[Silverback]

I have followed/am following all the discussions about %-age charging levels for the HV Battery & I have set AC to 80% on my 4+.
I have been told, though, that the battery should be charged to 100% on an AC charger (i.e. the one in my garage) 'on a regular basis'.
What are the thoughts about that, especially in these days where it is difficult to get the car out and about? (I'm retired, so very few 'essential' journeys possible let alone let's just take it out and play )
Would it be 'bad' for the battery to be 100% charged but sitting in the garage for days?
Silverback

 

[prawlin]

Taking the SOC to 100% is recommended periodically in order to balance the charge level across all the 98 series connected cell banks. It is recommended monthly in the user manual. However, keeping the battery at that 100% SOC for any length of time is not generally recommended. Yet some folks do it and their cars still work ok. Battery degradation may increase over time though it’s hard to verify this. I also don’t do lots of miles regularly. I aim for loosely 80% SOC mostly. I will go to 100% only very occasionally and will use some of it up soon afterwards. I wouldn’t store it for days or weeks at 100%.
Peter

 

[Xinix]

Yes, charging to 100% and leaving the car at that charge level for a prolonged period of time is bad. Never mind people telling you that 100% is not really 100% or that modern chemistries are resilient to parasytic effects or whatever. The higher the charge, the higher the degradation. Will you notice it immediately? No. Will it lead to degradation in 1 year? Probably not. But why take the risk? Charge to 80% if you don't need the range, charge to 100% when you plan a longer trip and that's it. In order to balance the cells it is indeed recommended to charge to 100% every month, or less if you do not use the car frequently. But don't leave it sitting at high levels of charge.

 

[idiotzoo]

My approach to this, given the general lack of driving at the moment, is to charge to 80% as the default and take it to 100% as it makes sense to do so. We had a day off and took a trip round the North York moors yesterday. Knowing I’d be covering more than 8miles, charged to 100% the night before. This means the car won’t get charged to 100% monthly.... to be honest I only really need to charge it monthly right now.

a lot of this is best efforts rather than set in stone rules. Keeping the car at 100% all the time is probably not great. Never charging to 100% is also not the best. But don’t really worry about it too much.

 

[DragonQ]

My approach to this, given the general lack of driving at the moment, is to charge to 80% as the default and take it to 100% as it makes sense to do so. We had a day off and took a trip round the North York moors yesterday. Knowing I’d be covering more than 8miles, charged to 100% the night before. This means the car won’t get charged to 100% monthly.... to be honest I only really need to charge it monthly right now.

a lot of this is best efforts rather than set in stone rules. Keeping the car at 100% all the time is probably not great. Never charging to 100% is also not the best. But don’t really worry about it too much.

Yep, go to 80% if you need to charge but won't be using the car for a few days. I actually went 2 months between charges recently due to severe lack of driving but other than that I've charged to 100% once a month.

 

[Rob Lazenby]

You need to research into the characteristics of lithium batteries if you want to provide the best for it. For example if you needed 70% charge in one go then it is better to charge to 80% and use down to 10% than it is charging to 90% and use down to 20%. Look into charge cycles for across the percentage range, it's really surprising how many more miles the battery will last if you were to keep it in the 40-60% range, though this may be somewhat impractical. Also consider discharge rates I. E. Motor Power use when temperatures are cold. Having said this the battery is huge and the efficiency is great so unless you want to be a nerd then don't need to worry too much as long as your not leaving it at very high states of charge for prolonged periods.

 

[Greg Elmassian]

All this over again?

no matter what, the more damaging thing to do to lithium ion is deep discharge. discharging to 10% is way worse than discharging to 20%... The concerns of charge to 90% or charge to 80% is way less important.

You told the previous poster to research into lithium batteries, I suggest that recommendation goes for you too... this fascination with how fully to charge the batteries is somehow overwhelming the more important things to follow on the care and feeding of lithium ion batteries....

Greg

 

[Kukkelikuu]

All this over again?

no matter what, the more damaging thing to do to lithium ion is deep discharge. discharging to 10% is way worse than discharging to 20%...

Sincere question: Why or what makes the deep discharge so damaging?

 

[idiotzoo]

Sincere question: Why or what makes the deep discharge so damaging?

A deep discharge can be fatal for lithium ion cells which is why an unused phone left uncharged for too long may not be chargeable again. Mobile phone batteries, for example, tend to have a protection circuit that shuts things off before the battery can be discharged to a damaging level.

The BMS in a car will do the same, calling the battery dead with sufficient margin to prevent the cells getting too close to actual full discharge.

From memory it’s something to do with causing material from the anode to be dissolved into the electrolyte and deposited onto the cathode, which basically knackers everything.

 

[Kukkelikuu]

A deep discharge can be fatal for lithium ion cells which is why an unused phone left uncharged for too long may not be chargeable again.

Thanks for clarification! This is something I have unfortunately experienced with my old mobile phone.

However to cause this, the battery has been lengthened time at “0%” charge. This is for sure something to avoid!

Why is it advisable to avoid discharging to 10% instead of 20% assuming it could be avoided?
Say, I know I need 70% energy for my trip, is charging to 80% worse than charging to 90%? (In reality I would charge to 100% and not worry about the range).

I know it doesn’t make big impact whichever I do but would be nice to learn a thing or two more.

 

[Xinix]

In general, it is less bad for the battery to discharge to a low SoC than charging it to a high SoC. Pedro Lima has a nice article on it: Battery charging: Full versus Partial - PushEVs

This is for Li-Ion. LFP is different of course