On the Technical Merits of Greater than 96S Battery Packs

[SageBrush]

I'm just a wannabe electrician (meaning I am much more likely to post something wrong) so consider this a case of musing out loud and inviting comments.

I know Tesla has in the past made battery packs that are more than 96S, but that has been the exception rather than the rule. Why ?
A nominal 415V or so would cut Amperage draw at Superchargers by ~ 15% for the same power. It would give Tesla room to grow Supercharger power in the future.

What are the downsides ?

 

[ucmndd]

A good article explaining the benefits and drawbacks:

Benefits and Design Challenges in Shifting EV Bus to 800V - EE Times Asia

Although most EVs today use 400-V batteries, there is a marked transition to the 800-V architecture.

www.eetasia.com

TL;DR:

It seems inevitable that future EVs will gradually transition to higher voltage architectures, including Tesla. They’ve already shown the NACS charging standard is good up to 1kv. IMO this is the only practical way to continue to increase charging speeds.

However, it will be a costly transition. Most commodity EV components are standardized to 400vdc. Many components need to change, from motors and inverters to more banal stuff like insulation and isolation requirements for conductors and every other part of the HV system. Hyundai/Kia have clearly shown this is possible, but certainly invested many hundreds of millions to build out their E-GMP platform. Not to mention needing to upgrade almost all the existing charging infrastructure spread all over the world.

 

[SageBrush]

A good article explaining the benefits and drawbacks:

I was wondering about a much more modest increase to ~ 415V, which I think is within the spec of the current Supercharger

 

[moa999]

At present it's really only a benefit in vehicles with larger batteries.

Little point with today's 50-80kWh cars going above 400W as you are limited by the c-rate anyway, as well as battery cooling.

Your 3/Y SR/RWD peaks at about 180kW, and the 3/Y LR/P 230kW

Maybe solid state or sulfide battery tech might change this in the future.

 

[SageBrush]

Little point with today's 50-80kWh cars going above 400W as you are limited by the c-rate anyway, as well as battery cooling.

Your 3/Y SR/RWD peaks at about 180kW, and the 3/Y LR/P 230kW

This is an old thread, but I hope it picks up since I still find the question topical and interesting

Some of the '800v' folks (Korea in particular) are advertising 15 minutes for a 20% -> 80% charge. That is a 2.4 C rate. Does Tesla match it across their model lineup ?

 

[moa999]

If you google charging curves for various Tesla models they are pretty similar
Starting from zero, they peak at over 3C from about 10% to 25%, and then straight line down roughly to 100%.

So charge rate from 20-80% averages somewhere near 2C.

Now it's important to note that it's an interaction with battery depletion and manufacturer warranty. The cars electronics set the charge rate - it could go higher if they let it.

Advertising a fast charge rate is no good if in a few years the failure/depletion rate both inside or outside warranty is higher than expected.