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I have been working on Energy Monitoring for OpenEVSE and a standalone unit for other charging stations. Here is my progress so far...
The live data can be viewed and manipulated here:
Energy Monitoring Dashboard
The live data can be viewed and manipulated here:
Energy Monitoring Dashboard
I assume so - I didn't see an external power supply. Either way, it's not just a CT loop.
mknox
Well-Known Member
Right. You need current (from the CTs) and Voltage (from the connection to the power lines) in order to calculate Power (kW) and Energy (kWh).
Solarguy
Member
The description pictures on the ebay listing linked by the OP shows a 4 screw terminal block on the rear of the device. 2 for the CT and 2 for L1 and L2 voltage/power feeds.
Below are the results I have after a week of tracking. I charged each night to a 75% SoC, for 2 nights at each charge rate.
Charge Rate (Amps)----- Avg Calculated Efficiency
20 ----------------------------76.8%
30 ----------------------------80.1%
40 ----------------------------75.9%
My plan now is to spend a week or so at charge rates around 30 amps, to minimize variability in my numbers and try to really hone in on the most efficient charge rate.
Charge Rate (Amps)----- Avg Calculated Efficiency
20 ----------------------------76.8%
30 ----------------------------80.1%
40 ----------------------------75.9%
My plan now is to spend a week or so at charge rates around 30 amps, to minimize variability in my numbers and try to really hone in on the most efficient charge rate.
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green1
Active Member
Interesting. It has often been theorized that the most efficient is near the top of the charger's capacity, but not at it, the 30a range on a single charger makes sense there. (With dual chargers the 60-70 amp range)
What concerns me a bit is that even your highest efficiency seems a little lower than I expected (was expecting more like 90%). Do you tend to pre-heat/pre-cool? Or do any other energy use things that might not show up on the tests?
What concerns me a bit is that even your highest efficiency seems a little lower than I expected (was expecting more like 90%). Do you tend to pre-heat/pre-cool? Or do any other energy use things that might not show up on the tests?
I do very little, if any, pre-conditioning. I was also somewhat discouraged by the results, but didn't expect them to be as high as the 90% maximum that Tesla lists.
Can you publish your raw data and calculations? And what happened about this 257V read? Is it confirmed by another source?
I haven't officially verified it, but at the moment the meter reads 256v and car reads 254v.
My numbers can be found in this spreadsheet Model S Charger Efficiency - Google Sheets
My numbers can be found in this spreadsheet Model S Charger Efficiency - Google Sheets
It's the average of each individual nightly charge session's calculated efficiency. Calculated efficiency is the energy used (as reported by the car) / the incremental energy reported by the meter.
It hasn't been much of a concern before, as all of my charge sessions have been comparable, but I will probably want to eventually use the calculated efficiency of the summed energy values, rather than the average of efficiencies.
That's what I feared...remember, the car doesn't report energy use when the car isn't driving, so part of your 'inefficiency' is actually vampire drain.
I took note of how much kWh = 1% SOC, so when I calculate charging from x% to y% I'm seeing charging efficiencies consistently in the low 90s or upper 80s
If the "energy used" column is what the car says it used since last charge (or any other metric of what was used to actually drive the car) then I think your efficiency number is the total efficiency of both charging and driving. You'd have to use the energy delivered to the battery during charging as reported by the car to determine just the charging efficiency. In theory this wouldn't affect the determination of ideal charge rate, but I would personally try to remove the effect of any additional variables (like driving and vampire losses).
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I never paid attention to how to get that number but I just went out to the car to see where that would be for last night's charging session. Before you remove the charging cable, the charge screen tells you either miles added or kwh added on the left side of the charge bar. You can change your units to "Energy" instead of "Miles" in the settings if needed and go back to the charge screen as long as you haven't disconnected the charge cable yet.
earcandy
Member
For what it’s worth, I had a few notes regarding charging efficiency. I use a Blink EVSE that is capped at 24 amps. At the end of each charging session, it shows the kWh used, and then I compared it to the kWh added to the battery (as reported by the Remote S app). Below are my results (sorry, I can’t charge beyond 24 amps at the moment).
Current Efficiency Rate
5 ............70%
10 ..........82%
12 ..........84%
14 ..........86%
24 ..........89%
One of these days, I’ll set up a meter like Brantse, and use my UMC to go to higher amperage settings.
Current Efficiency Rate
5 ............70%
10 ..........82%
12 ..........84%
14 ..........86%
24 ..........89%
One of these days, I’ll set up a meter like Brantse, and use my UMC to go to higher amperage settings.
Thanks guys, you're absolutely right. I need to use another method to obtain my actual energy delivered to the batteries. I suppose using visibletesla, which shows the charge percentage down to a single decimal, would be pretty accurate.
I'll have to check the information shown before removing the charging cable. I never took notice to it before.
I'll have to check the information shown before removing the charging cable. I never took notice to it before.
mknox
Well-Known Member
I posted this in another thread, but thought it might be relevant here in the discussion around charging efficiency:
"...yesterday I did a road trip where I supercharged on the way out and the way back. I drove from home to the Supercharger and charged to 90%. Later that day, I returned to the same Supercharger and again charged to 90%. My car said I had driven 139.5 miles and consumed 42.3 kWh, but my Charging display showed I had put 46 kWh back in to the car during that second charge."
So I guess that is telling me that I'm seeing about 92% efficiency at Superchargers...
"...yesterday I did a road trip where I supercharged on the way out and the way back. I drove from home to the Supercharger and charged to 90%. Later that day, I returned to the same Supercharger and again charged to 90%. My car said I had driven 139.5 miles and consumed 42.3 kWh, but my Charging display showed I had put 46 kWh back in to the car during that second charge."
So I guess that is telling me that I'm seeing about 92% efficiency at Superchargers...
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