Lithium batteries have become the most popular and power-efficient portable batteries for our electronics. The days have gone by where some AAA batteries will give you all the power you need.
Modern electronics require more power and that means using more reactive elements, like lithium.
Also called lithium-ion batteries, these are powerful batteries that can be used to charge many things around your home.
What makes lithium batteries superior to the alternatives? Put simply, they’re some of the most powerful battery types around right now.
This is due to their energy density, which we’ve explored below. They’re also versatile, especially the 18650 lithium-ion battery pack that you’ll learn to make in this guide.
Lithium Batteries & Energy Density
Lithium batteries are very popular because of their high energy density.
This allows more energy to be stored within a smaller surface area, something that lithium has over the elements used in other batteries.
This is why the most powerful and popular handheld devices all use lithium-ion batteries, along with larger electronics like Tesla cars.
Lithium is a powerful and reactive element that holds more electricity than lead or nickel alternatives.
For example, the average lead-acid battery will typically have 25 watt-hours of power in them for every kilogram.
Nickel-metal hydride batteries, on the other hand, store 100 watt-hours per kilogram.
Lithium-ion batteries beat both of those by providing 150 watt-hours of electrical power per one kilogram of battery.
What You Need To Make A DIY Battery Pack
Before we get into the step-by-step process you can use to make your own lithium battery packs, you should have all of your equipment ready first.
This allows you to follow those steps and create the batteries in one session, which is faster, safer, and more convenient.
You don’t want to have half-finished batteries lying around while you’re waiting for more parts to arrive.
To make your own lithium battery pack, you’ll need the following items:
- 18650 rechargeable lithium-ion battery.
- Battery Management System (BMS) to charge the batteries.
- A battery level indicator.
- A Li-Ion charger
- A rocker switch.
- A spot welder.
- M3 x 10mm screws.
- A nickel-plated strip.
- A DC jack.
- Wire cutters.
- 3D printer.
- Safety goggles.
How To Make DIY Batteries
Now that you know why lithium batteries are desirable and what equipment you’ll need, you can now start to make your own DIY batteries.
Make sure you have everything before starting, it’ll make the process much easier!
Don’t worry if you lack DIY experience, this guide is easy enough to follow. That said, there is a primer that beginners need to know, and that’s the difference between cells and batteries.
They’re commonly used interchangeably in everyday life, which is fine, but you need to know their specific definitions when building one.
Cells are the interior parts of the battery that hold power while batteries are the entire construct, which can be made from many cells.
With that covered, let’s take a look at the nine steps everybody can use to build their own DIY batteries.
Step One: Connecting The Battery Cells
To make a cohesive battery, you’ll need to connect the cells. If the cells aren’t connected then you’ll get a weak battery that can’t store much power in them, making them close to useless.
You connect battery cells together using nickel strips, so have those on hand.
Above we’ve called them nickel-plated strips but you can also use strips of pure nickel, which even work better because there’s less electrical resistance.
That means they’ll generate less heat, making it safer to handle and increasing how long the battery lasts. Nickel-plated strips are more affordable, however.
Make sure the cells are of the same or similar voltage when organizing your battery.
You’ll connect them in parallel, so the current will pass through all of the cells. This means that you can’t have low-voltage cells that won’t support the current that travels into them.
If you’re using old batteries that have been repurposed, you should make sure they’re all charged to the same voltage.
Step Two: Finding The Right Voltage & Capacity
You should have the right voltage and capacity when building your battery. If you don’t know how much power you need, how can you build a battery that can do the job?
Below you’ll learn how to create a battery pack that has a voltage of 11.1 and a capacity of 17Ah. Each cell will have a capacity of 3,400mAh and a voltage of 3.7 volts.
Step Three: Assembling The Battery Pack
Arranging your first battery pack can be intimidating but we can make the process easier. Your pack should have three groups of five cells each.
Arrange the fifteen cells that you’re using so that they support an electric connection and work with the Battery Management System.
Remember to keep them in three groups with the first five cells having their positive side up, the second five having their negative side up, and then the last five having the positive side up again.
Step Four: Cutting The Nickel Strips
Whether you’re using a pure nickel strip or a nickel-plated alternative, lay it across five of the cells.
It should cover all of its terminals with approximately ten millimeters to spare so that it can be connected to the Battery Management System.
Once that is done, you need to connect the first group’s negative terminal to the second group’s positive terminal.
Then you take the negative terminal of the second group and connect it to the positive terminal of the third.
Step Five: Spot-Welding The Strips
Those strips need to be fixed properly, which typically requires spot-welding. That’s where two contacting metal surfaces are joined together by a blast of heat, which is created via electric current.
You should use spot-welding to secure the strips with minimal damage or disruption to the pack.
The spot-welder should be laid against the strip and the battery terminal beneath it, then the switch should be pressed down to start the welding process.
Once it’s done and the area has cooled down, you can test the strip by trying to pull it up. If it comes off, you need to use a stronger current to produce a stronger bond.
Wear those safety goggles and gloves that we told you to get when doing any welding. Welding creates a lot of light and heat that needs to be kept from your vulnerable eyes and fingers.
Step Six: Connecting Your Battery Management System
The Battery Management System, or BMS, is key to monitor your battery pack and how it’s working.
When used properly, a BMS will correctly report the voltage of the battery pack along with how much the battery is charging and discharging.
It’s easy to get confused when trying to find the right BMS. Fortunately for you, this guide is focusing on how to build a specific lithium battery set, so we can tell you what to look for in your BMS.
For this set, the BMS should have a maximum operating current of 0~25A and a voltage range of 4.25 to 4.35 volts, give or take a variance of 0.05 volts.
Your BMS will have several soldering pads built into it. They should be labeled B1, B2, B+, and B-.
For the first parallel battery group, connect the positive terminal to the B1 and the negative terminal to the B-.
For the other parallel battery group, connect the positive terminal to B+ and the negative terminal to B2.
You can spot-weld the BMS to the nickel strips to keep it in place. If you’ve got a decent BMS that has quality construction, it won’t be damaged by the welding process.
Step Seven: Making A 3D Case
So far your battery is a loose bundle of cells and metal strips – you need to have a case to make it look like the real deal.
Note that creating a case for your battery pack is completely optional. That said, leaving the nickel strips exposed can cause the battery to short and malfunction.
You can buy cases online or put them together with your own hands.
Others advise using 3D printing to fabricate one, using cutting-edge technology to make a battery casing with relatively little effort on your part.
Step Eight: Connecting The Wiring
Electrical equipment is useless without wiring to join everything together.
You should know how to wire the battery pack if you’ve ever owned one before – you need to have one terminal for connecting the power load and another for charging the battery.
A battery level indicator is a great addition at this point, too. It’s a nice touch to the finished product and allows you to see how much power is left in the pack and when it’s properly charged.
To connect wiring, you’ll need a 5mm DC jack for your input and output, a rocker switch, and a 3S battery level indicator. It’s simple, follow these steps:
- Take the red wire connected to your rocker switch and solder it to the P+ on your BMS.
- Solder the DC jack’s negative wires to BMS P-.
- Once the wires have been connected, solidify their positioning by placing hot glue at the base of the battery enclosure.
- Use MC x 10mm screws to keep the battery lid in place. If there’s no lid, harmful debris can make its way into the battery and things can become dislodged.
Step Nine: Charging The Battery Pack
If everything has been followed correctly, you should now have a working battery pack.
It won’t work yet, however, because you still need to charge it first. Connect the battery pack with a 12.6 DC adapter and wait for it to be charged to operational capacity.
Battery level indicators are invaluable for seeing how much power the pack uses and when it’s being charged effectively. Use the battery after charging to see if it works!
Lithium Battery Cell Problems
Now that you know how to build your own lithium battery, you should also know the problems that come with them. If your pack isn’t working properly, it can be potentially dangerous.
Lithium-ion batteries can suffer from something called thermal runaway failure in the worst cases.
This is where the cells in the battery overheat or otherwise short circuit, drastically increasing the temperature until they explode.
There are many videos online detailing these reactions in lithium-ion gadgets, from your smartphone to electric cars.
Watch for these signs after setting up your lithium battery pack:
- Your battery needs longer charging times.
- The cells drop in voltage during rest periods.
- It makes a noise whenever you charge the battery pack.
- The cell becomes very hot during charging and active use.
- The cell’s capacity for a charge is higher than the discharge capacity.
Can You Use Old Batteries?
Many who express interest in DIY and electronics also care about being sustainable.
Not only does this save you money in the long run but it’s also better for the environment, so it’s a relatively guilt-free way of using electronic items.
You can reuse many old batteries but can you reuse lithium-ion batteries?
As mentioned above, it is possible to use old batteries to make your battery pack. That said, you should know some important details that will help you avoid any embarrassing or dangerous slip-ups.
First, lithium-ion batteries can and will lose their charge over time. This is because they’re sensitive to overcharging and undercharging, both of which sap at the capacity of the battery.
This stops them from holding as much charge, making them impractical and incentivizing a replacement battery pack instead.
That’s why you should measure the voltage before using any batteries that have been used in the past. Anything less than two volts is widely considered to be unusable.
There is a process to revive lithium-ion batteries, however. You only need to follow three simple steps:
- Connect a live cell that can still hold a charge to a dead cell, which is the one you want to revive. They should be connected parallel positive and both connected to the battery charger.
- From there, connect both cell terminals and leave them for approximately thirty seconds. You should see the voltage of the dead cell start to increase. Then leave it another ten seconds so that the charger recognizes the battery.
- Unplug both cells and connect the dead one to the charger to see if it has a voltage. It should be at a higher figure now than it was when you started despite no longer being attached to a powerful, live cell.
This method prevents lithium-ion batteries from being discarded permanently, where they pollute areas and even pose a fire risk should they thermally detonate at junkyards or other flammable locations.
Pros & Cons Of Lithium Batteries
So, why should you make your own lithium battery pack? Some clear advantages and disadvantages come with this DIY project and you should understand them before you start.
By knowing the pros and cons of these handy battery packs, you can foresee potential issues and better appreciate the good things when all the work is done.
Let’s take a look at those advantages and disadvantages.
- Lithium-ion batteries are lighter than most of the alternatives. This means it’s feasible to make your own battery pack and still be able to carry it around.
The main components are lithium and carbon, both of which are quite light.
- Lithium-ion batteries are very hardy, being able to withstand hundreds of charging/discharging cycles that will last you much longer than most other battery alternatives.
With a little elbow grease, you can create a battery that’ll last you a long time, saving you money in the long run.
- These batteries don’t have the memory effect. The memory effect is where the capacity and efficiency of batteries are weakened because they hold some charge, which needs to be drained so you can properly recharge them fully.
This isn’t an issue with lithium batteries, where you can recharge them freely. This is much more practical than batteries that suffer from the memory effect.
- Though it’s a slow process, lithium-ion batteries start to degrade when they’re first created. Even if you’re not using them, they’re slowly degrading, so get your fill while you can.
- This degradation process is faster in warm climates. While hardy and able to operate in most temperatures, hotter temperatures speed up the degradation process and cause the batteries to become inert faster.
- Battery packs require an onboard system that manages the discharging process of lithium-ion cells. This is because they are sensitive and prone to developing issues if not managed.
That system drives up the price of commercial batteries and is yet another part you need to buy when making one yourself, making these batteries more expensive.
- Last but certainly not least, there’s that thermal reaction we mentioned earlier. Lithium-ion batteries can and have exploded in the past.
The explosion is more of immolation that can be easily controlled if caught but it can start fires if not attended to.
This happens because the batteries short circuit, meaning the anode and cathode touch one another and cause the system to overheat.
To avoid this, the anode and cathode are typically kept separate by a piece of plastic but this isn’t foolproof, there is still a chance that something goes wrong. While rare, it’s still a risk.
Leaving the battery next to a heat source or piercing the cells with a bladed instrument can also start the thermal reaction, so batteries should be kept away from potential danger.
Lithium Battery Frequently Asked Questions
There are some burning questions that many ask when it comes to lithium-ion batteries.
We’ve gathered three of these frequently asked questions here, so check them out and learn something new about these powerful and convenient batteries.
How long do lithium-ion batteries last?
The mileage of individual batteries will depend on their construction quality and the environment that they’re being kept in.
That said, lithium-ion batteries are generally the most robust mainstream batteries we have today.
They’ll last anywhere between 300 to 500 charge cycles, which can be averaged out to approximately three years.
If you use the batteries more often, that time will be shortened.
Fortunately, the constant degradation of lithium-ion batteries means that using them more often is justified, so don’t worry about running them into the ground.
What even is a charge cycle?
If you don’t know what a charge cycle is, it can be hard to figure out our answer to the above question.
A charge cycle is commonly defined as the time of use where the battery goes from fully charged to completely discharged, where it’s then recharged for use again.
Of course, many of us don’t let the batteries lose all of their charges before we recharge them again, which is fine with lithium-ion batteries because they don’t suffer from the memory effect.
How do you dispose of dead lithium-ion batteries?
Getting rid of dead batteries is always a chore, especially when they’re lithium-ion batteries that have a very small but present risk of starting a fire.
There should be a collection point or a drop-off location for e-waste that has been assigned for battery recycling.
If you’re in a rural area, those points will be fewer and farther between, so you should check out main-in programs for recyclable materials.
Recycled lithium is good business, so somebody nearby should be willing to accept.
You can tape over the terminals and store the cells in separate plastic bags to keep them safe if you’re recycling in bulk. Don’t store them in an airtight container because they’ll give off some gases.
What we’ve learned today is that you don’t need to buy a lithium-ion battery to reap the benefits of this interesting technology.
With some know-how and elbow grease, you can create your own battery pack. After reading this page, you know the tools and information required to complete this project.