30 Kwh Leaf showing up on Nissan.ie

Internal resistance is used to indicate the condition of a battery though as extensively tested in the RC community and why so many decent RC chargers have IR measuring.

A higher IR will create a higher voltage sag for the same current, so as the battery ages the voltage sag becomes high enough it can trigger the BMS LVC or (low voltage cut off) to kick in meaning for the same C discharge rates you can no longer get the same capacity so what was maybe a 5 ah cell now becomes 4 and so on.

Heat will also be a concern, so in order to keep heat down on an ageing cell you need to reduce the current of the discharge and perhaps the charge which is what one person on the FB page has observed, he can't according to the charger KW display get more than 35 Kw which could be about 30 kw to the battery V my 2015 Leaf full 50 Kw at the charger display until the ramp down of course.

So the BMS must be monitoring this and telling the charger to back off, same with regen, people have noticed reduced regen as the battery ages.

This must then also be what is observed on a cold battery and/or the BMS monitors the temps and tells the charger to reduce power. Even though this contradicts what is published in certain papers but I will go along with it.

BoatMad

Given I fly quadcopters and hang with the RC crowd. Could you show me an RC chargers that uses internal resistance ! . All my 6 chargers uses cell voltage

I have to say I'm chuckling away here

Internal resistance is not a fixed " value " it's a complex non linear function that even today isnt accurately modelled Remember it's an " equivalent series resistance " ( actually it's an impedance rather then resistance ) and is used to " model " the battery. It's not like the battery has a fixed known resistance lol

The reason your friend can't get more then 30 kW into an ageing battery is the BMS has commanded that limit.

The logic follows thus:
in effect all lithium ageing or damage tends to simply result in a battery of smaller SOC capacity. All other factors tend to remain the same. This is primarily because age and damage affect the intercalation and de-intercalation rates.

Hence your 24 kW battery then becomes say 19 kW. ( 20 % less approx )

Now if Nissan have decided that say a full 24 kW can be charged at 40 kW , IE a 1.7 C charge rate , to maintain the same C rate the charger must be commanded down to maintain the same C rate , Nissan may also be a bit more conservative then linear proportions in scaling back the charge rate.

By the way is your leaf spy showing 50kw charging. The data on the forums ( and your own graph ) show its set for 40 kW. I'd be surprised Nissan are at 2C or greater

For temperature extremes , IE close to zero or below , or above around 40 % charge scale back is necessary. Though simple thermodynamics does mean at low temperatures there is less ion mobility. So charge and discharge rates fall. IE a 2C charge at 1 degree C is far more aggressive then a 2 C at 20 degree C and can result in undue voltage stress usually resulting in li plating of the anode

BoatMad

A higher IR will create a higher voltage sag for the same current, so as the battery ages the voltage sag becomes high enough it can trigger the BMS LVC or (low voltage cut off) to kick in meaning for the same C discharge rates you can no longer get the same capacity so what was maybe a 5 ah cell now becomes 4 and so on.

Just a note on this. While it may seem like this , it's actually not really what's occurring.

As a li battery ages , it's effective series impedance doe not change that much , I have already provided the battery university graph in previous posts.

What happens , is that the intercalation and de-intercalation rates reduce. This not only reduces net effective battery capacity , but also affects maximum charge and discharge rates as you would expect.

With li you do NOT see a change in resistance( well nothing that affects you ) , you just see that the battery dies sooner , but does maintain a similar discharge curve just ending sooner. This is particuisry true of high capacity li batteries in EVs. where the discharge rates are no where near the max de-intercalation rates.

In very high C discharge like RC , the lower de-intercalation rate has the " effect " of seeming increasing the equivalent series resistance , but remember this is a modelled result based on de-intercalation rates not that in effect there has been any internal change in series resistance

Can't reply to all now but I never said RC chargers "use IR" I said they "measure IR" the good ones anyway, and usually If you have used the function you'll see the Higher IR on the old lipo V the new LiPo.

BoatMad

BoatMad wrote: »

The reason your friend can't get more then 30 kW into an ageing battery is the BMS has commanded that limit.

Hence your 24 kW battery then becomes say 19 kW. ( 20 % less approx )

By the way is your leaf spy showing 50kw charging. The data on the forums ( and your own graph ) show its set for 40 kW. I'd be surprised Nissan are at 2C or greater

[/QUOTE]

yes I get the battery in effect becomes smaller and smaller in Kwh as it ages which is another reason it wouldn't spend long at the full charge rate however with about 10% capacity loss it should still charge at a higher rate than 35 Kw (from the charger) probably 30 kw into the battery.

My leaf according to Leaf spy will charge at 48 Kw depinding on SOC and temp absolute max for a min or two then quickly settle at 45 Kw then reduce gradually as the voltage rises.

BoatMad

yes I get the battery in effect becomes smaller and smaller in Kwh as it ages which is another reason it wouldn't spend long at the full charge rate however with about 10% capacity loss it should still charge at a higher rate than 35 Kw (from the charger) probably 30 kw into the battery.

My leaf according to Leaf spy will charge at 48 Kw depinding on SOC and temp absolute max for a min or two then quickly settle at 45 Kw then reduce gradually as the voltage rises.

I suspect Nissan are being very conservative with the charge parameters as the battery looses capacity,

Thats interesting , why only a minute or two, have you tracked a fast charge say from arriving with a 20% SOC, I would expect CC charging to be in the order of many minutes at that SOC level.

PS: can you check battery voltage , everything I've seems shows power not voltage , can you actually see cell voltages when charging?


48K is 2C , thats very aggressive for a big bank, I wonder , I must ask like you on mynissanleaf. I would have expected less then 2C charging , Ill answer all these when I get my own car, as I have a wifi OBDII link

BoatMad

Deleted User wrote: »

Can't reply to all now but I never said RC chargers "use IR" I said they "measure IR" the good ones anyway, and usually If you have used the function you'll see the Higher IR on the old lipo V the new LiPo.

how do they measure IR.

you seem to think IR is a fixed value?

Ive never seen any RC charger measure IR, and if you measure it and dont " use" it, whats good is that

TBi

Hey guys. Can we keep this thread about the Nissan leaf? If you want to discuss charge rates of batteries please make a new topic.

BoatMad

TBi wrote: »

Hey guys. Can we keep this thread about the Nissan leaf? If you want to discuss charge rates of batteries please make a new topic.

We are specifically talking about the Nissan Leaf battery. Thanks