Cellphone battery dead? No problem: Just borrow a charger from a friend. Oh, wait — you can’t, because your friend doesn’t have the same phone as you, and his charger won’t work with your phone.

That annoyance will end next year, for Europeans at least. Thanks to the efforts of the European Commission, most cellphones sold in Europe will have a one-size-fits-all charger starting in 2011. So far, 10 major cellphone makers, including Apple, Motorola, Samsung and Research In Motion, have signed on to the agreement.

Americans will have to wait. Without a government agency setting a deadline, it’s up to handset makers to make the switch to a single standard. All consumers can do is let their old chargers gather dust in a drawer, while hoping manufacturers will eventually converge on a standardized charger.

“For the FCC, this is probably number 5,000 on their list and it is legislative priority number 10,000 at this point,” says Joe Banos, chief operating officer for Wilson Electronics, which makes cellphone boosters and antennas. “We believe the US will ultimately follow Europe here, but the question is when.”

Today each cellphone ships with its own charger. Different companies use different connectors—and often different models from the same company do too, making it difficult for users to borrow a charger. And when it’s time to toss the phone, the charger also goes into the bin.

A universal charger means consumers don’t have to get a new charger with every mobile phone. As a bonus, it’ll be easier to borrow a charger when in need.

And if all that isn’t enough, there’s the green aspect. One-size-fits-all means fewer chargers will wind up in the landfill, less electronic waste, and fewer resources consumed in manufacturing chargers.

In 2009, the European Commission said it reached a voluntary agreement with handset manufacturers to use the micro-USB connector for the charger. Starting in 2011, all phone models sold in Europe would then have compatible chargers. Now, that agreement is taking effect.

Changing the rules in the US

Smartphone makers in the United States are moving toward something similar, but more slowly. Motorola and Samsung have said they will offer a standard charger here but haven’t committed to a deadline. It’s a complex game where each handset maker is optimizing for itself, but collectively those decisions might help realize the goal of having a universal charger, probably centered on micro-USB.

“For the most part it is already happening here with smartphones,” says Michael Gartenberg, an analyst at the Altimeter Group. “An HTC Evo charger will charge a Nexus One or Incredible, as long as it has a micro-USB connector.”

The major holdouts in the US are Apple and Research In Motion. Apple uses a proprietary 30-pin connector for its iPhone, while many BlackBerry chargers and devices are engineered so they will work only when paired together, says Wilson’s Banos.

But even among companies that use micro-USB, it’s still not a standard.

“There’s the flat, wide mini-USB connector; the short, squat micro-USB; and different versions in between,” says Allen Nogee, an analyst at In-Stat research. “They are all still using different versions of the USB connector.”

But if you can get a connector to fit into the phone, it doesn’t matter which model it is for or which company made it, because all USB-based chargers deliver the same voltage, say experts.

The push to change the situation in the US could come from accessories makers for smartphones, says Nogee. Today, when you buy a new battery pack or car charging kit, it comes with a little bag stuffed with connectors so users can pick the right ones for their phones.

“It is much more expensive for these companies to support different phones and connectors,” says Nogee. “But the problem is that so far, accessories makers haven’t had enough say in the phone manufacturing process.”

Ultimately, economics will force handset makers in the US to change, say industry experts. As companies move to a universal charger in Europe, they will bring the same connectors to US models.

It’s not clear how Apple will make the change, but it is certain that if the company moves to a micro USB-based connector for its new iPhone model in Europe, US customers can expect the same.

“It makes so much sense that I believe the US will follow,” says Banos. “It would be insane not to.”