[adityadeva]

This thread is for one of my colleagues who purchased a brand new Tata Tigor EV, a couple of weeks back.

He was told to charge his car at home to 100% once charge comes down to around 20%.

But once his charge dipped below 20% and he barely managed to reach home with 7% charge left. After this incident he has become a victim of range anxiety. He has a average run of 25 to 30 kms per day.

How should he charge his vehicle in order to have a good battery life.

He does have a solar charging at home.

After doing my bit of studies, I've advised him to charge up to 100% once in two days.

Initially I was under the impression that maintaining a charge between 20 - 80% was the best way to go as in the case of mobile phones ( it gives a really good life for the battery for mobile phone battery ).

But in case of ev, the battery pack is a cluster of cells in series -paralell combination. So 20-80 might not hold good as charge levels may not be uniform across the individual cells. Also, if any one of the individual cells goes faulty, it will affect the entire battery pack. Further, the BMS will never charge the battery pack to it's actual full potential - keeping some buffer.

The following YouTube video was taken as a reference.

https://youtu.be/FvihSie5hD8

[Lobogris]

After using the MG ZS EV for about 9 months, I can provide some advice. Tata uses LFP batteries that are somewhat resistant to ill effects of charging to 100%. These batteries are of slightly inferior quality due to budget constraints and thus people tend to see SOC drop issues from time to time. It is not uncommon to see the battery drop from say 60% to 20% very quickly. So charging them to 100% from a low of around 20% helps balance the cells and allows the BMS (battery management system) to calibrate. So my advice would be to charge routinely from around 20 to 40% mark to the 80 to 90% mark and charge fully to 100% every few times. For example, after 3 charge sessions to the 80% level, charge it fully to 100%. It is also good to drop it to as low as possible from time to time to allow the BMS to calibrate. This is a hybrid approach that will help improve battery life in the long run while taking care of the calibration issues prevalent in Tata EVs.
Please note that this advice is specific to Tata EVs. For non Tata EVs, it is better to avoid charging to 100% unless it is necessary.

[GTO]

Not an EV owner, but do a lot of reading on the subject as it greatly interests me. Some tips from an EV noob:

- For overnight charging, slow charging is best for long-term battery health. Related Thread (Why a cheap & simple 15A plug is just fine for home-charging your Electric Car).

- Top it to 80%, not 100%.

- Avoid regular / frequent fast-charging.

- Don't let the charge level drop below 20% on a regular basis.

- If the car is going to be parked for a long time (say, you are travelling or Covid lockdown), bring it up to 80% and leave it. Keeping a battery empty hurts it.

Just like engines, there will be cars with good batteries & bad batteries. For the cars with good batteries (a majority I reckon), nothing you do will seriously affect the initial 6 - 8 years. They are built very robust and most OEMs anyway offer 8-year warranties. However, I do think we will be seeing many car manufacturers struggle with battery quality, as it's a new space & supply chain for them. Related discussion (Electric Car Batteries: How concerned are you about the replacement costs?).

That being said, an 8-year old battery won't perform like a 1-year old battery. Just like a 100,000 km engine, how you maintain the battery over the years might have a direct impact on its range & performance at the 8-year mark.

[flanker]

This is not correct for lithium ion batteries. The state of charge at storage is directly proportional to degradation. They should be kept at lower SOC for extensive storage.

Originally Posted by GTO

- If the car is going to be parked for a long time (say, you are travelling or Covid lockdown), bring it up to 80% and leave it. Keeping a battery empty hurts it.

[SKC-auto]

Originally Posted by flanker

This is not correct for lithium ion batteries. The state of charge at storage is directly proportional to degradation. They should be kept at lower SOC for extensive storage.

Attachment 2315505

Are these graphs about maintaining 14% SOC, 50% & 90% throughout the storage for 2 years? Which means plug it in for 2 years with 14% SOC limit for better battery health?

I believe for short term storage of 20-60days it is better to maintain at 50% soc limit by keep charging or leave it at 90% if not charging. If you leave at 14% without charging, within few days it reaches to 0% SOC and will be left with no charge to condition the battery.

[prasanna_indaje]

Originally Posted by GTO

- Top it to 80%, not 100%.

- Avoid regular / frequent fast-charging.

- Don't let the charge level drop below 20% on a regular basis.

- Slow charging to 100% is better as cell balancing happens between 90% to 100 %. There are chances of facing critical error, if charging is stopped at 80% always.

- General recommendation is to go for 1 slow charging session after 4 consecutive fast charging sessions.

- Don't worry if the charge drops below 10% (or even 5%), charge to 100% and move on. (Note : Its a pain to drive below 10% SoC, with constant beeps and in limp home mode)

[flanker]

Originally Posted by SKC-auto

Are these graphs about maintaining 14% SOC, 50% & 90% throughout the storage for 2 years? Which means plug it in for 2 years with 14% SOC limit for better battery health?

I believe for short term storage of 20-60days it is better to maintain at 50% soc limit by keep charging or leave it at 90% if not charging. If you leave at 14% without charging, within few days it reaches to 0% SOC and will be left with no charge to condition the battery.

In most EVs, the HV is not bought online when parked. Tesla being different keeps draining HV for other purposes. In ZS EV the phantom drain is not even 1% a month. I had the car through the lockdown and I tracked the phantom drain.

The 14% is not an absolute number, one can leave at 20 to 30% and even in 6 months it will not be anywhere near zero.

Storing at higher SOC in higher temperature is sure way to degrade the battery faster. This result is not from one off study, there are many research papers with the same outcome.

[Rocketscience]

Originally Posted by prasanna_indaje

- Slow charging to 100% is better as cell balancing happens between 90% to 100 %. There are chances of facing critical error, if charging is stopped at 80% always.

Is it different from say Batteries in phone? I have almost always slow (5w) charged my phone till 80-85% and hardly let it dip below 20%, primary reason is Apple charges an unreasonable amount for its battery replacement. (Samsung for example charges less than ₹2000 for the same even for its flagships so one might not bother at all)

Now even after 680 cycles, my phone shows battery health at 82% and coconut battery shows it at 87%.
Apple themselves claim 80% health at 500 cycles post which we should replace it and it has exceeded that by a fair margin and still going strong.

So here slow 20-80% charging helped immensely, how is it different with cars and what is cell balancing? one possible reason i could think is phones have 1 battery as compared to several small cells in a car's battery pack, is that got to do something with battery balancing?

Also how does fast charging help its cause despite producing extra heat? My sister's phone for example got to 86% battery health after just 300 cycles of fast charging and always charging to full.

Pardon my ignorance and I would really love to know the reasons behind all this and how do these compare with phone's lithium ion batteries?

[Durango Dude]

I think with all the connected car tech, EV's must have an app over the phone where one can switch off charging once it reaches say 80-90% in the interest of battery health. It's a chore to go down and check the charge on your car. Have a doubt regards the quality of the individual cells used by Indian OEM's in the the interest of keeping costs down to suit Indian pockets. Plus like any car battery if an individual cell fails does it mean we change the whole battery pack or the faulty cell, only?

[DarthVeda]

Originally Posted by GTO

- Top it to 80%, not 100%.

- Avoid regular / frequent fast-charging.

the charge to 80% to 90% rule doesn't apply to LFP chemistry. All Nexon EV vehicles use LFP. Charge it to 100% no problem.
BTW, Please be aware that the 100% is not actually 100% of the battery. the Manufacturer set a buffer and ensure the battery is never at 100%. For Nexon EV, it's 30.2kwh capacity, but usable is 28.6Kwh.

I used fast charging predominantly till I started going to office, where I slow charge for free , I never had an issue with that. Too many people, correlate the EV battery to mobile, I mean it's not the same. The same thought process going for "what happens after battery dies", it's not like EV owners will dump the battery to a garbage bin

The battery is guaranteed for 8 years, enjoy those 8 years, after which it is not going to decide "hey, 8 years is over, let me die". It will reduce run at reduced capacity, but by then, the battery tech would have improved and hopefully, you can fit in a bigger capacity battery.

[sri_tesla]

Originally Posted by Lobogris

After using the MG ZS EV for about 9 months, I can provide some advice. Tata uses LFP batteries that are somewhat resistant to ill effects of charging to 100%. These batteries are of slightly inferior quality due to budget constraints and thus people tend to see SOC drop issues from time to time. It is not uncommon to see the battery drop from say 60% to 20% very quickly.

Please note that this advice is specific to Tata EVs. For non Tata EVs, it is better to avoid charging to 100% unless it is necessary.

The reason for the sudden SOC drop issues in Tata Nexon is not because Tata using some inferior quality batteries. It's due to difficulty in estimating the SoC of the LFP battery for BMS. Compared to other battery chemistries, LFP’s charge/discharge voltage curves are extremely flat. Basically, the voltage only rises when the battery is almost full and drops when it’s almost empty.

See the extremely flat charge/discharge curve of LFP (LiFePO4) batteries in below image:



Here is a detailed explanation and best charging behavior for LFP batteries that Tata uses:

https://pushevs.com/2022/04/21/best-...lfp-batteries/

This is the reason why Tesla also recommends fully charging the Model 3 cars that have LFP batteries because it helps the BMS (Battery Management System) to estimate the available battery capacity more precisely.

[aim120]

Originally Posted by sri_tesla

The reason for the sudden SOC drop issues in Tata Nexon is not because Tata using some inferior quality batteries. It's due to difficulty in estimating the SoC of the LFP battery for BMS. Compared to other battery chemistries, LFP’s charge/discharge voltage curves are extremely flat. Basically, the voltage only rises when the battery is almost full and drops when it’s almost empty.

See the extremely flat charge/discharge curve of LFP (LiFePO4) batteries in below image:

True about LFP. The moment the charger stops charging the LFP battery, the voltage drops from 3.6v to around 3.2* V.

Fun but informative trivia.
In 2010 when I used to race in Radio control cars, while most used to come with nitro engine powered cars, the few who came with electric RC cars all had LiPo batteries, while I was the only one in the track who had a LFP battery.

Because of this flat curve till the end of the capacity, my RC car had the same voltage after the race (5s battery 16.2v fresh out of the charger), while the guys with Lipo 4s battery had 16.8v fresh out of the charger and they lost about 4v by the end of the race (12.8v), while mine was still showing 15.75v and each extra volt gave me another 2000rpm at the motor, so I used to lap others. While the guys with lipo where all scratching their heads. (this was before any ROAR approved batteries for Race).

This flat curve was also a curse, my RC car used to stop abruptly, since there is no way of knowing the SOC. All that the RC cars had was a volt meter with LEDs mimicking the SOC percentage based on the battery volts. In my case the RC transmitter used to show the voltage which is of no use if you have a LFP.

So I disabled the low voltage cut off, which allowed me to limp back to the pit area and change batteries (this was only when racing in open class against nitro powered cars that could refuel). I could disable the low voltage cut off in the electronic speed controller or ESC because I had no reason to be concerned with thermal runaway since it's a LFP battery.

While the guys with Lipo used to set a alarm at 3.2v per cell, so that they could get back to the pits before the voltage falls dangerously below 2.8v per cell which can cause thermal runaway. Since with a small 4ah to 5ah battery these cars are pulling around 80 amps or more.

For LFP battery you need a kwh meter aka coulomb meter to accurately know the SOC.

Also some people report that there is no phantom drain in MG ZS, this could also be due to the LFP battery flat curve.

[Vitalstatistiks]

Originally Posted by Rocketscience

Now even after 680 cycles, my phone shows battery health at 82% and coconut battery shows it at 87%.

OT: Mind sharing how do you download/use this coconut battery? It’s not in form of an app on AppStore.

[Rocketscience]

Originally Posted by Vitalstatistiks

OT: Mind sharing how do you download/use this coconut battery? It’s not in form of an app on AppStore.

First of all it is an app for the mac and not iPhone itself.

Secondly, It is easy actually, there is a world of apps available outside mac app store (unlike iphone) and you can download and install setup files.

For this you can google this app (not posting link here, not sure if it is allowed or not) and download the DMG (setup) file, after that you will need to open the file and drag and drop to application folder or install it by following the on screen instructions just like an windows setup file.

You might need to allow applications from outside sources in security settings to run this app.

This app is pretty useful too, provides battery information including the number of cycles and its estimated battery health (which some consider better than apple's own) for both the macbook and iPhone/iPad connected using USB.

If you need more information you can DM me.

PS It has actually revised my battery health rating from 84/83 to 87%, because that 84 was 4 months ago when it was really cold outside and batteries usually don't perform optimally in those conditions, but now that it is super hot, it is showing hopefully the true battery health.
All this while from the past 6 months infact my phone is showing battery health at 82% and hasn't shifted an inch from there despite multiple software updates. (It is supposed to re calculate/recheck it during updates too), so take what you may from this.

[cool_dube]

Having owned an EV for almost 5 years now, I can safely say that slow-charging the battery to 100% is far from being detrimental. In fact, it is good for cell-balancing and better calibration of the battery by BMS. I've never come across a recommendation to cut the charging cycle off at anything below 100% SOC unless absolutely required (e.g. lack of time).

Also, letting the battery drain to 10-15% SOC is a good practice, as long as you plan it properly so as to not run out of charge on the road.

Essentially, letting a battery "traverse" through its SOC range to the maximum extent possible is good for battery longevity in general.