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.
The 18650 (18mm diameter and 65mm length ) battery is a size classification of lithium-ion batteries. It is the same shape, but a bit larger than a AA battery. AA batteries, by comparison, are sometimes called 14500 batteries because they have a 14mm diameter and 50mm height.
But the main problem is its weight, it is really heavy. The main weight of the Solar Generator is due to the heavy lead-acid battery inside it. So I decided to make a light and compact 18650 Li-Ion Battery Pack.
At the end of this project, I made a custom 3D printed enclosure for the battery pack.
These cells that have well-documented performance characteristics and excellent quality control. Reputed brand 18650 cells are generally costly, but if you consider for long time use then they are worth having it.
Don't buy any cells with the word FIRE in the name like Ultrafire, Surefire, and Trustfire. In reality, these cells are just factory rejects, purchased by companies like Ultrafire and repackaged in their own branded cover. Many used batteries are rewrapped as new and white-labeled. They sell the battery by marking capacity up to 5000mAh, but in actual their capacity is between 1000 to 2000 mAh. Another major problem with these cheap 18650 cells is the high risk of explosion when overheated during the charging or discharging.
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 in 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.
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 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.
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.
The 18650 (18mm diameter and 65mm length ) battery is a size classification of lithium-ion batteries. It is the same shape, but a bit larger than a AA battery. AA batteries, by comparison, are sometimes called 14500 batteries because they have a 14mm diameter and 50mm height.
But the main problem is its weight, it is really heavy. The main weight of the Solar Generator is due to the heavy lead-acid battery inside it. So I decided to make a light and compact 18650 Li-Ion Battery Pack.
At the end of this project, I made a custom 3D printed enclosure for the battery pack.
These cells that have well-documented performance characteristics and excellent quality control. Reputed brand 18650 cells are generally costly, but if you consider for long time use then they are worth having it.
Don't buy any cells with the word FIRE in the name like Ultrafire, Surefire, and Trustfire. In reality, these cells are just factory rejects, purchased by companies like Ultrafire and repackaged in their own branded cover. Many used batteries are rewrapped as new and white-labeled. They sell the battery by marking capacity up to 5000mAh, but in actual their capacity is between 1000 to 2000 mAh. Another major problem with these cheap 18650 cells is the high risk of explosion when overheated during the charging or discharging.
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 in 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.
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 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.
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