New Owner's Battery Charging Questions

[mfan]

Hi,

I'm a recent owner of a M3 LR AWD (July 2019). It's been driven less than 3,000 miles. Being new to electric cars, I'd like to better understand what's the best protocol in recharging the battery. I have gathered that the battery charge should, ideally, be maintained between 20% and 80%. My questions on battery health are:

• Is this always, or should the battery be "exercised" once in a while to, say, 5% or charged to 100%? If so, how often?
• What's the best way to charge the battery to maintain its health (not considering time, cost, convenience, nor efficiency)? Is it using the 110v, 220v, level 2, DC fast charge, or Tesla SC? Or, does it not matter?
• Do frequent/occasional fast charging shorten the battery life/health?

Thanks.

 

[Tam]

...should the battery be "exercised" once in a while to, say, 5% or charged to 100%?

Please, no exercise for a lithium battery. That's for older nickel hydride.

Deep discharge is bad for your battery but if you need to do it because you are on a road trip, then that's justifiable but it's not for routine practice.

That means if you use 10% per day, don't wait for 6 days or spending down 60% before plugging it in.

60% is deeper discharge than 10% so I wouldn't do it if I can avoid it.

So if you start your day at 80%, plug it in daily to raise it from 70% to 80% and not waiting 6 days to raise it from 20% to 80%.

...What's the best way to charge the battery to maintain its health (not considering time, cost, convenience, nor efficiency)? Is it using the 110v, 220v, level 2, DC fast charge, or Tesla SC? Or, does it not matter?

The manual does not say which one 120/240/DC is good or bad. It only says plug in as often as you can and there's no advantage in delaying.

...Do frequent/occasional fast charging shorten the battery life/health?

It's not clear. If it is bad then why taxi companies seem to do very well with Supercharging so far.

Tesloop has its "eHawk" for 440,093 miles so far. It uses Supercharging exclusively.

...20% and 80%...

It depends on who you ask.

A few members here were slapped with "poor charging habit" for setting the charge less than 90% and were told to charge at 90% on their service receipts.

While others got advice for 80%.

But Tesla battery is quite robust so I wouldn't be so overly concerned.

 

[toolman335]

I am a very new owner of this same vehicle. As a man I'm embarrassed to say....I read the manual lol.
Tesla says to top it off while the battery is warm every day. My salesman said that number is around 90%, so I have mine set to charge to 275 miles. I don't drive very much so I've been charging every 3 days or so when the battery gets to 190 miles.

 

[Saghost]

A plugged in Tesla is a happy Tesla.

There’s no reason to push it all the way to 100% or down to five percent, and going to either one is harder on the battery (it won’t break, but it may accelerate the degradation.)

Any charging method except Supercharging is the same in terms of battery health. Charging at 120V is significantly less efficient simply because the overhead for the computers and thermal management becomes a larger percentage of the available power. Supercharging is potentially worse for the pack, but as noted above some folks are doing it multiple times a day with fairly minor impacts.

The 80 vs 90% debate is an interesting one. Charging to 80 percent will have slightly less wear on the pack over time. But there’s a caveat.

Lithium batteries are challenging for a number of reasons; one of them is that the battery cells are at a constant voltage for much of the charge range, making it hard to know how much energy is left.

All the cars handle that with math models, tracking the energy in and out of the pack, but those models can drift over time.

80% is inside the constant voltage range. 90% is not. So by going up to 90%, the car gets a clear understanding of where the pack is right now, but it does a tiny bit more wear.

I’ve personally had cases where after a few days of parking where I couldn’t charge, I charged to 80% and was surprised by an apparent jump in degradation. Remembering the physics I just described, I pushed the limit up to 90% - and those missing miles suddenly reappeared.

So while I said there’s never any reason to go to 5% or 100% (aside from difficult trips, of course,) there is a good reason to occasionally get to 10-15% and 90% - not for the of the pack, but for the calibration of the math model of energy in the pack.

 

[toolman335]

I simply don't like how hot to the touch the Supercharger connectors are after a charge. I can't explain the science behind it to save my life, but my simple thought is "that can't be good for the battery degradation."

 

[Saghost]

I simply don't like how hot to the touch the Supercharger connectors are after a charge. I can't explain the science behind it to save my life, but my simple thought is "that can't be good for the battery degradation."

There’s very little connection between how hot the connector is and how hot the battery pack is.

Actually, the sessions where the connector stays cool are harder on the pack - because the car will slow the Supercharging session to limit the max connector temperature. I’m pretty sure that’s the main reason that sessions in the summer in the desert are slower than normal.

 

[mfan]

That means if you use 10% per day, don't wait for 6 days or spending down 60% before plugging it in.

60% is deeper discharge than 10% so I wouldn't do it if I can avoid it.

So if you start your day at 80%, plug it in daily to raise it from 70% to 80% and not waiting 6 days to raise it from 20% to 80%.

Hmmm, that's interesting to know. So, it's better to keep topping it off (to 80%) everyday than letting the battery level drop lower before recharging... I would have never guessed there's a difference in the frequency of recharging for the same amount of usage. That's surprising to me....

 

[ucmndd]

Hmmm, that's interesting to know. So, it's better to keep topping it off (to 80%) everyday than letting the battery level drop lower before recharging... I would have never guessed there's a difference in the frequency of recharging for the same amount of usage. That's surprising to me....

The more time a lithium battery spends near the middle of its capacity, the better. High charges and deep discharges aren’t necessary for any sort of battery health or maintenance.

For longer range cars, 80% is a good compromise between battery health and leaving enough energy in the battery for unforeseen events or circumstances that demand it.

Set your max charge, set a charge timer if your electricity is cheaper overnight, and plug in your car every evening when you’re done driving for the day.

it’s really that simple.

 

[jjrandorin]

Hmmm, that's interesting to know. So, it's better to keep topping it off (to 80%) everyday than letting the battery level drop lower before recharging... I would have never guessed there's a difference in the frequency of recharging for the same amount of usage. That's surprising to me....

This is actually in the owners manual for the car.
(directly from the tesla manual)

======================================

About the Battery
Model 3 has one of the most sophisticated
battery systems in the world. The most
important way to preserve the Battery is to
LEAVE YOUR VEHICLE PLUGGED IN when
you are not using it.

This is particularly
important if you are not planning to drive
Model 3 for several weeks. When plugged in,
Model 3 wakes up when needed to
automatically maintain a charge level that
maximizes the lifetime of the Battery.

Note: When left idle and unplugged, your
vehicle periodically uses energy from the
Battery for system tests and recharging the
12V battery when necessary.

There is no advantage to waiting until the
Battery’s level is low before charging. In fact,
the Battery performs best when charged
regularly.

Note: If the Model 3 Battery becomes
completely discharged in a situation in which
towing is required, the owner is responsible
for towing expenses. Discharge-related towing
expenses are not covered under the Roadside
Assistance policy.

The peak charging rate of the Battery may
decrease slightly after a large number of DC
Fast Charging sessions, such as those at
Superchargers. To ensure maximum driving
range and Battery safety, the Battery charge
rate is decreased when the Battery is too cold,
when the Battery’s charge is nearly full, and
when the Battery conditions change with
usage and age.

These changes in the
condition of the Battery are driven by battery
physics and may increase the total
Supercharging duration by a few minutes over
time.

Battery Care
Never allow the Battery to fully discharge.
Even when Model 3 is not being driven, its
Battery discharges very slowly to power the
onboard electronics. The Battery may
discharge at a rate of approximately 1% per
day. Situations can arise in which you must
leave Model 3 unplugged for an extended
period of time (for example, at an airport
when traveling). In these situations, keep the
1% in mind to ensure that you leave the
Battery with a sufficient charge level. For
example, over a two week period (14 days),
the Battery may discharge by approximately
14%.

Discharging the Battery to 0% may result in
damage to vehicle components. To protect
against a complete discharge, Model 3 enters
a low-power consumption mode when the
displayed charge level drops to approximately
0%. In this mode, the Battery stops supporting
the onboard electronics and auxiliary 12V
battery. Once this low-power consumption
mode is active, immediately plug in Model 3 to
prevent a jump-start and 12V battery
replacement.

Note: If the vehicle is unresponsive and will
not unlock, open, or charge, then the 12V
battery may have become discharged. In this
situation, contact Tesla.

Temperature Limits
For better long-term performance, avoid
exposing Model 3 to ambient temperatures
above 140° F (60° C) or below -22° F (-30° C)
for more than 24 hours at a time.
===================================

 

[AlanSubie4Life]

The Battery may
discharge at a rate of approximately 1% per
day. Situations can arise in which you must
leave Model 3 unplugged for an extended
period of time (for example, at an airport
when traveling). In these situations, keep the
1% in mind to ensure that you leave the
Battery with a sufficient charge level.

Now is a good time to mention that the current default drain rate for FSD/EAP vehicles at the airport with 2019.32.11.1 is about 5% per day due to Smart Summon Standby Mode (AP options, enabled by default). It’s clever, since it does not drain at work or at home (those locations are excluded). So you get a nice surprise when you leave your car at the airport (or anywhere else not in your Favorites). I lost 55 miles in 3.5 days at the North Rim of Grand Canyon (about 150W average drain) - employed all the other techniques to eliminate drain but forgot about this new option. Fortunately I had a way to recover the charge promptly and was not relying on 120V charging. They should really make these options accessible from the app, though it would not have helped me since there was no LTE access for the car and no way to access the car remotely anyway.

 

[jjrandorin]

Now is a good time to mention that the current default drain rate for FSD/EAP vehicles at the airport with 2019.32.11.1 is about 5% per day due to Smart Summon Standby Mode (AP options, enabled by default). It’s clever, since it does not drain at work or at home (those locations are excluded). So you get a nice surprise when you leave your car at the airport (or anywhere else not in your Favorites). I lost 55 miles in 3.5 days at the North Rim of Grand Canyon (about 150W average drain) - employed all the other techniques to eliminate drain but forgot about this new option. Fortunately I had a way to recover the charge promptly and was not relying on 120V charging. They should really make these options accessible from the app, though it would not have helped me since there was no LTE access for the car and no way to access the car remotely anyway.

Its a mistake by tesla to auto enable any option like this that keeps the car awake without explicitly having you select it. On the other hand, when they released summon, we all knew it was going to be a @!$@$@!@5 show, and it would be even worse if people started saying "it takes 30 seconds to even wake it up?!?!?!?!??!!??!" We know how many tesla drivers are, especially many of those who rush to "make a video".

I still think it was a mistake to auto enable that, and thank the people here who posted about that.