How to measure battery degradation

[Herm]

If just running at 90mph while jacked up is not enough load for a reasonable discharge time you could always make a pair of plywood paddles and bolt them in place of the front wheels, properly balanced of course.. no idea how strong they would have to be.

You will just have to trust what the dealership service dept tells you

 

[garygid]

TT,
Thanks.
So, apparently the Nissan 100% charging control does NOT protect the battery cells well ENOUGH.
Seems like 95% and 90% would be very useful choices as well, and it is a pain to always have to use the timer to charge to less than 100%, right?

 

[DaveEV]

So, apparently the Nissan 100% charging control does NOT protect the battery cells well ENOUGH.
Seems like 95% and 90% would be very useful choices as well, and it is a pain to always have to use the timer to charge to less than 100%, right?

We've rehashed this about a million times now, but it depends completely on your definition of well ENOUGH.

The closer to the middle of the pack's capacity you keep it the longer it will last. How close to the middle is enough?

Depends. How long will the car sit at 100% charge? How hot will it be when sitting at 100% charge? How many cycles do you want to get out of the pack? How many years do you want the pack to last?

Obviously 80% is better than 100%. But this is the case for all battery packs unless 100% (usable) is only 80% (total capacity) to begin with (as you would typically find on PHEVs or hybrids). At some point you hit a point of diminishing returns. So while 80% may provide a decent boost in battery life, 60% may not be significantly better.

You can be sure that Nissan has a very good idea how different maximum charge settings affect battery life. But for sure they won't be sharing that with us.

Definitely having a customizable charge stop setting besides 80% and 100% can be useful - many people have found that 80% does not leave them with enough buffer for their daily driving - but estimate that 90% would. I for one would like to see it customizable in 5% increments from 60%-100%. And be able to modify the setting through Carwings.

 

[garygid]

Start with 100 LA4 miles.
(all numbers are aporoximate)

keep 75% for real EPA usage = 75 miles
keep 80% after "long life" charging = 60 miles
keep 70% in losing Capacity = 42 miles
keep 80% in cold weather = 33 miles
keep 80% in hills, wind, snow = 26 miles
Then reserve 6 miles due to uncertainty of detecting "Low Battery" = 20 miles

So, a One-Way trip of only 10 miles (20 RT) ...
Where did that "100 miles" go?

Nissan's possible answer: "Well, we warned you."

 

[AndyH]

Anyone that suggests the Leaf's management system doesn't protect the battery is mistaken.

To get the best life from the battery, we need to keep a couple of parameters within limits: High and low cell voltage, charge and discharge current, and high and low temperature. That's it.

The Leaf's battery management system does much more than the minimum.

This info on the Leaf's management system comes from the service manual, section EVB:

Here we can see that the car's battery management controller keeps track of at least the info critical for pack longevity. We also see that the response is 'system main relay cut' - this means that if any cell discharges too far, the car stops and cannot be driven or charged. Same for overtemp, overvoltage, or over current.

In the following diagnostic trouble code table, that an 'x' in column A means "Pattern A: No Driving and Charge Stop". Overtemp? No charge and no drive. Voltage too high or too low? No charge and no drive. Charger slips a gear and decides to push 3-bazillion amps into the battery after the garage is hit by a meteor? Relays open - no drive and no charge.

<snip>

<snip>

We cannot damage the battery by charging to our 100% or by leaving the car in the garage for 2 years - the systems in the car are designed first and foremost to protect the battery.

 

[EVDRIVER]

There is no doubt Nissan would add strong pack management particularly for charging since there is an L3 port.