Optimal EV Charging

E

ecotourist

Joined
Jul 9, 2008
Messages
5,443
Location
British Columbia, Canada
This article is very interesting. It suggests that we're charging our Tesla batteries too fast, too often and too high. It also brings into question the concept of "always plugged in".

My daily drives are quite short and I could do 70 - 40% or 60 - 40% and charging only every few days quite easily. I've already turned down the rate of charge.

I'd be interested in what other EV owners and especially @JeffKeryk think about all this.

 
You can ABC(Always Be Charging) as it's famous to say, but setting a reasonable limiter. Sounds exactly like what Ws6 is doing. We just plug it in when it needs it or before we know we're going to do a lot of driving. It's also an LFP battery and it's recommended to full charge once a week, so we do that as well. All on 120v. It's worked for us.

Turning down the rate of charge is a good tool to use too when you know what your usage is like you've described. At the end of the day just having an approach that works well for your usage is all that matters. I have a feeling if we were using 220v that may be something we'd do occasionally, but most likely we'd retain the charge when we need to approach.
 
Good video. The off grid homes also cycle lithium ion batteries in a similar way. Extending the lifespan. Of note, the key factor seems to be avoiding a full charge.

The energy provided by the battery when charged 100% and discharged to 25% is 3/4's of it's capacity. Giving 1000 cycles. Or 75,000 KWh.

When using only 10% of battery capacity, by cycling between 75% and 65%, you get 85,000 KWh out of the battery.

Another issue is battery size, the larger the pack, the lower the stress on it, for a given job and charge rate.
 
Well, I am certainly not a battery scientist or expert... BITOG is lucky to have experts that can properly speak to topics like this.
I used to charge to 90% (Tesla recommended) because of range anxiety. And I charged every night.
2 things happened... One, I realized there was no reason to charge every day and Tesla changed their recommendation to 80%. Beyond that I started to relax and learn about EV ownership. These cars are different.

So now I charge to 80% when it is 60% or less. If I am driving further, I will charge to 90%; one time I charged to 95%. I have a dedicated 50A circuit; the car pulls 29 to 32 A.
Now, I live in an EV bubble because the weather is mild and there are Superchargers everywhere. If I Supercharge, I only top off, 5 to 10 minutes, generally 70% or less, just to get home.

I've heard of owners who only Supercharge and have not seen significant battery degradation over a few years but my guess is they are outliers. I would not count on that myself...

Tesla changed to a different battery chemistry in the Std Range a few years ago and declared it OK to charge to 100%, with minimal degradation. If this is valid, then that battery might be better than a long range battery in a few years due to rate of degradation.

In my case I have come to appreciate not wasting time going to gas stations and paying $80 or more to fill up. One would expect battery efficiency and hopefully prices to improve over time, but it won't happen fast. Bring a lunch, as they say...
 
Cujet said:
Another issue is battery size, the larger the pack, the lower the stress on it, for a given job and charge rate.
Click to expand...
Higher cost for larger pack though, but maybe as battery density increases and manufacturing costs decrease, maybe that will change.
 
I’ve been charging to 80% daily at 32A. If it’s going to sit for a week or so, I’ll leave it plugged in but only charge to 50%.
 
I'll wait until I get down to around 45% percent then add 20% overnight using the portable 1.7kW charger to bring it up to 65%. At least for this NMC cell chemistry the effect of sitting at some charge level on degradation is like a bathtub shape around ~50%.

If I needed more than 20% daily I would widen that span to suit and install a faster home charger. I'll go to 100% if needed for a trip, no reason not to.
 
JeffKeryk said:
Well, I am certainly not a battery scientist or expert... BITOG is lucky to have experts that can properly speak to topics like this.
I used to charge to 90% (Tesla recommended) because of range anxiety. And I charged every night.
2 things happened... One, I realized there was no reason to charge every day and Tesla changed their recommendation to 80%. Beyond that I started to relax and learn about EV ownership. These cars are different.

So now I charge to 80% when it is 60% or less. If I am driving further, I will charge to 90%; one time I charged to 95%. I have a dedicated 50A circuit; the car pulls 29 to 32 A.
Now, I live in an EV bubble because the weather is mild and there are Superchargers everywhere. If I Supercharge, I only top off, 5 to 10 minutes, generally 70% or less, just to get home.

I've heard of owners who only Supercharge and have not seen significant battery degradation over a few years but my guess is they are outliers. I would not count on that myself...

Tesla changed to a different battery chemistry in the Std Range a few years ago and declared it OK to charge to 100%, with minimal degradation. If this is valid, then that battery might be better than a long range battery in a few years due to rate of degradation.

In my case I have come to appreciate not wasting time going to gas stations and paying $80 or more to fill up. One would expect battery efficiency and hopefully prices to improve over time, but it won't happen fast. Bring a lunch, as they say...
Click to expand...

It's always about how well the temperature can be controlled. Theoretically, faster charging shouldn't be as much of an issue if a battery can be cooled, which most EVs do. But it's not really something that happens with most portable devices. Even the fans in my laptop computer are more about keeping the CPU from melting down and relatively cool, and not necessarily about protecting the battery. Semiconductor switching performance always goes down with heat and I remember seeing overclocked systems that used cryogenic cooling.

Of course depth of maximum charge level and minimum discharge level matter.

There's still controversy over LiFePO4 and whether or not a set 100% charge level is ideal for longevity. At least with the Model 3 RWD, they claim it's best for life and for battery calibration. For my parent's Model 3 RWD I've set it to 90% most of the time and let it get to 100% once a week.

Another thing is that whatever the 0% and 100% floor can be chosen. They're not absolute numbers, but whatever the manufacturer defines as the outer limits. I bring this up when it comes of Apple devices, where they have smaller devices (iPhones) with a defined 500 cycles before they're expected to reach 80% of original capacity and iPads/Macs where they define it at 1000 cycles. It's pretty simple - with the larger device they can slightly oversize the battery and use less of its overall capacity. And that's easy enough to do with a car battery.
 
One of the other things I've read recently is that you should demonstrate to your EV battery what is a full charge and what is a "full" discharge.

The suggestions is that rarely (something like every 6 or 12 months) it's a good idea to charge your EV to 100% then without letting it sit at 100%, drive it until it's down to 10% or even better 5%. Then without letting it sit too long at that low level, recharge it to your normal 80% or whatever.

I think the idea is for your EV and EV battery to see what a full charge and a "full" discharge look like. Supposedly the EV and EV battery will now display the true maximum charge (ie the true maximum range).

I haven't done this. Has anyone else heard about this or done it? It seems kind of contradictory to the recommendations in YouTube.
 
ecotourist said:
One of the other things I've read recently is that you should demonstrate to your EV battery what is a full charge and what is a "full" discharge.

The suggestions is that rarely (something like every 6 or 12 months) it's a good idea to charge your EV to 100% then without letting it sit at 100%, drive it until it's down to 10% or even better 5%. Then without letting it sit too long at that low level, recharge it to your normal 80% or whatever.

I think the idea is for your EV and EV battery to see what a full charge and a "full" discharge look like. Supposedly the EV and EV battery will now display the true maximum charge (ie the true maximum range).

I haven't done this. Has anyone else heard about this or done it? It seems kind of contradictory to the recommendations in YouTube.
Click to expand...

That used to be something Apple used to recommend be done at least once a month, and referred to it as a "calibration cycle" or something similar. However, they don't really recommend it any more. Many assume that having that deep a discharge isn't very good if one is looking to keep a battery for a long time. And there's far more advanced battery management hardware and software.

But again - the points that are defined as 0% and 100% are chosen for a performance goal in balancing usable capacity and longevity. I go back to portable devices as a comparison. If you can manage to use less of the capacity range by setting these points closer to the middle, that will likely increase overall longevity. I have a laptop computer with a maximum longevity setting, which I think is between 25-75% of the nominal capacity rating.

It's kind of an estimate, but I've heard that with many lithium-ion battery uses, the capacity could actually be doubled, but the longevity will be atrocious. Something like doubling a battery's capacity, but where a 500 cycle rating drops down to maybe 25-50 cycles.
 
Torrid said:
You can ABC(Always Be Charging) as it's famous to say, but setting a reasonable limiter. Sounds exactly like what Ws6 is doing. We just plug it in when it needs it or before we know we're going to do a lot of driving. It's also an LFP battery and it's recommended to full charge once a week, so we do that as well. All on 120v. It's worked for us.
Click to expand...

Being plugged in isn't necessarily the same as charging though. I believe many (most?) owners of EVs program them to charge at home at night to take advantage of lower time of use rates. But when it's not charging, the battery management system should provide power to the rest of the vehicle's systems.

Theoretically a Level 1 or Level 2 charging system can provide all the power needed for all the accessory stuff such that it doesn't need to draw from the battery. And drawing from the battery generally means more cycling of the battery.
 
Good discussion everyone.

Here's what I plan to do:
  • Reduce my home charging rate to 25 Amps at 220 Volts.
  • Reduce the maximum charge to 75% when we're only driving around our home base (but increase it to 80% for longer local trips).
  • Keep the car plugged in when not in use.
  • Not bother with the 100% to 5% routine unless I get more information about the value of that routine.
 
ecotourist said:
Good discussion everyone.

Here's what I plan to do:
  • Reduce my home charging rate to 25 Amps at 220 Volts.
  • Reduce the maximum charge to 75% when we're only driving around our home base (but increase it to 80% for longer local trips).
  • Keep the car plugged in when not in use.
  • Not bother with the 100% to 5% routine unless I get more information about the value of that routine.
Click to expand...
The only reason to do the full sweep of power range is if you suspect that the battery management is miscalculating battery state of charge. The LFPs are a bit more sensitive to it because they have a narrower voltage range full to empty which is why it states to fully charge an LFP car to full once a week. I does not say anything about running it as low as possible before doing the 100% charge.
 
Don't own an ev yet, but maybe in the future.
It wouldn't be our only transportation, but a great supplement to owning 2 full sized pickups powered by V8 engines. I would like to at home charge it most of the time using 110 volts, and only giving it a complete battery charge when we plan to go on a road trip. My fiance would drive it more than me, and at her work can actually plug it into 110 all day for free to her, which is a good option.
So no matter what the future holds, if I do buy an ev, it would have to be 110 volt compatible.
 
TimeFlies said:
Don't own an ev yet, but maybe in the future.
It wouldn't be our only transportation, but a great supplement to owning 2 full sized pickups powered by V8 engines. I would like to at home charge it most of the time using 110 volts, and only giving it a complete battery charge when we plan to go on a road trip. My fiance would drive it more than me, and at her work can actually plug it into 110 all day for free to her, which is a good option.
So no matter what the future holds, if I do buy an ev, it would have to be 110 volt compatible.
Click to expand...
110v gives you a measly 4 mph; almost worthless. I would not spend the extra for an EV if I were gonna use it that little. Unless I just wanted it, which is a reason many people use to justify their purchases.

I guess it could work, but if you needed to fuel up quickly, you would need to hit up a Supercharger. Alternatively, around here it is common to charge at work for a subsidized rate or even free.
Based on my experience, don't Mickey Mouse it; price in a 240v dedicated circuit or at least make sure your residence could add one.
The #1 reason EV owners go back to ICE is charging issues.

Good luck.
 
JeffKeryk said:
110v gives you a measly 4 mph; almost worthless. I would not spend the extra for an EV if I were gonna use it that little. Unless I just wanted it, which is a reason many people use to justify their purchases.

I guess it could work, but if you needed to fuel up quickly, you would need to hit up a Supercharger. Alternatively, around here it is common to charge at work for a subsidized rate or even free.
Based on my experience, don't Mickey Mouse it; price in a 240v dedicated circuit or at least make sure your residence could add one.
The #1 reason EV owners go back to ICE is charging issues.

Good luck.
Click to expand...
Oh I've tried to get someone out to install the outlet. 1 company came out to give a quote. The rest aren't returning calls and the 1 company isn't now either. They said they were too booked on bigger jobs to do it soon even when we got the quote. I know it's not that involved. If I had to drive the car daily I'd be occasionally using public charging just to keep going. I think it may just because it's winter. I'm going to revisit this in spring, but I will not be buying a second EV until that happens anyway.
 
Torrid said:
Oh I've tried to get someone out to install the outlet. 1 company came out to give a quote. The rest aren't returning calls and the 1 company isn't now either. They said they were too booked on bigger jobs to do it soon even when we got the quote. I know it's not that involved. If I had to drive the car daily I'd be occasionally using public charging just to keep going. I think it may just because it's winter. I'm going to revisit this in spring, but I will not be buying a second EV until that happens anyway.
Click to expand...
Not sure about where you live but here the Electric Utility will gladly hook you up with someone to install a level 2 charging station. They might even susidize the cost.
 
Astro_Guy said:
Not sure about where you live but here the Electric Utility will gladly hook you up with someone to install a level 2 charging station. They might even susidize the cost.
Click to expand...
They do that here too, but it's up to you to set the appointment with the electrical company. I just messaged one outside of town and got a message back in 10 minutes. They'll be here in 8 days. I think none of the companies in my small town want to deal with EVs. That's all I can figure.
 
You must log in or register to reply here.
Back
Top Bottom