Most people never think about the battery until it dies. Charlie Welch has spent his whole career thinking about nothing else.

On The Innovators, he walked me through what he is building at Proper Voltage. Before this, he was doing applied research in battery chemistry at Northrop, trying to get “interesting and exotic” chemistries into real military systems, from underwater gear to aircraft to special operations kits. The problem he kept hitting was not physics. It was integration.

Every new battery team heard the same thing from the customer. “We’d love to use your tech, if you redesign it for our system.” Every big OEM said the opposite. “We’d love to use your battery, if you redesign your system for us.” No one wanted to move first. No one wanted to touch legacy hardware. That standoff kept better chemistries on the shelf instead of in the field.

Proper Voltage is his attempt to cut through that. The company is not betting everything on one magic chemistry. Instead, they are building a kind of battery operating layer that sits between the cells and the product. They work with sodium ion, lithium titanate, niobium and other “odd” chemistries that each have their own strengths. Then they add a hardware and software block they call a voltage command unit. That unit makes voltage a programmable interface. One pack can now present itself as whatever the device expects, without the device designer having to rip up their boards or add twice as many cells.

He gave a clear example. Standard lithium ion cells sit around 3.7 volts. Many sodium ion cells sit closer to 2.3. If you try to drop sodium into a system that expects lithium and do nothing else, you need almost twice as many cells in series. That means more size, more cost, more weight, and energy you do not actually need. With a programmable voltage layer, the system sees what it expects. The chemistry can change underneath without touching the rest of the stack. The product team gets to pick sodium for safety and life, not walk away because the nominal voltage is “wrong.”

This matters a lot in defense and aerospace. There are standard formats like the 6T battery for vehicles or the soldier’s small tactical universal battery. There are missiles and aircraft that went through years of testing and certification. No one wants to open those designs just to squeeze in a new pack. Welch told me the only way that community moves is if the new unit is truly drop in. Same form factor, same pins, same expectations. If Proper Voltage can let new chemistries look and behave like the old packs from the outside, while giving better power and life on the inside, that is a real wedge.

We also talked about the state of the art. Phone batteries have been roughly the same “spicy pocket brick” for a long time. The gains are slow. Roughly a few percent each year in energy density. The reason you do not feel a huge leap is that every time battery teams squeeze out another watt hour, the chip and software teams spend it on more compute, more video, more background tasks. The pack improves. Your day of use feels about the same.

The big jumps happen when you change chemistry outright. Welch mentioned a humanoid robot project that switched from its old pack to a lithium titanate system. Charge time dropped from three hours to about six and a half minutes. Peak power went up by a factor of four. That is not a small tweak. That is a new class of behavior for the machine. Proper Voltage sits in the middle of moves like that, making sure the robot still sees smooth, stable voltage even when it is sprinting or jumping. When robots do high dynamic moves, voltage usually swings all over the place. Their system flattens that, so the robot sees the same “fuel” from full to empty. There is a small efficiency hit in the power electronics, but because the device can use more of the pack’s range without tripping over low voltage issues, you often end up with more usable energy, not less.

The near term focus at Proper Voltage is not sci fi robots, though that work is clearly a proving ground. The team is leaning into three markets. First is infrastructure, backup power for telecom sites, data centers, LNG plants, all the places that still sit on old lead acid banks. Sodium ion and other chemistries are well suited there, and Welch likes that the United States has the raw materials to build a domestic supply chain around them. Second is defense, from 6T vehicle batteries to drones and soldier gear. Third is “industrial” in the plain sense, robotics and machines where power, charge time, and lifetime are the difference between a lab demo and a real business.

There is a quiet lesson in how he talks about all this. We like big claims about a single breakthrough that will rewrite the rules. Proper Voltage is going after something more boring and more important. The connective tissue. The thing that lets new battery chemistries plug into old systems without fifteen rounds of redesign and risk. If they pull that off, we will not see it in a flashy consumer product first. We will see it in a Humvee that has reliable backup power, a cell tower that stays up during an outage, a robot that can run all shift without a fragile pack.

The future of batteries will not arrive as one perfect cell that solves everything. It will come as a lot of different chemistries, each strong in its own narrow way, finally getting a path into real hardware. Proper Voltage is betting that if you want that future, you need to fix the link between the lab and the product. That is not a hot topic on social media. It is the kind of ugly, necessary work that moves the field forward, one pack swap at a time.