Would level 1 "trickle charging" at work daily be okay

[ajdelange]

You're dreaming on 90% efficiency. There's probably 30% wasted to just keeping charging electrics and computers powered on. The power conversion factor might be 90% though...

My model X runs more like 92% most of the time. I just rounded to 90%.

There's probably 30% wasted to just keeping charging electrics and computers powered on. The power conversion factor might be 90% though...

Phantom drain is best accounted for by thinking of it in terms of lost miles or % SoC or kWh lost in a given time period rather than as an efficiency loss because it depends on the number of miles driven and when they are driven relative to charging. I'm an old gomer who doesn't drive very much so that my phantom drain of 4 kWh/d accounts, much of the time, for 50% or more of the kWh I put into the car over, say, a week. For someone who drives 100 mi per day it is more like 14%. For someone with a more typical 2 kWh/da phantom drain (what owners are seeing with the R1T after the OTA) it would be 7%.

Clearly phantom isn't included in the EPA numbers on the Monroney sticker and you don't want to include it in you decision making on the road because it isn't phantom drain when you are rolling. It is part of rated consumption then. But if you, for example, charge in the evening for a departure the next morning you need, using myself as an example, to account for the 2 kW hr lost to keeping the vehicle alive overnight. But when you calculate the wall kWh required to supply the car kWh you use the 92% effciency of the charger,

Sponsored

 

[ajdelange]

My response was in response to the benefits of L2 charging over L1 from a battery health perspective being present, but minimal.

Got it.

The issue with the BMS is without a minimal level of current, it has trouble achieving a proper battery balance. As long as you hit it with a L2 or a DC fast charger every once in a while you'll be ok, but for whatever reason the balancing of the batteries isn't as effectively achieved at super-low charge rates.

I'd have to know what "some reason" is. I, of course, have no idea what Tesla's balancing scheme is including when it is done and I am certainly no battery expert but I can't see any way in which the magnitude of the charging current would have an effect on the quality of balance.

Tesla for the same reason, accepts but does not recommend l1-only charging.

I do see in the (Tesla) owners manual an implied caveat against the excessive use of L3 charging but I do not see any similar caveat against excessive or even exclusive use of L1 charging in the manual nor have I ever seen such a caveat any where. Are there such caveats in the Rivian manual? More info on this please!

Really though, the efficiency on this thing as a form of transportation, makes it a poor l1 charging choice.

What thing?

Further making things worse is the high charging overhead compared to traditional vehicle architectures (IE: Canbus-based Leaf, etc.)

What does the com bus have to do with charging overhead? Are you conflating phantom draiin with charging efficiency again?

 

[pc500]

Got it.

I'd have to know what "some reason" is. I, of course, have no idea what Tesla's balancing scheme is including when it is done and I am certainly no battery expert but I can't see any way in which the magnitude of the charging current would have an effect on the quality of balance.

I do see in the (Tesla) owners manual an implied caveat against the excessive use of L3 charging but I do not see any similar caveat against excessive or even exclusive use of L1 charging in the manual nor have I ever seen such a caveat any where. Are there such caveats in the Rivian manual? More info on this please!

This is not going to be published anywhere, but has been mentioned in previous forums from conversations with Tesla service personnel. It's not common enough, nor drastic enough, to publish and confuse people with formal recommendations against (unlike l3), but the BMS needs higher amperage to effectively balance a pack of that size.




What does the com bus have to do with charging overhead? Are you conflating phantom draiin with charging efficiency again?

Are there such caveats in the Rivian manual? More info on this please!

This is not going to be published anywhere, but has been mentioned in previous forums from conversations with Tesla service personnel. It's not common enough, nor drastic enough, to publish and confuse people with formal recommendations against (unlike l3), but the BMS needs higher amperage to effectively balance a pack of that size.

What thing?

A Rivian R1t

What does the com bus have to do with charging overhead? Are you conflating phantom draiin with charging efficiency again?

The Rivian computers (and Tesla too) take a lot of power. I believe it takes some 500-700-watts to "activate" all the computers to support charging. When you're only pumping in 1.4kw, that's a lot of "waste" as a percentage of power delivered.

Compare that to vehicles that are not running real time operating systems (IE: Leaf, egolf, ID4) and use traditional Canbus architectures. They often only need 300 watts or so of "stuff" to activate the charging, resulting in more kwh/delivered to the vehicle battery per hour.

When you're 120v, you're loosing some 30-50% of your juice on a Rivian/Tesla, compared to a much lower figure on some other brand.

Combine with the poor efficiency (miles per KW), and its just a very poor l1-only vehicle.

 

[OrthoBlock]

My experience with charging an R1T with 110v is that it doesn’t really do anything. Best outcome is basically keeping the battery from discharging. Any actual charge increase is wishful thinking… your mileage may vary.

Ok, after some more experience with L1 charging, I will revise my statement above: It's possible to add sufficient charge overnight for short local commuting (10 - 20miles overnight).

For me, the big difference was turning off climate control, 110V outlets, etc, which allowed charge to accumulate.

 

[pklomboy]

Ok, after some more experience with L1 charging, I will revise my statement above: It's possible to add sufficient charge overnight for short local commuting (10 - 20miles overnight).

For me, the big difference was turning off climate control, 110V outlets, etc, which allowed charge to accumulate.

Good tip! I'm in between homes right now and would like to do a charger install once I finally move to my new home.

 

[ajdelange]

This is not going to be published anywhere, but has been mentioned in previous forums from conversations with Tesla service personnel. It's not common enough, nor drastic enough, to publish and confuse people with formal recommendations against (unlike l3), but the BMS needs higher amperage to effectively balance a pack of that size.

I was a practicing electrical engineer for 40 years. You cannot expect a professional to accept an assertion like this one based on the fact that yor brother in law's nephew heard it from a guy whose cousin used to work as a tech at Tesla. And it is not responsible of you to state the assertion as fact when you have no basis for it. You can say that you have heard that this is the case and where but you should not say it is true with no evidence.

The Rivian computers (and Tesla too) take a lot of power. I believe it takes some 500-700-watts to "activate" all the computers to support charging. When you're only pumping in 1.4kw, that's a lot of "waste" as a percentage of power delivered.

I think you are confused on energy (kWh) and power (kW). If by "activate" you mean "boot up" supposing that to require a minute to do and that it takes a minute to do you would use a kW-minute of 1/60th of s kWh. Surely you aren't suggesting thst the continuous computing load for managing charging is 500 - 700 W. That's absurd. The computers that do the heavy lifting in a Rivian wouldn't even be involved.

Now as I don't want to be a "Do as I say, not as I do" kind of guy I will clearly state that I am not familiar with the Rivian computing architecture. I make these statements based on the perspective gained by my many years as a practicing engineer and common sense (which is an important part of the engineer's toolkit).

When you're 120v, you're loosing some 30-50% of your juice on a Rivian/Tesla, compared to a much lower figure on some other brand.

Again it appears you are confused about phantom drain and efficiency. Phantom drain is a larger fraction of the charging rate when charging from a low power source than a higher powered one but it is there in any case even when you charge from a DCFC. It is true that the vehicle charger is somewhat less efficient at 120 than at 240 but that's a separate matter.

Combine with the poor efficiency (miles per KW), and its just a very poor l1-only vehicle.

Here it appears you are, again, confusing energy and power as well as efficiency with consumption. Efficiency is the ratio of (in this case) power out to power in. E.G. the charger in the cars which may put out 920 kW when the input is 1000 W (92% efficient) at 240 V but only 750W if the input is 1000W at 120 V (75% efficiency). Miles per kWh (note kWh i.e. energy, not power) is the reciprocal of the car's energy consumption per mile i.e. kWh/mile.

Certainly the mobile "charger" plugged into a 5-15 receptacle would not be most people's first choice for charging but it is satisfactory for quite a few. The main objection is that it takes a long time to add significant miles. The claim that you can't balance you battery if you use it is probably (a good engineer never says "defintiely" or "never") pure BS. It will be lossier (less efficient) than if operated at 240. It will not cause more phantom drain.
.

 

[pc500]

I'll try to simplify the second point greatly:

If I drive a Rivian or Tesla, and I charge "10kw" total power delivered at 1.5kwh, 7-8kw make it into the battery.
If I drive a leaf, bolt, or probably any number of other cars, closer to 9kw make it into the battery.

On the other hand if I charge at 6kw, the variance between the two is much much less.

And yes, those computers stay on while charging (or whatever else leads to the efficiency loss). . I can tell you the display remains full on, with the Rivian saying it's delivering 1kw (if its accurate).

I was a practicing electrical engineer for 40 years. You cannot expect a professional to accept an assertion like this one based on the fact that yor brother in law's nephew heard it from a guy whose cousin used to work as a tech at Tesla. And it is not responsible of you to state the assertion as fact when you have no basis for it. You can say that you have heard that this is the case and where but you should not say it is true with no evidence.



I think you are confused on energy (kWh) and power (kW). If by "activate" you mean "boot up" supposing that to require a minute to do and that it takes a minute to do you would use a kW-minute of 1/60th of s kWh. Surely you aren't suggesting thst the continuous computing load for managing charging is 500 - 700 W. That's absurd. The computers that do the heavy lifting in a Rivian wouldn't even be involved.

Now as I don't want to be a "Do as I say, not as I do" kind of guy I will clearly state that I am not familiar with the Rivian computing architecture. I make these statements based on the perspective gained by my many years as a practicing engineer and common sense (which is an important part of the engineer's toolkit).


Again it appears you are confused about phantom drain and efficiency. Phantom drain is a larger fraction of the charging rate when charging from a low power source than a higher powered one but it is there in any case even when you charge from a DCFC. It is true that the vehicle charger is somewhat less efficient at 120 than at 240 but that's a separate matter.

Here it appears you are, again, confusing energy and power as well as efficiency with consumption. Efficiency is the ratio of (in this case) power out to power in. E.G. the charger in the cars which may put out 920 kW when the input is 1000 W (92% efficient) at 240 V but only 750W if the input is 1000W at 120 V (75% efficiency). Miles per kWh (note kWh i.e. energy, not power) is the reciprocal of the car's energy consumption per mile i.e. kWh/mile.

Certainly the mobile "charger" plugged into a 5-15 receptacle would not be most people's first choice for charging but it is satisfactory for quite a few. The main objection is that it takes a long time to add significant miles. The claim that you can't balance you battery if you use it is probably (a good engineer never says "defintiely" or "never") pure BS. It will be lossier (less efficient) than if operated at 240. It will not cause more phantom drain.
.

 

[ajdelange]

If I drive a Rivian or Tesla, and I charge "10kw" total power delivered at 1.5kwh, 7-8kw make it into the battery.

OK. This confirms my suspicion that you do not understand power and energy. The kWh is a unit of energy. The kW a unit of power which describes how fast the energy is transferred. If you think of energy as water the kWh is like a gallon and the kW the flow - gallons per hour. And indeed kWh per hour would be written kWh/h. The hours cancel and kW are left.

The magnitude of a charge is a given amount of energy. You don't charge power. You charge energy. Thus your sentence should read something like "If I drive a Rivian or Tesla, and charge 10 kWh total power energy delivered at 1.5 kW", 9 kWh would make it to the battery. I corrected the delivered quantity to more realistically reflect what a Tesla would do with it's nominally 90% charging efficiency. Here is report based on measurements made by the car on yesterday morning's charging session:

This report shows that the charger took 4.39 kWh from the wall and delivered 89.1% of them (3.91 kWh) to the battery.

If I drive a leaf, bolt, or probably any number of other cars, closer to 9kw make it into the battery.

If the charger has the same efficiency (90%) as the Tesla's then, yes, the same amount of energy would wind up in the battery.

You MUST understand these concepts in order to be able to discuss the way BEV work. Until you do there is really little point in me trying to educate you on it.

On the other hand if I charge at 6kw, the variance between the two is much much less.

With your confusion over power and energy I don't know whether you mean if you deliver 6 kWh energy to the charger or deliver power at a 6 kW rate. Whichever you mean Tesla, RIvian or any other BEV with chargers of about 90% efficiency will load about 5.4 kWh per hour of charging. In any case there would be no difference between the Rivian/Tesla and any one of the other cars (provided they had 90% efficient chargers).

And yes, those computers stay on while charging (or whatever else leads to the efficiency loss). .

As I said several posts ago I think you are conflating phantom drain and charging efficiency. They are not related. If I go out to the car, turn on the A/C and the radio and sit there reading the manual I use energy. If the car is plugged in that energy comes from shore power. If I am not it comes from the battery and gets logged as phantom drain. If I am charging that does not get logged as phantom drain because it isn't coming from the battery. In no case does it get counted in calculating the charging efficiency. But I do have to count it if I want to calculate my annual total electrical consumption by the vehicle. That's why it is accounted for separately.

If I am plugged in, sitting in the car with the A/C running and the A/C draws power at a 2 kW rate and the pipe into the car can only carry energy at the rate of 1.44 kWh per hour then the pipe can't supply the A/C and it will take the extra it needs from the battery. Obviously I wouldn't be able to charge from that pipe while the phantom load is so high so the obious conclusion is that if you want to charge through a small pipe don't try to do it if phantom load is high.

Again, you will have to understand this if you want to understand how BEV systems work.

I can tell you the display remains full on,

I cannot speak to the Rivian as I haven't got one but I can to the Tesla. The displays do not stay on during charging (the driver's display comes on for a couple of minutes indicating that charging is starting and then goes off). It is totally absurd to assume that the FSD or Infotainment computers would run during charging.

with the Rivian saying it's delivering 1kw (if its accurate).

If the display is on and the power meter says there is a kW phantom drain then that's not a good time for charging through a thin pipe, is it? It has been widely recognized and whiged about here that the early release Rivian's had terrible phantom drain and that something needed to be done about it. Apparently something has been done though software OTA as reported phantom drain is much better than it used to be.

REPRISEhanton drain is not counted as part of charging efficiency but rather accounted for separately.

 

[pc500]

We got the units mixed up, but I think you're still missing the underlying point. I do not consider phantom drain that only occurs during charging as different from charging efficiency. If the drain only happens during charging, it's part of end to end charging efficiency.

The example you gave at 240v is not valid as I'm talking about L1.

Point is... There's significant downside in l1 charging in Tesla/rivian that does not exist in the other cars. You can rerun these examples at 200-300w loss for say, a leaf, and you'll see the percentage difference. That is loss per hour of charging time period, not loss per kWh power delivered.

Of course.rhe actual energy conversion loss is additive.




120v / 1440w - 540w loss = 900w is available to go in the battery in 1 hour.
This means only 900/1440 = 62.5% of the available power goes to the battery.

When the available power goes up, those constant system loss stays the same and charging efficiency usually increases too based on a curve. So using the same example above assuming same efficiency we get this example:

So a
240v / 2880w - 540w loss = 2340w is available to go in the battery in 1 hour
This means only 2340/2880 = 81.25% of the available power goes to the battery

Now this number increases up to a particular point where the charging efficiency starts dropping and being a bigger impact than the system loss. There was another thread where an individual determined that 25-30A @ 240v seems to be peak efficiency. Far below the max 48A input capacity of the Model 3 LR, but still reasonably fast. The overall efficiencies at those points is between 88 to 97% efficient.

OK. This confirms my suspicion that you do not understand power and energy. The kWh is a unit of energy. The kW a unit of power which describes how fast the energy is transferred. If you think of energy as water the kWh is like a gallon and the kW the flow - gallons per hour. And indeed kWh per hour would be written kWh/h. The hours cancel and kW are left.

The magnitude of a charge is a given amount of energy. You don't charge power. You charge energy. Thus your sentence should read something like "If I drive a Rivian or Tesla, and charge 10 kWh total power energy delivered at 1.5 kW", 9 kWh would make it to the battery. I corrected the delivered quantity to more realistically reflect what a Tesla would do with it's nominally 90% charging efficiency. Here is report based on measurements made by the car on yesterday morning's charging session:

This report shows that the charger took 4.39 kWh from the wall and delivered 89.1% of them (3.91 kWh) to the battery.


If the charger has the same efficiency (90%) as the Tesla's then, yes, the same amount of energy would wind up in the battery.

You MUST understand these concepts in order to be able to discuss the way BEV work. Until you do there is really little point in me trying to educate you on it.


With your confusion over power and energy I don't know whether you mean if you deliver 6 kWh energy to the charger or deliver power at a 6 kW rate. Whichever you mean Tesla, RIvian or any other BEV with chargers of about 90% efficiency will load about 5.4 kWh per hour of charging. In any case there would be no difference between the Rivian/Tesla and any one of the other cars (provided they had 90% efficient chargers).


As I said several posts ago I think you are conflating phantom drain and charging efficiency. They are not related. If I go out to the car, turn on the A/C and the radio and sit there reading the manual I use energy. If the car is plugged in that energy comes from shore power. If I am not it comes from the battery and gets logged as phantom drain. If I am charging that does not get logged as phantom drain because it isn't coming from the battery. In no case does it get counted in calculating the charging efficiency. But I do have to count it if I want to calculate my annual total electrical consumption by the vehicle. That's why it is accounted for separately.

If I am plugged in, sitting in the car with the A/C running and the A/C draws power at a 2 kW rate and the pipe into the car can only carry energy at the rate of 1.44 kWh per hour then the pipe can't supply the A/C and it will take the extra it needs from the battery. Obviously I wouldn't be able to charge from that pipe while the phantom load is so high so the obious conclusion is that if you want to charge through a small pipe don't try to do it if phantom load is high.

Again, you will have to understand this if you want to understand how BEV systems work.


I cannot speak to the Rivian as I haven't got one but I can to the Tesla. The displays do not stay on during charging (the driver's display comes on for a couple of minutes indicating that charging is starting and then goes off). It is totally absurd to assume that the FSD or Infotainment computers would run during charging.




If the display is on and the power meter says there is a kW phantom drain then that's not a good time for charging through a thin pipe, is it? It has been widely recognized and whiged about here that the early release Rivian's had terrible phantom drain and that something needed to be done about it. Apparently something has been done though software OTA as reported phantom drain is much better than it used to be.

REPRISEhanton drain is not counted as part of charging efficiency but rather accounted for separately.

 

[ajdelange]

I do not consider phantom drain that only occurs during charging as different from charging efficiency.

Fortunately the industry sees the folly in that. The charger in my Tesla has about 80% efficiency at 120V. 1440W in; 1152 out. If I choose to charge through a 1440W hose and take half that to run the cabin heater then I've only got 720W left to charge the battery. Does my foolish decision mean the charger is only 40% efficient? No. It is still 80% efficient.

As long as you persist in adhering to your own unique standard you are going to remain orthogonal to the rest of us. And, the thing we worry about, is transferring your misinformation to those new to BEV.

 

[pc500]

Fortunately the industry sees the folly in that.

I'm not sure what you're trying to say, but you have a set of electronics necessary to achieve charging. Those electronics are only necessary to achieve charging, during the charge session. Is the set of electronics necessary which lead to a variance of kwh measured at the plug and kwh delivered into the battery not charge efficiency?

By and far, the people on this forum are considering phantom drain as loss from parking the vehicle over night, and not a charge efficiency issue. I am not trying to address the engineering beyond this -- this is a product issue. Two cars, with the same EPA MPGe, would cost a customer 10-20% more to drive charging on l1 if its a Tesla/Rivian.

At the end of the day, the customer will charge for "x" hours, have "y" usable charge in kwh if they were to start driving immediately when the charge is complete, and pay "z+y" to the power company. That "z", or efficiency loss, is 10-20% greater at 120v charging. Or 5-10% on other vehicles. If they charge at l2/240v, that "z" is much less.

 

[RivianBowerbird]

Just remember that with EVs it is best if you leave them plugged in when you are not using them. The Rivian manual will tell you this as does the Tesla manual.

 

[ajdelange]

At the end of the day, the customer will charge for "x" hours, have "y" usable charge in kwh if they were to start driving immediately when the charge is complete, and pay "z+y" to the power company. That "z", or efficiency loss, is 10-20% greater at 120v charging. Or 5-10% on other vehicles. If they charge at l2/240v, that "z" is much less.

As I'm not having much success in getting you up to speed on thing like power and energy nor phantom drain and efficiency I will finalize by saying that if one charger is 10% less efficient than another then the driver using the 10% less efficient will have overall electricity cost 10% higher than the baseline guy. Totally independent of that fact is that if one driver's vehicle has 10% higher phantom drain than a baseline car he will pay 10% more for phantom drain electricity than the baseline driver.

The Rivian is a luxury car. It does things like sense when the driver walks up to it. The sensing requires sensors. They use energy. This causes phantom drain. That's really all there is to it.

 

[ajdelange]

I'm resurrecting this briefly because I know there are some here who do understand and I thought they (as was I) might be interested in the actual efficiency of the car's charger when it's input is 120V. Unfortunately I don't have a Rivian charger to test but I do have a Tesla. I plugged the UMC into a Yeti6000 and sent 1301 Watts into it for 3 hr 11 minutes which means 4.14 kWh of AC went into the car. According to TeslaFi 3.06 kWh wound up in the battery. Dividing those two numbers gives 0.7389 which says that the efficiency of the CHARGER is AT LEAST 73.89%. It would be exactly that if all that input power went to the charger but not all of it does. ON AVERAGE 167W goes to phantom drain. The problem is that we don't know what the phantom drain is over any particular 3 hour period. Thus the best we can do to rough in an upper bound is use that average number. If we use that number with the 3hr 11 min duration of the test in the supposition that 3 hr is long enough that the average phantom drain in that time period is close to that of the 24 hr average (167 W) that would give us 0.53 kW to allocate to phantom drain which gives us an efficiency estimate of 3.06/(4.14 - 0.53) = 84.78%. So the efficiency of the charger is probably around 80% when it is fed 120V as opposed to around 90% when fed 240. If these numbers are reasonable for the Rivian owner as well one who drives the average 10,000 miles/yr at .500 kWh/mi would use 5,556 kWh worth $722.22 (avg. US cost of 13¢/kWh) at 90% efficiency and 6,250 kWh worth $812.50 - a difference of $90.28 all per year, at 80% efficiency.

Thus there is a small apparent loss in efficiency if charging at 120 but nothing near so dramatic as some have claimed here. All the caveats about single experiment, limited data, etc.. of course apply but common sense tells those of us with experience in such matters that any efficiency loss should be modest. The major problem with 120V charging is, of course, that it is slow. It took me over 3 hr to add 11 miles to my X. In a Rivian at twice the consumption one would only add 5.5 in that time span. But if 120 is all that's available and you have the time then 120V charging is fine as many have demonstrated.

Sponsored