Standards until recently Tesla gave customers with supercharger enabled cars unrestricted access to its supercharger network regardless of how many miles they drove or how old their car was but earlier this year that policy switched to only providing 400 kilowatt hours of free power per year for those buying brand-new Tesla's with Tesla then offering customers the chance to buy additional supercharger credits as and when needed that policy change caused quite a ruckus among Tesla fans but over the weekend another supercharger story surfaced which suggests that some owners especially those who use the supercharger network a lot but experiencing maximum charge rates during their cars supercharger session.

That were far lower than the superchargers theoretical maximum power why well in recent months Tesla has been working hard to discourage supercharger use for all but long-distance travel promoting destination charging and home-based charging as a more sensible solution for the vast majority of Tesla customers but in this case the reduction in supercharger speed for Tesla cars with a high supercharger use isn't a punishment it's a way to protect the batteries and thus ensure the car continues to operate properly for many more years to come as our friends over at electric.

We're told by Tesla earlier today every Tesla features an advanced battery management system that does everything it can to ensure the individual cells in each battery pack are kept in the best possible health to ensure high performance and longevity over many years of use just like any other electric car battery pack the lithium-ion cells found that a Tesla electric car slowly and inexorably aged with time this aging process not only affects how much electricity each cell can store but also the amount of instantaneous power an electric car can safely provide or receive and while modern lithium-ion electric car battery packs especially ones with adequate thermal management like Tesla's are designed to safely charge and discharge at high rates with a minimal effect on the battery pack.

Continued extreme charging and discharging does induce premature battery pack aging do it in a really warm weather and the effects are even more pronounced it's worth noting here that I'm talking about a use case outside normal electric vehicle ownership most plug-in car drivers charge at home overnight visiting a rapid charging station like a CCS CHAdeMO or Tesla supercharger when making the occasional long distance trip which is all well within the limits that most manufacturers plan for it's only when cars go through multiple rapid charging cycles day after day after day that the risk of damaging the battery pack increases if charged currents are kept high Tesla.

Just like every other automaker is well aware of this limitation rather than allow supercharger use cars to continue to charge at ultra high rates thus leading to premature battery death Tesla's engineers opted to add a subroutine which gradually limits the maximum supercharger power the car can use this routine does gradually lengthen the time it takes to charge the supercharger station maybe five minutes or so overall but it does so in order to protect the battery pack and ensure continued battery pack health for high supercharger cars I should note here too that I've seen the same thing happen with a Nissan Leaf owning an early 2011 Nissan Leaf myself for four years in the UK.

I can attest to the fact that as the car aged it had 82,000 miles on it when I sold it it charged more slowly as the number of miles in compared to when it was new I suspect that Nissan applied a similar algorithm to Tesla in order to protect its battery packs but I can't say this for sure but I digress in the case of this particular Tesla Model S owner who noticed that their car was super charging more slowly than it once was and took their car to be checked out at the local Tesla service center their car had accumulated more than 6.6 megawatt hours of DC quick charging sessions at CHAdeMO.