Occasional use charger plug meltdown

As I do not have many L2 charging stations that are convenient to my commute to work, and my apartment building does not allow installation of L2 units, I regularly rely on the occasional use charging unit that comes with the car. When I'm at work, I can plug in for the day and top off my charge, so this actually works out quite well.

Recently I started using a different wall outlet in the garage and noticed that when removing charger from the wall plug it was quite hot. Very hot indeed. Most recently, I noticed it so hot that the plastic around one of the metal plugs was melted and soft.

I've called my dealer to get a replacement charger, but still have some unresolved questions:
- Has anyone else experienced the heating or melting?
- Does the last 20% of charging draw more current?
- Should I be using REDUCED for L1 charging (making slow even SLOWER)?
- Could it be the outlets had different amperage ratings?

If I understand where the melting occurred, the EVSE's plastic plug melted around one of its metal prongs. One cause could be that the electrical contacts inside the outlet became very hot with so much heat transferring to the plug's metal prongs that the plug began to melt. This is fairly common when excessive electrical resistance exists within the outlet or when the outlet's electrical contacts touch the plug's prongs in a very small area due to damage to the contacts. This resistance could be caused by oxidation on the surface of the contacts inside the outlet or where the electrical wires connect to the outlet. This did not happen with the first outlet because it was in better condition with no internal corrosion or damage to its contacts.

Reducing the charging current would reduce the amount of heat created by the corrosion or damage, but this would only mask the problem while slowing your charging considerably. The solution would be to replace the electrical outlet with a commercial quality outlet.

alohart said:

The solution would be to replace the electrical outlet with a commercial quality outlet.

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This! all OUC problems can be solved by having solid, clean and high quality outlets to plug into. It needs to fit nice and tight. See if you can have the outlet you use in the garage replaced with a commercial grade one.

Thanks for the feedback! I think you've both nailed it. The current outlet is a typical wall outlet, while the other outlet was a box. Also, since the cable hangs with the weight of the control box, the plug often slides out a little, making for less contact area. I need to find a way to suspend the control box so that it does not pull on the plug.

You should be able to relieve the mechanical loading problem of the plug with a short, high quality, heavy gauge extension cord. If the outlet is mounted with the ground plug down, a right angle plug cord might be helpful.

Also, why replace the entire OUC when all you need to do is replace the plug. Try something like this: http://smile.amazon.com/dp/B000L9TWAY

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My experience with OUC and extension cords:

Before they completed installing two Level 2 EVSEs, I charged for a few months at my workplace using a 50 foot 10/3 extension cord. I had no problems, and even after charging for 9 hours at the 12 Amp setting the plugs wouldn't be warm at all. (Closest outdoor outlet was a commercial grade 20-amp GFCI mounted about 60 feet away from nearest parking space. My employer is very LEED conscious (hence the two Level 2 EVSEs) and they provided me with the extension cord and encouraged me to run it over the lawn until the Level 2s were ready.)

To answer one of your questions, no, the last part of the charge is not greater, it tapers down as the batteries approach full, not up.

As others have said...the receptacle is shot...it needs to be replaced. There's a reason why code limits the load on a 15A circuit to a maximum of 12A with the EVSE load (80% rule)...this is to account for overheating on a long-term use device (they allow full amperage for short term use, but not long-term). That may not be enough if the receptacle is not up to snuff. It could have been loose contacts with the blade of the plug, and/or, the wires to the receptacle may not have been tightened or if they used the stripped jab contacts on the back, the length of the stripped section was not done properly (too short). Either one of those things will act like a heating coil from the resistance, and heat things up. Probably at least the spring tension on the contacts is too weak, as you said it would partially pull itself out of the socket. IF there is anything else on that circuit, the voltage may be low, and that might be an issue, too, as it would then try to draw more current so the power available remained similar (should never exceed the 12A pilot signal value, though). It should take some force to insert the plug - if it's easy, on a high load like the EVSE, it will often get hot maybe to the melt-down stage.

FWIW, there is also a maximum box fill, and if the box is too small for the number of wires and devices in there, they can't radiate heat properly, and things will get warmer than by design.

The result of L1 maximum charging in my garage when the car was new

I replaced the receptacle, but the plug still gets uncomfortably warm if:

The ambient temperature in the garage is high
and
charging a long time

I rarely drive far enough to discharge below ~50%


I exclusively use L1 Reduced ~8 amps which works with my schedule and range needs - the plug is cool on the warmest days



:arrow:

I'm surprised that there isn't a warning about this in any documentation. The fact that it can heat up to the point of melting, or worse fire, could be a real issue.

justanotherdrunk said:

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Really? Is that standard power receptacle fitting in the US?

Am I really seeing Active and neutral closer together than the width of the screwheads?

I33t said:

justanotherdrunk said:

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Really? Is that standard power receptacle fitting in the US?

Am I really seeing Active and neutral closer together than the width of the screwheads?

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Neutral and hot are on opposite sides of the receptacle...there are typically two screws on each side in case you want to use those terminals for a junction to daisy-chain to another device (although, I prefer to only run one lead and if more than one in the electrical box, tie them together there rather than on the device). Safety ground is at one end. There's a short jumper between the two hots and neutrals, in case you want to feed each half with separate power leads - it can be broken off to separate them.

BMW4Me said:

I'm surprised that there isn't a warning about this in any documentation. The fact that it can heat up to the point of melting, or worse fire, could be a real issue.

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There is warning and documentation about this, in the owners manual. This is why the car offers 3 different charge settings. The outlet should be protected by a proper circuit breaker box, if it gets too hot or comes close to fire a circuit breaker should pop.

I33t said:

Really? Is that standard power receptacle fitting in the US?

Am I really seeing Active and neutral closer together than the width of the screwheads?

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Yes

No

You must keep the maintenance up on any infrastructure for it to be reliable. A worn out receptacle (one that does not grip the plug's contacts well) or one with loose input power leads (usually caused by improper installation - ie., not properly torqued or the lead too short) WILL overheat if you try to power a high amperage device. It has nothing to do with it being the OUC...it would do the same thing powering a large motor or a resistance heating device (say a space heater or other heating appliance) for a longer time.

No appliances that I'm aware of come with warnings about the possible overheating of the receptacle. That is normally protected by the matching of plugs and receptacles; for example, a 20A device will come with a different plug, and could not be inserted into a 15A receptacle.

The reason the i3 offers to use restricted power on the level 1 input is because the receptacle in use may have to share power with other devices, and the combined power could trip the circuit's protection device (typically either a circuit breaker or a fuse). It has nothing to do with protecting the actual device from damage, it is about the inconvenience of it tripping the circuit. It would not be uncommon for the receptacle in the garage to share its load with say the electrical door opener. THings might work fine until you opened or closed the door. By limiting the i3's maximum draw, you should be able to not trip that protection...it has nothing to do with protecting it from overheating.

Ideally, you can provide a dedicated circuit for something that is going to use most of the power for a typical circuit in the USA (most common circuits are 15A). Then, assuming it is installed properly and you used a quality receptacle, it should never exhibit any issues. That more than one person has experienced problems is more likely a result of the cheap devices and haphazard installation practices by builders trying to save a few cents. What might work great to power say a table lamp could have major problems once you plug in a device requiring near the max power the device is designed to provide. FWIW, on a device that runs for longer than 3-hours, the US codes require it to not draw more than 80% of the available power which is why the US EVSE OUC which has a 15A plug on it is designed to draw no more than 12A, or 80% of the 15A circuit. IF everything is working properly, that derating should prevent the circuit from overheating. If the fill volume of the electrical box is not followed (too many wires/devices in the box), there's not enough room for convective cooling to occur, and that can concentrate the heat causing issues. There are codes that specify all of this, and those codes are not always followed...you cannot blame BMW or the supplied OUC for those issues.

The most recent codes in the US often require the circuit to be protected with an Arc Fault Circuit INterrupter (AFCI). If there is a loose connection, generally, it will create an arc, and if the circuit has one of these on it, it would trip and turn off the power, preventing things from overheating.

Jim,

You bring up good points. I guess if the power lead was longer from the plug to the box, it would lessen the likelihood of pulling on the plug. Maybe a short extension cord is the short term solution. But why they decided to have the box so close to the plug, when most outlets are not at floor level, is beyond me.

BMW4Me said:

But why they decided to have the box so close to the plug, when most outlets are not at floor level, is beyond me.

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The short cord length is required by the National Electrical Code article 625.

When the GFCI is in the EVSE itself (and not in the cord/plug) the maximum cord length allowed is 12 inches.

Leasi3 said:

BMW4Me said:

But why they decided to have the box so close to the plug, when most outlets are not at floor level, is beyond me.

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The short cord length is required by the National Electrical Code article 625.

When the GFCI is in the EVSE itself (and not in the cord/plug) the maximum cord length allowed is 12 inches.

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Good piece of trivia to know!

Any one know if it is possible to take the OUC apart and add a longer + thicker gauge cable + heavy duty male plug?

SSi3 said:

Any one know if it is possible to take the OUC apart and add a longer + thicker gauge cable + heavy duty male plug?

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Anything's possible, but you realize that if you open and change things, you'd lose any warranty on the thing plus, the UL certification would be void, and if there were some sort of accident, you'd be liable?

The wiring/plug size/etc. all meet the required safety standards, and if your home wiring is up to snuff, should work fine with no problems. A kitchen is often used with high current devices that draw very close to the circuit's limit. If they are used longer than they are designed for, the increasing heat can damage the spring tension in the contacts. That leads to resistance (like a heating coil) and things going south faster. There's a reason why the level 1 device won't let you use 15A on a 15A circuit (code limits it to 80% when used for longer than 3-hours), just to ensure it doesn't overheat things.

From a practical situation...if the plug goes into the receptacle easily or pulls out part way, the receptacle is shot...replace it with a new, quality one, not a builder's special. A good one does cost more, but it is not a break the bank thing.