Tesla delivered just over 22,000 vehicles in the second quarter, a 53 percent increase from the same time last year.

The electric automaker blamed severe production shortfall of 100 kWh battery packs. The company said production average 40 percent below demand, until early June. But once the issue was resolved, Tesla said production speed rebounded.

Of the 22,000 vehicles delivered, 12,000 were Model S and just over 10,000 were Model X. Tesla produced 25,708 vehicles in the quarter, bringing production for the first half of the year to 51,126.

Tesla also said it added more Model X cars to its test drive and display fleet because its stores had been running with too few, or in some cases, none at all.

“There appears to be substantial untapped sales potential for Model X,” the company said.

The electric automaker also claimed that “production quality and field reliability of the Model X, for which Tesla has been fairly criticized, have improved dramatically.” Tesla said that it’s now “rare” for a new Model X to have “initial quality problems.”

The first production of Tesla’s Model 3 that meets regulatory requirements will be finished this week and will debut on July 28.

Tesla shares have surged 65 percent so far this year amid lofty expectations for the Model 3, the automaker’s mass market car.

Delivery numbers are conservative, the company warned, saying final numbers could vary up to 0.5 percent. For the second half of the year, Tesla said deliveries will “likely exceed” those in the first half of the year.