My car MELTED my 16A socket!

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duckInferno

89 posts

Master Geek

#2433387 5-Mar-2020 21:05

Technofreak:

Somethings not adding up to me here, though I must admit I'm not an expert on charging EV batteries. Why was there sustained 18A charging session previously when you haven't seen these figures since you replaced the plug/socket? Having had a quick read about EV battery charging characteristics there was nothing there that indicated charging rates would vary upwards at higher battery levels.

2 amps above the rated 16 amp limit isn't likely to be your problem, providing the plug and socket is in good condition. I'm highly suspicious of the numbers you are seeing.

The entire EVSE was replaced, the old one was reporting up to 18.6~A, the new one isn't reporting above 15.2A. I didn't re-test the old one after the socket was repaired because I didn't want to put the effed up EVSE's plug anywhere near it.

The 'higher amps at higher %' is still a hypothesis tbh (posited by sparky). It consistently drew 18+A when plugged in after I got home from commute at 20-30% SOC. Whenever it did draw only 14A, I recall the car had a much higher SOC. I didn't do any testing because of aforementioned bung plug.

I don't know why it was drawing that much but it's been sent back and hopefully the manufacturer can tell us when they inspect it.

In the meantime I'm going to keep a close eye on the amps and keep my ears out for buzzing.

Technofreak

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#2433400 5-Mar-2020 21:36

duckInferno:

In the meantime I'm going to keep a close eye on the amps and keep my ears out for buzzing.

Good thinking, I'd be doing the same. Lets hope your problems are solved.

I wonder how many house fires could get started with this type of fault.

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Beccara

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#2433414 5-Mar-2020 21:53

J1772 EVSE's run on a PWM signal duty cycle to give the car the amount of amp's it can draw, Amps / 0.6 = Duty Cycle so the difference between 16 and 18 is only a few %'s. Either it was programmed to report being a bigger charger than it was or it's PWM circuit was whacked out by something

edit:// Even at 18a tho the connector shouldn't have cooked, thankfully the overtemp kicked in and stopped it going full fire

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duckInferno

89 posts

Master Geek

#2524985 17-Jul-2020 20:59

Forgot about this thread, here's an update a few months on.

The new EVSE has been behaving fine and doesn't even get close to charging at 16A so all is well there.

My electrician put it well in a follow up to me:

electrician:

Yes I agree that a bad connection would definitely cause a high resistance path causing both the plug & socket to melt together, this however does not factor at all into how the amperage was higher than the rated plug on this device itself, if anything a high resistance path would drop the amperage as I (amps) = V/R (volts divided by resistance)

As per our COC our Earth fault loop impedance was 0.39 Ohms which proves we had installed a low resistance outlet/circuit as this was tested from the socket itself.

Having a higher amperage being put through a plug that is underrated to take this load will cause damage to it.

The load (amps) is controlled via whichever is plugged into the source of power, the car or the device in hand, so I fail to see how a device that is rated at 16 amps maximum can be able to pull a load at 18 amps continually as you reported, this will deteriorate the plug that was supplied with the unit.

Or put more succinctly in my subsequent email to OEM Audio,

me:

1. A weak connection should drop the amperage, not increase it (I=VR). This effectively rules out the socket regardless of the quality of the connection in terms of the 18A issue

2. The thing that's plugged in is what controls the load, and the replacement unit + my car doesn't get anywhere near 15A

These strongly indicate that the unit may be faulty for drawing 18A - especially point 1 because even a terrible socket-plug connection would preclude the load we've seen.

In fact if the connection was bad, which it would have been from the start, the unit may have been trying to draw more than 18A and only been limited by the quality of the connection

I suggested the old unit be tried to see if it draws >18A on other setups, I even volunteered to try it again on my repaired socket, but OEMAudio has stopped responding to my emails.

My electrician bore the cost of the repair and even turned down my offer to pay for half of it so customer for life there - Magfox electricial if anyone is looking for a good, punctual and honest sparky.

elpenguino

3419 posts

Uber Geek

#2525008 17-Jul-2020 22:06

duckInferno:

electrician:

Yes I agree that a bad connection would definitely cause a high resistance path causing both the plug & socket to melt together, this however does not factor at all into how the amperage was higher than the rated plug on this device itself, if anything a high resistance path would drop the amperage as I (amps) = V/R (volts divided by resistance)

Or put more succinctly in my subsequent email to OEM Audio,

me:

1. A weak connection should drop the amperage, not increase it (I=VR). This effectively rules out the socket regardless of the quality of the connection in terms of the 18A issue

My electrician bore the cost of the repair and even turned down my offer to pay for half of it so customer for life there - Magfox electricial if anyone is looking for a good, punctual and honest sparky.

1. Error there. As stated by your sparkie, I = V / R. You are right that overall a weak (high resistance) connection will drop the total circuit current but what happens locally, at the weak connection, is that P(power) = I * V. You have some 'V' because you have some 'R' ( V = I * R ). The weak connection acts like a resistor, because it is one, and dissipates power. Connections are usually not made to do this, so they fail.

BTW the correct term for 'amperage' is current.

Otherwise we'd have words like volumage, dollarage, kilogramage . . .

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SomeoneSomewhere

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#2525020 17-Jul-2020 22:39

Resistive loads, like heating elements, will draw less current with less voltage. The point being made is that a faulty connection would not cause a resistive load to draw 18A instead of 16A - if anything it would draw less.

However, certain other loads will draw [b]more current[b]. to maintain a more-or-less constant power. Examples of these are induction motors and switchmode power supplies. The voltage drop across the plug would need this to be very significant though; a 10% current rise would need a 10 voltage drop and 18A x ~23V... 400W is going to start a fire fast.

I don't know whether a car charger would fall into this category. I would expect them to use a constant input current regardless of voltage until they moved into the float stage of charging. This is essentially a software issue for the charger designers; it is not a 'fundamental physics' issue.

I would be more concerned about whether the EVSE had DIP switches, rotary switches, trimpots, or some means of adjusting the output current. It's possible it could be set for a 20 or 25A supply. Worksafe guidelines say that if adjustable by 'the user', the plug fitted must be suitable for the highest adjustable current.

They also say that for a 16A plug, the charger must either be limited to 12A or have temperature sensing on the pins and be limited to 16A.

Hard wired Mode 3 charging is preferable if possible.

Scott3

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#2525026 17-Jul-2020 23:06

Don't pay too much attention to the V=IR equation. While the equation holds true, it traps one into the Resistance of the car charger is constant.
The reality is that the charger will vary it's resistance to draw the amount of current it need's to charge at maximum rate (bound by the maximum current PWM signal fed to it by the EVSE).

But given that the car was drawing more power than it was meant to, and this issue went away with a new EVSE, your conclusion seems to remain likely correct.

With regards to the max current draw of the leaf's, the smaller charger is rated at 3.6kW. Generally these are rated on the output side, so the input draw will be a bit more due to any inefficiencies. If we assume a 90% efficient charger, then input draw would be 4.0kW. At 217.4V, an 18.4Amp draw is required to extract this amount of power. 217.4V is within the +10%, -6% allowable variation of voltage at point of supply (connection to street), should be noted any voltage drop on internal wiring is additional to this.

The above was mostly to solve in my head if that current draw was workable on a leaf with the smaller charger. Many of my number's are guesses, and the 3.6kW may be a nominal or rounded figure.

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tripper1000

1617 posts

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#2526346 21-Jul-2020 08:42

EVSE plug might have been faulty, but the 18amps measured is either not correct or indicative of something wierd going on with the car electronics.

Many people plug JDM Leafs into EVSE that signal 32amp availablitiy and the cars never-ever draw 18amps or more. The cars on board charger simply won't draw that much current (this does not hold true for UK leafs which have more powerful on board chargers). It doesn't matter even if the EVSE is over-stating the current availablility, the car won't draw 18 amps.

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