This sort of chicanery could be detected by noting excessive supercharging verses miles accumulated on your car. And they could make the car to car transfer painfully slow compared to supercharging.
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Etiquette for stranded fellow Tesla
- Thread starter Shaddeau34
- Start date
This sort of chicanery could be detected by noting excessive supercharging verses miles accumulated on your car. And they could make the car to car transfer painfully slow compared to supercharging.
whitex
Well-Known Member
Which would beat the purpose of helping a stranded motorist. If you want painfully slow, you can do it today - just get a 12V DC to 110V inverter and charge the other car from that, at 1-3 miles per hour (depending on car and the kind of inverter you get).
dbldwn02
Active Member
What???! Why the hell not? I only have an Electrical Engineering TECHNOLOGY degree but all signs point to user error when they hook their Tesla up to a 15/20a out on a Goal Zero battery, and having it not charge. Of course, it'd be best to have the one with Pure Sine wave outputs. 120V/60Hz is 120V/60Hz in 120V/60Hz.
I imagine all of these charging techniques will be tested by drunk teens in the next 15-20 years.
Wouldn't you blow the fuse almost instantly if you tried to pull that kind of current out of any of the ordinary 12v taps available in the car?
I am 90% sure that there will be mobile level 2 charging kits for rescuing stranded BEVs If / when there are enough BEVs running out of juice out on the road to merit the investment.
I suspect that the number of peopel road-tripping with their EV and actually getting stuck is *really* small relative to the number of gas cars that break their 12V batteries or run out of gas or otherwise get stuck on the side of the road.
whitex
Well-Known Member
You can wire it directly to the 12V battery (adding a new fuse of course), some people do, then they can run coffee makers or small microwaves from the inverters (so 500W?).
As @cduzz mentioned earlier, it might not economical to pay for a rescue vehicle to spend an hour on the side of the road helping a BEV. If it wasn't level 2 but instead 150KW DC, then sure, but there is where you run into incompatibilities of DC charging systems, plus the need for the rescue vehicle to have a very expensive battery with them, and the need to charge it somewhere. It's probably more efficient, and faster for all parties involved to just flatbed a Tesla 10 miles to a supercharger.
Certainly a DC-DC converter is the best and most elegant solution. A cable with a high power resistor of fairly low value would probably work fine, if all the cars involved have the same nominal battery voltage.
Then you'd have a cable that plugs into both chargeports and the cars could close contactors like they do at a supercharger and move power easily - assuming you can control the maximum current, and teach the cars to speak directly to each other through the cable (modified Supercharger communications protocol?)
According to this thread, an empty 16 module car should be around 275V, while a full car could be up to 400V. So if all the cars are 16 module, the maximum voltage difference is ~125V. A 1 ohm resistor would ensure the current is no more than ~125A (and the battery internal resistance and other limits make is somewhat lower.)
If you really got 125A, though, that resistor could be seeing ~15 kW or so of heating if I'm doing my math right, so it'd have to be a big resistor (you can greatly reduce this with a stronger resistor - a 4 ohm would mean a 31A maximum and 4 kW of heating.) Might be better off cranking it up more - or even using a variable resistor that you can use to automatically hold a current value regardless of the differences.
That's starting to get complex and expensive, though, so maybe a compact DC-DC converter is better if you're going that far. Toyota builds 20-30 kW ones in huge numbers for the Prius that are compact and presumably cheap (the motors on all but the very first Prius run at 2-3x the voltage of the battery pack, the car converts all the power going to/from the battery.)
Tested already.
We were talking about another Tesla Car giving a boost to another. Even a 20A DC to AC inverter is very large and would only give 3-4 miles / hour (on a model 3).
Sure, a Service Truck could could probably do 40A+ AC or something. If it was Car to Car it would have to be DC to DC. If's a tow truck that's something else. Not sure how much hardware (cost and weight) would be involved doing DC to DC, but I assume it would be much better than doing DC to AC to DC (car to car). Certainly AC is more "compatible".
I think you just have to provide about 100K ohms between the neutral and ground connectors in the receptacle. It can be done by connecting the resistor between the neutral and ground connectors on a three prong plug and plugging it into one of the receptacles.
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Dithermaster
Member
I'm picturing a Model 3 parked on top of my Model S and not liking what it does to the glass roof. Or do I need to put them bottom to bottom? The mind boggles.
Of all the options mentioned here, it seems like using the motor inverter to produce a compatible AC waveform would work pretty well. Obviously would require additional hardware in the car to make it happen.
whitex
Well-Known Member
I never tried it, but it would make sense. I guess you'd need an adapter with a ground wire (an electrode to stick in the ground with a cross-connection to neutral)?
Neutral and ground are tied together in every circuit breaker box I have opened up. I don't know if that is really how it is supposed to be, but I do know that it does not cause the UMC to freak out.
I do not believe it would be possible for UMC is able to detect the difference between a ground-neutral short at the plug and a ground-neutral short in the breaker box. So if the UMC really does look for a ground, all you would have to do is wrap a wire between the neutral and ground pins on the UMC plug. (safe - probably not, but effective - it should be)
Push it!!! Lol...jk.
I'm planning on buying a Goal Zero Lithium Battery Bank. 3000Wh. Not for the car but just for backup at the house. If he was only a quarter mile from the charger, something like that would only take 15-20 minutes to get enough charge at 20amps. This only works if you have easy access to the battery. For road-trips, you're pretty much hosed unless there's a BigR or Cheap tool store you can go buy a $200 generator at. Any of those options beats a $200-300 flatbed tow for a quarter mile.
Hoping Tesla will eventually allow us to Car2Car transfer like Rivian will.
It looks like the 120v inverter is only good for 1500w (12.5 amps) continuous. At that rate it would take 2 hours to transfer the 3kWh to the car. It's probably only 90 % efficient so you end up with about 10 miles of range after 2 hrs. It may even take longer as inverters tend to loose power as the batteries discharge.
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That's the reason for the 100k ohms, so that you don't get more than 0.1 mA across your heart. Yet I believe it's enough to trick the car into sensing ground. A lot of small generators and portable power sources don't tie neutral and ground together.
As far as safety protocols, I imagine you can get a safe ground from somewhere outside, regardless of if it is a steel spike you drive into the ground or a street light or some other earthish structure nearby.
In some unspecified point in the future when a BEV driver runs their car flat, the dispatch may have the option of sending a rescue van / truck that has a 240v/30a generator or possibly a power wall like setup with a similar 240v/30a output.
This BEV rescue vehicle would have a 30a AC source, a mobile charger like a ClipperCreek HCS 30, a set of safety protocols to safely hook everything up to the car including proper ground, and a set of adapters to hook up a tesla, a leaf, a smart ego, a bolt, a tak-yon, a yetitron, etc to the HCS.
Such a rig would not require a driver with a CDL or any intensive training. It would likely be exactly the same Van/SUV that delivers fully charged 12v batteries to people who forget to change their batteries in their ICE vehicles every 12 years; it would likely be the same van where the driver helps a car's owner put on the spare tire if they get a flat tire.
It would not need to be a flat bed or truck able to actually tow a car.
Dumping 6 miles of range into most of these would likely take in the same amount of time as swapping a 12v ice battery, or a tire, or any number of other services that roadside assistance already provides.
In some unspecified point in the future when a BEV driver runs their car flat, the dispatch may have the option of sending a rescue van / truck that has a 240v/30a generator or possibly a power wall like setup with a similar 240v/30a output.
This BEV rescue vehicle would have a 30a AC source, a mobile charger like a ClipperCreek HCS 30, a set of safety protocols to safely hook everything up to the car including proper ground, and a set of adapters to hook up a tesla, a leaf, a smart ego, a bolt, a tak-yon, a yetitron, etc to the HCS.
Such a rig would not require a driver with a CDL or any intensive training. It would likely be exactly the same Van/SUV that delivers fully charged 12v batteries to people who forget to change their batteries in their ICE vehicles every 12 years; it would likely be the same van where the driver helps a car's owner put on the spare tire if they get a flat tire.
It would not need to be a flat bed or truck able to actually tow a car.
Dumping 6 miles of range into most of these would likely take in the same amount of time as swapping a 12v ice battery, or a tire, or any number of other services that roadside assistance already provides.
Yeah, this is wrong; they didn't add 10 miles. They towed 1 mile and added 4 miles. The mileage starts at 226 and goes to 230. Plus, while they are being towed they average about -1060 wh / mile over 1 mile. That means they added 1060 wh to the battery. The model 3 uses about 265 wh per mile, so that would provide 1060 wh divided by 265 wh per mile, or 4 miles. But I'm not sure what the significance of this is, other than, yeah, you can charge the car by towing it.
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