Power Up Your Boombox: Connecting KBT Batteries for More Capacity

KBT 12v 2.6ah battery pack

Building your own boombox is one of those projects where sound, style, and power all come together. You’ve probably picked your amp, wired your speakers, and maybe even thrown on some LEDs. But when it comes to power, there’s one simple upgrade that can make a big difference. You can connect multiple batteries in parallel to increase your runtime without changing voltage or adding complexity!

Why You’d Want to Do This

Most boombox amps run on a fixed voltage. Whether it’s 12 volts or 24 volts, going above that limit is risky and can destroy your gear. But that doesn’t mean you’re stuck with a short battery life. You can increase capacity, measured in amp-hours, without increasing voltage. That means longer playtime on the same system.

This is where KBT batteries come in handy. Many of their 12 volt lithium packs include both a male and female DC5521 connector. These aren’t just for charging and powering devices separately. They allow you to connect batteries together, as long as you know what you’re doing.

The Secret Behind the Plugs

KBT battery packs with male and female barrel connectors are usually wired internally so both plugs share the same terminals. That means you can plug the male from one battery into the female of another, and they’ll function as a single battery with more capacity.

This type of setup is called a parallel connection. When batteries are connected in parallel, two things happen:

The voltage stays the same. So two 12 volt batteries still give you 12 volts total.
The capacity adds together. Two 2.6 amp-hour batteries give you 5.2 amp-hours.

That’s double the runtime without touching your voltage. Perfect for a boombox.

How to Connect Them

Here’s how to safely link two or more KBT batteries in parallel:

Make sure all the batteries are the same voltage. Mixing a 12 volt battery with anything higher or lower can be dangerous.
Fully charge each battery before connecting them. This reduces the chance of imbalance or current surge between packs.
Plug the male connector from one battery into the female connector of another. That’s all it takes. The batteries are now combined.
Use the remaining connector to power your amp. Either the leftover male or female plug will work, since both are now part of the same parallel circuit.

If the batteries aren’t close enough to plug directly into each other, use a short DC5521 extension cable.

Real World Example

Let’s say you’re using two 12 volt 2.6 amp-hour KBT batteries. On their own, one battery might power your amp for around three hours. Add a second in parallel, and now you’ve got about 6 or 7 hours of playtime.

Add a third and you’re closer to 10 more hours. You can keep scaling up, as long as your wiring is clean and your batteries match.

To calculate total runtime, just multiply the amp-hours by the number of batteries. The voltage stays the same, so your amp stays happy.

A Few Things to Avoid

Don’t connect batteries of different voltages. That can cause damage or even create a fire hazard.
Don’t connect the male and female plugs on the same battery to each other. This won’t do anything useful and could cause internal issues.
Don’t assume these plugs support series wiring. Most KBT batteries are not designed for that, and if you try to run them in series, you’ll get 24 volts, which could blow your amp.

Optional Step: Test With a Multimeter

If you want to double-check your wiring, use a multimeter. Place the black probe on the outside barrel of the plug and the red probe inside the center. You should see around 12 to 12.6 volts, depending on the charge level. If you see something close to 24 volts, you’ve connected them in series by mistake and should disconnect immediately.

Final Thoughts

KBT’s battery design makes it easy to expand your power setup without having to solder, splice, or modify anything. You just plug them together and go. For boombox builders, that means more music and fewer interruptions.

Whether you’re powering a beach party, backyard gathering, or just taking your sound system on the move, this is one of the simplest upgrades you can make.