Building Your Own Rechargeable Battery Pack

Building your homemade battery pack to provide more voltage or amp hours is a fun project to tackle. You will save money in the process, as homemade batteries are more affordable.

You may have heard of a saltwater battery, Earth batteries, coin batteries, and other fixes, but we have the ultimate guide on how to make a legit, homemade battery right here — no aluminum foil or copper wire required.

You can build a rechargeable 12-volt battery pack out of NiCad batteries. Do you need a 24-volt deep cycle pack but only have some 6-volt AGM batteries available? No trouble. You can build a 24-volt battery pack in a few hours. Read on to learn how to make homemade battery(s).

Special Note:

We will not be discussing Lithium-Ion batteries. While they are great batteries, their special recharging requirements make them problematic when building homemade batteries.

Some additional research and equipment may be necessary if you use Li-Ion batteries. Damage to the batteries, including catching on fire due to chemical reactions, could occur.

What Is In A Battery Pack?

Did you know that the battery in every electric car is a bank of thousands of individual battery cells soldered together, functioning as a car battery as the electricity flows?

The battery pack in a security light is just three or five rechargeable AA batteries fused in series. A 12-volt car battery is nothing more than six 2-volt battery cells connected in series.

You can build any battery you need. With some parts and a little effort, you can make homemade batteries work.

Determining Your Need

It is best to have a specific goal before beginning a DIY battery-building project. What device do you need to power, and what is the problem with the current battery? Often, the original batteries do not last long enough. If that is the case, we will discuss wiring batteries in parallel to increase the Amp Hour (Ah) capacity.

Or, maybe you found a great deal on some 6-volt deep cycle batteries, but all of your equipment is 12-volt. Combining those 6-volt cells into a 12-volt homemade battery pack is easy.

Battery Basics

NiCad and Sealed Lead Acid Batteries are best suited for building battery packs. NiCads are suited for small electronic devices. Lead Acid cells are great for larger electrical devices. A lead-acid battery pack can also provide Alternating Current (AC) via an inverter.

 NiCad Batteries

Every type of battery is built to provide a specific voltage. How much voltage depends on how much electrical energy you’re looking for.

Typical Rechargeable Ni-Cad batteries (AAA, AA, C, D) provide 1.2 volts of electricity. The larger mass of each size enables it to provide more MilliAmp Hours of current.

  • AAA = Approx. 800 mAh
  • AA == Approx 2000 mAh
  •  C == Approx. 6000 mAh
  •  D == Approx. 15,000 mAh

You can use any Ni-Cad battery when building a homemade battery pack.

Recharging these cells is most straightforward with an appropriately sized solar panel, allowing you to easily produce electricity.

Lead Acid Batteries

Seal Lead Acid (SLA) or Absorbed Glass Mat (AGM) lead-acid batteries are the best choice when building a large battery pack. They can not spill like regular Flooded Lead Acid (FLA) batteries. They also do not require maintenance as FLA batteries do.

  • Typical Voltages of 6 and 12.
  • Amp Hour (Ah) ratings from 10 to 500 Ah
  • Wide variety of sizes.
  • Recharge by AC power source or solar.

 Building a Ni-Cad Battery Pack

You can build a Ni-Cad battery pack with just a few components and minimal effort. You can achieve any voltage required for a battery-operated device. The battery pack will be rechargeable via a solar panel or a plug-in charger.

Collecting Components

Determine the voltage required for the battery pack. A 12 volt, 800 mA pack will be the target for this example. Have all the parts on hand before you begin.

  • 8 AA Ni-Cad batteries.
  • 3 feet of 16 or 18 gauge stranded wire. Red and Black insulation.
  • Bottle of liquid electrical tape.
  • Wire cutters/strippers.
  • Soldering iron and solder.
  • Tape or glue to hold batteries together.
  • DC power connectors. There are many styles. Any two-wire connector will do.

 Arranging The Batteries

Batteries will be arranged side by side in an alternating orientation. The first battery will have the “+” positive terminal facing up. The second will have the “-” negative terminal up. Continue this sequence for all batteries. You will end up with eight batteries arranged as pictured.   Tape or glue the batteries together. If using tape, be sure that the terminals are not completely covered.

Prepare Interconnecting Wires

Cut seven pieces of wire approximately 1 inch long. Strip the insulation from 1/4 inch of each wire end. Flatten the exposed wire on each end of the pieces. The flattened end will facilitate soldering.

Soldering Connections

Use a clamp or other fixture to stand the batteries vertically. Solder one wire to the four “+” terminals facing up. When the solder has cooled, solder the free end of each wire to the adjacent “-” terminal. See figure below.  

Turn the battery pack over and repeat the process. DO NOT attach a wire to the last “+” or “-” terminals on the ends of your battery pack. See Diagram.

Measuring the voltage at the “+” and “-” terminals as indicated by the green arrows should show a voltage of 9.6 to 12.0 volts. Ni-Cad batteries tend to hold only 1.2 volts. A reading of 9.6 is correct. If your meter shows no voltage, check for a bad solder joint at one of the connection points.   

Finishing Up.

You can now attach a red lead wire to the “+” terminal and a black wire to the “-” terminal. The lead wires can be as long as you like. Paint all the battery terminal ends with a coat of Paint On Electrical Tape.

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The paint will protect the connections from damage or short circuits. The last step is attaching a plug to the end of the lead wires.

Charging Your Battery

The battery pack can be charged either with a 12-volt universal Ni-Cad charger or a small 12-volt solar panel. The current of the charging device should be no more than 100 mA. Charging dead batteries will take approximately 8 hours.

Building a Lead Acid Battery Pack

The construction of a large 12-volt homemade battery pack is similar to the small Ni-Cad pack. All of the parts are just bigger. We will consider building a 12-volt battery pack with 100 amp hours of service for this discussion. The batteries used for the pack will be 12-volt, 50 amp-hour batteries.

Collecting Components

The components used for this homemade battery pack are variable. The size of the batteries, the battery terminals, and the connecting plug you wish to use will impact the construction of the battery pack.

For that reason, this discussion will not include specific details about structure. It is, instead, a general guide to planning and developing your design.

  • Two 12 volt, 50 Ah sealed lead-acid (SLA) or absorbed glass mat (AGM)batteries.
  • 10 feet of 14 or 12 gauge stranded wire. Red and Black insulation.
  • Four battery terminal connectors, appropriate for your batteries.
  • An ice chest, plastic tote, or metal container large enough to contain the batteries side by side.
  • DC power plug set for connection to your devices.
  • Spray foam or other packing material to immobilize batteries in the container.
  • Reliable tape.

 Arranging the Batteries.

Set batteries side by side, with “+” terminals on the left and “-” terminals on the right. Tape the batteries together.

Creating Interconnect Wires

Measure the distance from the terminals on one battery to the same terminal on the other battery ( + to +) (- to -). Cut one length of red wire and one length of black wire 4 inches longer than the measured distance. Attach one end of the black wire to a terminal connector and one end of the red wire to another connector.

Connect the other end of these wires to the second set of terminal connectors. At the second connector, connect a length of wire long enough to exit the container you have selected. See the illustration below. 

Making the Connections

Connect the terminals with the black (-) wire to the “-” terminals of the batteries. Connect the terminals with the red (+) wire to the batteries’ “+” terminals. Be sure the wire and terminal connectors are in the same orientation as the black wires.

Tighten fasteners until snug but not overly tight.

Routing the External Wire

Estimate where you want the power wire to exit the container that will house your battery pack. Drill a hole in that location large enough to route the wires through. If you are using a metal box, rubber, or plastic insulators to protect the wire would be wise. If you plan to install a plug to the container box, drill the appropriately sized hole for the plug assembly.

Place the battery assembly in the box. Route the wires through the hole and connect them to the plug assembly or whatever external connector you have selected. Then, install the plug assembly.

Finishing Up

Once the batteries are in place, and external connections have been made, secure the batteries with whatever material you have chosen. If you use spray foam, only use enough to secure the batteries. If you fill the box, you will never be able to get the batteries out if they need changing. Install the top of your battery container and secure it as you see fit. You now have a 12 volt, 100 Ah battery to supply your devices.

Charging Your Pack

As with any lead-acid battery, charging is relatively easy. A 12-volt plug-in charger will handle this pack with no trouble. If you choose to go solar, a 12 volt, 100-watt panel with a simple charge controller will power the pack up in a few hours.

Final Words

Building a custom homemade battery pack is not an arduous undertaking. You can build volts by stacking batteries in series. Build amp hours by stacking batteries in parallel. Always remember that the batteries used in a pack MUST match.

Do not use an old cell with a new cell. Do not use batteries of different types. You can achieve whatever voltage and amp rating you need to run your camp with a bit of planning. Experiment and have fun making a homemade battery! 

Additional FAQ About Making Homemade Batteries

Q: Will I need a voltage meter to make a homemade battery?

A: A voltmeter is not required, but it will come in handy if you want to test the voltage of your pack.

Q: What about making a coin battery or a saltwater battery?

A: Coin batteries are a good way to get started in battery making, and salt water batteries are a fun way to learn about electrolysis. However, for more power, you will need to upgrade to the type of batteries described here.

Q: Are there any dangerous chemical reactions I should be aware of?

A: Yes, there are. Lead-acid batteries produce hydrogen gas when charging. This gas is explosive. Therefore, it is important to charge your batteries in a well-ventilated area. Batteries should never be charged indoors.

In addition, the sulfuric acid in lead-acid batteries is corrosive and can cause burns. It is important to handle batteries with care. If acid gets on your skin, rinse it off with water immediately. If acid gets in your eyes, flush them with water for at least 15 minutes and then seek medical help.

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