Charger overheating

[daveo4EV]

TLDR; the amount of amps advertised to the vehicle by the EVSE is a loose agreement/guess by the EVSE as to what it "thinks" it's plugged into - there is NO ACTUAL mechanism for an EVSE to interrogate any given raw-power circuit for it's size/capacity - so the EVSE "guesses" the amps based on the type of supply cable currently plugged into it - or in the Case of the Porsche Wall Charger for example it's a dip-switch setting "inside" the EVSE that you configure when you install the Porsche Wall charger - nothing prevents you from lying with this setting…but there is _NO WAY_ for a given EVSE to "know" the breaker size for a given raw-power feed - there is only loose agreements that you should not have a 30 amp breaker attached to a NEMA 14-50 plug…

gory details below…

there are 3 parts to an EVSE (EV charger)

1. the raw power supply cable/wire - from the AC power junction box or wall plug to the EVSE
2. the EVSE unit/device
3. the cable from the EVSE to the Vehicle charge port

#1 - the power supply cable is dumb there _IS_ no "smarts" protocol or any communication

it is RAW power with no "meta-data" - however there are "two ends" - one end attaches to the raw power supply - and the other end attaches to the EVSE device - different EVSE power supply cables can be made to "inform" the EVSE what type of plug they are attaching to - and therefore from that you can then imply/guess/assume the the AMERAGE of the circuit - in North America this is documented/implied in the NEMA plug specification​

• NEMA 5-15 = 120V 15 amps
  • NEMA 5-20 = 120V 20 amps
  • NEMA 6-20 = 240V 20 amps
  • NEMA 14-50 = 240V 50 amps
  • NEMA 6-50 = 240V 50 amps
  • NEMA 14-30 = 240V 30 amps
  • NEMA 6-30 = 240V 30 amps

nothing enforces these "settings" - but they can be implied based on the type of plug your using because the plug is supposed to match the wire gauge and amps for the circuit​

​

Nothing prevents you for example from putting a 30 AMP breaker on a NEMA 14-50 plug - but there is NO mechanism/meta data embedded in the raw-power feed that would tell any electrical device plugged into the 14-50 plug that there is actually only a 30 amp breaker on the other end - for those playing at home this would be bad juju- because NEMA 14-50 devices may pull 50 amps - and therefore overload the 30 amp circuit breaker - bad juju can then ensue…​

​

while the "raw power supply" end of the supply cable is dumb/passive/stupid - the end that plugs INTO the PMC+/PMCC is _NOT_ stupid - there are indexed connectors inside the PMC+/PMCC supply cable that indicate to the PMC+/PMCC the proper AMP setting for the current supply cable. So the PMCC/PMC+ "knows" which supply cable is attached - it can therefore "imply" what AMP level to communcate to the vehicle…but there is no actual interrogation of the actual power supply "feed" - it's all based on "if I'm a NEMA 14-50 supply cable" I _MUST_ be plugged into a 50 amp circuit - as noted above this could all be a lie - and the PMCC/PMC+ would happily inform the car it can safely pull 40 amps of power…​

#2 - the PMC+/PMCC/EVSE is a simple electronic device it does two things:

1. it only allow power to flow when the car tells it to for safety - so no power will ever flow until the cable is actually plugged in
2. it communicates the max AMP's to the vehicle that it can safely "pull"
   1. there are a few way the max AMPs can be determined by the EVSE
      1. could be a settings that is configured during in stall time (Tesla Wall Charger & Porsche Wall charger "fit" this category - it's a setting inside the charger -and you are supposed to set it "correctly" nothing prevents you from lying - you can tell the PoscheWall charger it's on a 100 amp breaker and wire it up to 30 amp breaker - and the Taycan will then happily pull 80 amps - there is _NO WAY_ for the Porsche Wall Charger to "know" what size breaker is on it's raw power feed.)
      2. could be a software setting - reference PMCC LCD screen AMP's setting
      3. it could come "hardwired" from the Factory - ClipperCreek chargers are this way - all the different amps they support are "hardwired/coded" at the factory - a ClipperCreek HCS-50 EVSE is a 50 amp breaker EVSE - NOTHING STOPS YOU FROM wiring it up to a 30 amp breaker or a 100 amp breaker - and if you do so it will still tell the EV it can charge at 40 amps
      4. the max AMPs can be "implied" based on the type of supply cable currently attached to the EVSE - Tesla UMC gen2, Mustart, and PMC+/PMCC all are EVSE's that determine the AMP's based on the type of supply cable currently attached.

#3 - the cable from the EVSE to the vehicle

in North America it has 5 "wires/connectors" - this is covered in the SAE J-1772 EV charging standard/protocol - two high-voltage lines for the "raw power" - 2 low-voltage communications "pins" for the vehicle/EVSE to communicate - 1 electrical ground connector - the appropriate amount of AMP's is told to the vehicle by the EVSE over the 2 low-voltage connectors when the plug is inserted into the vehicle's charge port. The communication pins are also how the car controls the EVSE to tell it to start/stop the power flow…​

​

the EVSE has _NO_ mechanism to "interrogate" a raw-power feed as to wire-gauge or breaker size - there is no way to do this - you can attempt to pull 100 amps from a 15 amp breaker - and the only thing keeping that safe is the 15 amp break will "pop" and cut off the power flow…​

but the EVSE can be "informed" as to the breaker size via various mechanisms that are either assigned, implied, configured, manually set - once the EVSE has been "informed" as the the breaker size it's dealing with - it will simply repeat that lie to the vehicle and we all hope for the best…

I hope this helps.

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[daveo4EV]

it's out of stock

it will be back in stock - this happens a lot.

 

[daveo4EV]

I thought one function of the EVSE to EV "protocol" was to inform the on-board charger how much power/current was available so the charger would not consume more current than was available.

this is correct - the EVSE "informs" the vehicle how many AMPS the vehicle is allowed to draw - 100% correct

the question is not "does the EVSE tell the car how many AMP's it can provide, it clearly does"

the question is "how does the EVSE know what AMPs to tell the car?" - I.e. where does the EVSE get this information to share with the vehicle - where does this data come from?

It is this question that is tricky - basically the EVSE is either told value via factory/installer configuration settings - or the EVSE "guesses/assumes/implies" this AMP value based on what type of supply cable is currently attached to it…

when you have the NEMA 14-50 Porsche supply cable attached to the PMC+/PMCC it "knows" to advertise 40 amps to the vehicle - it's a loose agreement implied by the type of cable currently attached…

if you for example purchase a $29 NEMA 6-20 to 14-50 adapter from Amazon - and plug in your PMCC/PMC+ via this adapter - you've plugged in a 14-50 supply cable to a 6-20 raw power circuit with a 20 amp breaker (presumably) - the PMC+/PMCC will happily tell your Taycan to pull 40 amps because that's the type of supply cable currently attached - it has no way of know there is only a 20 amp breaker and 14 gauge wire on that circuit - and it will try to pull 40 amps - and it will succeed for a brief moment in time until the breaker pops - we hope - if the breaker does _NOT_ pop it will overheat the wire, the insulation will melt, and the wires will short potentially causing a fire - because you plugged your NEMA 14-50 EVSE into 20 amp circuit via an adapter for that you should not have been using…

the PMC+/PMCC "know" the amps to advertise to the Vehicle based on the type of supply cable currently attached - this can all be a lie - 100% fabrication - and there is no way for the PMC+/PMCC to actually know/check/validate the wire-gauge and breaker "match" the current supply cable.

if I come to your house I can swap your 50 amp breaker for a 20 amp breaker in about 20 minutes - and there would be NO way for the PMC+/PMCC to know this swap has been made because you will still have the NEMA 14-50 Porsche supply cable attached to it…this is why swapping the 50 amp breaker for a 40 amp breaker will not stop a PMC+/PMCC from overheating - there is no mechanism for the PMC+/PMCC to know you've downgraded the breaker unless you also swapped out a supply cable - and Porsche does NOT Provide a 40 amp supply cable - because one doesn't exist for North America - the _ONLY_ way to have the PMCC pull 32 amps (Porsche's recommendation) with a 14-50/6-50 supply cable attached is to use the LCD screen and settings to override the PMCC default 40 amp setting and manually set it to 32 amps…

when using someone's else's home plugs when I'm visiting - I alway take the time to actually check the breaker associated with the plugs I"m about to use to make sure the breaker "matches" the NEMA plug amperage - sadly in the 9 years I've been doing EV's I've often found "loose/improper" relationships between a plug type and the actual breaker providing the power - it's not uncommon to find 20/30 amp breakers attached to a NEMA 6-50/14-50/10-50 outlet in various buildings/facilities I've visited - which means you really can't pull 40 amps on these circuits…cause for where ever reason who ever wired that circuit up didn't take the time to attach the proper NEMA plug type to match the breaker.

 

[daveo4EV]

another example:

you can purchase a NEMA 14-50 to NEMA 5-15 adapter from Amazon for less than $40…

1. plug the 14-50 ---> 5-15 adapter into the wall socket
2. attach the included NEMA 5-15 to your PMC+/PMCC
3. plug the PMC+/PMCC into the 5-15 outlet via the adapter cable you've purchased from Amazon
4. plug the PMC+/PMCC into your Taycan

your Taycan will be "told" by the PMC+/PMCC it can only pull 12 amps - because that is the correct setting any time you're using a NEMA 5-15 supply cable (the one that came with your PMC+/PMCC).

it has no way of "knowing" it's actually on a 50/40 AMP circuit

your Taycan will happily toddle along charging at 12 amps off this potential 40 amp circuit - because the supply cable currently attached to the PMC+/PMCC "tell" the PMC+/PMCC that only 12 amps are available.

this safe and not a problem - because the actual raw-power circuit is rated for 240V@50/40 amps - pulling 12 amps across this circuit is 100% safe…and not a problem…

Fun Fact: your Taycan will charge twice and fast from this circuit as it would from a "real" NEMA 5-15 circuit because this circuit is 240V and not 120V - turns out voltage doesn't matter - it's only AMP's - and the EVSE/Taycan will adapt and charge at 2.88 kW over this circuit rather than the expected 1.44 kW because it's actually a 240V raw power supply - the EVSE advertises AMP's - not voltage - and voltage is a passive outcome of the raw power feed…

in the J-1772 physical connector there are "two" high voltage "pins" or electrical connectors

when plugged into a 120V power source: one of these pins is "hot/powered" and the other "pin" Is the electrical "neutral" - that's 120 volts…
when plugged into a 240V power source - pin "1" is hot/powered, and pin "2" is hot/powers - and boom you automatically "get" 240 volts - or double the charge rate…it "just works"

so if you purchase a 14-50 outlet to 5-15 adapter from amazon - and then attach the 5-15 supply cable to your PMC+/PMCC - your Taycan will charge at 2.88 kW or 240V/12 amps - because the supply cable is "telling" the PMC+/PMCC that it's attached to a 15 amp circuit - and 80% of 15 amps is 12 amps. And it's safe because pulling 12 amps on a 50/40 rated circuit is with in specification…

and the PMC+/PMCC has NO way of knowing it's actually running on a 40 amp circuit.

 

[daveo4EV]

If the supply cable controls this, then how does PMC+ communicate that it has been switched to 50% instead of 100%?

the supply cable "informs" the PMC+/PMCC what type of cable it is passively - the software running on the PMC+/PMCC then assocates cable id #9 w/15 amps from a table in the firmware…this association is configuration data imbedded in the firmware running on the PMCC/PMC+…so there is entry in the table/firmwire for each discreet supply cable Porsche manufactures…

now the PMC+/PMCC "know" what type of supply cable is currently attached, from that they can imply the maximum AMP for a given supply cable…

nothing says however this information can not be "modified" by the PMC+/PMCC before it forwards that data to the vehicle - so when the 50% button is pressed the PMC+/PMCC simply sends 50% of the value it looked up from the table matching the supply cable

for the PMCC you can adjust the AMP's advertised by the PMCC to the vehicle via the settings screen on the PMCC's LCD display - the supply cable "tells" the PMCC it's a 50/40 amp supply cable (NEMA 14-50/6-50) - but you can configured the PMCC to only "tell" the car it can provide 37 amps…the J-1772 protocol even allows for this value to be adjust _DURING_ a charging session - so you can dial "down/up" the amps during the session and your EV will "follow" along and adjust it's demand to match the current AMP's provided by the EVSE…this is how shared/dyamic load EVSE's can charge multiple EV's at once, and dynamically adjust the amps the car is being told it can draw continuously during the charging session…

this "feature" of the PMCC and the 50% button on the PMC+ is what allows Porsche "off" the hook for the overheating problem - they can tell the customers to adjust the PMC+/PMCC to draw less amps via either the LCD screen on the PMCC or the 50% button on the PMC+ - if you adjust the AMPs on the PMCC to 32 or use the 50% button on the PMC+ the EVSE will advertise those lower AMP values to the Taycan and therefore when charging the Taycan will pull fewer amps to match the EVSE advertised setting - there by lowering the load on the PMC+/PMCC and avoiding it overheating - it's still plugged into a 50 amp breaker - but by lowering the demand from the vehicle it no longer overheats - we in essence tell the PMC+/PMCC to "lie" to the Taycan about the maximum amps available - and not knowing any better the Taycan happily complies and charges at either 20 amps for the PMC+ (50% button) or 32 amps for the PMCC (if that's what value you set on the LCD screen).

the supply cable "tells" the PMC+/PMCC how many amps it should be able to provide (max)
the PMC+/PMCC then decide what actual value to communicate to the vehicle - what the vehicle "sees" may not be the same value that matches the supply cable - as discussed…

there is nothing in the design of this system that will actually prevent a huge lie…

it's entirely feasible (trivial actually) for me to wire up a Porsche Wall Charger to a 120V 10 amp breaker (960 watt capacity) - and have it "lie" to the vehicle that it's on a 240V 100 amp breaker - if you have the 19.2 kW option on your Taycan and you plug into this "configuration" you Taycan will gladly attempt to charge at 19,200 watts on a physical circuit that is rated for 960 watts - you'll be luck to avoid burning down the building if you set things up this way…

the only how many "amps" can I draw right now - is simply a glorified "honor" system where everyone assumes all the parts are playing by the rules…

the plug matches the wire gauge the wire gauge matches the breaker rating and the supply cable/setting on the EVSE matches circuits capacity…so the EVSE then tells the vehicle the appropriate amount of power it can use…but there is nothing to prevent any of these things from being out of whack with one another…

 

[satchurator]

Part of this surprised me.
I thought one function of the EVSE to EV "protocol" was to inform the on-board charger how much power/current was available so the charger would not consume more current than was available.
If the supply cable controls this, then how does PMC+ communicate that it has been switched to 50% instead of 100%?
The output on my Wallbox with 14-50 supply cable can supposedly be switched to reduce the current drawn.
It seems like there must be something in EVSE other than supply cable size/connector that informs the on-board charger about how much current it may draw.

The supply cable does not control this. Some EVSEs have the ability to infer the maximum specced amperage based on a proprietary interchangeable pigtail / supply side plug - I think the PMCC knows if you’ve swapped from the L1 pigtail to the NEMA 14-50 because of something in the proprietary connector, but it has no inherent ability to read the home’s infrastructure, the gauge of copper, the upstream circuit breaker, the total home supply drop amperage etc.

More typically the max charge current defaults to the EVSE device’s own maximum rated amperage and the onus is upon the installer or owner to adjust the max charging current as appropriate - if that is a feature of the EVSE.

The PMC+, PMCC or PWCC all have a default/max Charging Current which can be set lower depending on the supply line’s rated max (or owner preference). They are then advertising that and only that number as what’s available to the vehicle (power line comms is part of the J-1772 spec) and the vehicle’s L2 charger is expected to honor that by drawing no more than that amperage. The EVSE uses switching relays and monitors the EV current draw to police it. If the vehicle misbehaves and attempts to draw more than the set Charging Current, a normal functioning EVSE would stop a charging session well before the supply line breaker gets tripped. EVSEs are glorified switches that negotiate charging with EVs and provide safety controls so that owners don’t get electrocuted and fires don’t get started.

Edit - took too long to post this!; all my points made in more detail and better accuracy by @daveo4EV

 

[mhockett]

@mhockett I'm a bit skeptical of the need to change your breaker - the PMCC has no way of knowing what the breaker amp rating is for the supply line its connected to.

As I understand it, you need to adjust the Charging Current limit setting within the PMCC. The only rationale for changing the breaker is to have an extra safety measure if the PMCC+Car combination misbehaves under charging and attempts to draw more than your set limit. In that scenario, you'll trip your breaker and charging will stop, rather than the cable overheating.

The charger that came with the car can't be adjusted. It accepts what's coming from the wall (50 amps) and knows the car can take 50 amps and just pushes the accelerator down. See pic

 

[mhockett]

the supply cable "informs" the PMC+/PMCC what type of cable it is passively - the software running on the PMC+/PMCC then assocates cable id #9 w/15 amps from a table in the firmware…this association is configuration data imbedded in the firmware running on the PMCC/PMC+…so there is entry in the table/firmwire for each discreet supply cable Porsche manufactures…

now the PMC+/PMCC "know" what type of supply cable is currently attached, from that they can imply the maximum AMP for a given supply cable…

nothing says however this information can not be "modified" by the PMC+/PMCC before it forwards that data to the vehicle - so when the 50% button is pressed the PMC+/PMCC simply sends 50% of the value it looked up from the table matching the supply cable

for the PMCC you can adjust the AMP's advertised by the PMCC to the vehicle via the settings screen on the PMCC's LCD display - the supply cable "tells" the PMCC it's a 50/40 amp supply cable (NEMA 14-50/6-50) - but you can configured the PMCC to only "tell" the car it can provide 37 amps…the J-1772 protocol even allows for this value to be adjust _DURING_ a charging session - so you can dial "down/up" the amps during the session and your EV will "follow" along and adjust it's demand to match the current AMP's provided by the EVSE…this is how shared/dyamic load EVSE's can charge multiple EV's at once, and dynamically adjust the amps the car is being told it can draw continuously during the charging session…

this "feature" of the PMCC and the 50% button on the PMC+ is what allows Porsche "off" the hook for the overheating problem - they can tell the customers to adjust the PMC+/PMCC to draw less amps via either the LCD screen on the PMCC or the 50% button on the PMC+ - if you adjust the AMPs on the PMCC to 32 or use the 50% button on the PMC+ the EVSE will advertise those lower AMP values to the Taycan and therefore when charging the Taycan will pull fewer amps to match the EVSE advertised setting - there by lowering the load on the PMC+/PMCC and avoiding it overheating - it's still plugged into a 50 amp breaker - but by lowering the demand from the vehicle it no longer overheats - we in essence tell the PMC+/PMCC to "lie" to the Taycan about the maximum amps available - and not knowing any better the Taycan happily complies and charges at either 20 amps for the PMC+ (50% button) or 32 amps for the PMCC (if that's what value you set on the LCD screen).

the supply cable "tells" the PMC+/PMCC how many amps it should be able to provide (max)
the PMC+/PMCC then decide what actual value to communicate to the vehicle - what the vehicle "sees" may not be the same value that matches the supply cable - as discussed…

there is nothing in the design of this system that will actually prevent a huge lie…

it's entirely feasible (trivial actually) for me to wire up a Porsche Wall Charger to a 120V 10 amp breaker (960 watt capacity) - and have it "lie" to the vehicle that it's on a 240V 100 amp breaker - if you have the 19.2 kW option on your Taycan and you plug into this "configuration" you Taycan will gladly attempt to charge at 19,200 watts on a physical circuit that is rated for 960 watts - you'll be luck to avoid burning down the building if you set things up this way…

the only how many "amps" can I draw right now - is simply a glorified "honor" system where everyone assumes all the parts are playing by the rules…

the plug matches the wire gauge the wire gauge matches the breaker rating and the supply cable/setting on the EVSE matches circuits capacity…so the EVSE then tells the vehicle the appropriate amount of power it can use…but there is nothing to prevent any of these things from being out of whack with one another…

With the "no screen" Porsche charger that came with the car, it takes the 50 amps from the wall and tries to feed 50 amps (40 amps reduced) to the car, which is too much for the 10g factory wire. The "dumb" charger thinks it can handle the higher amps - but it can't.

 

[mhockett]

Because I'd rather not replace the 50 amps with 40, which will reduce my charge to 32 amps and lengthen my charge time, I just purchased the Chargepoint Home Flex charger for $750. They "say" they can handle the 50 amps and guaranteed a return, if not. If that fails, I'm off to Home Depot to get a couple of 40 amp breakers. I'll be the sorry guy waving the white flag in my driveway.

 

[daveo4EV]

With the "no screen" Porsche charger that came with the car, it takes the 50 amps from the wall and tries to feed 50 amps (40 amps reduced) to the car, which is too much for the 10g factory wire. The "dumb" charger thinks it can handle the higher amps - but it can't.

agreed - but there is a 50% button - if you press this button it will only advertise 20 amps to the vehicle - and it will no longer overheat.

 

[daveo4EV]

the PMC+ can "lie" the vehicle about max amps via the 50% button - see picture below.

 

[satchurator]

The charger that came with the car can't be adjusted. It accepts what's coming from the wall (50 amps) and knows the car can take 50 amps and just pushes the accelerator down. See pic

With the "no screen" Porsche charger that came with the car, it takes the 50 amps from the wall and tries to feed 50 amps (40 amps reduced) to the car, which is too much for the 10g factory wire. The "dumb" charger thinks it can handle the higher amps - but it can't.

It can be adjusted, it’s just a very simplified interface. There is no transformer componentry inside the PMC+ to actively modify the current. That button is just taking the numeric amperage associated with the attached pigtail, dividing by two and communicating that number to the vehicle when negotiating a charging session.

 

[daveo4EV]

honestly just buy another EVSE for $400 or less and be done with it.

 

[Jhenson29]

@Tooney
There are two pins on the supply cable that have different resistances across them for different cable sizes

For example:
14-50 cable is 330 ohms.
14-30 cable is 100 ohms.

The PMC+/C can read this resistance when the cable is plugged in as a reference for maximum supply cable current.

 

[mhockett]

Porsche is giving you bad advice - they are clueless

if you ahve a PMCC you can adjust the amps down to 32 amps on the LCD screen

if you have the PMC+ you can use the 50% button to charge at 20 amps

either way I'd leave your breaker & circuit alone - and either adjust the PMCC/PMC+ _OR_ purchase a functinoal 40 amp charge for $300 or less...

a new 40 amp EVSE is going to be less than the cost of your electrician and it won't over heat, and it will charge at 40 amps.

the official "porsche" position on this has been clear since about Aug/Sept. of 2020 - where the provide the same response to other forum members - our 40 amp charger is only an 40 amp charger if you don't mind it overheating - otherwise it's a 32 amp charger.

my response: buy a different product that matches it advertised specs.

this charger for $200 will charge at full 40 amps all day long and not overheat

https://shop.tesla.com/product/corded-mobile-connector

but you'll need a TeslaTap to use it - but you should have one of those anyways since they are generically useful.

I have the generic charger that came with the car. No screen, therefore no adjustment capability. Just purchased a Chargepoint Home Flex for $750 because it's supposed to allow the 50 amp charging. If not - I'm off to Home Depot for some 40 amp breakers.

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