I have a short commute. The car is plugged in every night to charge. Given the low daily consumption, what is the best 5-8% of the battery to use for its health? 60-52? 50-42? Higher or lower? Current daily charge level is 60%, which is based on research on this forum and a couple other places.
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I drive 5-8% of the battery per day. WHICH 5-8% should I use?
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ucmndd
Well-Known Member
Don’t use 0-10 or 90-100.
Beyond that, it’s all needless hair splitting and navel gazing.
Beyond that, it’s all needless hair splitting and navel gazing.
pdx_m3s
Active Member
Lithium ion batteries are happiest in the middle. So anything around there is good.
I'm in the same boat. I just set it to 78% because I don't want to hassle with changing the number on the weekends when I do travel more. For what it's worth I'm still at 310 "rated miles" (Austin Power's Dr. Evil air quotes) at 100% after 1 year and 16,000 miles.
ralph142
Member
Same here, I run 70-60 typically, cold mornings kick it to 75 just before leaving to heat up the battery. FWIW, charging an 2019 mr on a 1220 v circuit, 7 k miles, max charge shows 262, exactly what it always has.
There are two logical choices, with different logic for each.
The least wearing cycle would be something like 46-54% (though below 80% the difference is minimal.)
The downside to that is from about 20% to about 80% the voltage is constant, so the only way the car knows how much charge is in the battery is a math model based on power flows in and out - and those models can get confused or drift over time.
Which leads to the other logical choice - charge to 90% and don’t worry about it.
That’s Tesla’s official recommendation these days, and I’m pretty sure they recommend that because it gives the math models something to work with - the cell voltage is slightly above the constant range, in an area where voltage corresponds quite consistently with state of charge, and the wear on the pack is only slightly greater.
I use around ten percent per day and take a lot of longer trips that aren’t really planned, so I picked something in the middle. I charge to 80% on a daily basis, and to 90% on trips and if the 80% number moves much (and I have seen it change by several miles and come back when I charge to 90%.)
The least wearing cycle would be something like 46-54% (though below 80% the difference is minimal.)
The downside to that is from about 20% to about 80% the voltage is constant, so the only way the car knows how much charge is in the battery is a math model based on power flows in and out - and those models can get confused or drift over time.
Which leads to the other logical choice - charge to 90% and don’t worry about it.
That’s Tesla’s official recommendation these days, and I’m pretty sure they recommend that because it gives the math models something to work with - the cell voltage is slightly above the constant range, in an area where voltage corresponds quite consistently with state of charge, and the wear on the pack is only slightly greater.
I use around ten percent per day and take a lot of longer trips that aren’t really planned, so I picked something in the middle. I charge to 80% on a daily basis, and to 90% on trips and if the 80% number moves much (and I have seen it change by several miles and come back when I charge to 90%.)
It isn't constant but it does not change much with respect to SoC so that augmentation by coulomb counting is necessary and even then an occasional "calibration" by visiting the high and low SoC regions is needed.
No doubt the best thing in your case is 4% between 30-40% and the other 4% between 60-75%. Stay away from the other brackets.
That is not changing the number of cycles. A cycle is defined as the full capacity of the battery, regardless of how many sessions you break that up into.
ucmndd
Well-Known Member
Wear leveling. If you use the same percentage range over and over again, that part gets worn out.
I like the way you think.
Eno Deb
Active Member
What you're currently doing is pretty much optimal. Don't overthink it.
Personally I also have a rather short commute and usually charge to 70%, but right now I've set it a bit higher because we've had some power outages related to the California fires.
nwdiver
Well-Known Member
A 35% cycle causes significantly more degradation than 7 5% cycles. Smaller cycles reduce degradation.
nwdiver
Well-Known Member
..... cycling from 75% - 40 - 75%% once causes more degradation than 75% - 70% - 75% 7 times.....
The point is that frequent charging is the best thing for your battery.
mtndrew1
Active Member
A 35% cycle causes significantly more degradation than 7 5% cycles. Smaller cycles reduce degradation.
I’m under the impression that one cycle is a complete 100%-0%.
For example, five 20% discharge/recharge events would be one cycle.
That said, I typically charge to 80% since I use about 10% per day. Lithium batteries are happiest avoiding the extremes.
nwdiver
Well-Known Member
Yes; (5) 20% discharge/recharge events would be one cycle.... which is why I was using (1) 35% vs (7) 5%... smaller cycles are key to a long lived battery. Avoiding the extremes is important too.
This is a little apples and oranges to this discussion as the x-axis is DoD.A 35% cycle causes significantly more degradation than 7 5% cycles. Smaller cycles reduce degradation.
So in other words this chart says that if you go from 100% to 50%, every time, then a typical Li-Ion batt would last 10,000 cycles (which would be 20,000 charges from 50% to 100%).
This chart says absolutely nothing about what it means for cycle life if you go from, say, 75% to 25% as it DoD charts always assume starting 100% SOC (state of charge).
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