Prior to and since delivery i’ve heard discussions on the Model S battery packs and A vs B versions and various owners concerned about which battery pack they have. I did some research to better understand what’s going on here.

Battery Pack Information

The first place to start is by getting your battery pack information. There’s a sticker on the battery pack under the car that is visible from just behind the front right (passenger side) wheel. The sticker (mine), looks like this:

The first and most important part of this information is the size of your battery. You can figure this out by looking at your range too, but its another good confirmation that you got the battery that you ordered. The next piece that has any potential use is the model of the battery. Thats the last letter at the end of the part number. So for the case above, this is a D battery pack.

Battery Pack Differences

The main difference between battery packs has been reported between the A and B battery packs. An improvement to the cooling system of the battery pack was made starting with the B packs that allowed for faster Supercharging. Those with A battery packs can only Supercharge at a maximum of 90kW while those with B battery packs and later can Supercharge at 120kW or possibly higher.

TMC has a Wiki tracking the battery part numbers and the basics are as follows:

• 1014114 is a new 85 kWh pack
• 1020422 is a new 60 kWh pack

There are also other part numbers out there and the community hasn’t yet nailed down what they designate. Some part numbers may be refurbished versions versus new versions. Just recently KmanAuto had a battery pack replacement on his 60kWh Model S and he got a part number not yet on that Wiki page which may indicate that it’s a refurbished 60 kWh pack.

Barring formal information from Tesla, the working theory is that the battery pack versions A, B and D, are the equivalent to model years in some cars — they’re evolutions of the same thing and each is better than its predecessor. Superchargers capable of greater than 120kW are just starting to pop up. The 100th Supercharger, recently installed in NJ, was a 135kW Supercharger.

From the forums, D batteries began shipping sometime in the second half of 2013 and are still the latest ones being installed. If you have a D pack you’ve got the latest.

If you have a D pack you’ve got the latest as of the Summer of 2014.

So far there have been no reported experience differences between the B battery pack and the D battery pack in terms of charge rates or performance but the current theory is that the B pack may be limited to charging at 120kW while the D pack may be able to go to 150kW when Superchargers support it. While the C pack was mentioned many times I never found a report of anyone with a C pack.

Summary

Despite opening up their patents, Tesla battery technology is a pretty much a mystery to most. While not necessarily the most efficient on the market, Tesla does have a lead in the size of the batteries and their Supercharger network and charge rates are an important key to Teslas success. Tesla is not forthcoming on the capabilities of the various versions of its battery packs and leaves its user community (and even Tesla Service personnel) to figure out what they can and can’t do with their battery in terms of charge rates, charging profiles and other attributes.

At a Supercharger your charge rate will vary due to a number of factors. One may be related to your battery pack, but more likely it will be related to the limitations or current state of the Supercharger or if you’re sharing a section of the Supercharger with a fellow Model S owner.

If you bought a Model S in later 2013 or 2014 you’re most likely using the latest and greatest battery from Tesla. Should things ever go wrong with your battery you may end up getting a replacement one. There have been reports of older “A packs” being used for refurbished parts which could lower your Supercharging rates. You do not want a replacement pack that is older than the one you had and the Service Centers don’t appear to be stopping this from happening. Just to be safe, check your battery model and version and take a picture for your records.

Check your battery model and version and take a picture for your records.