What's better, immediately putting a low battery on charge or leaving it 90 minutes before putting it on charge?

[MassDeduction]

It's easy to get lists of battery best practices, things such as wait 90 minutes before putting it on charge, not charging it above 80%, storing it near 50%, etc. But they rarely address the fact that some suggestions can be mutually exclusive. For example, if you finish a trip at 25% charge, you're well below the ideal charge to store the car at, but if you immediately put it on charge then you're not giving the battery any time to cool down beforehand.

My normal inclination is to wait 90 minutes, then charge the battery up to only 50%, then set a timer to get it up to 80% right before the next trip. But different battery chemistries benefit more, or less, from the "cool down" period before going on charge. And temperature makes a different too, so I suppose it can depend.

Thoughts on whether someone living in a mild climate with a 2016 Kia Soul EV would benefit more from a 90 minute cool down before any charging, or would benefit more from immediately charging back up to 50%?

 

[JejuSoul]

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My practice, if I arrive home at 6pm with 30% and don't need the car again that evening would be :
Plug in and set the timer to start at 11pm when rates are cheapest. Charge to 80%.
This lets the battery cool down first and charges when it is cooler.

I have a 32A charger. If you were charging at 6A you would probably have to start earlier.

 

[tinsley207]

I'm interested in this too. I'm new to the form BTW and I'm a proud new owner of a 2016 Soul with 15k miles on it! Today I ran it down pretty far, 14% left. I parked it and set the timer for 80% to start at 4am. That was about 3 hours ago. Should I give it a little "boost" right now to 50%? Or is it ok to sit for several hours at 14% until 4am? Thanks.

PS: I have a 32 amp charger.

 

[MassDeduction]

I'm interested in this too. I'm new to the form BTW and I'm a proud new owner of a 2016 Soul with 15k miles on it! Today I ran it down pretty far, 14% left. I parked it and set the timer for 80% to start at 4am. That was about 3 hours ago. Should I give it a little "boost" right now to 50%? Or is it ok to sit for several hours at 14% until 4am? Thanks.

PS: I have a 32 amp charger.

My current inclination is to think that 14% is too low, and that it would be best to immediately top it up to about 40-50%, then set the timer to later complete the charge to 80%. It's just as undesirable (if not more so) to have it sit below 20% than it is to have it sit above 80%.

I would never let the car sit more than 90 minutes before starting topping it up to at least 50%. And if it was 35% or lower I might put it on charge immediately. You're trading off the value of letting it sit fallow before being charged, vs. the detriment of it sitting at a low charge level longer than it needs to.

It can change from one battery to the next, as different chemistries are more/less tolerant of certain kinds of abuse, but in general I tend to wait 90 minutes, then top up to 50%, then set it for timed charging to whatever I want it at for its next use. The exception is if it's really low, then I put it immediately on charge to get it up to 50%. What's really low is subjective, I suppose.

 

[IanL]

I wonder how valid the "letting it cool down" is in temperate climates? To my mind, the battery will charge best if it is at "normal operating temperature", and if the ambient temperature is (say) less than 30C, it should be fine to charge straight away. I have not tested this, but I expect the cooling fan in the trunk will function during charging if required - I believe it takes in air from the cabin which I assume is replaced from outside.

A lot of assumptions there, so I'd welcome other views.

 

[ksoul2084]

I wonder how valid the "letting it cool down" is in temperate climates? To my mind, the battery will charge best if it is at "normal operating temperature", and if the ambient temperature is (say) less than 30C, it should be fine to charge straight away. I have not tested this, but I expect the cooling fan in the trunk will function during charging if required - I believe it takes in air from the cabin which I assume is replaced from outside.

A lot of assumptions there, so I'd welcome other views.

I agree with your assessment. To my knowledge it is more efficient/better to charge a battery that is already warm as it lowers resistance in the pack. Unless you are talking about a climate where it's >35c outside I'd charge as soon as I parked.

I believe with the latest firmware updates the car will engage the AC and the battery fan to control temp. if necessary. Living in Canada, and usually charging using Level 1 it's not something I've experienced.

 

[MassDeduction]

I wonder how valid the "letting it cool down" is in temperate climates? To my mind, the battery will charge best if it is at "normal operating temperature", and if the ambient temperature is (say) less than 30C, it should be fine to charge straight away. I have not tested this, but I expect the cooling fan in the trunk will function during charging if required - I believe it takes in air from the cabin which I assume is replaced from outside.

A lot of assumptions there, so I'd welcome other views.

I agree with your assessment. To my knowledge it is more efficient/better to charge a battery that is already warm as it lowers resistance in the pack. Unless you are talking about a climate where it's >35c outside I'd charge as soon as I parked.

I believe with the latest firmware updates the car will engage the AC and the battery fan to control temp. if necessary. Living in Canada, and usually charging using Level 1 it's not something I've experienced.

To be clear, I meant letting it cool down metaphorically rather than literally. It's frequently stated that the battery coming to rest first can be beneficial before re-charging it, with times in the 30-90 minute range frequently cited.

Higher temperatures are more efficient for battery charging and operation, but charging at cooler temperatures is better for long-term battery life. A battery will charge and operate more efficiently in Phoenix, but it will have a longer service life in Vancouver.

None of this explicitly confirms whether it's best to immediately start re-charging a very low battery, or to let it sit a bit beforehand. The evidence I've seen, however, suggests that a low charge level damages a battery a lot and putting it immediately on charge after use damages it only a little, so my current thinking is to put a very low battery immediately on charge. The trick is what is "very low"? I'm leaning to 35% as the dividing line, below that put it on charge immediately, above that wait 30-90 minutes before charging it back up to at least 50%.

 

[IanL]

Well, it rarely, if ever, gets to 30C here, so my practice of running down to 20-30% and then charging immediately seems ok to me. My car seems to agree:

(149 miles = 238 km)
(long-term efficiency is 5.3 miles/kWh)

 

[ksoul2084]

It's frequently stated that the battery coming to rest first can be beneficial before re-charging it, with times in the 30-90 minute range frequently cited.

Interesting, this is not something I'd heard of. Could you post a reference for followup?

If you think about the normal operation of the car it's continually switching between discharge and charge when driving about town due to the regenerative braking.

 

[JejuSoul]

...To my knowledge it is more efficient/better to charge a battery that is already warm as it lowers resistance in the pack...

This is an argument I have had with TeslaBjorn.
It is true that the battery will charge quicker and more efficiently when it is warm.
It also charges faster at the lower end of the SOC curve
His recommendation for long distance drives is to drive fast to a low SOC - then charge faster.

I think this is bad advice. Charging while the battery is hot degrades the battery faster, especially at the very low and very high ends of the SOC curve.
The air pump is not effective enough to counteract the heat build-up in the battery. Even if you have the air-con on full in the cabin.

I argue that it is better for the battery to drive a bit slower, and then charge a bit slower.
It takes a bit longer but it is much better for the long term health of the battery.

MassDeduction - I doubt that 35% SOC is very low. I would guess 15%.

IanL - 238 km at 8.5 km / kWh is great. The best I have got is 211 km at 7.5 km / kWh.
Either a) You have 100 cells - so your car has a higher voltage and hence is more efficient. or b) You have a softer foot than me. or c) your island's roads are much slower than mine. or d) a combination of all 3.

 

[ksoul2084]

...To my knowledge it is more efficient/better to charge a battery that is already warm as it lowers resistance in the pack...

This is an argument I have had with TeslaBjorn.
It is true that the battery will charge quicker and more efficiently when it is warm.
It also charges faster at the lower end of the SOC curve
His recommendation for long distance drives is to drive fast to a low SOC - then charge faster.

Well my recollection is that TeslaBjorn's optimal strategy (for long roadtrips) is to stop more frequently and keep your charge between 30-70% because that is the sweet-spot for the fastest charging rates at the supercharger (net is it's faster to stop more and wait less in total). This also should be better for the battery health in general vs. letting it drop/charge neither completely empty or full.

I think this is bad advice. Charging while the battery is hot degrades the battery faster, especially at the very low and very high ends of the SOC curve.
The air pump is not effective enough to counteract the heat build-up in the battery. Even if you have the air-con on full in the cabin.

Agreed that very high temps for the battery are harder on the battery. What do you base your statement on that the Soul battery fan isn't capable of keeping the battery cool enough, even with A/C on? In any case, that would only apply to fast-charging, Level 2/1 shouldn't be an issue in terms of heat buildup.

I argue that it is better for the battery to drive a bit slower, and then charge a bit slower.
It takes a bit longer but it is much better for the long term health of the battery.

Yes, slower discharge and slower charge rates are better for overall battery longevity, but maybe not enough to worry about if that means impacting your driving "lifestyle" materially.

TeslaBjorn had an epsiode where he compared the remaining battery capacity of his Model3 (frequently driving fast and fast charged) with a friend's that generally charged at home on level 2 and drove around town at lower speeds. Both with similar mileage.
His car had a noticeably lower remaining battery capacity, though still wasn't bad considering his more extreme driving habits.

MassDeduction - I doubt that 35% SOC is very low. I would guess 15%.

IanL - 238 km at 8.5 km / kWh is great. The best I have got is 211 km at 7.5 km / kWh.
Either a) You have 100 cells - so your car has a higher voltage and hence is more efficient. or b) You have a softer foot than me. or c) your island's roads are much slower than mine. or d) a combination of all 3.

Those are absolutely stellar efficiencies!

I have no chance here as the typical freeway speeds here are 110-125km/h. So even dragging along in the slow lane I'm going 110km/h which gets me closer to 20 kWh/100 kms. When I used to commute to the city to work everyday I could get 15kWh/100kms mixed freeway and city driving. Of course, strictly driving slowly in town is much better.

 

[MassDeduction]

It's frequently stated that the battery coming to rest first can be beneficial before re-charging it, with times in the 30-90 minute range frequently cited.

Interesting, this is not something I'd heard of. Could you post a reference for followup?

If you think about the normal operation of the car it's continually switching between discharge and charge when driving about town due to the regenerative braking.

It's not something I frequently hear in reference to electric cars specifically, but it is something I frequently hear in reference to lithium ion batteries generally. For example, here's a video for electric bikes that references it (fast forward to the 2:00 minute mark): https://www.youtube.com/watch?v=fy4M9hlf2YQ

Agreed that through regen it's doing a lot of recharging. But that doesn't mean it's ideal, it just means that they've chosen recapturing that energy as being preferable to oh-so-slightly better babying of the battery. Regen also does very small amounts of recharging, vs. putting it on charge for minutes or hours. There's also been some talk of future e-cars possibly using capacitors for regen and fast charging, and batteries for slower charging, which might be a partial acknowledgement that it's an issue (however minor).

 

[IanL]

IanL - 238 km at 8.5 km / kWh is great. The best I have got is 211 km at 7.5 km / kWh.
Either a) You have 100 cells - so your car has a higher voltage and hence is more efficient. or b) You have a softer foot than me. or c) your island's roads are much slower than mine. or d) a combination of all 3.

Yes, a) is correct. For b) it's difficult to say, but I do drive in Eco Mode. For c), most of our roads are either 30mph or 40mph, and to drive at 40 on some of them would be close to suicidal

 

[ksoul2084]

It's frequently stated that the battery coming to rest first can be beneficial before re-charging it, with times in the 30-90 minute range frequently cited.

Interesting, this is not something I'd heard of. Could you post a reference for followup?

If you think about the normal operation of the car it's continually switching between discharge and charge when driving about town due to the regenerative braking.

It's not something I frequently hear in reference to electric cars specifically, but it is something I frequently hear in reference to lithium ion batteries generally. For example, here's a video for electric bikes that references it (fast forward to the 2:00 minute mark): https://www.youtube.com/watch?v=fy4M9hlf2YQ

Agreed that through regen it's doing a lot of recharging. But that doesn't mean it's ideal, it just means that they've chosen recapturing that energy as being preferable to oh-so-slightly better babying of the battery. Regen also does very small amounts of recharging, vs. putting it on charge for minutes or hours. There's also been some talk of future e-cars possibly using capacitors for regen and fast charging, and batteries for slower charging, which might be a partial acknowledgement that it's an issue (however minor).

Well that video was filled with a bunch of pretty unspecific claims and advise.

If you really want to be careful with your battery you should just get the SoulSpy app and a suitable Bluetooth ODBC adapter for it and you can monitor the temps in your battery pack and use real data to determine if your car would benefit from a cooling off period after driving before charging or not. Also note that it's probably more important to not charge when the battery is very cold, but we have to assume the BMS and battery heater can manage those effectively.

 

[JejuSoul]

... What do you base your statement on that the Soul battery fan isn't capable of keeping the battery cool enough, even with A/C on? In any case, that would only apply to fast-charging, Level 2/1 shouldn't be an issue in terms of heat buildup..

Leaving the A/C on during charging was something a few of us tested back in 2016.
It seems a lot of the posted graph data from that time has been lost.
But these threads still make interesting reads.
There's some interesting Arizona data here - Palm Springs Summer TMS Torture Test!

...When I got home I charged briefly at 7.2 kW to bring the SOC up off the floor then remote-started the AC without initiating charging just to let the battery cool a bit and to get some data on how effective that is. I have overlaid L2 Charging kW on the fan status graph to give that some representation...

And some of my testing - TMS Behavior

I tested an L2 charge leaving the AC on during the entire time. Of course I had to get up and go outside to turn it off again when the charging finished.
AC set to 24C. Ambient was 27C. The battery temps began at 30C. Reached 33C after a while and stayed there.
The Battery cooling fan was running at the 2nd speed.
I will update this post after running a similar test without AC to see if the extra time (about 15 minutes), extra cost (about 10 cents) and extra hassle of getting up to turn the AC off is at all worthwhile. I am guessing not for nighttime charging. But might make a big difference when daytime temps are really high...

 

[ksoul2084]

Leaving the A/C on during charging was something a few of us tested back in 2016.
It seems a lot of the posted graph data from that time has been lost.
But these threads still make interesting reads...

That AZ post is an interesting read. My take away is that the battery fan wasn't able to control the pack heating effectively while Chademo fast-charging, at least with the high ambient temperatures he was experiencing at the time.

On my recent cross-province 6x fast-charging road trip I didn't have my ODBC dongle with me, unfortunately. It would have been interesting to see what the pack temps were doing during all that highway travel and then immediate fast-charging over 11.5 hours. Ambient temps were not a factor as they would have been 20c or less.

I read somewhere that a recent update tweaked the way the car manages the A/C system relative to charging, I wonder if they've improved the cooling potential during fast charging somehow? I just had all the relevant updates applied to my car before my trip and didn't notice the car starting the A/C system on its own or anything while it was parked fast-charging.

I would say that unless you live somewhere where the outside ambient temps can exceed 40c, you probably have nothing to worry about when L2/L1 charging relative to pack temps. A 33c pack temp while charging is just fine, probably optimal IMHO.

 

[JejuSoul]

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There is an upgrade to the BMS and FATC. described here BMS software update

July 21, 2020
Components, Electric System
NHTSA ID Number: 10177748

Manufacturer Communication Number: TSB_ELE203
TECHNICAL SERVICE BULLETIN: SERVICE ACTION: BMS/FATC OPERATION LOGIC IMPROVEMENT WHILE BATTERY CHARGING (SA427) - This bulletin provides the procedure to upgrade the Battery Management System (BMS) and Full Auto Temperature Control (FATC) software on some 2016-2017MY Soul (PS EV) vehicles, produced from May 21, 2015 through August 29, 2017, in order to improve air conditioning operation while the battery is charging.

No one has yet reported back to say what this does.

 

[ksoul2084]

Thanks for posting that.

It "sounds like" the BMS should be able to trigger the climate A/C automatically if needed to help bring colder air into the battery pack via the battery fan, which as we know pulls air from under the rear seat inside the cabin.

 

[EVDee]

I don't have actual numbers to prove or disprove what I'm experience, but in my experience since having my BMS updated:

- Fast charging no longer has the 84% limitation.
- Fast charging is much slower once you're at ~70%.
- The SoH update/calibration updates differently vs before.
- It now has a unannounced power limit factor when your battery is at a certain temperature.

Typically a fast charge would take me anywhere between 15-20 minutes before reaching 84%, whereas now I've had 30 minute sessions and only manage to get to 80% :shock:

It would also seem that the SoH gets updated more often vs before. My understanding was that it would only recalibrate once the battery had reached a low SoC and was charged up to 100%. Now I've noticed it updating itself despite my charging habits excluding those parameters. While this might seem like a bonus, it's really annoying when you're in the process of getting a battery replacement and they want to cherry-pick a favorable SoH reading. Long story short - when it recalibrates without a deep discharge, the SoH is higher vs when you do a deep discharge calibration.

Lastly, and I would have never noticed this had I not been using Torque at the time, if your battery is ~30-35C the power is limited without notice. I've had the power limited before and it actually tells you it has done so, and still does if it hits a certain limit, but now there's a grey area where a small fraction of power is limited. With my foot on the floor I usually peak at 87kW, but this grey area limited it to 79kW.

Sorry I don't have data logs and whatnot, but this is what I've observed since getting the BMS updated.
Hope it helps!

 

[ksoul2084]

I don't have actual numbers to prove or disprove what I'm experience, but in my experience since having my BMS updated:
...snipped...
Lastly, and I would have never noticed this had I not been using Torque at the time, if your battery is ~30-35C the power is limited without notice. I've had the power limited before and it actually tells you it has done so, and still does if it hits a certain limit, but now there's a grey area where a small fraction of power is limited. With my foot on the floor I usually peak at 87kW, but this grey area limited it to 79kW.

Interesting. I've had the "Power Is Limited" indicator/behaviour in the past when attempting to climb small hills at highway speed in very cold weather.

Are you saying that the "grey-area" limited doesn't apply at battery temps lower than 30cish (and obviously above 10c or whatever, no very cold)?