MIAMI — Bank of America (BAC) is one of the country's largest and most mass-market banks, but it isn't well-known as a pioneer of banking services for lower-income customers. Now the Charlotte company is trying to change that.

Since last year, B of A has been doing research on its least affluent customers, to understand how it can better serve people who earn less than $50,000 annually, co-Chief Operating Officer David Darnell said in a speech on Friday.

Those people are a crucial market for the bank, which does business with half of the households in the country. But the bank's reputation has been significantly battered in the past several years, due in part to its association with the foreclosure crisis and its ill-fated attempt to charge customers for using their debit cards.

Darnell acknowledged the amount of reputational repair still ahead for the bank: "We know there is a long-term profitable business in banking America, one that starts with earning back the trust of consumers and small-businesses," he said.

Some of the things that B of A has learned about its lower-income customers is that they want "full-featured banking access," including to branch tellers and automated teller machines; they want free online and mobile banking access; "they want no surprises … and they're comfortable with a flat, low monthly fee as long as that fee doesn't fluctuate based on behavior," Darnell said.

He stopped short of discussing specifically how Bank of America intends to address those needs, and the bank would not make him available for interviews.

The company has some catching up to do in terms of developing specific, widely-used products for lower-income consumers. Rival JPMorgan Chase (JPM), for example, last year unveiled a new prepaid card that functions like a bank account and debit card and is intended for customers who make less than $75,000 annually. That Liquid card and the similar Bluebird card from American Express (AXP) and Wal-Mart (WMT) have been praised for making prepaid cards a more mainstream alternative to the traditional deposit bank account.

Bank of America has been increasingly building out and emphasizing its mobile banking, which helps it serve more customers while cutting branch costs; it signs up 50,000 customers per week to mobile banking, Darnell said. He acknowledged that reducing expenses is an important imperative for B of a and all retail banks in the current low-interest-rate, low-revenue-growth environment.

Darnell spoke to an audience of about 750 bankers, startup executives and other industry members gathered at the annual Underbanked Financial Services Forum. The conference is co-sponsored by American Banker and the non-profit Center for Financial Services Innovation.