Range Extender Details from Patent

[mongo]

Tesla's Range extender patent US20260048683 was published

It was based on a 400V pack (to match the parallel voltage of the main pack) that interfaced to the truck HV via dual PCS modules.

Rough calculations:
Advertised range increase was 120 or so. Call it 35kWh. Based on PCS DCAC performance, that means 23kW peak transfer. That means a minimum drive time of 1.5 hours to drain it. With 155kWh total capacity, that limits system power draw to ~100kW to drain them equally.
This is not an unreasonable limit as it requires ~65MPH with a large trailer to acheive. It's less ideal if considering 55 MPH and a 15 MPH headwind.

On the adding energy side of things, charging would have been a weak point. If using an 500kW 800V fast charger, the extender could only charge at 23kW (1.5 hours to fill). So it looks like the truck would instead limit to 350kW at 400V where it could direct connect (once the voltages matched).
Starting at 800V, then switching to 400V wouldn't work well because the voltages would get out of balance.

It was going to use the pack drive unit connection for HV, with a pass-through for the second Beast rear motor.

For the patent, search for 20260048683 at https://ppubs.uspto.gov/basic/

This is similar to the approach the Rivian cannonball attempt vehicle used, but with better charging.

I had expected an 800V extender with the same split pack setup for 400V rather than needing the intermediate DCDC conversion.

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[jahansolu]

Tesla's Range extender patent US20260048683 was published

It was based on a 400V pack (to match the parallel voltage of the main pack) that interfaced to the truck HV via dual PCS modules.

Rough calculations:
Advertised range increase was 120 or so. Call it 35kWh. Based on PCS DCAC performance, that means 23kW peak transfer. That means a minimum drive time of 1.5 hours to drain it. With 155kWh total capacity, that limits system power draw to ~100kW to drain them equally.
This is not an unreasonable limit as it requires ~65MPH with a large trailer to acheive. It's less ideal if considering 55 MPH and a 15 MPH headwind.

On the adding energy side of things, charging would have been a weak point. If using an 500kW 800V fast charger, the extender could only charge at 23kW (1.5 hours to fill). So it looks like the truck would instead limit to 350kW at 400V where it could direct connect (once the voltages matched).
Starting at 800V, then switching to 400V wouldn't work well because the voltages would get out of balance.

It was going to use the pack drive unit connection for HV, with a pass-through for the second Beast rear motor.

For the patent, search for 20260048683 at https://ppubs.uspto.gov/basic/

This is similar to the approach the Rivian cannonball attempt vehicle used, but with better charging.

I had expected an 800V extender with the same split pack setup for 400V rather than needing the intermediate DCDC conversion.

Amazing find!

This was exactly what I mentioned in a post (in a different thread) about charging most likely being the Achilles heal to drag the project to it's knees. In theory this should and would've been a slam dunk, but in practice the charging rate would've been too slow.

To be honest, I'm shocked that Tesla engineers didn't think of this solution:
With the rollout of Tesla Megachargers (designed for Semis), they could've opened up these chargers to allow the Extended Range to charge at these specific locations. It would've easily received the 800v @ 500kW it needed and wouldn't take more than 15 min to charge up. The Cybertruck itself is rated to accept the 800v as well at 500kW. With the pass-through it could charge both the battery and the CT in about 45 minutes.

My guess:
They didn't want to open up the Megachargers to the CT or CT's RE as this might cause disruption to their Semi business and (unfortunately) the v4 charging stations aren't ramping up (in specs) like they used to. The jump from v1 to v2 to v3 was huge - each iteration introduced something new. However, with v4, it's been a slow and painful upgrade process; especially their cabinet situation. Not all v4 sites are truly v4 and we have Model 3 and Y to blame for this since they don't need more 350kW at 400V to charge.

I am sad to see the RE never come to fruition, however at the same time I do understand why they had to axe it - especially because of low CT sales volume. As mentioned before (in another thread), had CT sold 1m+ units by today, the RE would've been a reality.

Now the real question here is:
1) Does the early CT builds have a place for this passthrough?
2) Will there be any person / company that will make a 3rd party version?
3) If it's truly pass-through, does this mean the RE just needs it's own BMS and it should (in theory) be fine?

I wonder if someone can use this patent to figure out a solution for those who want to tow.

EDIT: Also this was Published Feb 19th, 2026... Perhaps the RE isn't as dead as we were led to believe. Perhaps if CT sales pick up, especially with this new price point and global sales, then RE might make a comeback?

Typing RE so many times makes me think of Resident Evil - tell me you're a gamer without telling me you're a gamer.

 

[mongo]

Amazing find!

This was exactly what I mentioned in a post (in a different thread) about charging most likely being the Achilles heal to drag the project to it's knees. In theory this should and would've been a slam dunk, but in practice the charging rate would've been too slow.

To be honest, I'm shocked that Tesla engineers didn't think of this solution:
With the rollout of Tesla Megachargers (designed for Semis), they could've opened up these chargers to allow the Extended Range to charge at these specific locations. It would've easily received the 800v @ 500kW it needed and wouldn't take more than 15 min to charge up. The Cybertruck itself is rated to accept the 800v as well at 500kW. With the pass-through it could charge both the battery and the CT in about 45 minutes.

My guess:
They didn't want to open up the Megachargers to the CT or CT's RE as this might cause disruption to their Semi business and (unfortunately) the v4 charging stations aren't ramping up (in specs) like they used to. The jump from v1 to v2 to v3 was huge - each iteration introduced something new. However, with v4, it's been a slow and painful upgrade process; especially their cabinet situation. Not all v4 sites are truly v4 and we have Model 3 and Y to blame for this since they don't need more 350kW at 400V to charge.

I am sad to see the RE never come to fruition, however at the same time I do understand why they had to axe it - especially because of low CT sales volume. As mentioned before (in another thread), had CT sold 1m+ units by today, the RE would've been a reality.

Now the real question here is:
1) Does the early CT builds have a place for this passthrough?
2) Will there be any person / company that will make a 3rd party version?
3) If it's truly pass-through, does this mean the RE just needs it's own BMS and it should (in theory) be fine?

I wonder if someone can use this patent to figure out a solution for those who want to tow.

The Cybertruck charge curve is cell limited, not charging equipment limited. It only maxes out a 325kW post until 20% SOC.

1) the HV connection was via the existing drive unit ports. For Beast that uses all three, the extender had a pass through. Existing coolant line would loop through the extender's heat exchanger.
2) It's possible to do, but is the result worth it? Without access to Tesla internals, you are likeky stuck with a DCDC interface and the existing charge curve. The Advantics converter modules allow 100A, 50kW of power transfer as long as the extender pack is lower voltage than the main and would give a decent recharge rate, but there are other options. Or give the extender its own fast charging port.
Still have the mass, packaging, and thermal issues though.
3) pass-through in terms of connections (A to C to B instead of A to B). If you could use the same cells at the same voltage at the same temperature with their own BMS, then theoretically you could just plug them into the HV bus (with proper monitoring and control)

 

[cyberhero32]

I don’t get it it’s a range extender so we’ll get :”445 miles instead of 320 or it’s a pass through to use outlets while I charge?

 

[jahansolu]

The Cybertruck charge curve is cell limited, not charging equipment limited. It only maxes out a 325kW post until 20% SOC.

1) the HV connection was via the existing drive unit ports. For Beast that uses all three, the extender had a pass through. Existing coolant line would loop through the extender's heat exchanger.
2) It's possible to do, but is the result worth it? Without access to Tesla internals, you are likeky stuck with a DCDC interface and the existing charge curve. The Advantics converter modules allow 100A, 50kW of power transfer as long as the extender pack is lower voltage than the main and would give a decent recharge rate, but there are other options. Or give the extender its own fast charging port.
Still have the mass, packaging, and thermal issues though.
3) pass-through in terms of connections (A to C to B instead of A to B). If you could use the same cells at the same voltage at the same temperature with their own BMS, then theoretically you could just plug them into the HV bus (with proper monitoring and control)

Yeah I was definitely thinking the RE would have it's own charging port. HV Charger --> RE Battery Pack --> Passthrough to CT.
You really know your stuff @mongo , eh? Impressive.

 

[mongo]

I don’t get it it’s a range extender so we’ll get :”445 miles instead of 320 or it’s a pass through to use outlets while I charge?

It was for more range. Passthrough was how it connected to the HV system .

Though, the patent did call out optional solar charge port.

 

[mongo]

Yeah I was definitely thinking the RE would have it's own charging port. HV Charger --> RE Battery Pack --> Passthrough to CT.
You really know your stuff @mongo , eh? Impressive.

Daisy chaining to the truck is an interesting concept. One connection, and extender passes the connections through when it's charged. It's an extension of the extender as a charger approach.

I've pondered variations on that theme where the extender increases the power request to the charger to account for its charging draw that the truck doesn't know about.

 

[jahansolu]

Any thoughts about the date on this patent though? Do you think it's still something Tesla might be actively working on in the background? Perhaps they refunded the reservation holders to shut them up from constantly asking "when? when? when?"

 

[mongo]

Any thoughts about the date on this patent though? Do you think it's still something Tesla might be actively working on in the background? Perhaps they refunded the reservation holders to shut them up from constantly asking "when? when? when?"

Filed August 15, 2024. I think it's dead. Larger main pack makes so much more sense.
Or trailer integrated to retain payload capacity.

 

[jahansolu]

Filed August 15, 2024. I think it's dead. Larger main pack makes so much more sense.
Or trailer integrated to retain payload capacity.

Pour one out for our hommie: RE; we hardly knew ya.

 

[mongo]

Pour one out for our hommie: RE; we hardly knew ya.

Who ran more range extender while towing scenarios, Tesla or me?
And don't get me started on my homegrown extender alternatives

 

[SlegMD]

I’ve got a 600 hamster wheel solution in the bed of the truck, requires all bed space unfortunately, and the smell is atrocious

 

[cyberhero32]

Who ran more range extender while towing scenarios, Tesla or me?
And don't get me started on my homegrown extender alternatives

Let’s get started I’m curious

 

[mongo]

Let’s get started I’m curious

You can theoretically fit 32kWh of Eve LFP cells in the frunk to make a ~100V pack. However, that low voltage would require 2-3 Advantics converters to fully utilize the capacity and each converter costs more than the cells ‍

More smaller cells gets a higher voltage but wastes space, I estimated only 18kWh.

Charging is where it hurts.

There's a EV group in Europe working on a system using non-lfp which looks promising.

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