The Hubble Space Telescope is famous for its pictures of galaxies. And I mean, who doesn’t love looking at pictures of galaxies? But this has left its batteries feeling a bit neglected, which isn’t entirely fair. These batteries are doing some pretty neat stuff.<\/p>\n
Hubble ducks into Earth’s shadow on every lap around the planet, and each of those laps takes about an hour and a half. And nobody is thinking about the batteries! Those batteries\u00a0get drained and topped back up more than a dozen times a day. NASA says the first set kept doing that for 19 years before astronauts swapped them out, and the replacements run on the same nickel-hydrogen chemistry.<\/p>\n
Nineteen years!? I’m lucky if I can get a PlayStation controller or laptop to last more than eight hours.<\/p>\n
Now that<\/em> chemistry has its own factory. EnerVenue, a battery startup out of Fremont, California, began production on September 24 at a new line in Changzhou, eastern China. This line was built to make what it calls the Aqueous Metal Cell. It’s basically a nickel-hydrogen battery reworked with cheaper materials for use on the ground, and the company says the first cell that met spec rolled out at the end of September.<\/p>\n It’s easy to see why you don’t think of a battery when you think of the Hubble Space Telescope. The cell doesn’t really look like a battery at all. It’s more like a tube about 6.8 feet long, roughly the length of a couch, and it weighs 152 pounds. EnerVenue’s cell datasheet<\/a> rates each one at 3 kilowatt-hours.<\/p>\n By my math, that’s a little more than one of Hubble’s six batteries holds. NASA<\/a> rates each of those at 88 amp-hours and 32 volts, which works out to about 2.8 kilowatt-hours, and it takes 22 cells to get there.<\/p>\n Because one side of the reaction is hydrogen gas. When you charge a nickel-hydrogen cell, hydrogen builds up inside it. Then, once you drain it, that hydrogen gets used back up, so the pressure inside rises and falls with the charge. That’s why NASA’s Goddard engineers keep an eye on battery pressure when they charge Hubble, and it’s why EnerVenue’s cell is really a sealed tank with electrodes inside. The liquid in there is water-based, so there’s none of the flammable solvent you’d find in a lithium-ion cell.<\/p>\n To perfect such an intruiging concept, the cell has changed a lot over the years. EnerVenue’s earlier cells used a metal canister. In the fourth-generation cell this line builds, the stack of electrodes goes into a plastic liner, the liner goes into a steel tube, the tube gets sealed, and the whole thing gets wrapped in glass fiber. In a video the company posted in August, CEO Henning Rath walks through the layers, and EnerVenue says the fiberglass adds strength and should cut the amount of steel each cell needs.<\/p>\n What I can’t<\/em> find anywhere in EnerVenue’s published specs is how much pressure the tube is rated to withstand. For a battery that’s essentially a pressure vessel, that seems like a strange number to leave off the sheet. Is it some deep government secret!? The datasheet covers size, weight, energy, voltage, and certifications… But, guess the pressure is currently unavailable.<\/p>\n From the looks of things, most of the effort went into the factory, and I think that’s the right call. According to EnerVenue, nobody else builds this kind of cell, so each machine had to be designed from scratch and proven out first on a research line a few miles away. Robotic carts shuttle cells between stations so nobody has to carry them (which, at that weight, I’d count as a perk). A camera-guided machine stacks the electrodes, and a winder lays the fiberglass on with its tension managed layer by layer, starting at the tube.<\/p>\n There’s a lot of numbers being thrown around here (except pressure, apparently), but there’s another interesting number I wanna add.\u00a0Every one of EnerVenue’s cells gets 41 checks at 11 test stations before it’s allowed out the door, covering the welds, leaks, and performance. “Anyone can make one good vessel,” TJ Hua, the company’s head of production, said in its production announcement<\/a>. His point is that a factory earns its keep by making thousands of cells that all come out the same.<\/p>\n So what’s the catch?<\/p>\n Why isn’t everyone using these batteries to charge their house, car, controllers….? Well, three kilowatt-hours in 152 pounds isn’t a great ratio by modern standards. I ran EnerVenue’s own figures against the battery-only add-on for Tesla’s Powerwall 3, the lithium-ion home battery you may have seen bolted to a garage wall, and the gap is pretty<\/em> big.<\/p>\n Basically, you’re carrying three to four times the weight for the same energy, depending on whether you count the bare cell or the finished rack. It’s safe to say nobody’s bolting one of these into a pickup bed. The rack also needs fans to push air through it, according to EnerVenue’s spec sheet. Weight matters a lot less for something that sits in one spot for decades, which is why grid storage keeps attracting heavy, unglamorous ideas like the graphite battery going up in Massachusetts<\/a>.<\/p>\n EnerVenue isn’t trying to win on weight anyway. The pitch is that each cell is built for 30,000 charge cycles, a figure the company gets by assuming as many as three full cycles a day, every day, for 30 years. Thirty years! I’ll remember\u00a0that<\/em> number. It also says the chemistry can’t go into thermal runaway, the self-feeding overheating behind most lithium battery fires, and that if something goes wrong, a relief valve in the cell vents water vapor. The datasheet lists UL 9540A, the fire-propagation test that the US fire codes point to, among its certifications.<\/p>\n Those are design claims, though, not a track record. EnerVenue says its oldest fourth-generation cells in the field have been working since November 2025 at a bus charging station in Jintan, a district of Changzhou. Towngas, the Hong Kong gas utility whose subsidiary runs the site, described it in May as a single rack, cycling for two to four hours every day alongside solar panels. That’s less than a year into a 30-year promise.<\/p>\n I’d also flag that EnerVenue’s datasheet and Towngas’s announcement don’t agree on how cold or hot these cells can run, so I’ve left temperature out of this entirely. If you’re in the US, the more relevant detail is that EnerVenue says cells have already shipped to American customers, naming PowerSecure among them.<\/p>\n This isn’t the factory EnerVenue originally pitched. Its first plant was supposed to be a 1-million-square-foot building in Shelby County, Kentucky, with a $264 million first phase and 450 jobs, according to the state’s announcement<\/a>. It seemed like a big deal, and Kentucky lined up tax incentives tied to those jobs. However, Reuters reports that EnerVenue dropped the plan about a year after it was announced.<\/p>\n So what happened?<\/p>\n Rath, who joined EnerVenue in April, told Reuters the Kentucky attempt was a “valuable learning experience” but that the technology wasn’t ready. The company went back and reworked the cell and the factory. As for why the new plant ended up in China, he pointed to engineering skills and the depth of the supply chain around Changzhou. Reuters also reports he made building there a condition of taking the job.<\/p>\n The new plant is a lot smaller than the originally planned Kentucky plant, at around 215,000 square feet against the planned 1 million. Rath wouldn’t give Reuters an exact cost, but he put it somewhere between $20 million and $50 million. The news agency says it’s almost entirely automated and should employ around 400 people by the end of the year. Which, admittedly, isn’t far off the 450 jobs listed for Kentucky.<\/p>\n Will any of this end up in the US? Maybe, eventually. Rath told Reuters that EnerVenue wants plants in Europe, the Middle East, and North America starting in 2028, with sites picked next year, though he said a US plant depends partly on legislation and regulation. Reuters also notes that nobody yet knows whether China-made cells can claim federal clean energy tax credits, since the 2025 tax law left those credits in place for battery storage but added limits on Chinese content and ownership.<\/p>\nSo why does a battery need a tank?<\/h2>\n
Nickel-hydrogen is heavy<\/h2>\n
Kentucky was supposed to come first<\/h2>\n