NEW YORK - Big banks, facing declining revenues and a regulatory climate that leaves them fewer creative ways to make money, are quietly introducing or experimenting with fees that are sure to outrage customers.

Bank of America was shouted down by angry customers last fall when it tried to impose a $5 monthly fee for using a debit card. JPMorgan Chase and Wells Fargo backed off plans to impose their own fees.

But the major banks have imposed or are testing other fees:

* Since November, Wells Fargo has charged $15 a month for some checking accounts unless customers have three accounts with the bank, maintain a minimum balance of $7,500 or have a Wells Fargo mortgage.

* Some Citibank customers are being charged $20 a month unless they keep $15,000 in their accounts, up from $6,000 before December. They're also being dinged with a $2 fee for using non-Citi ATMs if their balance falls below the minimum.

* Bank of America, even after a backlash last fall when it tried to impose a $5 monthly fee for debit card transactions, is testing a menu of checking accounts in Georgia, Massachusetts and Arizona with monthly fees of $6 to $25.

Banks aren't charities, and they say they need to make money, or at least cover the cost of doing business. Consumer groups - and customers, too, it's safe to assume - have a less forgiving view.

"Banks have a short-term memory," says Norma Garcia, senior attorney at Consumers Union. "These fees affect all consumers, but particularly impact the most vulnerable, who have the least capacity to meet minimum balances and avoid the fees."

Nothing in banking is free anymore. All of the largest banks in the United States offered free checking with no strings attached until 2009, and almost none do today, says Mike Moebs, the founder of Moebs Services, a financial research company.

And what wasn't free before costs a lot more these days: Moebs' research shows that cashiers' checks that used to cost $3 now cost as much as $12, and the cost to get money orders has doubled to $2 at the largest banks.

The big banks are public companies and are expected to make a profit somehow. And it's not as easy as it used to be.

Historically, banks have made money off of something called interest rate spreads. They borrowed money cheaply, loaned it out at higher interest rates and pocketed the difference.

But interest rates are at historic lows, making it harder for banks to charge high rates when they lend and squeezing their profits.

Regulatory rules since 2009 have also curtailed traditional bank fees, costing them billions of dollars. Banks were barred in 2010 from automatically enrolling customers in a service that charged them as much as $35 for overdrafts on their checking accounts.

Another law barred banks from charging fees and changing interest rates on credit cards without notifying customers.

Banks' revenues have dwindled since these laws came into effect. Bank of America's revenue last year was $93 billion, compared with $121 billion two years before. Wells Fargo took in $81 billion last year, down from $89 billion in 2009.

Jamie Dimon, the CEO of JPMorgan Chase, told an investor conference earlier this week that it costs the bank an average of $300 a year to maintain a bank account. About 85 percent of customers of the two largest banks in the U.S. - JPMorgan Chase and Bank of American - still qualify for free checking.

Banks are trying to figure out how to make up that cost. But their fees are landing hard on customers in a country with 8.3 percent unemployment, some of whom point out that it was taxpayers who bailed out the banks less than four years ago.

The $5 debit card fee that Bank of America announced on Sept. 29 became a flashpoint of anger, including for protesters in the Occupy movement.

The bank said it was triggered by a federal law championed by Sen. Dick Durbin, D-Ill., that went into effect Oct. 1. It capped what banks charge stores for debit card transactions at 24 cents, down from an average of 44 cents.

The law cut into quarterly revenue at Bank of America by $475 million, at JPMorgan Chase by $300 million and at Wells Fargo by $250 million.

Nevertheless, after public outrage, those three banks, plus SunTrust Banks Inc. and Regions Financial Corp., all backed down from plans to charge monthly fees for debit card purchases.

Bank of America says it is "not planning to increase checking account fees with our existing customers." Of the tests in Arizona, Georgia and Massachusetts, it says it is "continuing to learn" from them and has made no decisions.

Some bank executives say the political environment has made it difficult for them to charge for their services. Todd Maclin, head of consumer banking at JPMorgan Chase, points out that banking is cheaper than a cellphone, a cable TV or a gym membership.

"But still we don't expect that you're going to be able to increase in this environment," he says, referring to prices.

Still, Chase and the other large banks have increased monthly fees by an average of $10 for checking accounts in the last two years. They also introduced fees of $2 and $3 for small services like printed statements and canceled checks.

Consumer advocates say they worry that the fees will push people out of banking and toward more expensive services, like payday lenders and loan sharks.

"A significant part of the population will be squeezed out of banks because they can't afford it," says Nancy Bush, founder of banking research group NAB, and columnist at SNL Financial, "and that is absolutely wrong."