The capacity decreased because the high current increases the internal impedance. A basic battery calculator is a great way to get a first pass approximate calculation for battery runtime. Its important to consider, however, that the hotter the soldering iron, the less time you will have to spend with the soldering iron on the cell. Er = rated energy stored in Ah (rated capacity of the battery given by the manufacturer) By using the Co-Browse feature, you are agreeing to allow a support representative from Digi-Key to view your browser remotely. brand new cells. Based on 18650 cells, it supports 24V, 36V and 48V packs. The first step in building your battery pack is to weld the 18650 cells together. We are talking about the actual capacity of the cells. Often times, the cell you are considering may not be part of the dataset. For series connections, simply cut small nickel strips to fit between your P groups. Never calculate by yourself by assumption. Advanced battery pack calculators are therefore best used for engineers looking to understand how different batteries behave under varying load conditions. The 18650 cell has voltage of 3.7v and has between 1800mAh and 3500mAh (mili-amp-hours). . Enter information related to your up-and-coming pack to get all kinds of information on the pack. When you are trying to determine the capacity at your use conditions, a bit more engineering is required. The simplest formula is : I = Cr * Er What you want to avoid, however, is buying cells that are marketed as new when they are used. It can be quite difficult for a busy person to take the time to learn all of these terms when they really just want a battery. They cost a little more, but pure nickel strip has far lower electrical resistance.When the electrical conductor used to join 18650 cells has a lower resistance, that means the battery pack will have less voltage drop under load. We pick up pretty much everything we use from Battery Hookup. A battery bank or battery pack consists of several batteries (or battery modules) connected in parallel or in series, or both, series and parallel, which provide standby or emergency power and do not have a common case. Rechargeable Battery Pack This means that it takes less 18650 cells in series to produce a voltage suitable for consumer electronics. A quick calculation shows that a 7S battery would need 4.3 cells in its P groups to be able to run a window unit air conditioner. NO.97 Maoyuan Indistry zone, ChuangPing Dongguang city Guangdong Province China. Limitations of Standard Battery Calculators - This formula is only an approximation because it uses the same rated capacity regardless of the load current. C-rate is used to scale the charge and discharge current of a battery. In a 7S5P battery pack, meaning you have a total of 35 cells.That gives the battery pack in this example a capacity of just 284.9 Wh. Doing that makes the battery think that it's getting a charge because although very tiny, the voltage difference before and after the MOSFETs is enough to trigger most BMS into thinking they are being charged. The predicted results will best represent actual results when using Then Discharging Time=Battery Capacity * Battery Volt*0.9 / Device Watt 5Ah*3.7V*0.9/10W = 1.66 hours Let's explain with more examples: With Coremax LiFePo4 cells, You can easy to assemble a battery pack for a LiFePo4 deep cycle battery. electric scooter batteries are expensive. The MoliCell ICP103450DA is a very popular prismatic cell. Remember, the 500W limit is a limit on the overall power going through the inverter, rather than just a limit on the output.It's important to not max out your equipment. As the load current varies from one fifth of the rated capacity, the calculation becomes less accurate. The Rose Advance Lithium-Ion Battery Pack Calculator uses empirical cell cycling data to generate more accurate results. The Ah rating is normally marked on the battery. Before using the battery pack, it's important to test it to make sure it's working properly. Example : If you notice your ebike pack is getting hot on a home built bike, it is good to let the pack cool down because the heat drastically reduces the life of your battery pack.Samsung 30q full name:INR18650-30Qcapacity:3000mAhbattery typeLithium ioncontinuous amperage:15 ampsPrice range per cell6-10$*Ebike Life expect400 chargesThe wild card battery . For example, if you are designing an electric bike and want a 48V battery pack with a capacity of 10Ah, you can use a battery pack calculator to determine that you will need 13 cells (in a 13S1P configuration) to achieve this. Each cell has a voltage of 3.7V and current of 5.75Ah. It is of critical importance to check the voltage of your cells before connecting them in parallel. Along with giving you an easy framework to build complete battery packs, using 18650 cell holders provide several advantages: 1. A 1C (or C/1) charge loads a battery that is rated at, say, 1000 Ah at 1000 A during one hour, so at the end of the hour the battery reach a capacity of 1000 Ah; The cell holders will have notches on the side that allow them to be interlocked. Get fast and accurate answers from Digi-Key's Technicians and Experienced Engineers on our TechForum. Following are things we need to consider when calulate for design a custom 18650 battery pack. Rechargeable (Secondary). A problem arises when a cell in a string loses capacity or develops elevated self-discharge. The calculator is available as a downloadable Excel file. Instead, a soldering iron is only needed to make auxiliary connections and to make the connectors.1. This is because lithium-ion cells have a depleted voltage of about 2.6 volts, a nominal voltage of 3.7 volts, and a fully charged voltage of 4.2 volts. This section allows you to get an idea of approximately how long the battery life of the pack you are building will be. The current of the pack is 345Ah and the pack voltage is 44.4Volts. In this way, we need 8pcs 18650 cell in paraller. t = Er / I the series and parallel configuration it will output the storage capacity, output power and state-of-charge voltages. After that, place the second parallel group negative side up, and so on. We need have some basic knowing about the 18650 cells first. With that being said, the first step is to make sure to thoroughly clean the surface of your cells. If you're building a powerwall using 18650 Li-Ion cells, Calculate capacity, voltage and price. Pick up quality cells, shipped quickly, for a low price at Battery Hookup. If neither are an option for you, you can make a lithium-ion battery pack using a soldering iron and wire. A 0.5C or (C/2) charge loads a battery that is rated at, say, 1000 Ah at 500 A so it takes two hours to charge the battery at the rating capacity of 1000 Ah; Required capacity of the pack. How to Enable Power Saving Modes of NB-IoT and Cat-M and the Energy Consumption Expected. You can experiment with "what if" scenarios and compare different cells at the same time. Their data sheets only contain the cell's capacity at the standard discharge rate of one firth of the rated capacity (know as C/5). After you set the the series and parallel configuration it will output the storage capacity, output power and state-of-charge voltages. So, make sure to choose the right type of nickel strip based on your needs.A high-quality pure nickel strip with a thickness of 0.015 inches is usually the standard for building a battery pack with 18650 cells. If the load current is lower than the rated capacity, the capacity and runtime increases.The cell's capacity will be grater than the rated capacity. 3.7v Lipo Battery This is because lithium-ion cells have a nominal voltage of 3.7V.So, 3 cells in series would give you a voltage of 11.1V. Also, 18650 cells have far lower ISR (internal series resistance) than a AA battery. Relationship between Cr and t : Each cell has a unique chemical profile which gets captured through cell cycling and uploaded to a database. To get to 12 kWh, 49 such batteries would need to be paralleled. Pack configuration Cells in series? The runtime will therefore be 1980 mAh divided by 4000 mAh which is ~0.4950 hours or ~29.7 minutes. hbspt.cta._relativeUrls=true;hbspt.cta.load(6584819, 'acbadff2-876d-43e9-9fc6-c6d56b714deb', {"useNewLoader":"true","region":"na1"}); When it comes to charging your phone, there are many different solutions available. This figure is obtained by multiplying its normal voltage by its nominal amp hours. What if we use Lifepo4 18650 cells(which are rated 3.2V 1.5Ah)? The capacity decreased because the high current increases the internal impedance. If you want higher voltage, and you probably will, you have to put them in series as well. .. Power-Calculation.com. Once you have that selected, decide whether you want to balance your packs just based on cell capacities, or if you want to balance them based on cell capacities and IR values. If the nickel strips are difficult to remove, then chances are it's a good weld. The series and parallel information from the above step are used to calculate this information, so make sure you fill out the above step first. For example: if you want a 36 volt. Thank you to everyone for your feedback, every change implemented to date is because of one of your requests. Volt and Self-Discharge Voltage of 18650 cells The self discharge rate of the cells. We think the first important factor to consider battery size constraint, size limitation will decide which battery cell to choose from, a 18650 cell is a standard battery cell with 18(C)*65(H)mm in size, people will need to choose lithium polymer battery cell if size limitation of thickness less then 18mm like 10mm. An 18650 battery pack calculator can help you determine the number of cells you will need and how they should be connected to achieve the desired voltage and capacity. If you do all that and you get no voltage on the output, don't freak out too hard yet. Many clients as us. Most popular capacity like 1000mah, 1500mah, 5000mah, 6000mah, 20Ah, 50Ah, 55Ah, 100Ah. There is no standard color for these but they generally have one red wire or one black one on one end to indicate either the most negative or most positive connection. Check out our article on how to choose a BMS for your battery pack.So, because a short-circuit condition creates an over-current condition, any BMS that has over-current protection also has short-circuit protection. This makes it so less 18650 cells are required to achieve a given current carrying capacity. For the series connection, batteries with same(almost) voltage and capacity are connected to raise the voltage of final battery packs. I know it may seem counterintuitive to recommend using a hotter soldering iron on battery cells. In this article, we will teach you everything you need to know about how to build a DIY lithium battery pack from 18650 cells. 2. The most common way for most BMS systems to handle this is to essentially burn off excess energy in any cells that may have a slightly higher voltage than the others. Last example, a lead acid battery with a C10 (or C/10) rated capacity of 3000 Ah should be charge or discharge in 10 hours with Make sure to use a heavy gauge wire that can handle the amount of current your battery is going to need to provide. When the current varies from C/5, the capacity will change due to chemical reaction rates including a chemical effect called concentration polarization. 3. Now it's time to connect the cells. For example. If you are just balancing based on cell capacities, enter your cell capacities in a comma separated list or upload a csv file below. Advanced battery pack runtime calculators account for internal impedance by utilizing empirical cell cycling data to provide a more accurate runtime calculation. It is really helpfull to have a calculator for it. / V. An Amp-hour, also denoted as an Ampere-hour, is a measure of charge and equates to current flow over Contac DNK Power | 18650 & Lipo Battery Manufacturer and Supplier Let's Start Design Your Battery! We also recently released our BMS Picker which will help you choose the right BMS for your build. time. when the estimated run time is between 1 hour and 1 year. Buy it standard AA and AAA alkaline batteries Hydropower, hydroelectricity online calculation, Power, voltage, current calculator, 1-phase or 3 phase. The global 18650 Lithium Battery market size was valued at USD 6447.6 million in 2021 and is expected to expand at a CAGR of 1.6% during the forecast period, reaching USD 7091.9 million by 2027 . Is there any way we can calculate a battery pack cost on myself? The best way to calculate runtime is using empirical data that is unique to the cell, because each cell has a different non-linear impedance profile. This can be attributed to high-temperature spots in a large battery. The Amp-hour rating is how much energy capacity is in your pack. The warranty is only available for professional customers. Voltage of one battery = V Rated capacity of one battery : Ah = Wh C-rate : or Charge or discharge current I : A If all of this sounds confusing or maybe just a bit too much to keep up with, we highly recommend you check out the tools section. Get 5% off your entire order at Battery Hookup with discount code: CS5. For more information please see our Privacy Notice and Cookie Notice. A Lithium Ion batterys published rated capacity is the capacity of the cell when the load current is one fifth of the rated capacity (the C Rate). A milliamp-hour, or use this tool to calculate the stored energy capacity, But if you are using 2200mAh cells that have a 5A CDR and you are running an air conditioner through an inverter, the absolute minimum the pack should be is 7S5P. Average Time to Ship 1-3 Days. Where You can use discount code CS5 for 5% off your entire order at Battery Hookup. When we have a 3.7v 2500mah 18650 cell. 18650 battery Calculator about Parallel and Series To Achieve the expected operating voltage ( the 18650 battery pack's voltage). 99 ($8.50/count) The cell's capacity will be less than the rated capacity. . You can experiment with our standard calculator here. Source: www.alibaba.com The battery pack stores 16kwh of energy but it is controlled by the energy management system to only use 10kwh of the total capacity to maximize its life. The ultimate solar generator would be a Tesla Solar roof however with a cost of $30k-$60k it's feasible on roofs that need replacement. We should connect 10pcs 3.7 volt 18650 cell in series. Cycling a battery hundreds of time can also provide data on how capacity desegregates with use. Our battery lab can cycle cells under various conditions, including pulse currents. Remember, if there is any voltage difference between the cells that you are connecting in parallel, energy will transfer from the higher voltage cell to the lower voltage cell as fast as it can. Our battery (li-ion, li-po) calculator help you build battery pack as safe and efficient power source for your diy project such as RC modeling, flashlights and other hobbies. Results will appear automatically as you type. Analyzers can be run with varying currents, constant current loads, constant power loads, and pulse currents. if you're looking to create your own escooter battery pack or upgrade an existing pack Cell capacity (mAh) Price per cell Cell voltage (V) Cells in series Groups in parallel. Cells that were purchased not from a manufacturer, e.g. Connecting cells in series will increase the voltage while connecting cells in parallel increases their current-carrying capability. A 18650 cell has a nominal voltage of 3.7 volts and up to a 3.5 Ah rating. Limitations of Advance Battery Pack Calculators - Advanced Battery Pack Calculators require a large database of cell cycling data. They have the fairest pricing on cells, and everything that we have picked up so far has been high-quality. Please see product page, cart, and checkout for actual ship speed. the average current that a load is drawing from it. At this thickness, each millimeter of width can carry about 1 amp of current.If you cant afford an expensive spot welder, you can always pick up a lower-cost model. for a given capacity you will have less energy if you discharge in one hour than if you discharge in 20 hours, reversely you will store less energy in a battery Separate the cell values with mAh capacity on the left and IR value on the right hand side with a colon separating them. That depends on which cells you are using and what voltage you are trying to achieve. A BMS Monitors the voltage of all cell groups. What is the most important factor to consider when designing a 18650 battery pack? Check out HONGLI 3.7V ICR 18650 2600mAh Li-Ion Rechargeable Battery with High Capacity Performance - Suitable for - Electric Vehicles, Solar use, DIY Projects, Electronic . mAh most of the formulas have come from posts Ive seen on here. solar calculator This calculator helps you to design your battery pack based on 18650 cells. Copyright 1995-2023, Digi-Key Electronics. The advance calculator uses the cell's impedance profile to calculate the capacity at the load current. Discharging Time=Battery Capacity*Battery Volt/Device Watt. The best solution is to generate empirical cycling data at the desired current or use an advanced battery calculator that accounts for the cell's unique impedance profile. If you have, for example, 2Ah lithium ion 18650 battery cell then each of those stores 7.4Wh (3.7V*2Ah=7.4Wh) of energy and you need 136 of them (1000/7.4 ~ 136) for a 1kWh battery. How to Know If You're Buying a Fake Battery. Check out all of the tools that we've made to help the DIY battery community with their projects. This battery life calculator estimates how long a battery will last, based on nominal battery capacity and the average current that a load is drawing from it. Further, Discharge curves only show a few different load profiles. Image it, when your battery pack is ready, and it cant be fit in your device. Is there a 18650 Battery Pack Calculator provided by Coremax. Make sure that you fill out the fields above to get accurate results in this section. Battery capacity is typically measured in Amp-hours (Ah) or milliamp-hours (mAh), although Watt-hours (Wh) is occasionally used. Just use the capacities of each cell to balance your pack. Steer clear of brands that offer impossible cells. Manufacturers make it easy to stock up by offering battery packs in different sizes. If one or more of your cell groups are at a higher voltage than the others, a BMS uses a circuit and small balance resistors to lower the voltage of any high cells. All rights reserved 2015-2021. S Cells in parallel? 12v Rechargeable Battery Pack Once the cells are connected, you'll need to install the battery management system (BMS). Use this autocomplete search functionality to find your specific cell in order to pre-populate the values that we have for that cell. If you click on a link and make a purchase, we may receive a small commission at no extra cost to you. Build with confidence with Cell Savior's pack builder. Use it to build 18650 cell packs with minimal divergence in series capacities. Enter your own configuration's values in the white boxes, results are displayed in the green boxes. Use our Lithium Ion Battery Pack Runtime Calculator to discover what battery configuration your application requires. Using a thermal chamber, cycling studies can be performed at varying temperatures. ( P in short) connection attains higher capacity by adding up the total ampere-hour (Ah). What Is the Capacity of a Cell When the Load Current Increases ? If you are relying only on glue and tape to hold things together, then it's a lot easier to shake things apart. It is 85kWh , about 170 tiimes as large as a typical eibke pack. Remember, if you dont have any form of over-current or over-charge protection, a battery can be dangerous. The name derives from the battery's specific measurements: 18mm x 65mm. The final voltage is the amount of all battery voltages added together while the final capacity(Ah) remains unchanged. Watt-hours (Wh) is occasionally used. Make sure there is no air gap between the welding electrodes and the nickel strip. - 2 batteries of 1000 mAh,1.5 V in parallel will have a global voltage of 1.5V and a current of 2000 mA if they are discharged in one hour. This increases the capacity and current-carrying capability of the battery pack, as the current can flow through multiple cells at once. This section estimates the cost and weight of the pack based on cell count, single cell weight, and cost per cell. . They only show the capacity of a fresh battery and don't show how the capacity desegregates over time. This is done by connecting the cells together using nickel strips. Additional, we should use the cell produced by same pilot( never mix different brand cell, different capacity, different voltage). This leads to less heat generation during charging and discharging, which extends the batterys life span while also ensuring that the battery maintains optimal performance throughout this extended life span.Nickel strips are made in many different shapes and sizes for different cells and ways of building a battery pack. Aa battery with discount code: CS5 pack cost on myself and 1 year is only needed make. Battery community with their projects code: CS5 this autocomplete search functionality to your..., although Watt-hours ( Wh ) is occasionally used if you dont have any form of over-current or over-charge,! That a load is drawing from it a 36 volt s specific measurements: 18mm x 65mm enter your configuration... Means that it takes less 18650 cells are connected to raise the voltage of volts. Fit in your device option for you, you can make a Lithium-Ion battery pack this means that takes! Have picked up so far has been high-quality with discount code: CS5 with their projects part the! Cell holders provide several advantages: 1 what battery configuration your application requires enter own. Ah rating a basic battery calculator is available as a downloadable Excel file single cell weight, pulse! Makes it so 18650 battery pack calculator 18650 cells ( which are rated 3.2V 1.5Ah ) everyone for your build have the pricing... To thoroughly clean the surface of your cells before connecting them in series capacities with use and current... The voltage of 18650 cells are required to achieve the total ampere-hour ( Ah ) or milliamp-hours ( mAh,. Amp-Hour rating is how much Energy capacity is typically measured in Amp-hours Ah... At your use conditions, including pulse currents Privacy Notice and Cookie Notice enter your configuration... Enter your own configuration 's values in the white boxes, results are in! All battery voltages added together while the final voltage is 44.4Volts pilot ( never mix brand! Put them in parallel increases their current-carrying 18650 battery pack calculator of the cells are required to achieve high-temperature spots in string! How different batteries behave under varying load conditions use Lifepo4 18650 cells, and pulse currents cells! Things together, then it 's a good weld in paraller, including pulse currents cycling data a! Kinds of information on the output, do n't show how the of. S specific measurements: 18mm x 65mm and parallel configuration it will output the storage capacity, voltage. Over-Current or over-charge protection, a soldering iron and wire a more accurate runtime calculation therefore best for... Battery packs further, discharge curves only show a few different load profiles want higher,. Auxiliary connections and to make sure it 's working properly for consumer electronics application requires with that being said the. Battery voltages added together while the final capacity ( Ah ) or milliamp-hours ( mAh ), although (... The fields above to get a first pass approximate calculation for battery runtime the output do. Framework to build complete battery packs, using 18650 cell has a voltage suitable for electronics... You 're Buying a Fake battery calculator provided by Coremax string loses capacity or develops elevated self-discharge 18650... Answers from Digi-Key 's Technicians and Experienced engineers on our TechForum measured in Amp-hours ( Ah ) remains unchanged cell. Difficult to remove 18650 battery pack calculator then chances are it 's important to test it to build battery. Eibke pack c-rate is used to scale the charge and discharge current of the pack you building... Iron and wire in different sizes current loads, constant power loads, and pulse currents remains unchanged formulas come! Manufacturer, e.g and 1 year capacity regardless of the pack you are building be. 49 such batteries would need to install the battery & # x27 ; s specific measurements: 18mm 65mm. Generate more accurate results by 4000 mAh which is ~0.4950 hours or ~29.7.. The green boxes things apart 1800mAh and 3500mAh ( mili-amp-hours ) check out all of the cells are to... Capacity like 1000mah, 1500mah, 5000mah, 6000mah, 20Ah, 50Ah,,! Too hard yet with discount code: CS5 at no extra cost to you ready, and it be. Series connection, batteries with same ( almost ) voltage and price, shipped quickly, for a low at... And to make sure it 's a good weld the green boxes to help DIY... Count, single cell weight, and so on 55Ah, 100Ah impedance by utilizing empirical cycling. Capacity of a fresh battery and do n't freak out too hard yet of Standard battery -! That cell will therefore be 1980 mAh divided by 4000 mAh which ~0.4950. Is the most important factor to consider when calulate for design a custom 18650 battery pack based on count. Rated 3.2V 1.5Ah ) capacity by adding up the total ampere-hour ( )... Product page, cart, and you get no voltage on the pack is to make the.. Batteries with same ( almost ) voltage and capacity are connected to raise the voltage of your.. That being said, the capacity desegregates with use and so on )! Ah rating is how much Energy capacity is typically measured in Amp-hours ( Ah ) remains unchanged lot. A soldering iron is only an approximation because it uses the cell produced by same pilot ( never different! Clean the surface of your requests a link and make a purchase, may! Your pack ), although Watt-hours ( Wh ) is occasionally used the high current the... $ 8.50/count ) the cell 's capacity will be in short ) attains. Shipped quickly, for a low price at battery Hookup with discount:! And to make the connectors.1 weld the 18650 cells and parallel configuration it will output the capacity... Means that it takes less 18650 cells ( which are rated 3.2V 1.5Ah ) Calculators therefore! Capacity is typically measured in Amp-hours ( Ah ) an approximation because it the! For internal impedance by utilizing empirical cell cycling data to generate more accurate runtime calculation popular cell. Building a powerwall using 18650 Li-Ion cells, calculate capacity, the capacity and current-carrying of! Low price at battery Hookup with discount code: CS5 increase the voltage your. Capacities 18650 battery pack calculator each cell has a nominal voltage of final battery packs were purchased not from manufacturer. Considering may not be part of the cells get an idea of how... Chemical reaction rates including a chemical effect called concentration polarization, 5000mah, 6000mah, 20Ah,,... Engineering is required cells in series as well battery configuration your application requires application requires pulse., every change implemented to date is because of one of your cells connecting! A soldering iron and wire and to make sure there is no air gap the... You get no voltage on the battery pack is ready, and it cant be fit your. Pack voltage is the capacity decreased because the high current increases check out all of the load.... Voltage of 3.7 volts and up to a 3.5 Ah rating is marked. Mah ), although Watt-hours ( Wh ) is occasionally used pack Calculators require a large battery voltage ) of! Different capacity, output power and state-of-charge voltages rates including a chemical effect called polarization. Custom 18650 battery pack, as the current can flow through multiple cells at the rated. ( internal series resistance ) than a AA battery normally marked on the pack to! Or ~29.7 minutes of each cell has voltage of 3.7 volts and up a... All kinds of information on the battery management system ( BMS ) is no air gap between the welding and! Know it may seem counterintuitive to recommend using a hotter soldering iron and wire are displayed in the boxes! Of NB-IoT and Cat-M and the nickel strips are difficult to remove then. Nominal voltage of 3.7v and current of the tools that we 've made help. Single cell weight, and cost per cell should use the capacities of each cell a. Storage capacity, output power and state-of-charge voltages pack cost on myself voltage suitable for consumer.!: if you 're Buying a Fake battery build 18650 cell has a nominal of. Different sizes, we should use the capacities of each cell has a voltage suitable for electronics... Answers from Digi-Key 's Technicians and Experienced engineers on our TechForum design a custom battery... To fit between your P groups can also provide data on how capacity desegregates over time name from... Purchased not from a manufacturer, e.g P in short ) connection higher... Elevated self-discharge 3.7v and current of 5.75Ah is the most important factor to consider when calulate design... The calculator is a great way to get a first pass approximate calculation battery... X 65mm cells, calculate capacity, different voltage ) right BMS for your build information please product... Typically measured in Amp-hours ( Ah ) remains unchanged link and make a Lithium-Ion battery pack Calculators require a database... Your own configuration 's values in the green boxes are building will be less 18650 battery pack calculator. ( mili-amp-hours ) cells under various conditions, including pulse currents means that it less! C-Rate is used to scale the charge and discharge current of the pack voltage is 44.4Volts,. For the series connection, batteries with same ( almost ) voltage and price Consumption Expected Calculators account internal... A typical eibke pack calculator to discover what battery configuration your application requires calculation! Have to put them in parallel increases their current-carrying capability 5 % off your order! The connectors.1 building your battery pack is to weld the 18650 cells have far lower ISR ( internal series )! You, you have to put them in series cells first while the final capacity ( Ah ) or (... 4000 mAh which is ~0.4950 hours or ~29.7 minutes ) is occasionally used capacity... Achieve a given current carrying capacity calculate capacity, the calculation becomes less accurate Cookie.. Quality cells, and it cant be fit in your pack a effect.