HPWC Hacking

[Cosmacelf]

I'll ask again: Is the theory of operation of using a PWM signal for a DC coil contactor that you are reducing a rectified 340V DC voltage down to an average 240V by adjusting the pulse on time? ie. the PWM signal is "on" 240/340 = 70% of the time? Or are you effectively reducing the power, and just letting the coil see the high voltage, but for a shorter period of time? Presumably you are assuming a 240V DC coil can take short periods of 340V? Wouldn't the rectifier and capacitor by itself reduce the DC voltage well below the 340V DC peak anyways?

I'm just trying to understand why a PWM signal is better than a resistor - I guess the overall power usage is less, even without a lower power hold circuit?

 

[Ingineer]

Because of the inductance of the coil, it effectively averages any PWM voltage put to it, so yes, PWM is a way to reduce the input voltage without needing to burn off excess in a resistor. Because the contactor needs a lot more power to pull in versus hold, PWM is a way of ensuring you have full power for initial pull-in, but then you can reduce your power to a much lower value for holding. Once the plunger stops moving in a contactor, all the power put in is turned into heat, so it pays both in efficiency and heat to reduce it. In the HPWC, you already have high temperatures across the contacts due to I2R losses, so why add a bunch of unnecessary heaters too?

My HPWC was getting HOT HOT HOT in normal use, so I set out to reduce it, and I was able to more than half the loss and thus heat build up. That level of heat is not good for many reasons! For one, it speeds oxidation, which in turn increases resistance, and if not checked this can spiral out of control and lead to early failure as we have seen in a number of units.

The HPWC takes in 240v line voltage and full-wave rectifies it and then smooths it with an electrolytic capacitor. This means about 320VDC in practice available to the SMPS and the contactor drive circuit. Tesla added the resistor to drop the voltage from 320 to 240, but IMHO it's still too much for contactor hold.

One trick you can do if you want to stick with resistors is to put a large electrolytic cap across the resistors so the when first enabled, the capacitor passes full voltage to the coil. As the cap charges, the voltage is reduced. Set the resistor values so that you see about 100 volts across the coil instead of 240 and size the cap so that you see the at least 240 volts for about 50ms. You can use a smaller cap if you amplify it with a pass transistor. Seems silly to me though when you have a microcontroller there to do it all, no resistors needed.

 

[Cosmacelf]

So what was your HPWC mod, Ingineer, to reduce waste heat?

 

[Ingineer]

I posted this in the HPWC thread, but basically I beefed up all the internal connections, did away with the input screw terminals and fuses, and put a coil economizer in there.

 

[wk057]

I posted this in the HPWC thread, but basically I beefed up all the internal connections, did away with the input screw terminals and fuses, and put a coil economizer in there.

No fuses?! Scary...

 

[Ingineer]

The breaker is going to trip if the car shorts. Also, Tesla has fuses in the car.

Not worth the heat penalty.

Most EVSE's don't come with fuses. Including some that are engineered much better.

 

[miimura]

Can't you also move the fuses into the disconnect switch? One of my prior house's A/C compressor disconnect had fuses in it.

 

[Ingineer]

Can't you also move the fuses into the disconnect switch? One of my prior house's A/C compressor disconnect had fuses in it.

My subpanel is so close to my HPWC that I don't need a separate disconnect. Yeah, I could have added a box with fuses, but code doesn't require it, and I don't think it's necessary from an Engineering standpoint.

 

[wk057]

*shrugs*

I'm a big fan of OCPDs. The fuses in the HPWC don't get nearly as hot as the other components. Plus I've seen cases where breakers have failed to trip in the past... a few fuses are worth the peace of mind.

 

[Yoda101]

I assume this project is currently on priority 3?
1 - Battery Pack BMS
2 - HVAC upgrade project
3 - Solar Status monitoring (and possible external data exposure)
4 - HPWC upgrade in spare time
5 - Other things we don't know of
6 - Wife? - Looking for trouble!

Hahaa!
I really enjoy your projects and reports!

 

[Ulmo]

Any update? How did wk057 end up charging his cars?

 

[llavalle]

Any update? How did wk057 end up charging his cars?

The whole idea was to tune charging speed to the solar output. He did manage to adjust the charge current directly on the car itself (root access) but I think it isn't working with the newer, gen 3 chargers (the refresh S and X).... so I guess this project will be back on the table!

 

[Pwwik]

Question from newbie ..

I also want to start / stop charge or up down current based on excess solar generation.

Rather than change input / charger .. could the app API not be used via say a Pi to use car remote controls ?

Ty

Peter

 

[Ulmo]

It seems to me someone needs to hack the SuperCharger protocol. Unfortunately, this would require:

1. SuperCharger eligible car
2. OTA Update eligible car
3. Out of warranty (since it wouldn't be good value to do this on a warrantied car)
4. Possibly but not necessarily root access to do diagnostics and snooping of the SuperCharger protocol
5. time to work on this
6. purpose to do it
7. family that allows it

Basically, the DC charger would have to mimick a SuperCharger. It shouldn't be that hard for an electrical engineer and programmer that is experienced at backwards engineering.

@wk057 is not eligible because of #3 & probably #5 above (I could be wrong about #3). @Ingineer is ineligible due to #5 & #6 & possibly others on the list above. That means someone else would have to do it.

 

[jaguar36]

It seems to me someone needs to hack the SuperCharger protocol. Unfortunately, this would require:

1. SuperCharger eligible car
2. OTA Update eligible car
3. Out of warranty (since it wouldn't be good value to do this on a warrantied car)
4. Possibly but not necessarily root access to do diagnostics and snooping of the SuperCharger protocol
5. time to work on this
6. purpose to do it
7. family that allows it

Basically, the DC charger would have to mimick a SuperCharger. It shouldn't be that hard for an electrical engineer and programmer that is experienced at backwards engineering.

@wk057 is not eligible because of #3 & probably #5 above (I could be wrong about #3). @Ingineer is ineligible due to #5 & #6 & possibly others on the list above. That means someone else would have to do it.

It has already been done, The prohibitive cost of the hardware and the lack of usefulness rather limit its application though.

 

[Ulmo]

It has already been done, The prohibitive cost of the hardware and the lack of usefulness rather limit its application though.

Are there references to this? I'd like to build on that work if possible.

 

[jaguar36]

Are there references to this? I'd like to build on that work if possible.

Nope, like most things relating to Tesla hacking nobody is sharing anything.

 

[verygreen]

Nope, like most things relating to Tesla hacking nobody is sharing anything.

This is certainly not true. But people certainly don't share their knowledge to everybody coming. There's still some trade in information and services, though.

 

[WinterDragoness]

I'd love to mod my HPWC to vary power based on output from my solar system. Sadly it sounds like this project is dead...

I was also thinking maybe the secret CAN bus connector under the main screen could be used to remotely tell the car to change charging speed, but I assume that connector is read-only and can't be used to send such commands. Rooting my car is farther than I want to take such a project, at least until it's out of warranty.

 

[miimura]

I'd love to mod my HPWC to vary power based on output from my solar system. Sadly it sounds like this project is dead...

I was also thinking maybe the secret CAN bus connector under the main screen could be used to remotely tell the car to change charging speed, but I assume that connector is read-only and can't be used to send such commands. Rooting my car is farther than I want to take such a project, at least until it's out of warranty.

eMotorWerks recently announced that feature for their system. They introduced a new WiFi connected box called JuiceMeter that measures your solar output and communicates to a JuiceBox EVSE so that it can follow the solar generation. I've not tried it and I'm not affiliated with the company.

JuiceMeter - Universal Energy Meter