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All this talk about hilltop mode vs DCFC vs 15kw home chargers (hypothetically) has me wondering if batteries take a performance hit based on the number of times they've been charged. For example, one thread compared a Leaf and a Model S doing a set mileage - let's say 50k miles (using up to ~80% of battery capacity). The Leaf would likely need to be charged 700+ times, whereas the Model S might only need <200 charges. In this scenario, the Bolt might get away with 250 charges.

The question I have is (assuming you own the car for the long term): if you commuted 30-40 miles a day, would it be better to charge every night, or once a week?
Would 700 charges at 7kw be better or worse than 250 charges at 15kw?
 

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Li-ion batteries are happiest around half charge. Given this, my sense is that allowing the battery to discharge over the course of several days and charging at 15 kW would best preserve battery health given your scenario. That said, the best practice would be to utilize hilltop reserve and charge every night or 3 at 15 kW.

The Leaf suffers 2 problems. First, it is more likely to be discharged deeper due to the relatively low capacity, and it is more likely to be fully charged since the full capacity is more often needed. Second, it has no active thermal management, and accumulates damage over time.
 

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;)I prefer to keep things simple. I charge to 100% on every charge. Just like when I get gas, filler up. Charging to 100% give me almost unlimited range for where I might go. I normally recharge between 25-50 miles remaining, using my 40A EVSE. Most things in life, we encourage full potential. Battery abuser, I don't think so.
 

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Charging often may reduce battery capacity sooner because the charge releases heat which does affect the cell chemistry. That is why the Volt and Bolt EV have active cooling that uses up extra energy to keep the pack at the nominal temperatures during a charge.

So a full charge once a week is slightly better than a daily charge, except if the battery was discharged deeply due to a long trip.
 

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All this talk about hilltop mode vs DCFC vs 15kw home chargers (hypothetically) has me wondering if batteries take a performance hit based on the number of times they've been charged. For example, one thread compared a Leaf and a Model S doing a set mileage - let's say 50k miles (using up to ~80% of battery capacity). The Leaf would likely need to be charged 700+ times, whereas the Model S might only need <200 charges. In this scenario, the Bolt might get away with 250 charges.

The question I have is (assuming you own the car for the long term): if you commuted 30-40 miles a day, would it be better to charge every night, or once a week?
Would 700 charges at 7kw be better or worse than 250 charges at 15kw?
This should give you some answer

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
 

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The question I have is (assuming you own the car for the long term): if you commuted 30-40 miles a day, would it be better to charge every night, or once a week?
Would 700 charges at 7kw be better or worse than 250 charges at 15kw?
There are 2 major killers of lithium chemistry batteries: 1) Operating the battery with extreme high or low cell temps, and 2) Spending time at a high or low battery SOC (state-of-charge).

The concern of battery temp is, for the most part, taken care of by the battery thermal management (except for those poor leaf owners). This leaves the primary factor in battery longevity up to the owner to keep the battery SOC away from the extremes. Keeping battery SOC over 30% and under 90% is huge to extending the life of lithium batteries. The fact that the Bolt has "hilltop reserve" option to keep the battery under 90% is critical just for that reason.

To answer your question exactly, if I drove 35 miles/day, which is 15% battery capacity at EPA rating, the absolute best charging method for battery health is to charge from 45% up to 60% SOC nightly. This would be have to be done by programming the car to charge for 1.5 hours per night at a 7kW L2 speed. Slightly worse would be charging nightly (73-88% SOC) with hilltop reserve on.

If you have hilltop reserve off so the car charges to 100%, you are much better off charging once per week, to avoid the battery sitting above 90%.

Charge speed (7kw vs 15kW) will have very little effect on battery life, although 44kW or 110kW fast charging will have a slightly worse effect on battery life than L2 charging. The key is to watch battery temp and SOC.
 

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We should also not forget that Chevy / Opel advices to leave the car plugged in when it is very cold / very hot, as this allows the thermal management system to do it's work even when parked. So rather than not plugging in, we should use charge scheduling if we do not want to charge every day when it is very cold or hot.

BTW: I don't see myself occupy a charge bay at work during a very cold day, just to allow the thermal management system to operate, as it will deny others the opportunity to charge.

Charging often may reduce battery capacity sooner because the charge releases heat which does affect the cell chemistry. That is why the Volt and Bolt EV have active cooling that uses up extra energy to keep the pack at the nominal temperatures during a charge.

So a full charge once a week is slightly better than a daily charge, except if the battery was discharged deeply due to a long trip.
Two partial charges will result in two small increases in temperature, with the opportunity to cool down again in between. Two larger chargers will result in one larger increase. Assuming what you say is right, then from a temperature perspective, I would say more frequent partial charges should be better than less frequent full charges.
 

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We should also not forget that Chevy / Opel advices to leave the car plugged in when it is very cold / very hot, as this allows the thermal management system to do it's work even when parked. So rather than not plugging in, we should use charge scheduling if we do not want to charge every day when it is very cold or hot.

BTW: I don't see myself occupy a charge bay at work during a very cold day, just to allow the thermal management system to operate, as it will deny others the opportunity to charge.

Two partial charges will result in two small increases in temperature, with the opportunity to cool down again in between. Two larger chargers will result in one larger increase. Assuming what you say is right, then from a temperature perspective, I would say more frequent partial charges should be better than less frequent full charges.
The battery temperature management works always whether plugged in or not. It just takes it from your battery. The advantage of being plugged in and charged is that when it runs it uses plug in power and not the battery.
 

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I'll let everyone know how mine fares. I discharge to on average 50% every weekday (55% fall, 45% winter) and charge to full. I may start using hilltop reserve soon now that I have a firm grasp on the worse-case driving scenario for me in winter.
 
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The battery temperature management works always whether plugged in or not. It just takes it from your battery. The advantage of being plugged in and charged is that when it runs it uses plug in power and not the battery.
Are you sure about that? For sure, I hope you are right about that, but the Bolt owner manual says (page 231):

It is recommended that
the vehicle be plugged in when
temperatures are below 0 °C (32 °F)
and above 32 °C (90 °F) to
maximize high voltage battery life.
It says "maximize battery life", not "maximize battery charge" or "maximize range". To me, that kinda suggests conditioning only takes place when plugged in .... I have kept my car plugged in every night last two months, even when I did not need the extra charge. Would be happy to drop that habit. How would I be able to know that conditioning is going on when not plugged in, apart from bunking next to my car? :crying:
 

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Are you sure about that? For sure, I hope you are right about that, but the Bolt owner manual says (page 231):



It says "maximize battery life", not "maximize battery charge" or "maximize range". To me, that kinda suggests conditioning only takes place when plugged in .... I have kept my car plugged in every night last two months, even when I did not need the extra charge. Would be happy to drop that habit. How would I be able to know that conditioning is going on when not plugged in, apart from bunking next to my car? :crying:
I have the same concern for this summer. I'll be busting the 90F in the garage. Added a thermometer in the garage yesterday. Others have monitored the cars energy screen to watch for battery conditioning. Speculation is the car stops battery conditioning when unplugged if the battery drops below 30%. Also for cold, it appears to widen the allowed battery temp extreme. Not sure what it does for warm temps. One forum member had a great suggestion that would be great if it's viable. Plug in, but tell the car through software to not charge.
 

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This from a different article at Battery University...

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The EV battery also ages and the capacity fades, but the EV manufacturer must guarantee the battery for eight years. This is done by oversizing the battery. When the battery is new, only about half of the available energy is utilized. This is done by charging the pack to only 80% instead of a full charge, and discharging to 30% when the available driving range is spent. As the battery fades, more of the battery storage is demanded. The driving range stays constant but unknown to the driver, the battery is gradually charged to a higher level and discharged deeper to compensate for the fade.

Once the battery capacity has dropped to 80%, the oversize protection is consumed and the battery maintenance system (BMS) applies a full charge and discharge. This exposes the EV battery to a similar stress level of a mobile phone and the driver begins noticing reduced driving range.
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http://batteryuniversity.com/learn/...atteries_do_not_last_as_long_as_an_ev_battery

So, if this article is correct, this is why the Bolt is spec'd with a 66Kwh battery but is advertised as having 60Kwh of capacity. This gives 10% more capacity which is used to compensate for battery loss during the initial life of the car so that we don't notice decreased ranged immediately. Makes sense from a customer perception point of view. If customers noticed a decrease in range starting from day one, there would likely be complaints and a perception of lower quality of the battery and range. So, from what the article states, we don't actually charge to 100% (regardless of what the cars says) until the battery loses the extra charge capacity overhead that the manufacturer built into the battery. This puts off a loss of range likely for a significant amount of time unless you are putting tons of miles in the car. This is also the likely reason Chevy says it is ok to consistently charge to "full capacity" since full capacity is really 90% when the car is new.
 
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