The world is shifting away from fossil fuels and will one day become fully electric. In the present world, Lithium-ion is the most promising chemistry of all batteries. Most of the battery packs used in Laptops, RC Toys, Drones, Medical devices, Power tools, e-bikes, and electric cars (EV) are based on 18650 batteries. It is one of the most mature Li-ion formats available, is produced in high volume, and enjoys a low cost per Wh.
In this Instructable, I will show you, how to make a 18650 battery pack for applications like Power Bank, Solar Generator, e-Bike, Power wall etc. The fundamental is very simple: Just to combine the number of 18650 cells in series and parallel to make a bigger pack and finally to ensue safety adding a BMS to it.
At the end of this project, I made a custom 3D printed enclosure for the battery pack.
Disclaimer: I cannot be held responsible for any loss of property, damage, or loss of life if it comes to that. This tutorial was written for those who have knowledge of rechargeable lithium-ion technology. Please do not attempt this if you are a novice. Stay safe.
To make the battery pack, you have to connect the 18650 cells together by means of nickel strips or thick wire. Generally, Nickel strips are widely used for this. In general two types of nickel strips are available on the market: nickel-plated steel strips and pure nickel strips. I will suggest buying a pure nickel. It is a little bit costlier than nickel-plated steel, but it has much lower resistance. Low resistance means, less heat generation during the charging and discharging, which leads to longer useful battery life.
Nickel strips come with different dimensions and lengths. Choose the strips according to the current rating.
You have two options two connect the 18650 cells together: 1. Soldering 2. Spot Welding
The best choice is always Spot welding, but Spot Welder is much costlier than a good quality Soldering Iron.
Soldering:
You should know why spot welding is preferred over soldering, the problem with soldering is that you apply a lot of heat to the cell and it doesn't dissipate very quickly. This enhances the chemical reaction in the cell which damages the cell's performance. Ultimately you will lose some capacity and life of the cells.
But if you are not interested to buy a costly Spot Welder, you can solder the nickel tabs to the cell by following some precaution and tricks:
1. To minimize the contact time of your soldering iron on the cell, make sure the surface is scuffed up sufficiently and you use plenty of flux to allow for fast solder flow.
2. It is better to have a good quality high wattage ( min 80W ) iron with good thermal capacity so it can deliver the heat to the joint quickly so you don't have to hold the iron to the battery for ages and let the heat seep into it, causing damage to the battery.
Spot Welding:
The reason we spot weld is because it securely joins the cells together without adding much heat to them. There are two grades of spot welders currently available in the market: hobby grade and professional grade. A decent hobby-grade Spot welder costs around $200 to $300, whereas a good professional grade may cost around ten times more. So I will suggest buying a hobby-grade spot welder from any online store like Banggood, Aliexpress, or eBay.I am using the
Before connecting the cells in parallel, first, check the individual cell voltages. For paralleling the cells, the voltage of each cell should be close to each other, otherwise a high amount of current will flow from the cell with a higher voltage to the cell with a lower voltage. This can damage the cells and even result in fire on rare occasions.
If you are using brand new cells, the cell voltage is near 3.5 V to 3.7 V, you can join them together without worrying much. But if you are going to use an old laptop battery, be sure the cell's voltage is nearly the same, otherwise, charge the cells to the same voltage level by using a good Li-Ion Battery Charger.
The world is shifting away from fossil fuels and will one day become fully electric. In the present world, Lithium-ion is the most promising chemistry of all batteries. Most of the battery packs used in Laptops, RC Toys, Drones, Medical devices, Power tools, e-bikes, and electric cars (EV) are based on 18650 batteries. It is one of the most mature Li-ion formats available, is produced in high volume, and enjoys a low cost per Wh.
In this Instructable, I will show you, how to make a 18650 battery pack for applications like Power Bank, Solar Generator, e-Bike, Power wall etc. The fundamental is very simple: Just to combine the number of 18650 cells in series and parallel to make a bigger pack and finally to ensue safety adding a BMS to it.
At the end of this project, I made a custom 3D printed enclosure for the battery pack.
Disclaimer: I cannot be held responsible for any loss of property, damage, or loss of life if it comes to that. This tutorial was written for those who have knowledge of rechargeable lithium-ion technology. Please do not attempt this if you are a novice. Stay safe.
To make the battery pack, you have to connect the 18650 cells together by means of nickel strips or thick wire. Generally, Nickel strips are widely used for this. In general two types of nickel strips are available on the market: nickel-plated steel strips and pure nickel strips. I will suggest buying a pure nickel. It is a little bit costlier than nickel-plated steel, but it has much lower resistance. Low resistance means, less heat generation during the charging and discharging, which leads to longer useful battery life.
Nickel strips come with different dimensions and lengths. Choose the strips according to the current rating.
You have two options two connect the 18650 cells together: 1. Soldering 2. Spot Welding
The best choice is always Spot welding, but Spot Welder is much costlier than a good quality Soldering Iron.
Soldering:
You should know why spot welding is preferred over soldering, the problem with soldering is that you apply a lot of heat to the cell and it doesn't dissipate very quickly. This enhances the chemical reaction in the cell which damages the cell's performance. Ultimately you will lose some capacity and life of the cells.
But if you are not interested to buy a costly Spot Welder, you can solder the nickel tabs to the cell by following some precaution and tricks:
1. To minimize the contact time of your soldering iron on the cell, make sure the surface is scuffed up sufficiently and you use plenty of flux to allow for fast solder flow.
2. It is better to have a good quality high wattage ( min 80W ) iron with good thermal capacity so it can deliver the heat to the joint quickly so you don't have to hold the iron to the battery for ages and let the heat seep into it, causing damage to the battery.
Spot Welding:
The reason we spot weld is because it securely joins the cells together without adding much heat to them. There are two grades of spot welders currently available in the market: hobby grade and professional grade. A decent hobby-grade Spot welder costs around $200 to $300, whereas a good professional grade may cost around ten times more. So I will suggest buying a hobby-grade spot welder from any online store like Banggood, Aliexpress, or eBay.I am using the
Before connecting the cells in parallel, first, check the individual cell voltages. For paralleling the cells, the voltage of each cell should be close to each other, otherwise a high amount of current will flow from the cell with a higher voltage to the cell with a lower voltage. This can damage the cells and even result in fire on rare occasions.
If you are using brand new cells, the cell voltage is near 3.5 V to 3.7 V, you can join them together without worrying much. But if you are going to use an old laptop battery, be sure the cell's voltage is nearly the same, otherwise, charge the cells to the same voltage level by using a good Li-Ion Battery Charger.
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