MacGuyver-Frankenstein Edition Tesla P113.5D

[buttershrimp]

Buttershrimp's Crazy Idea:

FIRST STEP) Buy Power Wall.

SECOND STEP) Place Power Wall in the Trunk of P100D

THIRD STEP) Drive over to the houses of @verygreen, @jimmy_d, @lunitiks with several bottles of alcohol.

FOURTH STEP) Somehow convince them to help me modify my car so I can add to my battery capacity for long road trips (Even though the battery cells are different)

FIFTH STEP) Drive a whopping 40 additional miles without supercharging!

SIXTH STEP) Win First Annual Rube Goldberg Prize from Tesla.

 

[lunitiks]

Sounds good to me!!

 

[buttershrimp]

Can this project be done? How difficult do you think it would be?

 

[bonnie]

Can this project be done? How difficult do you think it would be?

You already skipped your third step. You shouldn't even ASK this question until after you've delivered copious amounts of alcohol. #amateur

 

[buttershrimp]

You already skipped your third step. You shouldn't even ASK this question until after you've delivered copious amounts of alcohol. #amateur

@bonnie, thanks for your tips....I've taken your advice to heart... how is this?

STEP 1, Kidnap and Chloroform @verygreen and @jimmy_d, and offer @lunitiks a year's worth of free aquavit if he helps me...

STEP 2 CONTINUE REST OF PLAN

Seriously though, someone has to have thought of this little modification. It would potentially sweet for road tripping.

 

[jimmy_d]

Can this project be done? How difficult do you think it would be?

Two levels of difficulty depending on what you're willing to settle for charging wise.

It would be easy to put a NEMA 14-50 on the powerwall and just make it into a big portable battery that you can charge at home and then use to recharge the car when there's no power nearby. Of course it means you have to stop to charge, and that you'd be charging up the powerwall separate from the car. But for some kind of one-off need it's the easiest thing to implement. I was thinking that for the guys that like to take their car to the drag strip and need something to top off their battery between runs that this could do the trick.

To wire the powerwall straight into the inverter on the car is hard. The powerwall inverter isn't compatible with the vehicle inverter in any simple way. The battery strings in the powerwall are at a different voltage than the ones in the vehicle. The powerwall battery cooling system would have to be coupled to the car's cooling somehow. And the charge cycle you want for the powerwall is different than what the vehicle battery wants. A lot of the matching can be handled by software, but the electronics is not simple unless you do something really ugly and inefficient. Because of the tradeoffs there are a couple of different ways to go at it with probably the easiest being to build a custom high powered bidirectional inverter to couple the two systems. Note that 'easiest' here does not mean 'easy'. The whole project is hard enough that taking the cells out of the powerwall, tossing it's inverter, and making your own inverter to couple them to the car inverter is probably about the same work as far as the electrical end goes. But at that point you could just get regular prismatic cells from LG to do it. You might be able to avoid active liquid cooling for the cells if you do a slow continuous discharge of the supplemental cells while the car is cruising at highway speeds, but you'd probably still need a fan and access to outside airflow.

See what you've done? Now my head hurts.

 

[rkarmark]

I would just buy some used tesla car batterys of ebay. This would mean compatibility and capacity for 200? Kwh of batteries

 

[Half Dollar Bill]

You're approaching the project the wrong way. Instead of changing the car, change the power wall to:
A) accept charge from a supercharger and
B) output to your car's charge port while the vehicle is moving.
When your initial charge starts to drain, you plug in the power wall and do a hot transfer while still on the road.
When you DO have to pull into a supercharger, you plug both your car and the power wall in and wash, rinse, repeat.
Think Tesla will read this and offer me a job?

 

[buttershrimp]

See what you've done? Now my head hurts.

That’s just the chloroform wearing off...

Seriously though, this is what I was looking for, such an informative post.

We shall nickname you “professor”

 

[croman]

Honestly wk or ingineer are the hardware wizards. btw_ftw would also be an invaluable resource. Not to take anything away from the ones you've named who certainly are knowledgeable and verygreen is particularly knowledgeable in software. You need someone who will ensure you don't die while driving your frankenTesla.

The whole idea is not going to work with a powerwall but as suggested above, adding some additional Tesla batteries in a homemade enclosure with a modified BMS might work. A company did this for Nissan Leafs but the loss of trunk space is regrettable.

 

[bonnie]

Are you going to get net positive on range, once you factor in the weight of the powerwall and/or additional batteries?

 

[buttershrimp]

Honestly wk or ingineer are the hardware wizards. btw_ftw would also be an invaluable resource. Not to take anything away from the ones you've named who certainly are knowledgeable and verygreen is particularly knowledgeable in software. You need someone who will ensure you don't die while driving your frankenTesla.

as yoda would say, posted much jimmy_d not on this forum... but I sense the force is strong with him.

Are you going to get net positive on range, once you factor in the weight of the powerwall and/or additional batteries?

Good question... I've found the weight effect to be fairly negligible on my range testing relative to wind and speed... I was pretty shocked by this.... turns out another 300 pounds doesn't limit range as much as I thought.

If this idea were to be doable... I would just want it to be something that could slowly charge the main battery on long road trips while driving, and then go disconnected and unloaded. A 5 seater model X would be ideal with no back seats... it would fit.... lllllike a glove!

With the supercharging network, this idea is just dumb.... but I know I'm not the only whack job that thinks this way.... surely someone has thought about some weird road trip to Alaska or through Mexico.

I mean, if we are all willing to break our pelvis during a 3 g rocket launch to get to Japan in 30 minutes then surely an extra battery in the trunk isn't too nuts?

 

[jimmy_d]

We shall nickname you “professor”

Can I have "professor X" ? That sounds COOL.

 

[jimmy_d]

Are you going to get net positive on range, once you factor in the weight of the powerwall and/or additional batteries?

Probably some, but you wouldn't be getting the equivalent the full 13.5 KWh in the powerwall.

The incremental weight is less of an issue than potential impact on the performance of the existing electronics and losses from the additional inverter stages. It would be pretty easy to have a negative impact on the efficiency of the existing inverter / battery / motor combination and that could be pretty disastrous from a range standpoint. Avoiding that limits your options WRT how you would add batteries.

Anyway, this is just a thought experiment. If you really wanted to add 10% more range to your car and were willing to mess it up some a much more effective approach would be to get @verygreen to help you hack the battery management software to squeeze the margin out of the current battery. For safety and lifetime issues there's going to be a significant amount of padding in there and if you take it out you can likely get a one-shot range increase of more than 10%.

 

[jimmy_d]

You're approaching the project the wrong way. Instead of changing the car, change the power wall to:
A) accept charge from a supercharger and
B) output to your car's charge port while the vehicle is moving.
When your initial charge starts to drain, you plug in the power wall and do a hot transfer while still on the road.
When you DO have to pull into a supercharger, you plug both your car and the power wall in and wash, rinse, repeat.
Think Tesla will read this and offer me a job?

That's a good point - i.e. changing the powerwall can be more useful than changing the car. Your specific suggestions might run into some issues though. The current car inverter and cooling control system is likely to be modal in that it can charge the battery or draw down the battery but not both at the same time - so charging the car battery while it's driving might not be easy. If it's not modal, but rather has dual inverters (one in, one out) that can be run simultaneously then things get a lot easier and it might just be software (or inverter firmware) changes. And the supercharger thing might be kind of messy because, with high speed DC chargers like the supercharger it's the inverters in the supercharger that drive the charging session. So to fake a supercharger into charging a powerwall you'd have to figure out how to trick the supercharger into thinking the powerwall was a car and know how to instruct the supercharger with respect to proper care and feeding of a powerwall battery. But the upside of that, if you could do it, is that it would make the electronics for charging the powerwall pretty easy since the superchargers have very flexible and powerful inverters in them already and you'd be leveraging the capability of that existing hardware.

I guess things might get even easier with some really creative approach. I wouldn't be surprised if there's a trick or two that could make it turn out a lot better than my brute force analysis suggests. The idea of reverse engineering the supercharger control protocol is a neat one.

 

[wdolson]

Back in 2014 or something like that, Tesla patented a li-ion chemistry that would not have the lifetime of the chemistry currently used, but would be effective for road trip range extension. They obviously never put it into production, but something may have been built into the firmware to support it. Though that may have been removed now.

The biggest problem would be the voltage. The DC side of the Powerwall is only 50V, which is the equivalent of two Model S/X modules. The inverter is probably designed to expect 350-400V input. Possibly down to around 300V for a low charge battery pack. 50V in might trip the car's bad pack sensors.

This would require changing the firmware, which is beyond any of the hackers out there to do safely (only Tesla has the source code), but you could have the auxiliary battery kick in when the car is in coast or regen and feed it into the regen system. So every time you let off the go pedal when you're not feeding into the drive motors, the regen system goes to max regen. Depending on where you're driving, that may or may not kick in much. But if you're going up and down hills, you would get max regen going down the hills and effectively get more into the battery pack on the downside than you put in on the upside.

 

[Dameon]

It'd be easier (safer?) to salvage a 100K pack from a donor car and "secure" it to the bottom of your car. Crank the air suspension all the way up and wire it in parallel to your current pack.

 

[buttershrimp]

Back in 2014 or something like that, Tesla patented a li-ion chemistry that would not have the lifetime of the chemistry currently used, but would be effective for road trip range extension. They obviously never put it into production, but something may have been built into the firmware to support it. Though that may have been removed now.

The biggest problem would be the voltage. The DC side of the Powerwall is only 50V, which is the equivalent of two Model S/X modules. The inverter is probably designed to expect 350-400V input. Possibly down to around 300V for a low charge battery pack. 50V in might trip the car's bad pack sensors.

This would require changing the firmware, which is beyond any of the hackers out there to do safely (only Tesla has the source code), but you could have the auxiliary battery kick in when the car is in coast or regen and feed it into the regen system. So every time you let off the go pedal when you're not feeding into the drive motors, the regen system goes to max regen. Depending on where you're driving, that may or may not kick in much. But if you're going up and down hills, you would get max regen going down the hills and effectively get more into the battery pack on the downside than you put in on the upside.

I really like the idea of doing this through super effective regen.. so the main battery wouldn’t have to be fiddled with... that idea could be pretty darn effective since regen varies so much depending on slope of hill and the driver’s behavior ... I would think this whole idea would be easier with the new motor but I don’t understand how one could to get current to flow back into the battery without making it go through the motor

 

[dsnows]

Buttershrimp's Crazy Idea:

FIRST STEP) Buy Power Wall.

SECOND STEP) Place Power Wall in the Trunk of P100D

THIRD STEP) Drive over to the houses of @verygreen, @jimmy_d, @lunitiks with several bottles of alcohol.

FOURTH STEP) Somehow convince them to help me modify my car so I can add to my battery capacity for long road trips (Even though the battery cells are different)

FIFTH STEP) Drive a whopping 40 additional miles without supercharging!

SIXTH STEP) Win First Annual Rube Goldberg Prize from Tesla.

You missed one. Step 3.5 Drink said bottles of alcohol.

 

[wdolson]

You missed one. Step 3.5 Drink said bottles of alcohol.

Always a good idea to drink heavily when working around 400V DC. If you are bucking for a Darwin Award...