Charging with 110

[jaygeewin]

I recently got a 240v outlet installed so I can use the NEMA 14-50 plug to charge. Before this, I was using the regular wall outlet to charge. I was getting 3 miles per hour. Lol.

 

[eevee-fan]

I'm going to say yes... you're dumping almost 1kwh into the wires/outlets in that circuit. If you're using a really long run that heat's spread out over a lot of wire and probably not much to worry about, but even so I'd find someone with a thermal camera and see what's heating up.

Long run is actually bad. Otherwise, we should all make our electrical runs loop around the house a few times.

 

[cduzz]

Long run is actually bad. Otherwise, we should all make our electrical runs loop around the house a few times.

Well, losing 1kwh in a 300 foot run is bad, losing it in a nema 15-40 is a fire. So... there are degrees of bad...

Lots of this math is similar to "should I buy my cable modem?" -- depending on an complex array of short and long term costs and savings, it may or may not make sense. Similarly, investing $200 for N% improvement in charging vs investing $5000 for N*2 % improvement depends on lots of factors.

A long thin cable with lots of heat loss may be fine if the alternative is trenching through your driveway...

 

[cduzz]

You need to go to Skillshare and take some lessons on electricity. Or you can go pick up a pack of extension cord at the store and read the labels. Longer runs tend to make the wire run hotter. .. meaning shorter run would run much cooler.

I appreciate your interest in my education!

My understanding is that the current carrying capacity of a wire is based on the gauge of the wire and the insulation of the wire. Narrow wires have more resistance and thus heat up more than larger gauge wires for the same current. Also some wires such as those made of aluminum will have higher resistance than others for the same length of wire and so will have a different current rating.

The thing we don't want to happen is for the insulation of the wire to fail. That typically happens when the wire gets so hot it damages the insulation, but sometimes it happens if the wire is chemically or physically attacked. It also happens at junctions where you can have poor mechanical junctions. The areas with higher resistance will heat up and typically that heat causes even more resistance and you have a thermal runaway and the wire melts (or it trips a circuit breaker). If the higher resistance is spread across a large surface area, you just get ... heat, which is wasteful but not specifically dangerous unless there is so much that it harms the insulation. Another concern may be heat cycles where junctions will work their way loose and you then get an under-speced joint (see thermal runaway). Heat cycles are especially a concern if you're joining dissimilar elements (aluminum/copper) as they'll expand at different rates and potentially work their way loose and (see thermal runaway).

So a wire with insulation that copes with high heat may be allowed to have a narrower gauge. Let's say your contractor put some narrow gauge but high temperature wire under your driveway. It is "safe" but will heat up more than is "ideal" but if the alternative is to dig up the driveway, you may just live with it. Just like an extension cord may heat up over a long run (and cause a voltage drop!) but it is fine because you want to plug your Christmas lights in and there isn't a convenient plug on this side of the house.

Oh, and you shouldn't test a circuit by licking it.

How'd I do?

 

[eevee-fan]

Bad.

Compare:
#16 wire pushing through 120V @ 8A for 3 ft (AKA Short).
#16 wire pushing through 120V @ 8A for 300 ft (AKA Long).

Which one will burn the house down?

 

[cduzz]

Bad.

Compare:
#16 wire pushing through 120V @ 8A for 3 ft (AKA Short).
#16 wire pushing through 120V @ 8A for 300 ft (AKA Long).

Which one will burn the house down?

According to
Wire Ampacity Chart with Rated Amperage - StayOnline Ampacity Chart
if the insulators are "SVT" whatever that is, neither will fail. Otherwise, you're exceeding the rating of the long wire and will (probably/maybe) cause something to fail. The 16 gauge wire will get hot and is a terrible idea, regardless, for this application.

You'll note that Ampacity Charts - Cerrowire has different current ratings for the same gauge wire depending on the insulation. There are modifications to how these different current ratings are applied depending on how/where the wires are run, but the point is that "it is fine, in some circumstances, for long wires to get hot" The operative word is "fine" not "good".

I'm not sure I understand what you're selling here. I would much rather dump 1kwh over a long wire than into a nema 15-50 receptacle. It is perfectly possible to have a long wire that "safely" has a voltage drop as discussed above. It isn't really possible to dump 1kwh into a receptacle or junction and have it survive for more than a brief flash.

Neither is good.

 

[eevee-fan]

My point is that this will lead people to think long runs are better. For a given draw, you want the shortest run possible to reduce heat on the wires.

Agreed, neither is good.

 

[specialgreen]

I believe that 20a/240 would cover the vast majority of my needs

Agreed. I had a detached garage with a dedicated 20 amp outlet I could repurpose (with 12/2 wiring), so the breaker was swapped for 2-pole, and I charge at 16A 240v = ~12.8 miles/hr., or 100 to 150 miles per night. I average less than 125 miles per day, so it's not a problem. To go beyond that, I would either need to trench a new feeder (& probably upgrade the house to 200A), or have a second utility service added in the garage.

 

[Cosmacelf]

Agreed. I had a detached garage with a dedicated 20 amp outlet I could repurpose (with 12/2 wiring), so the breaker was swapped for 2-pole, and I charge at 16A 240v = ~12.8 miles/hr., or 100 to 150 miles per night. I average less than 125 miles per day, so it's not a problem. To go beyond that, I would either need to trench a new feeder (& probably upgrade the house to 200A), or have a second utility service added in the garage.

Out of curiosity, did that garage have a separate circuit for light(s) and/or another receptacle?

 

[EVDRVN]

I appreciate your interest in my education!

My understanding is that the current carrying capacity of a wire is based on the gauge of the wire and the insulation of the wire. Narrow wires have more resistance and thus heat up more than larger gauge wires for the same current. Also some wires such as those made of aluminum will have higher resistance than others for the same length of wire and so will have a different current rating.

The thing we don't want to happen is for the insulation of the wire to fail. That typically happens when the wire gets so hot it damages the insulation, but sometimes it happens if the wire is chemically or physically attacked. It also happens at junctions where you can have poor mechanical junctions. The areas with higher resistance will heat up and typically that heat causes even more resistance and you have a thermal runaway and the wire melts (or it trips a circuit breaker). If the higher resistance is spread across a large surface area, you just get ... heat, which is wasteful but not specifically dangerous unless there is so much that it harms the insulation. Another concern may be heat cycles where junctions will work their way loose and you then get an under-speced joint (see thermal runaway). Heat cycles are especially a concern if you're joining dissimilar elements (aluminum/copper) as they'll expand at different rates and potentially work their way loose and (see thermal runaway).

So a wire with insulation that copes with high heat may be allowed to have a narrower gauge. Let's say your contractor put some narrow gauge but high temperature wire under your driveway. It is "safe" but will heat up more than is "ideal" but if the alternative is to dig up the driveway, you may just live with it. Just like an extension cord may heat up over a long run (and cause a voltage drop!) but it is fine because you want to plug your Christmas lights in and there isn't a convenient plug on this side of the house.

Oh, and you shouldn't test a circuit by licking it.

How'd I do?

Never use wire in a wall and rely on the insulation rating as the factor, never.

 

[EVDRVN]

.... why would a fire start if you start charging at 110v? Resistance + Current makes heat. The car limits current to what the line can handle. If the resistance is low there's no heat.

Like I said... it's voltage DROP that's important. If you're pulling 12A and voltage drops from 125 to 110v that's 180w being dumped somewhere. If voltage drops from 110v to 108v that's ~24w being dumped somewhere. It's voltage DROP that's the critical value.

For starters there is no 110V in the USA it is 120/240V and there has not been for a very long time. Voltage drop is not the sole issue, 120V circuits are not designed for constant loads like an EVSE which is why they need to be on a dedicated circuit and many are not. Secondly there are many failure points on a 120V circuit as the outlets tend to be worn, have loose connections or poor quality outlets. The heating and cooling of repeated constant loads also can cause terminal connections to come loose and this causes increased resistance. Common at breaker panels. In reality no one should be using a shared 120V circuit to charge an EV, this is just bad advice and has more downstream issues. If the circuit is dedicated it is better to convert to a 6-20R and use on 240V and even at say 12A if you can for safety. Even the 6-20 is not a great outlet solution as they are not as robust as other 240V outlets. This still give you more than double the charge speed and a much safer setup. Never use extension cords, they fail and that includes short "good" ones as they are not built well. Never use a long run 120V circuit and when in doubt hire a licensed and experienced electrician not a handyman and not a journeyman.

 

[cduzz]

Never use wire in a wall and rely on the insulation rating as the factor, never.

Thank you for that clarification -- yes it is my understanding that running a wire where the current is based on heat-tolerant insulation has a large number of provisions (in a conduit with other wires, in a wall, etc). I didn't mention that even though I should have.

To be honest insulation rated wires seem like a dicey proposition in almost any situation. I can imagine uses, but I'd have to work pretty hard to justify them.

Regardless, I suspect that code is not actually completely reasonable for EV charging -- there are too many areas where running a circuit at 80% of maximum capacity for hours at a time will expose imperfections, especially once you wander past 30a. I suspect there will be added provisions (with the teeth of "insurance companies will deny claims") for things like "NEMA attached devices may only draw 60% of the circuit/plug's rating" (see also: 32a on a NEMA 15-50).

 

[EVDRVN]

Thank you for that clarification -- yes it is my understanding that running a wire where the current is based on heat-tolerant insulation has a large number of provisions (in a conduit with other wires, in a wall, etc). I didn't mention that even though I should have.

To be honest insulation rated wires seem like a dicey proposition in almost any situation. I can imagine uses, but I'd have to work pretty hard to justify them.

Regardless, I suspect that code is not actually completely reasonable for EV charging -- there are too many areas where running a circuit at 80% of maximum capacity for hours at a time will expose imperfections, especially once you wander past 30a. I suspect there will be added provisions (with the teeth of "insurance companies will deny claims") for things like "NEMA attached devices may only draw 60% of the circuit/plug's rating" (see also: 32a on a NEMA 15-50).

EVSE wire is often rated for higher heat but it is outside the wall of course. EV charging is easy, put in a proper outlet and don't use 120V for primary charging only as a last result or when you are stuck somewhere.

 

[eevee-fan]

Thank you for that clarification -- yes it is my understanding that running a wire where the current is based on heat-tolerant insulation has a large number of provisions (in a conduit with other wires, in a wall, etc). I didn't mention that even though I should have.

To be honest insulation rated wires seem like a dicey proposition in almost any situation. I can imagine uses, but I'd have to work pretty hard to justify them.

Regardless, I suspect that code is not actually completely reasonable for EV charging -- there are too many areas where running a circuit at 80% of maximum capacity for hours at a time will expose imperfections, especially once you wander past 30a. I suspect there will be added provisions (with the teeth of "insurance companies will deny claims") for things like "NEMA attached devices may only draw 60% of the circuit/plug's rating" (see also: 32a on a NEMA 15-50).

50A breaker+wire+receptacle for 32A EVSE is probably a good recommendation. That's what I thought when I had my 240V installed. If you need faster charging than 32A, probably time to get a DC charger installed.

 

[EVDRVN]

50A breaker+wire+receptacle for 32A EVSE is probably a good recommendation. That's what I thought when I had my 240V installed. If you need faster charging than 32A, probably time to get a DC charger installed.

Good advice, This is more than adequate in fact most people over size their charging needs.

 

[Evstrat]

Have only had my model S for one month and was intending to only use superchargers but have now read it is recommended to charge constantly. Will charging at home on a 110 and also using the superchargers when I want quicker charging be ok to maintain the battery?

120 volts, not 110. And here come the cows, moseying on home. I've made no argument for 120v over 240v, that wasn't the point. Use whatever you want, what works for your situation and what is convenient. In truth, it makes no difference for battery life, 120v 16 amps or 240v 48 amps, for example, slow is slow, how patient can you afford to be? I wouldn't go out of my way to use a 120v circuit but if that's what you have and it serves your needs/works in your situation, no worries. There is no disadvantage to the 120v except speed, which as I said is exaggerated at low temperatures. The dogma here is a 240v circuit is a minimum for home charging. I don't disagree with that as a practical matter and for convenience. And if you are installing a circuit, by all means, install a 240v circuit. On the other hand if you need to use a 120v circuit and your circumstance allows, it's just fine.

If you have the time 110 is fine, it is also much better for your battery as it charges slowly and therefore much less battery degradation Compared to the 220 V system, although 220 is probably a bit more efficient and certainly more convenient.

 

[ucmndd]

If you have the time 110 is fine, it is also much better for your battery as it charges slowly and therefore much less battery degradation Compared to the 220 V system

I’m not sure why you bumped a 2.5 year old thread for this advice, but this is just false. I’d argue there’s precisely zero measurable difference in “battery degradation” between 120 and 240v AC charging of any speed.

 

[Cosmacelf]

I’m not sure why you bumped a 2.5 year old thread for this advice, but this is just false. I’d argue there’s precisely zero measurable difference in “battery degradation” between 120 and 240v AC charging of any speed.

Correct. If anything 120V charging is worse because it uses more energy (car systems must be on when charging, and these very little energy left over for actually charging the battery).

 

[dhanson865]

If you have the time 110 is fine, it is also much better for your battery as it charges slowly and therefore much less battery degradation Compared to the 220 V system, although 220 is probably a bit more efficient and certainly more convenient.

The US has been on 120v and 240v since sometime last century. Regular outlets are 120v unless you are in some weird sort of setup where there isn't modern electrical service. Occasionally you'll get someone that is on 3 phase power that has lower voltages on regular outlets because they are in a business setting (condos on the edge of a business district in Canada, or a loft apartment over a business in the US) but those are rare.

Any normal residential power outlet in North America should be 120v and it's relative is the 240v outlet.