Vice President Mondale returned to Minnesota this weekend to sell the strategic arms limitation treaty (SALT II) and the idea of a massive effort to speed development of synthetic fuel to cope with the nation's energy crisis.

As Fritz Mondale, leader of the Minnesota Democrat-Farmer-Labor (DFL) Party, he was here most of all to sell the 1980 Carter-Mondale ticket, which in his home state transposes for practical purposes into the Mondale-Carter ticket.

Politically, his trip climaxed today with the formal inauguration of the Minnesota reelection committee at a $1,000-a-person fund-raising champagne brunch at Charlies Cafe Exceptionale, a fancy downtown restaurant, attended by 150 political, labor and business establishment figures.

The fund-raiser came 13 days after Rep. Richard Nolan (D-Minn.) staged a draft-Kennedy meeting in Minneapolis where a similar number of participants paid $5 a head for brunch in a University of Minnesota cafeteria in support of a 1980 presidential campaign by Sen. Edward M. Kennedy (D-Mass.).

Mondale's trip home signaled a decision to put his personal popularity and official prestige on the line to capture Minnesota's 75 delegates to the 1980 Democratic National Convention - delegates who are chosen in a free-for-all system that starts at the precinct level Feb. 26.

Asked today about Nolan's defection, Mondale would say only that he liked the congressman, that it was a free country and that Minnesota had an #open" political tradition.

Including the receipts from Mondale fans who paid to go to the brunch but didn't, the affair netted an estimated $190,000 for the national Carter-Mondale Presidential Committee, the first pre-convention committee bearing the name of the vice presidential half of the ticket, according to a committee aide.

Mondale, who was joined by his wife, Joan, at the meal, was in an exuberant mood. And while he praised President Carter as a "brilliant, honorable, honest and open man" with unprecedented foreign policy accomplishments, the vice president said:

"We are not perfect. We won't run on a perfection ticket. We won't try."

While Mondale, a former Minnesota senator and state attorney general, was basking in the company of his friends, some of whom he's known throughout his 30 years in politics, the Republican National Committee was meeting a few blocks away in a downtown hotel. Rep. Guy Vander Jagt (R-Mich.) told participants there that Carter would be easier for the GOP to beat next year than would Kennedy.

As vice president, Mondale has made about 20 mostly routine trips home, but this one had the flavor of a real campaign swing, complete with motorcade, police cars, squads of Secret Service agents - all of it garnished with receiving lines, handshaking and joshing.

The political aspect of the homecoming was an effort to bring together the factions of the DFL Party whose quarreling produced major election defeats last November, notably the loss of both Senate seats and the governorship. The trip's policy aspect is a preview of Mondale's planned trips in mid-July to sell SALT II in at least six states whose senators - like Minnesota's - are uncommitted.

This trip began with a news conference Friday at which Mondale defended the administration's decision to cancel a regulation giving preference to farmers on diesel fuel in an effort to aid truckers.

He then spoke to 750 lawyers and their spouses at the Minnesota State Bar Association's annual convention in a suburban Bloomington hotel.

Mondale joked with his fellow lawyers - he graduated from the University of Minnesota Law School - and in his speech made an emotional appeal for SALT II as a treaty that would preserve the nation's "unsurpassed" military power while lessening the chance of "nuclear holocause."

He coupled that with a warning that the energy crisis was real and dangerous" and urged the lawyers to stop "dreaming up conspiracies that don't exist." He called for a "massive national effort" in the development of synthetic and alternative energy resources such as sun and wind power and the use of peat, which abounds in Minnesota.

Mondale later spoke at the Friday sabbath service in Temple Israel, where he was introduced as "one of the most important people on the face of the globe." He repeated his message on energy and SALT II in a biblical context and told eight Soviet immigrants "we welcome you with open arms and the love of the American people."

After today's fund-raiser, the vice president set out for the annual celebrity golf and tennis tournament at Rolling Green Country Club. One of his opponents in a doubles tennis match was Ahmad Rashad, a wide receiver with the Minnesota Vikings profootball team.

Mondale would up his trip at a reception for Donald Fraser, the DFL-endorsed candidate for mayor of Minneapolis. The former liberal congressman was defeated in a senatorial primary last year by conservative Bob Short. Both are now on the Minnesotans for Carter-Mondale reelection committee.