All this technical stuff hurts my head. In simple terms I was told that these batteries PREFER to be charged at 40amps and up, the only time I slow mine down is so it will finish about the time I am ready to leave in the morning so it doesn't sit at a high rate (full charge) for any length of time. SO if I am doing a range charge I slow it down to finish at drive time. The rest is way too technical for me.
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dhanson865
Well-Known Member
Given that It would be good to see efficiency of 39 amps vs 41 amps or 35 amps vs 45 amps. Something near the combo point
80a (max rate)
70a
60a
50a
45a
41a near the dual charger split point
39a equal distance below the dual charger test point above
35a
30a
25a
20a (call this minimum reasonable rate?)
It would be interesting to find not only the most efficient but also the least efficient and any non linearity to the curve. If the effeciency curve is interesting enough and 10a jumps are too coarse you can add more points later.
toto_48313
CAN P #5
I wonder what is better from a wear and tear perspective. I've been told that charging at 20 A is better for the battery ( but seem not efficient) => Dilema
Resistance doesn't change with current, but resistive heating (and the power it wastes) does increase with the square of the current. So at 80A, you waste 4x as much power in heat as at 40A.
But that may be somewhat pedantic - without knowing the resistance in the circuit, it's hard to know if the total heating losses are significant.
I doubt you've been told that by Tesla. Do you really think then the battery knows the difference between 20A and 40A, when A during supercharging are order of magnitude higher?
I was told that by the people at the service center a long time ago, and disregarded it based on my learnings here.
I *am* interested in wear and tear to the chargers, though. If higher A means more wear and tear, the best useful A to use would be 41.
There are other concerns besides charger efficiency. If a battery is at a very low SoC, say at an indicated range of under 10 miles, charging at 80A would significantly reduce the time spent at low SoC, and would enhance battery longevity.
If you are trying to go from 40% to 60% it isn't as much of a concern, but at low SoC, reducing wear on your battery should be the biggest concern.
Similar, charging up to 100% before a long trip... A faster charge would reduce the time spent above 90% if you planned for the charge to finish just before leaving, so this would also reduce battery wear.
If you are trying to go from 40% to 60% it isn't as much of a concern, but at low SoC, reducing wear on your battery should be the biggest concern.
Similar, charging up to 100% before a long trip... A faster charge would reduce the time spent above 90% if you planned for the charge to finish just before leaving, so this would also reduce battery wear.
You are talking about a matter of hours. Nothing on those time scales would have any negative impact upon the battery. Even days or weeks would probably have only negligible impact.
With my small sample so far, I'm surprised that there's no statistically significant difference in kWh/Ideal Mile between 40, 60 and 80 amps.
I'll try 30, maybe 20 this weekend, when I can let the car charge to completion.
I'll try 30, maybe 20 this weekend, when I can let the car charge to completion.
what about supercharging?
If going from 110 volts to 240 volts cuts losses by about 30%, is there an argument to be made that bumping up to 300+ volts on a supercharger improves it further? Obviously a more complicated question, given the significant amount of peak heating that can occur at those much higher current levels, the need to engage the vehicle's cooling system, the cooling equipment operating in the superchargers as well, the effect of ambient temperature, etc.
If going from 110 volts to 240 volts cuts losses by about 30%, is there an argument to be made that bumping up to 300+ volts on a supercharger improves it further? Obviously a more complicated question, given the significant amount of peak heating that can occur at those much higher current levels, the need to engage the vehicle's cooling system, the cooling equipment operating in the superchargers as well, the effect of ambient temperature, etc.
The supercharger system moves the charging off-vehicle. It is probably less efficient given the increased cooling required but that is on Tesla's dime.
I'm pretty sure it's actually MORE efficient. The rectification of converting AC (from the utility) to DC (for the battery to gobble up) is a lossy operation. Doing this:
at a supercharger: ~100kw with commercial-grade equipment in large dedicated mechanical enclosures (i.e. where space and weight aren't a huge issue)
seems easier than doing it in the car itself:
at <=40kw in a tight, confined box, where making it fit in the car, making it light, making it small, making it crash and/or impact resistant matters, etc etc etc
So I think that while the total cooling required is obviously WAY more for a supercharger, the per-kw cooling would be less.
That's a moderately educated guess - feel free to poke holes in it. ;-)
supercharger losses
I was thinking the same thing. The fact that the charging is happening on multiple, parallel dc chargers makes me think there wouldn't be any extra losses there, per se. But, whatever efficiency you gain by running at a higher input voltage might be offset by needed to do more active cooling to protect the battery.
I was thinking the same thing. The fact that the charging is happening on multiple, parallel dc chargers makes me think there wouldn't be any extra losses there, per se. But, whatever efficiency you gain by running at a higher input voltage might be offset by needed to do more active cooling to protect the battery.
OK - I didn't know that, but it makes a ton of sense for Tesla to use the same design and just stack them in a supercharger cabinet.
With that in mind, I doubt seriously that the input voltage makes much difference in the efficiency - I did some work with power systems a little smaller (the 3-8KVA range, the tesla ones are closer to 12KVA) but in any case the input voltage didn't really change the efficiency.
With that in mind, I doubt seriously that the input voltage makes much difference in the efficiency - I did some work with power systems a little smaller (the 3-8KVA range, the tesla ones are closer to 12KVA) but in any case the input voltage didn't really change the efficiency.
As far as I know from what those who've actually measured have said:
1. A faster charge is more efficient, but only slightly more efficient than a 32 amp charge.
2. Charging below 32 amps is inefficient.
3. The longer the run, the less efficient given the same wire gauge.
4. The more connections, the less efficient, so an HPWC would be more efficient than a UMC.
The big one in almost all cases is going to be charging at 16 or 20 amps vs charging at 32 amps or greater.
I'll have to move this to the wiki since I can't update the first message anymore, but I did the first 20 amp charge last night. Aside from taking a long time, there's still no difference in kWh consumed per Ideal Mile:
Code:
[TABLE="width: 410"][TR][TD]
[/TD][TD]Summary[/TD][TD]
[/TD][TD]
[/TD][TD]
[/TD][TD]
[/TD][TD]
[/TD][/TR][TR][TD]Amps[/TD][TD]# Samples[/TD][TD]Min kWh/Ideal[/TD][TD]Avg kWh/Ideal[/TD][TD]Max kWh/Ideal[/TD][TD]StdDev kWh/Ideal[/TD][TD]Avg Minutes/Ideal[/TD][/TR][TR][TD]40[/TD][TD="align: right"]3[/TD][TD="align: right"]0.292[/TD][TD="align: right"]0.295[/TD][TD="align: right"]0.303[/TD][TD="align: right"]0.006[/TD][TD="align: right"]1.8[/TD][/TR][TR][TD]80[/TD][TD="align: right"]3[/TD][TD="align: right"]0.264[/TD][TD="align: right"]0.284[/TD][TD="align: right"]0.298[/TD][TD="align: right"]0.018[/TD][TD="align: right"]0.9[/TD][/TR][TR][TD]60[/TD][TD="align: right"]4[/TD][TD="align: right"]0.278[/TD][TD="align: right"]0.285[/TD][TD="align: right"]0.297[/TD][TD="align: right"]0.008[/TD][TD="align: right"]1.1[/TD][/TR][TR][TD]20[/TD][TD="align: right"]1[/TD][TD="align: right"]0.286[/TD][TD="align: right"]0.286[/TD][TD="align: right"]0.286[/TD][TD="align: center"]#DIV/0![/TD][TD="align: right"]3.4[/TD][/TR][/TABLE]
[TABLE="width: 410"][TR][TD]
[/TD][TD]Deciles[/TD][TD]
[/TD][TD]
[/TD][TD]
[/TD][TD]
[/TD][TD]
[/TD][/TR][TR][TD]Amps[/TD][TD]# Samples[/TD][TD]Min kWh/Ideal[/TD][TD]Avg kWh/Ideal[/TD][TD]Max kWh/Ideal[/TD][TD]StdDev kWh/Ideal[/TD][TD]Avg Minutes/Ideal[/TD][/TR][TR][TD]40[/TD][TD]3[/TD][TD]0.292[/TD][TD]0.295[/TD][TD]0.303[/TD][TD]0.006[/TD][TD]1.8[/TD][/TR][TR][TD] 40[/TD][TD]2[/TD][TD]0.292[/TD][TD]0.292[/TD][TD]0.292[/TD][TD]0.000[/TD][TD]1.8[/TD][/TR][TR][TD] 10[/TD][TD]1[/TD][TD]0.303[/TD][TD]0.303[/TD][TD]0.303[/TD][TD]#DIV/0![/TD][TD]1.9[/TD][/TR][TR][TD]80[/TD][TD]3[/TD][TD]0.264[/TD][TD]0.284[/TD][TD]0.298[/TD][TD]0.018[/TD][TD]0.9[/TD][/TR][TR][TD="align: right"] 30[/TD][TD]1[/TD][TD]0.298[/TD][TD]0.298[/TD][TD]0.298[/TD][TD]#DIV/0![/TD][TD]0.9[/TD][/TR][TR][TD="align: right"] 50[/TD][TD]2[/TD][TD]0.264[/TD][TD]0.277[/TD][TD]0.290[/TD][TD]0.018[/TD][TD]0.9[/TD][/TR][TR][TD]60[/TD][TD]4[/TD][TD]0.278[/TD][TD]0.285[/TD][TD]0.297[/TD][TD]0.008[/TD][TD]1.1[/TD][/TR][TR][TD="align: right"] 20[/TD][TD]2[/TD][TD]0.278[/TD][TD]0.281[/TD][TD]0.284[/TD][TD]0.004[/TD][TD]1.1[/TD][/TR][TR][TD="align: right"] 30[/TD][TD]1[/TD][TD]0.297[/TD][TD]0.297[/TD][TD]0.297[/TD][TD]#DIV/0![/TD][TD]1.1[/TD][/TR][TR][TD="align: right"] 40[/TD][TD]1[/TD][TD]0.283[/TD][TD]0.283[/TD][TD]0.283[/TD][TD]#DIV/0![/TD][TD]1.1[/TD][/TR][TR][TD]20[/TD][TD]1[/TD][TD]0.286[/TD][TD]0.286[/TD][TD]0.286[/TD][TD]#DIV/0![/TD][TD]3.4[/TD][/TR][TR][TD="align: right"] 60[/TD][TD]1[/TD][TD]0.286[/TD][TD]0.286[/TD][TD]0.286[/TD][TD]#DIV/0![/TD][TD]3.4[/TD][/TR][TR][TD]Grand Total[/TD][TD]11[/TD][TD]0.264[/TD][TD]0.288[/TD][TD]0.303[/TD][TD]0.011[/TD][TD]1.4[/TD][/TR][/TABLE]