Ways to preserve battery capacity (besides charging to 80%)?

[AndyH]

yes they do, but charging to 100% increases the potential to lose some battery capacity and charge cycles. 80% not only eliminates overcharging caused by temperature changes, but also helps to extend total battery life by keeping it within the optimum charging range.

basically, the ONLY drawback to keeping the battery at an SOC between 40-80% (which you would be in if charging daily) is the reduction in range.

I agree completely with one exception - the temperature change concern. I don't see even unnatural temperature swings causing pack overcharge.

Yes - capacity drops when the battery's cold, but 'normal' capacity is typically around 25°C/77°F. I've seen a chart that shows 105% at about 40°C/104°F. If our cells respond the same, and if we charge to consumer 100% (90-95% of actual pack capacity), and if we heat the pack to 40°C, then we'll still not be overcharged.

The Leaf has pack and outside temperature sensors, and the charging and range systems use temperature as an input. I don't think we have to second-guess the car's management system.

 

[ENIAC]

In my CARWINGS account, under "Driving History" & "Annual" tab, it shows my "Electricity Consumption" is 204.1 kWh. I'm assuming thats the total from the battery through the motor, which would cover all charging as well as regen. So can I conclude I've used 204.1kWh / 24kWh (pack size) = 8.5 cycles thus far?

 

[JimLovewell]

Rules for optimal prolong lithium battery life and how to measure by using the Leaf 12 bar fuel gage.

Bar Note: there are 12 bars, 2 red (0 to 17%) and 10 white (25% to 100%) on the Leaf. The 2 bottom red bars are not counted in the bar numbers listed below. So, 2 bars is really 2 red bars and 2 white bars.

1) Only charge to 80%, 8 bars.
2) Maximum miles from the battery is obtained by running from 80%, 8 bars, to 30%, 2 bars.
3) Do not discharge to more that 30%, 2 bars if it can be avoided.
4) Charge to 80%, 8 bars, when I get to work. If I am making several stops before going home then start charging to 100% one hour before I leave. The same is true for home. Charge to 80% when I get home. If I am going to make a long trip start charging to 100% one hour before I leave.
5) Do not store for long periods of time at 90%, 9 bars and above (4.1V/Cell). Best storage is at about 40%, 5 bars on the fuel gage.
6) Do not store for long periods of time below 30%, 2 bars.
7) Do not store for long periods of time above 86°F.
8) The Ideal operating range is between 50 °F to 120 °F.
9) The optimal storage temperature (just above freezing) is not the same as the ideal operating temperature.

 

[planet4ever]

• First, there really are no "red bars" in the state of charge display, only in the battery capacity display. So your attempt to renumber the SoC bars is only confusing.
• Second, I'm not sure where you are getting the % SoC you are assigning to each bar, but while it can be correlated in a rough way to the published numbers, it appears to be quite a ways off from the adjusted numbers as of the April firmware upgrade. (I say "appears" because we know the bars have been moved and resized, but we don't know exactly where or how much.)
• Third, unless I am misinterpreting what you are saying, you seem to be assuming that Nissan is willing to let us use the total capacity of the battery, if we are so foolish as to do that. That is very much an extreme and minority position on this board.

With the dual caveat that (a) I am not a battery expert and (b) that SoC is really a derived statistic which I understand is largely based on voltage for lithium cells, here is my current guess as to what the SoC bars are telling us, assuming we have the firmware upgrade:

If that is anywhere close to correct, you are actually advocating use of only about 40% of the total battery capacity. I consider that far too conservative. It will reduce the car's usefulness dramatically.

Ray

 

[Herm]

Jim, I would simplify your list a bit.. store at 50% charge (storage is a month or longer), and charge it as soon as you can to 80%, 100% if needed and just before you will use it, never store it at 100%.. drop dead temp for lipos is around 130° F but perhaps Nissan has increased it.. I would stop the car if the battery temp ever got to 130° F.

I think gentle driving would also prolong battery life.

 

[DarkStar]

Due to the latest firmware update, the SOC bars have no meaning anymore. A bar may not be anywhere close to 10% SOC and charging to 80% may not even be truly 80% SOC anymore...

Unfortunately this is a futile discussion since the best way to preserve battery capacity would be to charge to 50-60% SOC and then park the car and never drive it again...

Until we can pull the raw data to monitor the real-time voltage and amperage, while discharging and recharging over the CAN-bus and the traction battery is dissected, we don't even know how large the battery is and how much of it we are using. We have a lot of assumptions without any processes to test them...