage (12V or 24 V or 48V depending upon how many batteries you are planning to use) This will automatically calculate the Ah required for the battery with inverter. The duration of the WLTC cycle is 1800 s (0.5 h), which gives an energy of 215 Wh for the auxiliary loads. Can you please mention the source for all equations. To calculate how long your solar panels will take to charge a solar generator or battery bank, you need to know battery capacity and solar power output. So far sampled-data modeling and sensitivity analysis are mostly used for such purpose. A low voltage limit can cause poor battery performance and sulfation buildup on the negative battery plate. If you are not OK with the manual calculations, you may use the battery bank size calculator right after the solved example for battery size calculations. The size and mass of the high voltage battery are very important parameter to consider when designing a battery electric vehicle (BEV). 4471 0 obj <>/Filter/FlateDecode/ID[]/Index[4462 16]/Info 4461 0 R/Length 62/Prev 944328/Root 4463 0 R/Size 4478/Type/XRef/W[1 2 1]>>stream x@ @ Our battery will have a minimum rating of 200Ah at an 8-hour rate, or C8. The 125% multiplier accounts for this voltage drop to ensure the battery is not undersized. All calculations are done automatically. Could you check if there is any author contact info? We can now recalculate the battery pack total energy E bp [Wh] as the product between number of strings N sb [-] and the energy content of each string E bs [Wh]. Notify me by email when the comment gets approved. The number of battery cells connected in series Ncs [-] in a string is calculated by dividing the nominal battery pack voltage Ubp [V] to the voltage of each battery cell Ubc [V]. Your email address will not be published. Batteries are the lifeline to substations, providing backup power. For our electric vehicle battery design we are going to start from 4 core input parameters: A battery consists of one or more electrochemical cells (battery cells) which are converting chemical energy into electrical energy (during discharging) and electrical energy into chemical energy (during charging). One of them being the need of bigger spacing between electric components in order to avoid short circuits. Note: Since battery cells manufacturers come up with newer models continuously, it might be the case that the data used in this example is obsolete. Hello We need a passport to add some load data. , : _("$"* #,##0.00_);_("$"* \(#,##0.00\);_("$"* "-"? For example, 3 strings connected in parallel will triple the capacity and current capability of the battery pack. First of we have to enter the Electrical Load Detail in Electrical Load Sheet .The following are input values we have to enter in the Columns :-. Individual battery cells may be grouped in parallel and / or series as modules. I am afraid the C rate of Toshiba LTO cell is wrong in here. A high number of cells might causeadditional problems in areas of wiring, voltage monitoring, battery reliability. Solar panel power needed = 4.5 kW. As an off-the-cuff reply, you probably would need to replace the charger, but there are other variables you need to consider too. Battery Sizing. This gives operators an 8-hour window to fix any AC power supply issues before things start going haywire. Keep microprocessor relays, control circuits, emergency lighting, and communication equipment powered up, Ensure power is uninterrupted when you need it most, Trigger power circuit breaker trip and close coils, Keep motor-operated air breaks, valves, pumps, and fans in motion, k = efficiency factor (1.1 for lead acid batteries), C = calculated Ah discharge from the battery based on the duty cycle. Therefore, the result of the calculation is rounded to the higher integer. While noting, as the voltage drops on a DC system, the current drops as well (assuming a constant resistance). Battery voltage is something you define as input parameter. Battery Depth of Discharge (DOD) Input Total. Testing and Monitoring Methods for Stator Insulation Systems. The lead-acid battery performance is comparatively stable but reduces with the passage of time. But the protection loads are all powered by 48V DC. "@context": "http://schema.org", Instead, IEEE standard , Physical properties like dimensions, weight, and battery terminals, Electrolyte density in case of lead-acid batteries at a full charge, Cell end-of-discharge voltage (EODV) of cell. It has 2 zones and each zone can equip maximum 25 detectors. The mass and volume are calculated only at cell level, taking into account the cell dimensions andmass. For more accurate sizing, including using your location . The battery sizing can be initiated once we have the following information: The calculations performed are based on , Step 3: Choose the type of battery and determine the cell characteristics, The backup (autonomy) time is frequently provided by the customer. The ups is important for low current systems such as fire alarm, CCTV (security cameras) and other systems that needs power source all the time. Step by Step Procedure with Calculation & Diagrams. In Lead-acid batteries, a voltage dip occurs in the early phases of battery discharge followed by certain recovery. Your calculations utilize the nominal voltage of 125VDC but battery load profiles will show you that the battery voltage will continuously taper off during the load draw. References [1], [2], and [3] include a detailed discussion on battery sizing calculations for three common types of batteries used in electrical substations. UPS Battery Sizing Calculator Electric power in kVA Battery cells per string: Power Factor Operating Time *Calculations are based on the full rating of the UPS - anything other than full load will affect the inverter efficiency and warrant the calculations inaccurate. You have masked that by adding all of your % increases but ultimately it will not be sized sufficiently for the full life cycle. The total battery pack voltage is determined by the number of cells in series. We assumed the following values in order to calculate number of cells required: Maximum number of cells required to be connected in series: \[{{N}_{\text{maximum}}}=\frac{{{V}_{dc}}\left( 1+{{V}_{\text{load,max}}} \right)}{{{V}_{\text{charging}}}}=\frac{120\times \left( 1+0.2 \right)}{2.25}=64\text{ Cells}\]. The same results can be plotted in bar graphs for an easier comparison between the different types of battery cells.