Last summer, Tesla introduced both a new and bigger 90 kWh battery pack and the ‘Ludicrous mode’ upgrade for a higher level of performance on the already insane Model S. The automaker offers the upgrade for a $10,000 premium when configuring a Model S P90D or as a retrofit for Model S P85D owners who, at the time, had just witnessed their less than 1-year old cars already outperformed by the new version.

Tesla ended up significantly reducing the price of the retrofit to just $5,000 for the P85D and now for the first time, the automaker is offering the upgrade as an aftermarket retrofit for the Model S P90D – meaning that someone configuring the Tesla’s top of the line vehicle could decide to pass on the ‘Ludicrous mode’, but later add it for the same price plus labor.

The company added the option on its Tesla Gear website today (hat tip to spaceballjedi for spotting it).

The Ludicrous upgrade consists of two improvements to the electronics of the Model S’ battery pack. The first improvement is the replacement of a standard fuse to an “advanced smart fuse” which enables the monitoring of current to the millisecond, and makes it possible to cut the power with “extreme precision”.

For the second improvement, Tesla replaced the main pack contactor to use Inconel instead of steel. Inconel is a space-grade superalloy well suited for extreme high temperature environments. This superalloy is primarily use in the aerospace industry, and one of its more famous use is in the novel manufacturing process of SpaceX’s SuperDraco engine.

The two improvements combined allow Tesla to increase the max power output of the Model S’ battery pack from 1300 to 1500 Amps, which enables higher performance. Tesla writes on the Ludicrous upgrade listing:

“Upgrade the level of performance in your existing P90D from “INSANE” to “LUDICROUS”! This upgrade will decrease 0-60 mph time by 10% to 2.8 seconds with a quarter mile time of 10.9 seconds. The time to 155 mph is now 20% faster than a standard Model S Performance.”

And you get a line under your “P90D” badge to show that you have a “ludicrous” car.

TL;DR/Takeaway: Tesla now not only offers the Ludicrous battery upgrade as a retrofit for the Model S P85D, but also for the P90D. Until now, it was only available at the configuration (when ordering) of the vehicle.