(Bloomberg) —Samsung Electronics Co., under pressure from consumers for longer-lasting batteries that charge faster, pushed the limits of lithium-ion technology. The effort backfired when some of its new Note 7 handsets caught fire and exploded.

Building a better battery has long bedeviled the tech industry. Smartphones are constantly improving, with sharper displays, improved software and cameras rivaling those used by the pros. Not so the batteries, which despite advances still die faster than consumers like and take too long to recharge.

“It’s the race to add new capabilities and features to the phone that demands a more capable battery,” said Martin Reynolds, a Gartner analyst.

On top of the demands placed on their performance, batteries are getting slimmer and smaller, as smartphone makers try to win over consumers with thinner devices. That’s putting strain on the manufacturing process, and raising the risk of defects that can lead to the kind of malfunctions seen in Samsung’s phones.

The Note 7 was supposed to stand out with its stylus, large edge-to-edge display and faster charging technology. Samsung rolled out the device in August, just before Apple Inc. unveiled a new batch of iPhones. It was a opportunity for the Suwon, South Korea-based company to outshine its biggest smartphone rival. Instead, it backfired.

Usually, smartphone makers and wireless providers rigorously test products before they reach customers, although the process is mainly focused on making sure the devices are compatible with wireless networks. Samsung provided carriers with the typical amount of testing time before the launch date, according to people familiar with the matter. Samsung first showed prototypes of the Note 7 to carriers in April and testing began in May, said the people, who asked not to be identified because the arrangements aren’t public.

At least one major Samsung partner is reassessing its testing procedures to catch issues like this in the future, according to a person with knowledge of the matter. The South Korean manufacturer is holding multiple meetings each week with major carrier partners to discuss the latest details from its investigation and assist in mitigating the issue, the person said.

Headaches involving the production of lithium-ion batteries aren’t unique to the smartphone industry. Overheating battery packs made by Sony Corp. led to the recall of millions of laptops made by Dell Inc., Toshiba Corp. and others in 2006, while Boeing Co.’s 787 Dreamliner suffered from electrical fires after the airplane’s 2011 debut.

“Based on our investigation, we learned that there was an isolated issue with the battery cell,” Samsung said in an e-mailed response to questions. “Overheating of the battery cell occurred when the anode-to-cathode came into contact with each other, causing a very rare manufacturing process error.”

Samsung is working to fix the problem. While only about three dozen cases were reported, the company is seeking to replace 2.5 million Note 7 phones, an endeavor that could cost as much as $2 billion. On Wednesday, Samsung placed advertisements in South Korea’s major newspapers to apologize for the incident. In an effort to prevent any more device explosions, the company is also rolling out a software update on Sept. 20 that will limit the battery charge at 60 percent. Availability of that update outside South Korea will vary depending on each market, Samsung said.

The Note 7 features a larger battery than its predecessor, one that can store 3500 milliamp hours of electric power, compared with 3000 mAh for the Note 5 (Samsung skipped a number this year, to match its flagship Galaxy S7). By comparison, the iPhone 7 Plus, the Note 7’s main competitor, has a 2900 mAh battery. While Apple has also sought to upgrade its battery technology to support better screens and faster graphics, it hasn’t often promoted battery life as a feature itself. Last week’s iPhone event was an exception, when the company highlighted that the iPhone 7 can last almost two hours longer than its predecessor thanks to better software and processor design.

Samsung SDI Co. was the main battery supplier for the Note 7, according to a person with knowledge of the matter. The batteries failed because a separator within the cells was too thin and electrodes weren’t properly insulated, according to a government quality inspection agency in China, where almost 2,000 Note 7s were distributed as test devices. Samsung, which is preparing to get replacements into the hands of customers from Sept. 19, said in a statement that “all Galaxy Note7 replacement devices will be equipped with the battery from other suppliers.”

For the past few years, Samsung has adopted Quick Charge, a technology developed by Qualcomm Inc., throughout its product lineup, including the Note 7. Using specialized chips, circuits and software, the mechanism works in tandem with a specific charger to speed up the process. While that has enabled rapid charging — up to 50 minutes faster than its predecessor — it’s also pushing up against the physical limits of the materials and design used in battery technology. Gartner’s Reynolds noted that fast charging is essentially a solution to the problem of short battery life.

“It’s a feature driven by short battery life in general, not something that people really want,” he said.

The first batch of Note 7 batteries probably had a flaw in their design that didn’t work properly with the chemistry in some units, according to Kyle Wiens, creator of iFixit, a popular website that dissects the innards of gadgets to gauge the ease of repairing the devices. Fast charging “crams as much energy as possible into the battery, and the closer you push it to the edge, the more of a potential safety issue there is,” he said.

–With assistance from Elliott Snyder, Jing Cao and Sohee Kim. To contact the reporters on this story: Mark Gurman in San Francisco at mgurman1@bloomberg.net ;Alexandre Boksenbaum-Granier in Paris at aboksenbaumg@bloomberg.net To contact the editors responsible for this story: Robert Fenner at rfenner@bloomberg.net ;Jillian Ward at jward56@bloomberg.net Reed Stevenson