Heat generated in the circuit is going to be based on current squared. So, if my morning math is right, 48a is going to generate 44% more heat in a resistor (the wire, breaker, connection, etc) than 40a. 44a would be 21% more heat.
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48 amp wall connector on 50 amp circuit for track days?
- Thread starter destructure00
- Start date
Yes, it will take a bigger problem for something to go wrong. That's part of the point I was trying to make. "Things going wrong" are partially built into the NEC. For example if you have a worn contact in the 14-50 outlet it will get hot. At 40A it probably won't start a fire. At 48A and 44% more heat it's much more likely something bad will happen.
Honestly I'm not worried about you. You have an IR thermometer and you've listened carefully to all the warnings. But I wouldn't advertise what you're doing - I'm sure you know some of the types who show up at track days who won't be as careful as you.
8 years ago I would have dismissed these comments I'm making as over-reactionary, the NEC wouldn't rate it for 50A if it couldn't handle it, can't happen here, etc. I would have pulled into the RV park, plugged in at 48A and gone for a walk. I've seen a few close calls since then.
Agreed on all points. Good discussion, and definitely something for anyone looking to do this to keep in mind.
So far so good....sustained 48 amps for an hour or so charging up before 1st session. No issues with hot components.
The unseen problem is the conductors- their size, the run length, insulator heat rating, etc. You can very easily char and melt the insulator on wire, causing it to short, and potentially causing a very dangerous situation for someone other than you. It isn't advisable to do this, and if someone were to get hurt or property was to be damaged you're 100% liable. Whether or not anything bad will happen completely depends on the contractor that installed all of the equipment up to that 14-50 outlet, and I'm betting the track didn't hire the highest qualified union crew to do the work using quality components.
Failures in these systems rarely happen immediately. There just isn't enough energy, as crazy as that sounds. Just look at all of the people with HPWC that weren't connected properly, causing the terminal block to melt and eventually short. Look at all the posts by people that just hired a professional to install a 14-50 outlet in their garage, and now it's charred and not working after a year of use.
Failures in these systems rarely happen immediately. There just isn't enough energy, as crazy as that sounds. Just look at all of the people with HPWC that weren't connected properly, causing the terminal block to melt and eventually short. Look at all the posts by people that just hired a professional to install a 14-50 outlet in their garage, and now it's charred and not working after a year of use.
If a conductor in their 50 amp circuit melts with a 48 amp draw after an hour or two, they have much bigger problems than me.
Thanks for the reminder to update this thread, the wall connector worked great the whole day, and I was able to get a constant 48 amp charge rate throughout the day. Although I had to sit one of the four sessions due to brake problems, the charge and discharge rates were about what I expected. This means that going from 40 amps on the Gen 1 UMC to 48 amps on the HPWC is the difference between hoping for a 2 hour break to leave and supercharge vs being able to stay on-site and finish all 4 sessions.
Thanks for the reminder to update this thread, the wall connector worked great the whole day, and I was able to get a constant 48 amp charge rate throughout the day. Although I had to sit one of the four sessions due to brake problems, the charge and discharge rates were about what I expected. This means that going from 40 amps on the Gen 1 UMC to 48 amps on the HPWC is the difference between hoping for a 2 hour break to leave and supercharge vs being able to stay on-site and finish all 4 sessions.
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doghousePVD
My grandfather’s car
Not really. It is 50 amps for up to 2 or 3 hours. Paak current can be well over 70 A, like a motor starting, and will not trip a breaker or cause a fire. A proper circuit (not always the case) should have no problem running at 48 A for two hours. If something failed in this scenario, most likely the electrician did not adequately tighten the connections, a wire is damaged, or it is a cheap connector that has worn out.
You're not going to change my mind that there's anything wrong with what I'm doing. Others may agree with you, and that's fine, but you're wasting your time on me.
doghousePVD
My grandfather’s car
The OP specifically said he wanted to use a 48 A draw for two hours, which is within the spec of a proper 14-50 50 A circuit.
dhrivnak
Active Member
While it can be done and there are places it has worked successfully for me, I have found more places where it does not work. Not all NEMA 14-50 plugs are top quality. Not all electrical connections are good and fully secure and not all 50 amp breakers truly handle 48 amps even 32 amps at some places. So watch it and occasionally touch it and the plug to make sure no hot spots develop. It it starts getting hot dial it back.
Not surprising another long-time Roadster owner has lots of experience to speak on this topic. We learned a lot in the days of 70A AC charging and no superchargers. Now we take our Model 3 on long trips but I wouldn't trade those early adventures for anything.
