Battery Pack DIY: Methods and Capacity

A battery pack is a collection of batteries or individual battery cells that are all (ideally) similar. To offer the necessary voltage, capacity, or power density, they can be set in series, parallel, or a combination of both. When it comes to cordless tools, radio-controlled hobby toys, and battery electric vehicles, the term "battery pack" is frequently employed.

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Seeing the importance of battery packs, it is pivotal for us to have them for our batteries. If you don’t have one, no worries! We can make one as we learn about it in this article. 

18650 Battery Pack DIY Kit

Before we start making our own 18650 battery pack DIY kit, let’s talk about the battery first and get to know the battery better. 

An 18650 battery is a lithium ion rechargeable battery. Their formal name is "18650 cell." The 18650 cell has a capacity of 1800 to 3500 mAh and a voltage of 3.7 volts (mili-amp-hours). The nominal voltage of an 18650 is 3.7 volts, although it can have a voltage range of 2.5 to 4.2 volts or a charging voltage of 4.2 volts.

The two categories are protected and unprotected. 18650 batteries with protected cells are highly recommended. Protected cells have a protective circuit that protects them from being overcharged.

Unprotected cells can overcharge and explode, producing a fire, unless the battery is protected by suitable electronics. In devices that are designed to handle unprotected 18650s, only utilize the popular LG HG2 and Samsung 25r batteries. We also advocate using 18650s from well-known companies that are of good quality. The quantity of mAh on knockoffs may be exaggerated.

In a 3.7v 3400mAh 18650, about 2 aH to 3.5 aH may be stored in a 18650 battery. It has a 10 to 13 watt hour capacity. A small air conditioner with a cooling capacity of 9000 BTU uses around 1100 watts per hour to operate. More than 110 18650 batteries would be required to power the air conditioner for an hour.

Three 12v 40 amp automotive batteries, on the other hand, would be necessary. Three vehicle batteries, on the other hand, are smaller than 110 18650s.

DIY 18650 Battery Pack Charger

18650 lithium-ion battery cells are likely to be the best choice if you're creating a DIY battery pack for a project. 18650 batteries are abundant and inexpensive, especially when recovered from old laptop battery packs or other sources. They must, however, be balanced before they may be utilized properly.

For the soldering project, we'll need the following tools and supplies:

●Soldering wire

●Pliers

●Soldering iron

●PCBs

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Step 1: To assemble the PCB, just arrange all of the components on the board in the order provided. We started with the charging boards and worked my way up to the larger components.

After We finished soldering all of the smaller components, we soldered the cell holders, Noe that the polarity of the cell holders and the PCBs are the same. One module took us less than 10 minutes to complete after all of the components were in place. Now we are going to put this one to the test before we construct any more modules.

Step 2: To test the module, we used a micro USB cable to connect one of the TP-4056 boards to my phone charger. This allows us to charge up to three batteries simultaneously.

To charge eight batteries, we used a PC power supply with a 5v input and an XT-60 connector. The module precisely charges each cell. The light over the charging board turns from red to blue when the cell is completely charged, and we may turn off the switch for that cell to save power.

Step 3: we have developed some additional modules to complete the charging grid now that we need to charge a lot more cells.

Because we didn't have the required standoffs, we joined the modules together using nut and bolts after they were completed. To power the entire grid, we used the same power supply as in the previous stage. Because each module is connected in series across the standoffs, supplying electricity to any one of them will power the whole grid.

The entire endeavor paid off handsomely, as we now have a custom charger that can charge as many batteries as we want. The entire charging grid costs a fraction of what professional chargers do, yet they can't charge nearly as many.

How many 18650 batteries do you need for 1 kwh?

To begin with, a battery pack with a capacity of 1kW is not practical. The difference in price between a 1kWh and a 2kWh battery pack is significant. 1000 watts = 1 kW, and 1000 watts per hour equals 1 kWh, the amount of energy stored in the battery.

For a 1kWh battery, which can come in a number of physical sizes/shapes and electrical combinations, there is no standard or THE ONE answer.

If you have 2000mAh 18650s, each one stores 7.4Wh of energy, thus you'll need 136 of them to produce a 1kWh battery (1000/7.4 136). By connecting 136 cells in parallel, a 1kWh battery with a nominal voltage of 3.7V may be created.

You'll need to connect them in series if you want a higher voltage, which you nearly definitely will. A LiIon battery should last at least 7 seconds before it has to be recharged. A 7s20p layout requires 140 cells since 136 cells cannot be evenly distributed throughout 7 packs in series. The battery will have a nominal voltage of 25.9V (7x3.7V) and a capacity of 40Ah (20x2000mAh), for a total capacity of 1036Wh (25.9Vx40Ah).

However, we can make a calculation about it. A 18650 battery has a 3.7 volt nominal voltage and a 3.5 Ah capacity. It would need 19 cells to make a 70-volt battery. A 245 Wh battery is included. To get to 12 kWh, 49 of these batteries would have to be connected in series. The battery must have a total of 931 cells to do this.