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Charging percentage

28K views 20 replies 12 participants last post by  Mr B 
#1 ·
The E-Tron Owners Manual suggests charging the battery to 80% for normal use and only charge to 100% when the range is needed. I also understand that the e-Tron is programmed to not give access to the full battery—only 80%. Is that the same 80% and charging to 100% is already protected by the limited access?
 
#3 ·
We have taken to charging ours to the 80% mark when at home, but leave it to charge to 100% when it is at our freebie office charger. While the car internally manages the battery pack to only utilize 83.5% or so of the actual 95kWh capacity Audi and other car manufacturers basically tell you to avoid total top ups if you don't really need them as it will reduce overall wear on the batteries. Since we don't really need the range most of the time, we leave it around 80% or so. Depending on how you drive the car and where you can charge should dictate your charging routine.

Likewise, leaving it plugged in for long periods of time (like a month) is probably not a great idea. We accidentally did that to a BMW PHEV and found the capacity had been reduced significantly on its small capacity.

I am hoping that Audi can programmatically improve efficiency of this model over time (as Tesla did with the original Roadster) since the range is the biggest downside on this car.
 
#4 ·
80% protects the top, 83.6 kWh protects the bottom

The e-tron has a 95 kWh battery. But only 83.6 kWh (88% of 95 kWh) is available to the driver. I believe (but I'm not sure, if anyone has evidence to the contrary please provide it) that the remaining 11.4 kWh protect the bottom of the battery, so it never goes fully empty. So the 80% recommendation is to protect the top (so that the battery does not get fully charged). Lithium-ion batteries do NOT like being fully charged, which is why your iPhone battery loses about 15% of its capacity every year: because you use it all the time and you charge it full at least once a day. I set my charging target to 80% except when going on longer trips (more than 70 miles away), or when encountering a free charger (yes, there are still some available); in those cases I charge to 100%.
 
#7 ·
80% protects the top, 83.6 kWh protects the bottom

The e-tron has a 95 kWh battery. But only 83.6 kWh (88% of 95 kWh) is available to the driver. I believe (but I'm not sure, if anyone has evidence to the contrary please provide it) that the remaining 11.4 kWh protect the bottom of the battery, so it never goes fully empty. So the 80% recommendation is to protect the top (so that the battery does not get fully charged). Lithium-ion batteries do NOT like being fully charged, which is why your iPhone battery loses about 15% of its capacity every year: because you use it all the time and you charge it full at least once a day. I set my charging target to 80% except when going on longer trips (more than 70 miles away), or when encountering a free charger (yes, there are still some available); in those cases I charge to 100%.
interesting. What is your charging practice? Do you believe in more Shallow micro charges or less frequent charges where u let the battery fall to 20-25% and then recharge?
 
#5 ·
Very interesting points by both @bradhinkle & @ioannisk. But basically both are saying the opposite of each other. I’m still confused. should you charge you battery to 100% (which is let’s say approx 80%-88% in reality as Audi doesn’t let you use your full battery) or should one charge at 80% ( which in reality will be 80% of useable battery by Audi) ?
 
#8 · (Edited)
Hello. I’m a new member and just leased my Audi 2021 E-Tron last week.

So was there a definitive answer to this question? Should we be charging the car to 80% or 100%? I’m assuming that for reasons already mentioned above charging to 80% (meaning 80% of the 80% that the car only lets you charge to by default) is better for the battery 🔋? Whenever I charge to 100% I only get about 198 mi - 201 mi range which I’m assuming is the 80% that car only lets you charge to by default.

Anyone have a definitive answer or best practice?
 
#9 ·
Hello. I’m a new member and just leased my Audi 2021 E-Tron last week.

So was there a definitive answer to this question? Should we be charging the car to 80% or 100%? I’m assuming that for reasons already mentioned above charging to 80% (meaning 80% of the 80% that the car only lets you charge to by default) is better for the battery 🔋? Whenever I charge to 100% I only get about 198 mi - 201 mi range which I’m assuming is the 80% that car only lets you charge to by default.

Anyone have a definitive answer or best practice?
 
#10 ·
80% or less is better for the battery. This graph comes from a paper on a Li-ion battery that was leading edge in 2012... I'd expect that today's batteries are better. Also at 35C, and hotter makes batteries wear out faster, and your batteries will be cooler. And at 1C charge/discharge rate. Or quick charge followed by BOH driving. Full equivalent cycle is 0-100%, or ten times 45% to 55% or similar.

25%-75% cycle (actual SOC) would be about 35% to 80% SOC as reported by the car.

The "miles" on the GOM reflect lots of things besides the state of the battery. How fast you drive, climate control use, outside temperature, ....

GOM is Guess O Meter.

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#12 ·
Is there anything that can be done to make driving to the back easier? Parking mirrors?

Being able to plug in at night is one of the best parts about EV ownership. Otherwise, see how it goes and start with a 40 mile buffer IMO.

Plugshare and A Better Route Planner are invaluable for finding chargers and planning trips.
 
#20 ·
No. Of course you know that the Audi maintains an upper buffer (that you cannot fill) and a lower buffer (that you cannot drain) in order to protect the battery. Now, I have never had it happen to me, but supposedly, as you get below 20% or so, the car will begin to shutdown functions that might drain the battery. As you get down to zero (which is actually about 8%), the car will stop. After that, the car will let you start it up and limp for a few yards (a couple of times, I think) to allow you to get to a safe spot.
 
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