Sales of electric cars and plug-in hybrids took a dive in May, but the segment may still have enough momentum to reach a significant milestone in the coming months.

May's total of 13,111 electric passenger cars sold was down 16 from April.

But the European Alternative Fuels Observatory (EAFO) expects sales to pass the 500,000-unit mark by August.

DON'T MISS: Plug-In Electric Car Sales Report for June: more of the same

The total number of electric cars sold in Europe reached 458,000 in May, and the EAFO expected strong June sales, although data is not available yet.

The cars leading that charge remain models produced by the Renault-Nissan Alliance, according to the running tally of electric-car and plug-in hybrid sales kept by the EAFO.

The Nissan Leaf racked up 9,516 sales between January and May, and had the largest market share of any model, at 12 percent.

Renault Zoe electric cars on the Outer Hebrides

Renault Zoe electric cars on the Outer Hebrides

It was followed by the Renault Zoe, with 9,388 sales in the first five months of the year.

The Renault-Nissan pair have traded the lead in European sales throughout the year, while the Tesla Model S has remained close behind in third place for the most part.

Through May, the Model S achieved 5,360 sales.

ALSO SEE: Plug-in electric car sales in Canada, June 2016: volte-face for the Volt

The EAFO uses registration data to determine its figures, which is how it can calculate monthly Model S sales despite the fact that Tesla does not release official monthly sales results.

Following the Model S were a pair of German electric cars: the Volkswagen e-Golf, with 3,397 sales, and the BMW i3 with 2,165 sales.

2016 Tesla Model S

2016 Tesla Model S

Further down the rankings sat the Kia Soul EV (1,739 sales) and Mercedes-Benz B250e (1,280 sales).

Rounding out the top 10 were three small electric city cars.

MORE: Tesla delivers 14,370 electric cars in Q2, fewer than planned

The Volkswagen e-Up achieved 1,155 sales, while the Peugeot iOn and Citroën C-Zero reached 806 and 622 sales, respectively.

The Peugeot and Citroën are both re-badged versions of the Mitsubishi i-MiEV.

2017 Mitsubishi Outlander PHEV

2017 Mitsubishi Outlander PHEV

Plug-in hybrids: Mitsubishi's streak continues

The Mitsubishi Outlander Plug-In Hybrid retained its title as the best-selling plug-in hybrid vehicle in Europe through May.

It accounted for 11.9 percent of the European plug-in hybrid market, and maintained a comfortable lead over the second-best seller, the Volkswagen Golf GTE.

The VW managed 4,964 sales, and was followed closely by the Volvo XC90 T8 "Twin Engine," with 4,252 sales.

Another Volkswagen—the Passat GTE—followed the Volvo, with 3,535 sales.

Next in line were the Mercedes-Benz C350e and Audi A3 e-tron, with 3,504 and 2,885 sales, repectively.

2017 BMW 330e i Performance

2017 BMW 330e i Performance

The bottom four places in the top 10 list for plug-in hybrids were all occupied by BMW models.

The X5 xDrive40e SUV took seventh place with 2,143 sales, followed by the 330e i Performance sedan, which logged 1,834 sales.

Just behind the 3-Series plug-in hybrid was the i3 REx, with 1,806 sales.

The extended-range electric i3 REx is considered a plug-in hybrid for the purposes of the EAFO tally.

Finally, the 225xe Active Tourer rounded up the top 10 with 1,516 sales.

Active Tourer hatchback models use a front-wheel drive platform, and are unrelated to the rear-wheel drive 2-Series coupe and convertible sold in the U.S.

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