Charging on a 3 prong 240 outlet

[RiviEra]

I have an old 3 prong 240 outlet. Do I just buy an adapter to convert to a 4 prong to use the portable charger on my R1S? Any thing else I would need?

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[Thedude]

You’ll need to check the specifics for that plug’s rated amperage and the breaker that feeds it. You may need to manually set the amps in the truck prior to initiating charging to keep it safe.

You can find a variety of EV adapters on various websites and Amazon so that should be easy. Example - https://acworks.com/collections/adapters-for-tesla/tesla-adapter

 

[Zoidz]

It's not the best or safest thing to do. You should be aware of a number of issues:
1) This is probably a dryer outlet. They were not physically designed for frequent plug/unplug operation. The outlet will not hold up over the long term.
2) It's very possible that it is a 30 amp circuit - wiring and circuit breaker. The Electrical Code specifies, for your fire safety, that you can only draw 80% of the rated circuit power. So you need to manually ALWAYS set the vehicle to draw 24 Amps or less, which means it will take longer to charge. Otherwise there is a very real risk of overheating and fire hazard. You REALLY need to determine the breaker and wire size to set the proper charging rate.
3) Provided you consider the above, an adapter will usually, but not always work.

It's a MUCH better and safer plan to get an electrician in to evaluate the circuit and perhaps just upgrade it to a 50 amp circuit (new wires and breakers) if feasible, especially if the breaker panel is nearby.

 

[ndmiller]

Get a NEMA plug installed on a 50 amp breaker and get a charge point flex. 25 miles of recharge per hour. Easy to overnight charge from zero if you really need to.

 

[DeanB1452]

Since last May, I’ve been using my 30-amp dryer outlet. The outlet hasn’t been used in 20 years since I converted the dryer to gas. I have a 50-ft NEMA 10-30 extension cord running from the washer/dryer area, up and over the side door in the garage and drops down at the front of the garage. I have a holster mounted to the wall for my portable charger. I have an adapter that connects the charger with the extension cord. Haven’t had any problems with it. Remember the 80% rule and set your Rivian to draw 24 amps on a 30-amp circuit. I’m still waiting on work to be done to install a dedicated 60-amp circuit for my 48-amp wall charger.

 

[MacO512]

Since last May, I’ve been using my 30-amp dryer outlet. The outlet hasn’t been used in 20 years since I converted the dryer to gas. I have a 50-ft NEMA 10-30 extension cord running from the washer/dryer area, up and over the side door in the garage and drops down at the front of the garage. I have a holster mounted to the wall for my portable charger. I have an adapter that connects the charger with the extension cord. Haven’t had any problems with it. Remember the 80% rule and set your Rivian to draw 24 amps on a 30-amp circuit. I’m still waiting on work to be done to install a dedicated 60-amp circuit for my 48-amp wall charger.

There aren't any EV chargers that are approved to work on an extension cord.

I'd probably use one temporarily such as traveling. I would not use one for normal regular charging. You lose the safety of the heat sensor in the plug. Also add resistance (thus heat) as well as more points of failure with additional connection points.

 

[MacO512]

I have an old 3 prong 240 outlet. Do I just buy an adapter to convert to a 4 prong to use the portable charger on my R1S? Any thing else I would need?

Assume this is a nema 10-30 old dryer outlet, or 10-50 stove. If it's a 10-50 might be simple to change to a 6-50 receptacle. Tesla portable charger has a plug to work with the 10-30. If you don't have that you can probably buy an evse charger with a 10-30 plug. Rivians charger kind of sucks and doesn't have adapters or a 30amp one. I wouldn't use an adapter for regular charging as then you don't have the evse plug temperature sensor on the receptacle nor the correct amp limit. I'd also be concerned of the old wiring not being strong enough for 80% many hours long continuous charging. But if you can see the wire is a good quality copper of a large gauge, with a quality breaker termination and quality industrial level receptacle it could work.

Probably best to replace the receptacle if it's old or inexpensive non industrial quality one.

Now in terms of what can "work" yeah an adapter or using old or nonEV quality receptacle will charge the car. There is a lot of risk of melted plus or fires, often many months down the road. Internet is full of pictures of this, search for home Depot leviton outlet EV failures.

 

[240vPlug]

We need more info. What type of 3 prong plug? Can you post a pic of it?

You need to know if its a 30 amp or 50 amp circuit. Also, I would still have an electrician inspect this plug to make sure it is safe for a continuous load for many hours.

As I always say, if this is a permanent home charging install the best and safest way to do it is to hard wire a quality home charger.

I have two videos on my website showing my home charging setup & showing how I installed my Tesla Wall Connector. https://www.electrifiedoutdoors.com/ev-charging

 

[racekarl]

Another consideration is that a 3 prong outlet means there may be no ground, and there have been reports of failure to charge (especially from the Rivian EVSE) when there isn't a stable ground potential.

 

[Blueassassin]

I run my truck with the mobiil charger on my 30a welder / dryer outlet no issues. If you run at full amps "which you shouldn't" the breaker will start getting warm. I tested this for science

 

[jb0063]

I have an old 3 prong 240 outlet. Do I just buy an adapter to convert to a 4 prong to use the portable charger on my R1S? Any thing else I would need?

Better to replace the acceptable. You want to be sure the tongs that receive the plug are tight and not loose. A loose connection can cause arcing, which can cause a major fire. I had it happen to me with my R1T, using an older dryer receptacle with the portable charger. Luckily, I smelled the melting plastic inside the receptacle before it burned any further.

 

[hilld]

The fact that it is 3 prong vs. 4 prong is a non-issue, make sure you get a plug that is the correct amperage and set the charger to match that amperage. I have opened up many EVSE chargers (to hardwire them) and none of them (the ones I have opened up) use the neutral wire (4th prong), the use L1, L2 (hots) and ground only.

Personally I think that Nema 14-50 (4 pin) was chosen vs Nema 6-50 (3 pin) as the defacto standard is that 14-50's outlets are present in many locations such as RV parks. But you can generally buy chargers with either a 14-50 or 6-50 plug, which should indicate that the neutral wire is not used.

 

[Zoidz]

The fact that it is 3 prong vs. 4 prong is a non-issue, make sure you get a plug that is the correct amperage and set the charger to match that amperage. I have opened up many EVSE chargers (to hardwire them) and none of them (the ones I have opened up) use the neutral wire (4th prong), the use L1, L2 (hots) and ground only.

Personally I think that Nema 14-50 (4 pin) was chosen vs Nema 6-50 (3 pin) as the defacto standard is that 14-50's outlets are present in many locations such as RV parks. But you can generally buy chargers with either a 14-50 or 6-50 plug, which should indicate that the neutral wire is not used.

The fact that it is 3 prong vs. 4 prong can be an issue. The Rivian portable EVSE has GFCI built in. Depending on what the built in GFCI "sees" it has been known to nuisance trip on 3 wire connections. That's been discussed here in the past, and that's why I said in my first post that it may work, but not always.

 

[hilld]

The fact that it is 3 prong vs. 4 prong can be an issue. The Rivian portable EVSE has GFCI built in. Depending on what the built in GFCI "sees" it has been known to nuisance trip on 3 wire connections. That's been discussed here in the past, and that's why I said in my first post that it may work, but not always.

Fair enough, but portable ones are a special case as they are designed to run on both 120V (neutral required) and 240V (2 hots). I was making my statements on permanent (non-portable) EVSE's.

 

[Zoidz]

Fair enough, but portable ones are a special case as they are designed to run on both 120V (neutral required) and 240V (2 hots). I was making my statements on permanent (non-portable) EVSE's.

Agree, just clarifying since OP's post specified portable Rivian charger.

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