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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 (n))
Would it be 'bad' for the battery to be 100% charged but sitting in the garage for days?
Silverback
 

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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
 

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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.
 

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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.
 

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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.
 

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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.
 

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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
 

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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.
 

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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.
 

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Wrong.... please read information from the battery manufacturers.... I really don't know where you get your "data"....

A single deep discharge can kill a li-ion battery permanently.... It is the top danger that we can do, since we cannot overcharge our batteries, we can definitely really harm them faster by deep discharge...

I really wish you would get your information from a real company that manufacturers li-ion batteries... you are really doing a disservice by continuing to regurgitate information from people who are not authoritative.
 

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Sorry, but I'm definitely with Greg on this one guys. Neither 100% nor 10% is great for best longevity, but low end SOC is way more harmful to the cells than high end is. Small differences in cells individual capacity become much magnified at lower SOC. For long storage, somewhere around 40-60% is optimal. Plus also it’s high risk that car will suddenly stop if you go too low, so why do it if it’s avoidable? This sudden stoppage can possibly even happen before you get to zero on the GOM! Further, the available propulsion power becomes noticeably reduced by the BMS when you get below ~15-20% (Especially so if it’s cold = cells high internal resistance) It does this to try and minimise the accelerated battery degradation that is actually occurring in that lower SOC state. I’m sure sooner or later we will all inadvertently go a bit too low, just don’t do it too often, is my advice.

Also bear in mind that when Eniro displays 100%, the battery is actually only at 95% in reality. (This is why regen braking still works pretty well even at 100% displayed).

Please see this interesting excerpt taken from this useful resource.
Peter.......

State of Charge
The voltage restrictions necessary to avoid the problems outlined above can be translated into recommendations for the operating range of the State of Charge of the battery shown in the following diagram.
State of Charge Operating Window
Operating outside of these limits will adversely affect the life of the battery. See more about State of Charge and how to measure it.
Temperature Effects
Heat is a major battery killer, either excess of it or lack of it, and Lithium secondary cells need careful temperature control.
  • Low temperature operation
  • Chemical reaction rates decrease in line with temperature. (Arrhenius Law) The effect of reducing the operating temperature is to reduce rate at which the active chemicals in the cell are transformed. This translates to a reduction in the current carrying capacity of the cell both for charging and discharging. In other words its power handling capacity is reduced. Details of this process are given in the section on Charging Rates
    Futhermore, at low temperatures, the reduced reaction rate (and perhaps contraction of the electrode materials) slows down, and makes makes more difficult, the insertion of the Lithium ions into the intercallation spaces. As with over-voltage operation, when the electrodes can not accomodate the current flow, the result is reduced power and Lithium plating of the anode with irreversible capacity loss.
  • High temperature operation
  • Operating at high temperatures brings on a different set of problems which can result in the destruction of the cell. In this case, the Arrhenius effect helps to get higher power out of the cell by increasing the reaction rate, but higher currents give rise to higher I2R heat dissipation and thus even higher temperatures. This can be the start of positive temperature feedback and unless heat is removed faster than it is generated the result will be thermal runaway.
  • Thermal runaway
  • Several stages are involved in the build up to thermal runaway and each one results in progressively more permanenet damage to the cell.
    • The first stage is the breakdown of the thin passivating SEI layer on the anode, due to overheating or physical penetration. The initial overheating may be caused by excessive currents, overcharging or high external ambient temperature.The breakdown of the SEI layer starts at the relatively low temperature of 80ºC and once this layer is breached the electrolyte reacts with the carbon anode just as it did during the formation process but at a higher, uncontrolled, temperature. This is an exothermal reaction which drives the temperature up still further.
    • (Lithium Titanate anodes do not depend on an SEI layer and hence can be used at higher rates.)
    • As the temperature builds up, heat from anode reaction causes the breakdown of the organic solvents used in the electrolyte releasing flammable hydrocarbon gases (Ethane, Methane and others) but no Oxygen. This typically starts at 110 ºC but with some electrolytes it can be as as low as 70ºC. The gas generation due to the breakdown of the electrolyte causes pressure to build up inside the cell. Although the temperature increases to beyond the flashpoint of the gases released by the electrolyte, the gases do not burn because there is no free Oxygen in the cell to sustain a fire.
    • The cells are normally fitted with a safety vent which allows the controlled release of the gases to relieve the internal pressure in the cell avoiding the possibility of an uncontrolled rupture of the cell - otherwise known as an explosion, or more euphemistically, "rapid disassembly" of the cell. Once the hot gases are released to the atmosphere they can of course burn in the air.
    • At around 135 ºC the polymer separator melts, allowing the short circuits between the electrodes.
    • Eventually heat from the electrolyte breakdown causes breakdown of the metal oxide cathode material releasing Oxygen which enables burning of both the electrolyte and the gases inside the cell.
    • The breakdown of the cathode is also highly exothermic sending the temperature and pressure even higher. The cathode breakdown starts at around 200 ºC for Lithium Cobalt Oxide cells but at higher temperatures for other cathode chemistries.
      By this time the pressure is also extremely high and it's time to run for the door.
    • Law suits will follow.
 

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Wrong.... please read information from the battery manufacturers.... I really don't know where you get your "data"....

A single deep discharge can kill a li-ion battery permanently.... It is the top danger that we can do, since we cannot overcharge our batteries, we can definitely really harm them faster by deep discharge...

I really wish you would get your information from a real company that manufacturers li-ion batteries... you are really doing a disservice by continuing to regurgitate information from people who are not authoritative.
Not what I said. Or at least what I meant. The test I linked to clearly shows that degradation is worse when e.g. charging to 100% and discharging to 20% (1000 cycles) than charging to 90% and discharging to 10% (1500 cycles.). When charging to 80% and discharging to 10%, cycle life shoots up to 3000.

I have never claimed it is OK to drain a battery to 0%. Of course that kills the battery. And by the way, our cars protect against overcharging, but also against deep discharging. The BMS will cut off the battery before it gets to 0%.
 

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Not what I said. Or at least what I meant. The test I linked to clearly shows that degradation is worse when e.g. charging to 100% and discharging to 20% (1000 cycles) than charging to 90% and discharging to 10% (1500 cycles.). When charging to 80% and discharging to 10%, cycle life shoots up to 3000.

I have never claimed it is OK to drain a battery to 0%. Of course that kills the battery. And by the way, our cars protect against overcharging, but also against deep discharging. The BMS will cut off the battery before it gets to 0%.
and maybe that's a decent point, 1,000 cycles with 200 miles range is "good enough". Car is likely to be off the road before it reaches 200,000 miles, never mind 600,000!
 
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