If you need to double the voltage level according to your system needs while maintain the same capacity or ampere hour (Ah) rating of batteries.
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For example, If you have two 12V, 10Ah hour batteries and you need 48V system for installation.
Simply, connect four batteries in series where you will get 48V and the same ampere hour rating i.e. 10Ah.
What you need to keep in mind is that battery discharge slowly in series connection as compared to parallel batteries connection. You can do it with any number of batteries i.e. to get 24V, 36V, 48V, 72V DC and so on by connecting batteries in series.
At present, the charging of lithium battery packs generally adopts series charging, mainly because the series charging method has a simple structure, low cost and easier to implement
However,
due to the differences in capacity, internal resistance, attenuation characteristics, self-discharge and other properties between single lithium batteries,when charging the lithium battery pack in series, the single lithium battery with the smallest capacity in the battery pack will be the first to be fully charged.
At this time, other batteries have not been fully charged. If you continue to charge in series, the fully charged single lithium battery may be overcharged. Overcharging lithium batteries can seriously damage the performance of the battery, and may even cause explosions and cause injuries. Therefore,in order to prevent overcharging of single lithium batteries, lithium battery packs are generally equipped with a battery management system (BMS) when used, which protects each single lithium battery from overcharging through the battery management system. When charging in series, if the voltage of a single lithium battery reaches the overcharge protection voltage, the battery management system will cut off the entire series charging circuit and stop charging to prevent the single battery from being overcharged, which will cause other lithium batteries to be unable to be fully charged.
There is a charging and discharging process of the battery. Even if the voltage of the battery of different materials is exactly the same in the initial state, the battery cannot be connected in parallel. With different battery materials, the energy density ratio is different, and the discharge characteristic curve is inconsistent when discharging, which will cause the voltage of the two batteries to be inconsistent. At this time, a battery with a high voltage may charge a battery with a low voltage, causing serious heat generation.；
When charging, due to the inconsistency of the remaining charge, the charging speed will inevitably lead to inconsistency. If the battery is fully charged, there will be overshoot, which will also cause problems with the battery, and it will catch fire or even explode in severe cases. Therefore, batteries of different materials must not be connected in parallel.
Battery pack manufacturers have a strict screening process when screening single-cell batteries. The same batch of batteries will be charged and discharged in multiple rounds at the same time, and the batteries with inconsistent characteristic curves will be selected. After multiple rounds of charge and discharge screening, the batteries with basically the same charge and discharge characteristics are connected in series and parallel to form a battery pack and handed over to the user for use. If there is a certain battery in the middle that is inconsistent with other batteries, the high-voltage battery will charge the low-voltage battery, causing the temperature in the local area to rise faster, and there is an overshoot phenomenon. Over time, this situation will spread, resulting in serious attenuation of the battery pack, and even accidents.
Therefore, the single-cell batteries that make up the battery pack must be batteries of the same material, and the charge and discharge characteristic curves must be basically the same. Do not use batteries in parallel at will.
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When you need to double the battery capacity or ampere hours (Ah) rating according to your system needs while maintain the same level of voltages.
For example,
If you have two 12V, 200Ah hour batteries and you need 12V system for installation. Simply, connect both of the batteries in parallel where the overall battery capacity would be 400Ah and the same voltage level i.e. 12V.
Keep in mind that battery discharge quickly in parallel as compared to series batteries connection. You can do it with any number of batteries i.e. to get the same level of voltage while increase the battery capacity in ampere hours in parallel batteries connection.
When lithium batteries are charged in parallel, each lithium battery should be charged in a balanced manner, otherwise the performance and life of the entire set of lithium batteries will be affected during use. Commonly used balanced charging technologies are: constant shunt resistor balanced charging, on-off shunt resistor balanced charging, average battery voltage balanced charging, switching capacitor balanced charging, step-down converter balanced charging, inductance balanced charging, etc.
1.) One Lithium battery with protection plates and one lithium battery without protection plates cannot be charged in parallel. Batteries without protective plates are easily damaged by overcharging.
2.) Batteries that are charged in parallel usually need to remove the protection board that comes with the battery and use a unified battery protection board.
3.) If the battery charged in parallel does not have a lithium battery protection board, the charging voltage must be limited to 4.2V, and a 5V charger cannot be used.
4.) After the lithium batteries are connected in parallel, there will be a charging protection chip to charge and protect the lithium batteries. When making parallel lithium batteries, lithium battery manufacturers have fully considered the characteristics of the changes after the lithium batteries are connected in parallel, and the current design and battery selection are also carried out in accordance with the above requirements. Therefore, users need to follow the instructions for parallel lithium batteries to charge step by step to avoid damage that incorrect charging may cause to the battery.
When you need to double the battery capacity or ampere hours (Ah) rating as well as batteries voltages according to your system needs.
For example, If you have six batteries each of 12V, 200Ah hour and you need 600Ah capacity and 24V system for installation. Now you have two sets of three batteries, simply, connect two sets of three batteries in series and then connect the two set in parallel (as shown in fig above) where the overall battery capacity would be 600Ah and level of voltages would be 24V.
You can do it with any number of batteries i.e. to get different level of voltages as well as increase the battery capacity in ampere hours in series-parallel connection of batteries.
The advantages of lithium batteries in parallel and then in series
Disadvantages of lithium batteries in parallel and then in series
The advantages of lithium batteries in series first and then in parallel
1. ) First connect in series according to the capacity of the lithium battery cell, such as 1/3 of the capacity of the entire group, and finally connect in parallel, which reduces the probability of failure of the large-capacity lithium battery module; first connect in series and then it is of great help to the consistency of the lithium battery pack.
2.) From the perspective of the reliability of the connection of the lithium battery pack, the development trend of voltage inconsistency and the impact of performance, the connection method in parallel and then in series is better than the connection method in series and then in parallel, and the topology of the lithium battery in series and then in parallel is conducive to the detection and management of each lithium battery cell in the system.
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Precautions for ithium Battery
1.Lithium batteries must use a special charger, otherwise they may not reach the saturation state and affect their performance.
2.The lithium battery does not need to be fully discharged before charging.
3.Do not plug the charger into the socket for a long time, and remove the battery from the charger as soon as possible after it is fully charged.
4.The battery should be removed from electrical appliances that have not been used for a long time, and the battery should be emptied and stored.
5.Do not insert the positive and negative electrodes of the battery in reverse, otherwise it will cause the battery to bulge or breakNickel chargers and lithium chargers cannot be mixed.
Building a custom battery pack offers both businesses and DIY enthusiasts the ability to tailor power solutions to their specific needs, whether for electric vehicles, robotics, drones, or energy storage systems. For businesses, it ensures optimal performance and longevity, critical in high-demand applications. For DIYers, it’s a rewarding project that allows for flexibility in voltage and capacity. In this guide, we provide step-by-step instructions, tips, and safety precautions to help you assemble a reliable battery pack with a BMS module, regardless of your experience level.
Before you begin, gather all the necessary materials to ensure a smooth assembly process:
Contact us to discuss your requirements of Lithium Battery PACK Assembly. Our experienced sales team can help you identify the options that best suit your needs.
Safety should be your top priority when working with battery cells.
The performance of your battery pack depends heavily on the type of cells you use. If you’re unsure which lithium battery cells are best for your project, check out our guide on choosing the right lithium battery cells to make an informed decision.
Cells in Series (S): Increases voltage. For example, connecting 4 cells in series (4S) multiplies the cell voltage by 4.
Example: A 4S2P configuration means 4 cells in series and 2 cells in parallel, totaling 8 cells.
Learn more about choosing the right lithium battery cells in this article: https://www.danenergy.com/blog-posts/choosing-right-lithium-battery-cells-essential-tips-enhanced-performance
When connecting battery cells, nickel strips are typically the best option due to their low resistance and reliability for spot welding. To understand why nickel strips are favored over other materials, you can learn more in our article about choosing the right welding materials.
⚠️ Warning: Ensure nickel strips do not touch unintended terminals, which could cause a short circuit.
The BMS plays a critical role in managing and protecting your battery pack. However, if you're unsure whether you need a full BMS or if a simpler PCM (Protection Circuit Module) would suffice, you can learn more in the article about the differences between BMS and PCM.
Identify BMS Connections:
Connecting the BMS:
???? Tip: Use a multimeter to verify the voltage between each connection point to ensure correct wiring.
After soldering and insulating with heat shrink tubing, use heat-resistant tape (kapton tape) to wrap around any exposed or sensitive areas, such as connections near the BMS module or nickel strips. Kapton tape offers excellent thermal resistance and prevents short circuits, especially in high-temperature areas like near the BMS and battery terminals.
⚠️ Caution: Monitor the temperature of the cells during testing to prevent overheating
After ensuring all your connections are secure and insulated:
???? Tip: Make sure there are no exposed wires after shrinking the wrap to avoid accidental short circuits.
For enhanced protection, especially in environments where the battery pack may face physical impact or vibrations:
???? Note: Using a hard case is especially important for portable projects or high-impact environments like electric vehicles or outdoor applications.
Once the shrink wrap or protective case is applied:
By carefully following these steps and prioritizing safety, you can successfully assemble a custom battery pack with a BMS module tailored to your needs.
At Dan-Tech Energy, we focus on creating battery packs that meet the exact needs of your project. Our approach involves close collaboration with you to develop and prototype designs that ensure your battery system is both efficient and reliable, tailored to your specific requirements.
Ready to get started? Submit your battery pack specifications via Toolbox and we’ll work together with you to develop a custom-designed battery pack with BMS to fit your exact requirements.
Q1: Why is a BMS module necessary?
A: A BMS monitors and balances the cells within a battery pack, preventing overcharging, over-discharging, and overheating, which can lead to cell damage or safety hazards.
Q2: Can I use different types of battery cells in one pack?
A: No, it's strongly recommended to use identical cells in the same battery pack. You should always use cells from the same manufacturer, with the same specifications and date code. This ensures consistent performance and safety, as mismatched cells can lead to imbalances in charge, discharge rates, and lifespan, which may compromise the battery pack's reliability.
Q3: What if one of the cells is defective?
A: Replace any defective cells before assembly. Using a faulty cell can compromise the entire battery pack's performance and safety.
This article is for informational purposes only. Following the instructions provided is done at your own risk. We strongly recommend consulting or using the services of an experienced battery assembler or designer to ensure safety and proper assembly. Dan-Tech Energy is not responsible for any damage, injury, or issues arising from the use of this guide. Always follow safety guidelines and manufacturer recommendations when working with battery cells and electronic components.
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