charging etiquette - re park feature

Tinker71

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I am just thinking out loud here. If people were just cool or Tesla built something into their user agreements so if a vehicle was done charging any other user of the charging station could unplug the vehicle and plug theirs in either using an adjacent parking spot or even better autopilot could move the charged vehicle to a close empty parking spot.

Also maybe this already exist , but if the tesla charging network could display countdown to full charge people could anticipate an empty charging location.

Besides encouraging business t o provide level 2 charging stations, this would go a long way towards making charging available and easy.
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ajdelange

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if a vehicle was done charging any other user of the charging station could unplug the vehicle and plug theirs in either using an adjacent parking spot or even better autopilot could move the charged vehicle to a close empty parking spot.
Currently things are configured to prevent this. The owner of the vehicle (or someone in possession of his fob or keycard) must be present to remove the charging plug. If you have ever tried to use "Summon" you would withdraw your suggestion about having the autopilot move the car.

Also maybe this already exist , but if the tesla charging network could display countdown to full charge people could anticipate an empty charging location.
The owner is sent messages indicating that the charge will be complete in a certain number of minutes. If he doesn't get his car out of the stall within 5 minutes of completion he gets assessed "idle fees" of a buck a minute if more than half the stalls at the station are occupied.

These considerations pertain at busy stations many of which have lots of stalls. It seems to me that a human attendant at such station could do a lot for smoother operation. He could check people in, tell them that they will be going to stall n (he would have a display as to which stall is freeing up next), at owner request move a finished car from a stall to a separate parking are etc.
 
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Tinker71

Tinker71

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Currently things are configured to prevent this. The owner of the vehicle (or someone in possession of his fob or keycard) must be present to remove the charging plug. If you have ever tried to use "Summon" you would withdraw your suggestion about having the autopilot move the car.

The owner is sent messages indicating that the charge will be complete in a certain number of minutes. If he doesn't get his car out of the stall within 5 minutes of completion he gets assessed "idle fees" of a buck a minute if more than half the stalls at the station are occupied.

These considerations pertain at busy stations many of which have lots of stalls. It seems to me that a human attendant at such station could do a lot for smoother operation. He could check people in, tell them that they will be going to stall n (he would have a display as to which stall is freeing up next), at owner request move a finished car from a stall to a separate parking are etc.
Thanks for the info. Hopefully the summon feature will improve. Again I think if positive etiquette could be instilled the stress of idle fees could be alleviated and more stalls would be available at a given time. Personally I would like to take a walk or get a drink and not have to worry about fees or being tied to my car. As for the fob or keycard hopefully that could be reprogrammed/engineered. It is just a low voltage overlay on the expensive parts of the charger.
 
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Tinker71

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Currently things are configured to prevent this. The owner of the vehicle (or someone in possession of his fob or keycard) must be present to remove the charging plug. If you have ever tried to use "Summon" you would withdraw your suggestion about having the autopilot move the car.

The owner is sent messages indicating that the charge will be complete in a certain number of minutes. If he doesn't get his car out of the stall within 5 minutes of completion he gets assessed "idle fees" of a buck a minute if more than half the stalls at the station are occupied.

These considerations pertain at busy stations many of which have lots of stalls. It seems to me that a human attendant at such station could do a lot for smoother operation. He could check people in, tell them that they will be going to stall n (he would have a display as to which stall is freeing up next), at owner request move a finished car from a stall to a separate parking are etc.
The attended charge station is a good alternative and idea. Get your windows washed, maybe a lounge area, walk the dog.
 

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The the-charge-is-over-before-you're-done-resting is a real thing with DC fast charging. Since you aim to charge from 20-80% to maintain battery balance and highest acceleration these are short stops. An extra five minutes in line or eating eats it up rather quick.

Tesla has demo'd automation in their chargers before, but they are not in the wild yet - as summon is not all there yet, either.

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Again I think if positive etiquette could be instilled the stress of idle fees could be alleviated and more stalls would be available at a given time.
You are right, of course. Were it not for stalls being unavailable because they were blocked by cars that were no longer charging Tesla (and other manufacturers too) would not have had to institute the fees. And, indeed, if half or more of the stalls in a Tesla station are not occupied the fees are not imposed.

Personally I would like to take a walk or get a drink and not have to worry about fees or being tied to my car.
Of course you would and so would I. What is needed is an "intelligence" that detect when your car is finished, removes the plug and moves the car to a bullpen. Right now and for the foreseeable future that intelligence has to be human because there is nothing out there than is remotely capable of doing this job. People have experimented with battery laden robots that wander a parking garage looking for cars that need to be charged, charging them and then returning to a central station to get charged themselves. Not too practical.

As for the fob or keycard hopefully that could be reprogrammed/engineered. It is just a low voltage overlay on the expensive parts of the charger.
As long as you understand that the "charger" is part of the car - not the thing in the lot - then yes, it would require modification to the car's authentication system. It would allow anyone with a Tesla fob or key card to unlock your charge port, remove the connector and move your car. Geofencing could be used to prevent theft but I am still not sure I'd be happy with anyone whose only qualification is that he's a Tesla owner be allowed to do that. A bonded Tesla employee - yes, OK.
 
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Tinker71

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You are right, of course. Were it not for stalls being unavailable because they were blocked by cars that were no longer charging Tesla (and other manufacturers too) would not have had to institute the fees. And, indeed, if half or more of the stalls in a Tesla station are not occupied the fees are not imposed.

Of course you would and so would I. What is needed is an "intelligence" that detect when your car is finished, removes the plug and moves the car to a bullpen. Right now and for the foreseeable future that intelligence has to be human because there is nothing out there than is remotely capable of doing this job. People have experimented with battery laden robots that wander a parking garage looking for cars that need to be charged, charging them and then returning to a central station to get charged themselves. Not too practical.

As long as you understand that the "charger" is part of the car - not the thing in the lot - then yes, it would require modification to the car's authentication system. It would allow anyone with a Tesla fob or key card to unlock your charge port, remove the connector and move your car. Geofencing could be used to prevent theft but I am still not sure I'd be happy with anyone whose only qualification is that he's a Tesla owner be allowed to do that. A bonded Tesla employee - yes, OK.
I built an EV out of a kit so I do understand level 1/2 charging. I admit I don't understand DC fast charging other than there is no need to convert. I recently purchased 2 ea 570 watt solar panels for my electric bus, I also purchased 2 boost transformers to bump the output to 120V to my 100V nominal (tesla S) battery system. I know my charger puts out 130 V at the peak of the charging curve. If I were to include the wiring diagram would you be able to tell me the best place to tie in?
Also any advice on the need for diodes or what a constant 120V into a full battery (124V)would do?
My plan right now is to drive it a couple days a week to keep in the sweet spot as far as capacity. My pack is 26Kwhr and I do realize I will only 5 mile miles per day.
 

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The S has a 385 V battery (nominal) so I'm confused when you say you have a 100V battery from a Tesla S.

What is in a Tesla S is a box, the charger, that accepts 120/240 VAC and converts it to DC at around 385 V. The actual voltage it produces is whatever voltage is necessary to push the desired level of current, as determined by some computer in the vehicle (perhaps it is even in the charger) into the battery.

In a DC fast charger the charger is in the equipment cabinet behind the fence. Rumor has it that in the days of the V2 charger it was the same charger as in the car or rather a raft of them in parallel in order to be able to provide the higher current. When fast charging is used the paralleled output of the charger modules in the equipment cabinet is routed to the battery terminals instead of the output from the charger in the car.

The rest of the post confuses me too. I can't tell whether you are talking about AC or DC in some places. If you connect a 120 V DC source to a 124 V battery the battery will supply current to the lower voltage source unless you have a diode in place to block flow in that direction.

There are some places where novices should not tread. I would not dream of doing anything to or with the battery in my car. There is far too much about it and its control system that is hidden in proprietary software in the BMS and I don't understand batteries that well. But I'd be happy to look at a wring diagram if you'd like to post one. Maybe I'd understand your questions better.
 
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The S has a 385 V battery (nominal) so I'm confused when you say you have a 100V battery from a Tesla S.

What is in a Tesla S is a box, the charger, that accepts 120/240 VAC and converts it to DC at around 385 V. The actual voltage it produces is whatever voltage is necessary to push the desired level of current, as determined by some computer in the vehicle (perhaps it is even in the charger) into the battery.

In a DC fast charger the charger is in the equipment cabinet behind the fence. Rumor has it that in the days of the V2 charger it was the same charger as in the car or rather a raft of them in parallel in order to be able to provide the higher current. When fast charging is used the paralleled output of the charger modules in the equipment cabinet is routed to the battery terminals instead of the output from the charger in the car.

The rest of the post confuses me too. I can't tell whether you are talking about AC or DC in some places. If you connect a 120 V DC source to a 124 V battery the battery will supply current to the lower voltage source unless you have a diode in place to block flow in that direction.

There are some places where novices should not tread. I would not dream of doing anything to or with the battery in my car. There is far too much about it and its control system that is hidden in proprietary software in the BMS and I don't understand batteries that well. But I'd be happy to look at a wring diagram if you'd like to post one. Maybe I'd understand your questions better.
Thanks for the DC fast charger explanation and for taking a look at my set up. Everything in my post is VDC. The panels have diodes, but I am not sure how they are rated. I have attached the wiring diagram, panel cut sheet and the boost transformer. If it matters I will run one panel per boost transformer in case I have a shade issue. I am in the process of adding a more sophisticated BMS I am currently playing with fire and undercharging/manually charging.

Tesla Cybertruck charging etiquette - re park feature Boost cutsheet


Tesla Cybertruck charging etiquette - re park feature panel cutsheet


Tesla Cybertruck charging etiquette - re park feature wiring diagram
 


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You can't use a DC-DC board to provide the voltage needed to DC fast charge a car. It's just too inefficient and too small.

You'd need your solar system to be MPPT and set to that specific voltage of the pack. That's some serious high-voltage stuff.

I've seen trickle chargers set up for 12v to 100v before, but it doesn't seem like it would work for car-sized batteries.

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My advice would be to get in touch with the manufacturer and seek their advice or if that's not possible try to find a users group for their products. What you want to do is probably doable but unless you are careful and know what you are doing you have the potential to damage your battery. I think the general approach would be to connect 1 panel to each of the DC/DC converters (those thing are not transformers) and use them as current sources. I note that in your post you called the panels 570 W but the spec sheets list them as 270 W. If they are 270 W panels they will only produce a bit over an amp at 120 V, the maximum the DC/DC converters can produce. Now if the battery voltage is 124 V a 120 V DC/DC converter cannot charge it. What might work, and I emphasize might, is putting the DC/DC converters in series and setting them in current source mode at a little over an amp each. So what is the fully charged open circuit voltage of the battery?

One thing you would have to do for sure is intercept the overcharge signal from the SoC meter and use it to disconnect the panels/converters if it senses full charge.

Getting something like this to work requires extensive knowledge of the battery's charging characteristic and would require extensive experimentation to come up with a safe, effective solar charging system. Saying this as politely as I can your posts indicate that you do not have the necessary knowledge. Therefore I would not recommend that you undertake anything beyond adding in off the shelf components in accordance with manufacturers instructions. Keep in mind that the 500 W you get from two 270 W panels will only add 4% SoC to a 25 kWh battery pack for each hour of FULL sunlight.
 
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Tinker71

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My advice would be to get in touch with the manufacturer and seek their advice or if that's not possible try to find a users group for their products. What you want to do is probably doable but unless you are careful and know what you are doing you have the potential to damage your battery. I think the general approach would be to connect 1 panel to each of the DC/DC converters (those thing are not transformers) and use them as current sources. I note that in your post you called the panels 570 W but the spec sheets list them as 270 W. If they are 270 W panels they will only produce a bit over an amp at 120 V, the maximum the DC/DC converters can produce. Now if the battery voltage is 124 V a 120 V DC/DC converter cannot charge it. What might work, and I emphasize might, is putting the DC/DC converters in series and setting them in current source mode at a little over an amp each. So what is the fully charged open circuit voltage of the battery?

One thing you would have to do for sure is intercept the overcharge signal from the SoC meter and use it to disconnect the panels/converters if it senses full charge.

Getting something like this to work requires extensive knowledge of the battery's charging characteristic and would require extensive experimentation to come up with a safe, effective solar charging system. Saying this as politely as I can your posts indicate that you do not have the necessary knowledge. Therefore I would not recommend that you undertake anything beyond adding in off the shelf components in accordance with manufacturers instructions. Keep in mind that the 500 W you get from two 270 W panels will only add 4% SoC to a 25 kWh battery pack for each hour of FULL sunlight.
From my earlier post I am aware that my range increase is only 30 miles per week. If I wanted economics I would buy a Nissan leaf. This is nothing but a hobby.

I am building the rack for the panels now. For simplicity I might just use an off the shelf solar MTTP charge controller (as Crissa suggested) to charge some lead acid AGM batteries @24VDC with the option to dump power periodically through an inverter to my traction pack via the on board charger. Lots of additive losses this way but it would be would be fool proof.

Then as an option through switches or simply reconfiguring some wires I could task my panels to charge the traction pack via the converters. 120vdc is a fairly safe voltage for my battery pack, peak charge rate is 130VDC. I could literally go for days from a 10% SoC to 90% SoC. High voltage cut off is 125Vdc. While not ideal for battery life, what is the worst that could happen when the converters reach equilibrium with the traction pack @ 120vdc? BTW while my naming conventions are not spot on, the math is not that complicated.
 

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I am building the rack for the panels now. For simplicity I might just use an off the shelf solar MTTP charge controller (as Crissa suggested) to charge some lead acid AGM batteries @24VDC with the option to dump power periodically through an inverter to my traction pack via the on board charger. Lots of additive losses this way but it would be would be fool proof.
That would clearly be the minimum risk approach but is such a kluge and so out of the spirit of the endeavor that I didn't even suggest it.

Then as an option through switches or simply reconfiguring some wires I could task my panels to charge the traction pack via the converters. 120vdc is a fairly safe voltage for my battery pack, peak charge rate is 130VDC. I could literally go for days from a 10% SoC to 90% SoC. High voltage cut off is 125Vdc.
I don't know anything about your converters other that what is in the spec sheet. The spec sheet implies that they can be configured as current sources. You could configure each of them to be a 2 A current source. Then whatever the battery state and whatever the sunlight available they will adjust the PWM to try to push 2 A each into the battery at whatever voltage it is charged to. If the battery is charged to below 120 V the converter will adjust its voltage (by modulating the PWM) to whatever voltage is necessary to push the 2 A. If the battery is charger to a level such that 120 V cannot push 2 A the charger will simply go to the highest voltage it can, 120, and whatever current flows will flow. Clearly if the battery is charged to above 120 V the converter cannot deliver any charge to it.

This makes for a very simple connection. Simply wire each converter to the battery bus through an isolating diode (so that if 1 converter is at 118 V and the other at 117 V the former's current will go to the battery and not the lower voltage converter. These diodes also prevent a battery charged to 124 V from feeding power to the converters at less than 120 V.


While not ideal for battery life, what is the worst that could happen when the converters reach equilibrium with the traction pack @ 120vdc?
As I've indicated in the earlier posts when the battery voltage exceeds the converter voltage no current can flow in either direction because of the diode.

With respect to the battery safety: if the pack open circuit voltage is 120 V at some safe SoC such as 80% this arrangement will never charge it above 80% but it will never hurt it either. If the safety boundary is at some lower voltage you can still configure a safe system by simply setting the converters' voltage limits to that safe voltage.

Now what you really want is a converter that reprograms its output current periodically and stays at whatever current maximizes the output from the panel. I am referring, of course, to one that does MPPT.

BTW while my naming conventions are not spot on, the math is not that complicated.
Yes but telling an old EE that you have a transformer when you actually have a DC/DC converter surely confuses the hell out of the old guy.
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