Homemade Battery Packs

Battery packs are sets of batteries arranged in a pack – which can mean parallel, in series, or both – that are used to deliver a certain output. These can range from a small pack of two or three for a flashlight or similar small item to a large set that soaks up and redistributes solar power, with any number of options in between.

A battery pack should always contain batteries that are the same. They should be either identical (which is preferred) or at least the same type. The most common battery packs are those that are found in remote control toys or certain flashlights, as well as power banks for recharging mobile devices such as cell phones. Battery packs are usually rechargeable, but can be made from disposable batteries, as well.

There are three output elements – voltage, power density, and capacity. A battery pack is made to deliver a certain level of one or more of these.

Replacing a battery pack commercially can be quite expensive. Sometimes the cost of a new battery pack is more than the cost of the original device. However,building one at home is not as difficult as one might think and is usually much lower cost.

The first requirement is voltage. The pack that is being replaced will usually tell the voltage, but if it does not, the device itself will often list the voltage requirement. Add up the individual batteries to reach the required voltage. If using disposable alkaline batteries, the individual battery voltage for AA, AAA, C, and D are 1.5 volts, while rechargeable batteries of the same sizes put out 1.2 volts each. Physical size often equates to capacity, so a device needing a larger voltage will also require a larger battery pack.

If the battery pack will be used to recharge a device rather than to simply power one, it will require other components – a booster module and a charger module. Lithium-ion (Li-ion) batteries designated 18650 are the best choice for this type of pack due to the high capacity (3000-5800mAh, depending on the battery). These are slightly larger than a standard AA battery, which is sometimes called a 14500. These numbers indicate the diameter and length of the batteries – the 18650 is 18mm in diameter with a 65mm length).

The battery will need a holder of some type – these can be purchased or handmade from PVC pipe or other non-conductive material. The battery holder is then attached to the charger, which is attached to the booster, which is attached to the charger, which is attached to the battery holder. That is, the charger has two positives and two negatives: one set is attached to the battery holder and the other set is attached to the DC-DC booster.

Batteries for larger uses, such as powering an entire camping setup, including a mini fridge, lights, and devices, can also be built. While portable power at this level is available commercially, the products tend to be quite expensive. Building a homemade version often costs half or even a quarter of the commercial price. One camping family built their own using a 35Ah battery, a battery box, a charge controller, 12V outlets and a 12V charging plug. The controller and outlets are attached to the battery box externally, with the battery inside. This does involve drilling a few holes in the battery box for wires to go through, but it keeps the battery safe. The 12V plug attaches to the controller and allows the battery to be recharged through the vehicle’s charging port (cigarette lighter port) while the engine is running.

Most battery packs require a spot welder to attach the batteries together. This can be bought commercially or homemade, also; however, those who have not studied welding and electricity may want to skip trying to make the spot welder themselves. A new device is in the works that will allow batteries to be snapped together easily; originally on Kickstarter, the bricks and connectors may be available elsewhere soon.

Even batteries and battery packs that are homemade may have periods of not being used. During this time, it is important to know how to store batteries for longer life. This usually involves keeping them at cool room temperature (the best temperature for storing batteries) while disconnected from anything that may drain their charge.

Product
Visual
Where to Buy
DIY Lithium Batteries: How to Build Your Own Battery Packs Paperback
DIY Lithium Batteries: Beginner’s Guide To Building Your Own Battery Pack Paperback
Pure Nickel Strip- 0.15x6x50mm 99.6% Nickel for 18650 Soldering Tab for High Capacity Lithium, Li-Po Battery, NiMh and NiCd Battery Pack Battery and Spot Welding, 50 Count, a U.S. Solid Product
18650 Battery Case Holder, 4 Pcs 4 Slots x 3.7V DIY Battery Storage Box, in Parallel Black Plastic Batteries Case with Pin for Soldering 4 x 18650, by Ltvystore
DIY Battery Pack PVC Heat Shrink Wrap Tube 180±3MM Width 3M Length for Big Battery Pack Power(If You are not Sure What Size You Need,Pls Email to me When u Place The Order)
2Pcs 3S 11.1V 12.6V 25A W/Balance 18650 Li ion Lithium Battery PCB Protection Board
18650 High-Capacity 9800mAh Li-ion Rechargeable Battery 3.7V Batteries 18mmX65mm (20-Pack) for Flashlight
Amprobe AM-510 Commercial/Residential Multimeter with Non-Contact Voltage Detection
Protective Safety Glasses (HEAVY DUTY INDUSTRIAL STRENGTH SAFETY GOGGLES) Crystal Clear & Anti-Fog Design - High Impact Resistance - Perfect Eye Protection for Lab, Chemical, and Workplace Safety
Magid Safety M011B9 Electrical Gloves | ASTM D120-09 Compliant Class 0 Rubber Electrical Insulating Gloves with Straight Cuff, Work, 11" Length, Size 9, Black (1 Pair)

 

Resources

These books and components can be helpful when creating a do-it-yourself battery pack.

DIY Lithium Batteries: How to Build Your Own Battery Packs

Written by the creator of the bricks and connectors do-it-yourself pieces, this book details how to put together a safe and effective battery pack that suits your own needs.

DIY Lithium Batteries: Beginner’s Guide To Building Your Own Battery Pack

Because lithium battery packs can be expensive, building one can be an enticing idea. This book details the process of building a pack and using it, defines the terminology used, and offers step-by-step instructions to complete a project that works.

Pure Nickel Strips

50 strips of pure nickel are ready to be used in a battery pack. Nickel does not corrode, making it an excellent choice for battery applications.

Battery Case Holder

Four slot holder has pins for soldering batteries in place for use in a battery pack.

Heat Shrink Wrap

This plastic shrinkable tube can be used to support a battery pack and keep it from separating.

PCB Protection Board

This circuit board is made to protect batteries when charging them. It can be added to any homemade battery charger whether it is charging homemade battery packs or commercial batteries.

18650 9800mAh Li-ion Rechargeable Batteries

These high capacity rechargeable Li-ion batteries are an excellent option for creating battery packs.

Multimeter

Determining the voltage of a battery or battery pack is much easier with a multimeter. This one measures up to 600V, as well as current, resistance, frequency, capacitance, and more.

Safety Glasses

Industrial strength safety goggles will keep eyes safe while working with potentially hazardous materials such as those included in battery pack assembly.

Insulated Safety Gloves

While these may not be necessary for smaller battery packs, it may be wise to use them for larger projects. These gloves will protect the wearer from electrical surges when working with electrical components, up to 1,000V AC and 1,500V DC.