DIY Range Extender. (Seeking EEs or Electricians)

[Pops]

Its great that Tesla is offering a range extender. That implies that the truck is ready to connect to additional battery packs in parallel, presumably under the bed there is a ready connection point.

There is a guy out there that has already done something similar with a few different EVs. He has a trailer with a used 98 kWh Tesla battery pack in a trailer. When he tows it he connects the trailer's battery in parallel to the EV's battery. It basically doubles his towing range.


The advantages are clear:

• Extended range only when you need it (towing)
• It could be scaled down to a smaller pack in the bed.
• Only use extra bed space when you want extended range.

I just want to get the conversation started and when some of us have CT we can start to tinker and share knowledge.

Some technical notes I have made:

• Connecting two battery banks will balance from high voltage pack to lower voltage pack.
• Its important that the voltages of the 2 packs are not far apart or the amp flow could be too great.
• CTs battery pack is 816V but can split into two 408v packs when charging.
• Its unknown what the voltage of the Tesla Range Extender will be.
• It would be important to have an electric switch and logic to prevent connecting the batteries if the voltage is not close enough
• Some EVs completely sever the connection to the battery when they are off, so balancing would only be possible when the vehicle is on. Unless you interface right at the battery.
• I do not know if DC to DC converters are available that could match the 400v/800v of the CT, but if they are it could be very useful.
• 800v will cook you very quickly.

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[Diveflyfish]

Outside of Tesla engineering , Jehu, is one of the best, who has the inventive genius to make this happen. Perhaps if enough of us want to make some form of removable pack that is still manageable to use for range extension or emergency backup if remote, a solution could be founds. https://jag35.com/pages/collabs

 

[TickTock]

I think adding the battery to the trailer is the best solution but would do it differently. Instead of dealing with 800V and large gauge wires, add drive to the trailer wheels and tap into the accel/brake messages on the canbus etherloop. Can send those on smaller, low voltage wires and can get regen braking from the trailer.

 

[webspeedracer]

Count me in for funding support on this idea. I opted for the Range Extended but disappointed that I lose bed space vertically. I note that a salvage Tesla pack should fit in the bed, like the idea of only losing 6” vertical and gaining 100kWh, though securing it and making coolant/HV connections seem to be a challenge. Also load distribution is awkward, loss of payload/towing is a conundrum.

I tow a 19’ 4-season Oliver camper with our ‘18 MX100D, have done in winter/summer over ~30k miles, was banking on the “500-mile” CT to get no-stress 180-mile segments towing. I have two Rivian Max Pack orders on hold, simply because NACS is superior. I had thought CT would be vastly superior but turns out not. I still hit go on the FS CT Dual-Motor.

I agree with the trailer drivetrain concept too, but I want to explore range extenders AND battery/motor in the trailer. I have early orders for the Lightship and Pebble Flow, but I need the CT to have a longer towing range for going deep into the desert/mountains, and to allow supercharging flexibility skipping SCs in long-hail scenarios in the Rocky Mtns and Desert SW where options are charging is somewhat limiting, and for towing a boat over distance (challenging to put a battery under a boat trailer).

 

[jdown26ty]

I would like to see a hybrid option. I’m looking for a small power unit with dc output. This would supplement the load while towing and extend the battery.

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