Resting battery before charge?

[sonic88]

Is there any truth, or benefit that one should let the battery rest (i.e for a few hours) before charging where possible?

Obvious it would not be convenient in situations where you need to charge at a stop off, in order to continue your journey.
But in other instances, where you come back from home after a long trip then this might be different. However, if you arrive home from a low soc (i.e. just below 10%) then naturally i would think its best to charge asap to get it back up above 20% or so?

Curious what the general benefit is for letting the battery rest after a drive before charging; and if this something you one should aim to do even in the scenarios of arriving home at a low soc (10% or low etc)?

Cheers

 

[Candleflame]

this has been advised by some tesla service technicians...

I do think there is some truth to that but only if you charge relatively fast (i.e. 5kw or more) as this generates more battery heat on an already warm/strained battery.
Im not convinced if you charge from an outlet at i.e 2 or 3 kw that it makes any difference though i do let my battery rest for an hour or so if i come home and there is only 5% charge left.

There isnt much (if any) evidence that sitting at i.e. 5% charge (true 10%) damages the battery more than 90% (true 85% or so). I'd argue a battery at 5% will probably last longer than one sitting at 90%.

 

[Silicon Desert]

this has been advised by some tesla service technicians...

Really? Haven't heard that one. I think I'd rather hear from a battery chemistry expert rather than my Tesla tech Maybe yours are smarter.
Gives me an idea though. I will start telling the wife that I need to rest a long time after taking a trip before being asked to do house chores

 

[sonic88]

I do think there is some truth to that but only if you charge relatively fast (i.e. 5kw or more) as this generates more battery heat on an already warm/strained battery.

Yes it makes sense from the point of view that less heat is better for the battery.
However, thinking about the inbuilt protection within the car; does it not auto cool the battery when required for these sorts of situations, therefore ensuring that the battery wont be strained?

t
Im not convinced if you charge from an outlet at i.e 2 or 3 kw that it makes any difference though i do let my battery rest for an hour or so if i come home and there is only 5% charge left.

There isnt much (if any) evidence that sitting at i.e. 5% charge (true 10%) damages the battery more than 90% (true 85% or so). I'd argue a battery at 5% will probably last longer than one sitting at 90%.

I have the standard 7kw charging at home, which is what i use.
Normally i charge when the car hits 20-30% back up to 90%. Within these ranges, i tend to let the car rest and sleep a good couple of hours before charging (which supposedly lets the car take OCV readings to improve BMS accuracies?)
However, wondered if its worth doing this when one reaches lower soc (5-10%) i.e. letting it rest/sleep for at least 3hrs before giving it a charge.

 

[KenC]

Is there any truth, or benefit that one should let the battery rest (i.e for a few hours) before charging where possible?

Obvious it would not be convenient in situations where you need to charge at a stop off, in order to continue your journey.
But in other instances, where you come back from home after a long trip then this might be different. However, if you arrive home from a low soc (i.e. just below 10%) then naturally i would think its best to charge asap to get it back up above 20% or so?

Curious what the general benefit is for letting the battery rest after a drive before charging; and if this something you one should aim to do even in the scenarios of arriving home at a low soc (10% or low etc)?

Cheers

Can't remember everything I've read, but vaguely recall @EV-Tech Exp recommending plugging in after driving, to charge while the battery is still warm, to prevent lithium plating, then warming up the car and doing a little charging before driving in the morning. There's a thread with lots of good info. Search the word "scientific" and you'll find a 10 page thread. I'd read @EV-Tech's comments particularly.

 

[XLR82XS]

No. Just follow the manual's advice.

 

[ucmndd]

Anecdotally speaking - if I L2 charge my Model S at home immediately after arriving with a hot battery (my home is at the top of a very steep hill so this is usually the case) the cooling system runs at full tilt for 30-60 minutes, trying very hard to bring the temp down. This never happens if I let the car sit for an hour or two first.

The car’s software really wants the pack temp lower when charging. Not cold, mind you, but surely not hot either. Read into that what you will.

 

[sonic88]

Anecdotally speaking - if I L2 charge my Model S at home immediately after arriving with a hot battery (my home is at the top of a very steep hill so this is usually the case) the cooling system runs at full tilt for 30-60 minutes, trying very hard to bring the temp down. This never happens if I let the car sit for an hour or two first.

The car’s software really wants the pack temp lower when charging. Not cold, mind you, but surely not hot either. Read into that what you will.

Yes i think concluding its not a bad thing to do, and def worth doing. I'm probably over thinking it, and probably wont make much of a difference coming from a colder climate to you. Currently either single or low double digits degrees Celsius.
However, i probably wont be doing this if my final soc of pretty low (<10%) and will end up just charging on L2 to get things back up.

 

[XLR82XS]

Battery thermal management system people.

 

[Rockster]

We were told by the service center that if we arrive home and the battery is at less than 10% that we should wait an hour or two before charging it.

 

[animorph]

If your destination is a Supercharger the car preconditions the battery by making sure it is warm enough for the fastest supercharging. IIRC that's something like 104F, much hotter than you might think. That goes away if you wait. Of course during our Southwest summer road trips the X is working hard to cool the battery once supercharging is well underway. Though waiting in 110F weather won't help in that case either.

The one specific case I can think of when you shouldn't wait is in near freezing weather. In that case supercharge on arrival to take advantage of the warm battery. If you wait a few hours (or overnight) supercharging will be very slow until the battery has been warmed up.

I wouldn't worry about AC charging at all. I haven't read about waiting to AC charge until now. I don't know of any battery life reason to wait. That said, I do use scheduled charge so I am essentially waiting a few hours after use before AC charging.

 

[ucmndd]

No. Just follow the manual's advice.

Following the manual's advice is not mutually exclusive to the question being asked, unless you can produce a section of manual that states definitively what to do in this case.

Battery thermal management system people.

As I posted upthread - the thermal management system is a good thing to take a cue from in this case. If it's howling in protest desperately trying to lower the pack temp while you're charging, that's probably a sign it doesn't like what's going on. Detrimental to the battery? Doubtful. But also a waste of energy and stress on the cooling system unless you NEED to be charging right then. If not, seems perfectly reasonable to let the heat bleed off naturally for a few hours and then charge later.

 

[Candleflame]

Yes it makes sense from the point of view that less heat is better for the battery.
However, thinking about the inbuilt protection within the car; does it not auto cool the battery when required for these sorts of situations, therefore ensuring that the battery wont be strained?



I have the standard 7kw charging at home, which is what i use.
Normally i charge when the car hits 20-30% back up to 90%. Within these ranges, i tend to let the car rest and sleep a good couple of hours before charging (which supposedly lets the car take OCV readings to improve BMS accuracies?)
However, wondered if its worth doing this when one reaches lower soc (5-10%) i.e. letting it rest/sleep for at least 3hrs before giving it a charge.

the battery does cooled but only to stay below 30 degrees. 30 degrees is still quite hot. Anything below 20 is neglibile.

 

[Candleflame]

Really? Haven't heard that one. I think I'd rather hear from a battery chemistry expert rather than my Tesla tech Maybe yours are smarter.
Gives me an idea though. I will start telling the wife that I need to rest a long time after taking a trip before being asked to do house chores

teslas official advice is to do what is most comfortable to the customer i.e. pluggin in every day setting range to 90% not necessarily whats best for the battery. as long as the battery doesnt go down to 70% of capacity before their warranty is over its all good. However people here are generally preoccupied with trying to keep it above 95% which requires a lot more tinkering.

 

[Gasaraki]

this has been advised by some tesla service technicians...

I do think there is some truth to that but only if you charge relatively fast (i.e. 5kw or more) as this generates more battery heat on an already warm/strained battery.
Im not convinced if you charge from an outlet at i.e 2 or 3 kw that it makes any difference though i do let my battery rest for an hour or so if i come home and there is only 5% charge left.

There isnt much (if any) evidence that sitting at i.e. 5% charge (true 10%) damages the battery more than 90% (true 85% or so). I'd argue a battery at 5% will probably last longer than one sitting at 90%.

I don't believe that one bit. The max at home charging speed is 11kw. If you are on a road trip and you stop at a super charger, you get 50kw-250kw. Now you're telling that a little slow 11kw charge at home is going to damage the battery? Really? You think that the battery get "too hot" from a normal drive? You think that the car has no way to regulate the temperature of the battery while driving to keep it at a good temp?

 

[Gasaraki]

Anecdotally speaking - if I L2 charge my Model S at home immediately after arriving with a hot battery (my home is at the top of a very steep hill so this is usually the case) the cooling system runs at full tilt for 30-60 minutes, trying very hard to bring the temp down. This never happens if I let the car sit for an hour or two first.

The car’s software really wants the pack temp lower when charging. Not cold, mind you, but surely not hot either. Read into that what you will.

The batteries like to be charged at 40C-50C.

People can disagree all they want.

 

[ucmndd]

The batteries like to be charged at 40C-50C.

Clever of you to “disagree” with my first-hand observation which I state is anecdotal.

Are you suggesting I’m lying about how my car behaves?

Your assertion that the batteries “like” to be charged at temperatures approaching 50C is simply false. Others observing the BMS during supercharging preconditioning have observed that the target temp appears to be somewhere around 40C, but the objective there is to enable charging as QUICKLY as possible, which is not the same thing as an optimal temperature for charging efficiently or with minimal component stress.

 

[Rocky_H]

Is there any truth, or benefit that one should let the battery rest (i.e for a few hours) before charging where possible?

I've watched this thread play out for a little while to see what people would come up with first.

this has been advised by some tesla service technicians...

Yes. There is some truth to this, but only with respect to Supercharger charging rates I believe, not the very low power rates of home AC charging. Do you remember the stories of when the first Tesloop vehicle had gone over 400,000 miles? It was reported several places, and one of the things they did mention was that it did have to get a battery replacement because the high mileage had gotten it into some kind of condition where it wasn't reading the energy correctly. Here is an excerpt from the Tesla service notes about its battery replacement:

"Found internal imbalance in HV battery due to consistent supercharging to 100% from a low state of charge (SOC) without any rest periods in between. HV battery has been approved to be replaced. Also recommend that customer does not Supercharge on a regular basis and does not charge to 100% on a regular basis. We also recommend that the customer use scheduled charging to start charge 3 hours after end of drive at low SOC."

Here's how a Tesla Model S holds up after 400,000 miles in 3 years - Electrek

So yes, basically all of that. Immediate Supercharging right after running it down to very low state of charge without rest was noted by Tesla service as the main factor causing whatever this kind of problem was.

But as with a lot of battery things with Teslas, I would be fairly sure that since discovering this, they have made changes in newer cars and battery packs, so I doubt the Model 3 or Y packs would have this same issue.

 

[ucmndd]

Thank you for finding that. I knew I had read this somewhere but couldn’t find it for the life of me.

There is some truth to this, but only with respect to Supercharger charging rates I believe, not the very low power rates of home AC charging.

...

Here is an excerpt from the Tesla service notes about its battery replacement:

"...We also recommend that the customer use scheduled charging to start charge 3 hours after end of drive at low SOC."

One point, “scheduled charging” and starting to charge 3 hours after end of drive at low SoC is clearly referring to home AC charging and the “slow” rates associated with that. There’s no scheduling a charge at a supercharger...

 

[Rocky_H]

One point, “scheduled charging” and starting to charge 3 hours after end of drive at low SoC is clearly referring to home AC charging and the “slow” rates associated with that. There’s no scheduling a charge at a supercharger...

Oh yeah, I hadn't picked up on that. Maybe that applies some on regular charging too then. When you're jumping from Supercharger to Supercharger on a trip, though, it's going to mostly be unavoidable.