4 ms·

How can round trip efficiency be 90%, when the one-way 240V charging losses to my Tesla alone are greater than that (at 83.61%)? Is it lack of three phase powe

How can round trip efficiency be 90%, when the one-way 240V charging losses to my Tesla alone are greater than that (at 83.61%)? Is it lack of three phase power in the US that is killing me?

orwin 6y ago
You can't ask for three phase power in the US? Surely it have to be there but restricted to business, no? I remember seeing laundries and restaurant in small towns
- selectodude 6y ago
  Large factories can get 480V 3 phase power in the US, but even laundries and restaurants get 240V “split phase” which is technically still single phase, just two power lines that would normally be going to two houses instead going to the same place. We have a very wonky power grid here due to how early on it was built. The rest of the world had the ability to see our mistakes and fix them after WW2.
  - rsynnott 6y ago
    I'm not sure if it's age so much as bad (in the long run) choices at the time. European power grids have been around for a while (and some have their own oddities; the historical use of ring circuits in UK and Ireland domestic installations produced lasting weirdness, for instance).
  - frosted-flakes 6y ago
    That's not quite correct. Any building in an industrial area could conceivably get three-phase power if it's on the poles along the road, not just large factories. My friend owns a small manufacturing shop (probably 6k to 8k square feet with less than 10 employees), and he has three-phase power. Also, all buildings in the US/Canada have split phase power, not just businesses like laundromats and restaurants. Split phase is one of the three 240 V phases split into two 120 V lines. Electric ranges, dryers, and baseboard heaters in residential buildings commonly use 240 V by utlizing both 120 V lines.
  - Obi_Juan_Kenobi 6y ago
    This is incorrect. Nearly all transmission and most distribution in the US is done with three phases. Commercial and industrial access to three phase is very common, though this will vary by region/utility. Residential access is less common, but not that unusual. In some places, you just call up the utility, tell them what equipment you'll be using (i.e. what amperage you'll require) and provided it's enough demand to justify it, they'll run the lines at no or minimal cost. Residential split phase is usually based on pole-mounted transformers that serve a limited number of customers. They are, themselves, operated off the three-phase distribution.
- PhantomGremlin 6y ago
  You can't ask for three phase power in the US? The USA has literally hundreds if not thousands of power companies. So the answer is "it depends". But it's not very popular for residential. If for no other reason than it gives you 120V/208V, whereas most high power appliances prefer/need 240V. In my experience you can get three-phase even in small towns for commercial/industrial. For example, I've seen it for water heaters in on-premises laundry rooms in apartment buildings. Up until "recently", you could even get DC power in NYC. Here's an article about its demise: https://www.trainorders.com/discussion/read.php?11,1541316 https://www.trainorders.com/discussion/read.php?11,1541316
  - wolfgang42 6y ago
    San Francisco still has a DC grid, and AFAIK no plans to shut it off: https://spectrum.ieee.org/tech-history/dawn-of-electronics/san-franciscos-secret-dc-grid https://spectrum.ieee.org/tech-history/dawn-of-electronics/s...
    - PhantomGremlin 6y ago
      That's a great article. HN loves to talk about "technical debt", but software problems pale in comparison to supporting power distribution decisions made 141 years ago. Harder to "refactor" copper cables than it is to rearrange lines of code. Still, they seem to have done a good job updating things while maintaining "backward compatibility".
_ph_ 6y ago
As far as I know, the charge efficiency in a Tesla is much better with 3 phases.
goodcanadian 6y ago
Wow! I'm amazed that the Tesla onboard charger is that inefficient. Anyway, we are not using Teslas, we are using Nissan Leafs. And, we are using DC charging. Our (single phase) inverter is >95% efficient making the round-trip >90% efficient. It is possible that there are some battery losses that are neglected in the calculation, but it is about right. Regardless, even 80% efficiency is comparable to pumped hydro, so I am not sure that 80% efficiency would be damning.

How can round trip efficiency be 90%, when the one-way 240V charging losses to my Tesla alone are greater than that (at 83.61%)? Is it lack of three phase power in the US that is killing me?

orwin 6y ago

You can't ask for three phase power in the US? Surely it have to be there but restricted to business, no? I remember seeing laundries and restaurant in small towns

selectodude 6y ago
Large factories can get 480V 3 phase power in the US, but even laundries and restaurants get 240V “split phase” which is technically still single phase, just two power lines that would normally be going to two houses instead going to the same place. We have a very wonky power grid here due to how early on it was built. The rest of the world had the ability to see our mistakes and fix them after WW2.
- rsynnott 6y ago
  I'm not sure if it's age so much as bad (in the long run) choices at the time. European power grids have been around for a while (and some have their own oddities; the historical use of ring circuits in UK and Ireland domestic installations produced lasting weirdness, for instance).
- frosted-flakes 6y ago
  That's not quite correct. Any building in an industrial area could conceivably get three-phase power if it's on the poles along the road, not just large factories. My friend owns a small manufacturing shop (probably 6k to 8k square feet with less than 10 employees), and he has three-phase power. Also, all buildings in the US/Canada have split phase power, not just businesses like laundromats and restaurants. Split phase is one of the three 240 V phases split into two 120 V lines. Electric ranges, dryers, and baseboard heaters in residential buildings commonly use 240 V by utlizing both 120 V lines.
- Obi_Juan_Kenobi 6y ago
  This is incorrect. Nearly all transmission and most distribution in the US is done with three phases. Commercial and industrial access to three phase is very common, though this will vary by region/utility. Residential access is less common, but not that unusual. In some places, you just call up the utility, tell them what equipment you'll be using (i.e. what amperage you'll require) and provided it's enough demand to justify it, they'll run the lines at no or minimal cost. Residential split phase is usually based on pole-mounted transformers that serve a limited number of customers. They are, themselves, operated off the three-phase distribution.
PhantomGremlin 6y ago
You can't ask for three phase power in the US? The USA has literally hundreds if not thousands of power companies. So the answer is "it depends". But it's not very popular for residential. If for no other reason than it gives you 120V/208V, whereas most high power appliances prefer/need 240V. In my experience you can get three-phase even in small towns for commercial/industrial. For example, I've seen it for water heaters in on-premises laundry rooms in apartment buildings. Up until "recently", you could even get DC power in NYC. Here's an article about its demise: https://www.trainorders.com/discussion/read.php?11,1541316 https://www.trainorders.com/discussion/read.php?11,1541316
- wolfgang42 6y ago
  San Francisco still has a DC grid, and AFAIK no plans to shut it off: https://spectrum.ieee.org/tech-history/dawn-of-electronics/san-franciscos-secret-dc-grid https://spectrum.ieee.org/tech-history/dawn-of-electronics/s...
  - PhantomGremlin 6y ago
    That's a great article. HN loves to talk about "technical debt", but software problems pale in comparison to supporting power distribution decisions made 141 years ago. Harder to "refactor" copper cables than it is to rearrange lines of code. Still, they seem to have done a good job updating things while maintaining "backward compatibility".

_ph_ 6y ago

As far as I know, the charge efficiency in a Tesla is much better with 3 phases.

goodcanadian 6y ago

Wow! I'm amazed that the Tesla onboard charger is that inefficient. Anyway, we are not using Teslas, we are using Nissan Leafs. And, we are using DC charging. Our (single phase) inverter is >95% efficient making the round-trip >90% efficient. It is possible that there are some battery losses that are neglected in the calculation, but it is about right. Regardless, even 80% efficiency is comparable to pumped hydro, so I am not sure that 80% efficiency would be damning.