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Best charging practice

Best charging practice

I know this has been asked but I still haven't seen an answer to this situation:

Most of the week I use 10-15% per day battery capacity. On weekend though I charge fully and often stop at a supercharger to add charge and arrive home with about 20% SOC. I've read here that a plugged in battery is a happy battery and I've also read that discharging to 30% and recharging to 80% is the sweet spot for the battery.

So, should I charge nightly which would charge the battery from say 65 to 80%, leave the car unplugged until it drops down to 30- 50% before I charge or just leave it plugged in each night but don't charge until I get to the 30-50% range? Is plugging the car in helping with anything other than charging? (keeping the battery warm, etc.)

Thanks

Kathy Applebaum | 28 gennaio 2019

What you're doing is just fine. I have 19k miles on mine with no degradation -- I go from 90% to 70% three days a week, more on weekends. I don't stop at a charger unless I'm going to arrive home with < 5%.

Elon has said it's fine to charge to 90% frequently and to go below 5% frequently. The car will tell you if it doesn't like the way you are charging (like if you were just using 5 miles a day and charging every night).

SteveWin1 | 28 gennaio 2019

I've been charging to 90% lately and have seen a drop in my range. Might just be a fluke with my battery or just random noise, but I've lost 2% battery capacity (according to TeslaFi) between 2470 miles and 7630. Not a huge loss and that's just one data point. Not sure what others are losing as far as capacity.

I think overall, its not something you should worry too much about. If you obsess over stuff like that, it will make owning your car less fun. Just keep it plugged in when you're home and supercharge as needed.

gmr6415 | 28 gennaio 2019

@OP, this is a very broad subject and a lot depends on circumstance. I'm not in a position to charge every day, so I charge to 75% (used to do it to 70%) and then drive it down to about 30% and charge when convenient.

The only reason I changed from 70% to 75% is I like the additional range which results in me charging about once a week. I've got roughly 10K miles on the car with no degradation. The only time I've really charged nightly was when out of town doing a lot of sightseeing during the day, and I was plugging into a 110v outlet every night and charging up to about 90% as well as pre-warming in the mornings while plugged in. Mainly that was just to mitigate having to drive 20 minutes or so to get to the closest supercharger and also trying to limit supercharging.

I think as long as you limit the times you are charging to 100% as best you can, and use superchargers only when needed you'll be okay. I've also gone down below 5% on a couple occasions between superchargers.

When traveling I charge to 100% just before leaving home, but when hitting superchargers it's just a waste of time to sit there an additional 20 minutes or so to get that last 10%.

The benefits I can see for plugging in every night would be if you have an emergency situation you've always got a higher SOC before you leave, and in either exceptionally cold or hot weather you are eliminating some of the phantom drain by staying plugged in.

calvin940 | 28 gennaio 2019

If I am only going down to 70-75% each day, should I still be charging it back up to ~80% or should I do a couple days driving before recharging? I have been plugging my car in nightly regardless up to this point (with a couple exceptions here or there) but for such a short range of travel does it make sense to continue to do that ?

gmr6415 | 28 gennaio 2019

@SteveWin1, it might just be calibration. You may need a couple cycles charging 100% down to 10% or so, then go back to normal charging. I've never had to do it, but I've read here that in most cases it does work.

Kathy Applebaum | 28 gennaio 2019

@gmr6415 is right. I had "lost" a couple of miles of range until I went on a road trip that involved a couple of sessions of 100% down to 15%. After that I started getting 310 again.

SteveWin1 | 28 gennaio 2019

@gmr6415, good point. I may try that if it keeps dropping. At 2%, I'm not really bothered by it -- still way more range than I need.

Earl and Nagin ... | 28 gennaio 2019

@SteveWin1,
2% is within experimental error. One cannot measure battery life or state of charge that accurately. It will be more greatly affected by temperature variation, usage, current draw, etc. This is why Tesla's apps don't try to split such hairs.

SteveWin1 | 28 gennaio 2019

@Earl,

A 2% slow drop in something without much random noise during the slow drop is a real drop. Its either caused by a systemic error in how Tesla determines rated range (as suggested above) or its real battery degradation.

Where did you hear that 2% is within experimental error? Is that from Tesla?

Earl and Nagin ... | 28 gennaio 2019

@SteveWin1,
Yes, 2% is a real drop. Is it significant? Is it caused by what you think caused it?
I've been working peripherally with batteries for a while (long before Tesla).
I'm not a battery expert but I know a bit about their characteristics. You can also look at current -vs- capacity and temperature -vs- capacity curves for batteries and get a good understanding about the variations one would expect to see under those different conditions. It also may be caused by the range estimation algorithms instead of physical properties.

PT733 | 17 febbraio 2019

If a charge to voltage option is added, 3.8 V (approx 60% for Panasonic) is an excellent voltage to "hibernate" at (daily topup) for short-distance trips to maximise the calendar life (and not worry about the state of charge percentage estimate error from low state of charge and repeated shallow depth of discharge).

High state of charge (>>80%) will reduce how many cycles you get before sudden collapse of capacity, even if degradation so far has been shallow. Even 90% is a lot better than 100%.

https://www.youtube.com/watch?v=9qi03QawZEk

I'm hoping on road trips (if a voltage display is available) to stay between 3.65 and 3.95 V resting voltage, and slow charge at home whenever possible, e.g. <= 7 kW (C/10).

On my Android phone I use Accubattery to notify when above 70% so I can pull the plug. I personally try to stay within 40% and 80% when possible, and never drop below 20%.