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Keeping your EV Battery healthy during this difficult time

Keeping your EV Battery healthy during this difficult time
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For EV owners across the nation. Being on lockdown is bad enough but not driving your EV is even worse. Not because they are so nice to drive, but it can be unhealthy for the battery if left stationary for a long time. Luckily! I found an interesting video which will hopefully answer all your questions. 

What do you normally do? After checking my car, luckily its on around 76%.


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Hi EV owners - a potentially stupid question here:

 

Battery health: does every model of EV allow monitoring of batter health, in terms or mileage, duration, charging time etc?

 

Does this visibility vary per model?

Yes, every EV will track battery capacity and battery impedance. This is necessary to establish the available charge, to predict the range, and to limit the battery power to safe levels, and it is a standard function of the BMS. 

However, not every car will tell you these values. Often you need to resort to third party tools to find out the estimate. OEMs often want to keep the details secret, but so far it seems that every car has been “hacked” eventually to get the information. 

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Thank you for that feed back. That's reassuring to know. 

Userlevel 7

Hi EV owners - a potentially stupid question here:

 

Battery health: does every model of EV allow monitoring of batter health, in terms or mileage, duration, charging time etc?

 

Does this visibility vary per model?

Userlevel 3

@NoPoke true, but then again there's the physics and the manufacturer software that combined may make some difference. We keep our car settings at low or medium charge speed as this should be a decent compromise between convenience and battery protection. I'm not sure we've ever had it set at the highest charge speed as we generally only aim at a top up on the very occasional public charger we might use, not aiming to refill totally. I don't know all the details of battery tech, and tbh I don't feel I need to, but overall, if BMW manual says leave it plugged in when we are away, then it feels the best thing to do.

Having said that, in summer we often leave it unplugged for 2 or 3 nights for the 20 mile round trip commute. 

One issue in the winter though is vehicle preconditioning cycle. Its great to get into a cosy vehicle in freezing weather, and it's also best for the battery if its warmed a little before driving off, but in frosty temperatures that can pull on the battery a lot if it isn't plugged in. So we always plug in overnight in winter. Also we live in a rural area where there is some risk of getting stuck in snowy weather. It wouldn't be wise to set off with only a partial battery charge. 

 

Overall, re 30-80 % charge, I'm not sure how much real life difference it makes, especially when we are unlikely to keep this car for more than 4 years. EV tech has been fast moving since we got our car in 2017, and we are on pcp, so we are likely to look at what's new next year anyway. We do our best to take care of the battery, but don't obsess about.

 

And as I think I all ready said, the nation needs healthcare workers so I'm still working unless we are ill and the car is getting used 4 days a week anyway. 

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Hi @ITGeek123 , Yes, I’ve been plugging mine in to charge to 80% every morning, I guess it typically sits at around 79% until lunch, when some of the battery may be used to help out the grid, but the level doesn't typically drop much from there until tea time.  I’ve been keeping an eye on the degradation of the battery since Jan where battery was at 86.5% as of last Saturday it’s now at 85% will be interesting to see the impact during this stay at home business.

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I should have mentioned it is plugged into a VTG charger all the time at the moment. It’s just a 2016 30kWh Acenta.  Yes I’m using leafSpy, been interesting to see the fluctuations, with the SOH actually going up on one occasion, so I assume it’s not a perfect measure of the health, but better than the overly simplistic 12 bars, I should expect to lose my first bar any day now.

Oh wow! Yeah I would be interested to know dude. Please do post screenshot of your SOH when you get chance

Userlevel 6

This is such an important post, @ITGeek123, I’ve made it into a news article, this is definitely going to benefit a lot of other members! 

@John_Treehouse @Stephen Bell  @Steve587 @UC Bear @Scotty22@PeterR1947 @Simonfea @MajorSqueeze @Gum168 @JimTraynor @ITGeek123 @Fred Rick @Delboy @SianiAnni@joss@Transparent take a look :eyes:

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Thank you @Amy_OVO :heart_eyes:

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I’m not convinced about the accuracy of leafspy, here’s mine:

This shows that Hx is 118.81%, I believe that Hx isn’t supposed to be greater than 100%

 

My SOH reduced fairly rapidly, car is currently two years old and mileage 17666, 2018 40kWh vehicles seem to be similar in this respect

Userlevel 5

Tesla’s NCA cells seem to prefer to be stored at less than 50%SOC.  That is well below the 50% mileage based UI SOC.

I’m trying to maintain the cells below 3.6V  Which means I have to periodically plug in due to the notorious vampire drain and have to unplug early to avoid the car going to 50% indicated which is above 3.6V

ref https://www.researchgate.net/publication/312275993_Calendar_Aging_of_NCA_Lithium-Ion_Batteries_Investigated_by_Differential_Voltage_Analysis_and_Coulomb_Tracking



For all Li-ion cool is better than warm

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Interesting, however BMW claim to have some clever tech that means we should keep our car plugged in when not using it, even for weeks at a time. It's all very fuzzy, they don't seem very clear on how it works, but that's the official line from the manufacturer. I don't think we can set a maximum charge, because BMW claim we don't need to, due to this bit of tech magic. No idea if it works, but when we are using the car daily for work then we don't always charge overnight. We car share as we work near each other. And anyway, at the moment, we are still both working as we are key workers, so we only get semi lockdown, car still used 3-4 days a week. 

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I’d rather put my faith in electrochemists, battery researchers and manufacturers than the author of a handbook/ user guide which will be heavily influenced by marketing.  There is nothing special about BMW batteries, there is no BMS that can change the laws of physics within a cell.

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That's where we are today. The car was registered May 2017. This is a 94Ah Rex, so I believe brand new the battery should have been 33. Mileage 37,901. So roughly a 10.4 % drop. Obviously both age and miles need to be taken into account... Not sure how good or bad our degradation is compared to typical for that profile of use. 

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From the manufacturer manual. So we follow that really. 

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That's where we are today. The car was registered May 2017. This is a 94Ah Rex, so I believe brand new the battery should have been 33. Mileage 37,901. So roughly a 10.4 % drop. Obviously both age and miles need to be taken into account... Not sure how good or bad our degradation is compared to typical for that profile of use. 

This is amazing! I wouldn’;t call this a bad degradation at all! Whatever BMW have in place appears to be doing good! Thank you so much for sharing this. It’s really interesting.

Userlevel 7

Great info on the ways an EV will monitor battery health, @MrPuds.

 

Just for the uninitiated here, what is meant by BMS (battery monitoring system?) and OEM?

 

Very interesting to hear that this is not always easily checkable on every car - given the increasing second-hand EV market I wonder if these hacks will have to be made official at some point? :thinking:

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It would also be interesting to know the SOH of the battery after this lockdown. Am I right in guessing you are a 40/62kw Leaf owner? If so, do you have Leaf spy on your phone? 

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I should have mentioned it is plugged into a VTG charger all the time at the moment. It’s just a 2016 30kWh Acenta.  Yes I’m using leafSpy, been interesting to see the fluctuations, with the SOH actually going up on one occasion, so I assume it’s not a perfect measure of the health, but better than the overly simplistic 12 bars, I should expect to lose my first bar any day now.

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As I understand it, the Indra/Kaluza algorithm exports from the battery in digital format. Ie it’s delivering as nigh on 16A to the grid or nothing.

 

I wonder whether these pulses are beneficial or detrimental to battery life.

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@Gum168 Is this with the BMW i3? I think I may need to read up on BMW and their BMS in the cars.

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Yes, that's the i3. Ours is 2017. 

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@Gum168 it would be really interesting to know your cars battery SOH 🤔 not sure if there is an app you can use for i3. But you can see the maximum the battery can store through the menu.

 

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