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How to DIY a Power Tool Battery Pack
Materials and Components Needed for Battery Pack DIY
Primary element - Battery
If you want to know how to DIY power tool battery packs, understanding the cell components is the first step. For an electric tool battery pack, the batteries are the most indispensable part. So you need to buy some batteries first, which can be purchased from local stores or online. The individual batteries must be charged and discharged first. And then the perform capacity and internal resistance should be tested. Large instantaneous discharge currents is required for electric tools to achieve a certain level of power. Therefore, it’s best to choose batteries with an internal resistance of around 16 to 17 and a capacity between 2001 and 2078mAh.
Chinese Battery Brands vs. Panasonic vs. Samsung
Many batteries of Chinese brands may not have as high a capacity as Panasonic or Samsung batteries, but they are certainly better than the counterfeit Panasonic and Samsung batteries on the market. Therefore, opting for cost-effective Chinese battery brands is much smarter than ending up with expensive counterfeits. One such recommended brand is Guangxi Donglai New Energy Battery Manufacturing Factory, a leading cell manufacturer in China with its own R&D team and a variety of product capacities.
In addition to its own brands, Donglai New Energy also has a large inventory of top-tier brands in the industry to meet the diverse power needs of customers, such as Highstar 2000mAh-10C, 2200mAh-5C, 2500mAh-8C batteries, and DMEGC 2600mAh-5C, 2900mAh-3C, 3200mAh-3C batteries.
If you want to DIY power tool battery pack with a voltage of 21V, you can also choose the ZE 21700 battery with a capacity of 4000mAh. The overall cost is lower than using 18650 cells.
Because using 21700 4000mAh for a battery pack in a 5S2P configuration, the total capacity reaches as high as 8Ah.
Another element - Casing
The accessories for making battery packs for power tools also include a casing, spot welder, solder wire, and stainless steel flux, among others. Common Chinese casing brands for the battery packs for power tools include:
Makita Brand – 21V, including full set of 18650 cells in in both 10 and 15 pieces configurations.
Dayi Brand – including full sets of 18650 cells in both 10 and 15 pieces configurations, and full sets of 21700 cells with 10 batteries. Remember to purchase the full set of accessories.
For other tools such as welders, testers, you can refer to the Lithium-ion Battery Spot Welder, from which you can know about the detailed information on tools like the Lithium-ion Battery Spot Welder.
Some possible problems during DIY power tool battery packs
Problem 1: Weak Spot Welding, Weld Points Detaching.
While welding nickel strips with the spot welding machine using 100A current with a 10-second delay, the machine lacked power, and the weld points came off easily. Then, I experimented with a discarded 18650 battery and found that the welding was normal. Suddenly, I realized that I had been spanning two battery cells with the welding to secure the nickel strip, which resulted in insufficient power. The correct method is to weld one cell at a time.
Problem 2: Sparking During Welding.
After welding one side, when I went to weld the other side, there were sparks, melting all the nickel strips. But I didn’t encounter this issue before and I had already checked the battery arrangement before welding. Upon rechecking, I found that I had reversed the arrangement when welding the first side, causing problems when welding the other side. To address this, I removed the nickel strips, fearing that sparking could affect the battery capacity. After disassembly, I recharged all the batteries and then welded them again. In this process, many nickel strips were scrapped.
Conclusion
DIY battery packs is an interesting process, but please ensure to select appropriate battery cells and prioritize safety during welding.
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