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Re: The 40KWH Battery Topic

Posted: Fri May 10, 2019 6:27 am
by lorenfb
SageBrush wrote:
lorenfb wrote:
SageBrush wrote:
What you say makes sense: if baseline heat generation in the battery is say 2% of the power draw then a 25% increase in resistance would presumably (?) increase heat generation up to 2*1.25 = 2.5% of the power draw. No big deal.
above is battery power loss - from an increase in battery resistance only
SageBrush wrote: But then I start from
P = I*I*R and I conclude that an increase in R to R1 would lead to a drop in I = sqrt (R/R1)
Then e.g., an increase in R of 25% would lead to a drop in I to sqrt(0.75) = 86.6%
above is total power loss - from a total load resistance increase

You're confusing the two different situations.
I'm obviously being dense about this, thanks for the patience.

If I just consider the battery in isolation, is my use of I*I*R correct ?
That is, does an increase of R to R1 reduce the current to sqrt(R/R1) ?
Yes, for a short circuit test of the battery, i.e. you connect the two terminals of the battery together (no load) and the battery resistance
increased. Typically the resistance would decrease as it heated. Or you used to different external resistors and did that test.

Re: The 40KWH Battery Topic

Posted: Fri May 10, 2019 9:11 am
by SageBrush
lorenfb wrote:
SageBrush wrote:
lorenfb wrote:
above is battery power loss - from an increase in battery resistance only



above is total power loss - from a total load resistance increase

You're confusing the two different situations.
I'm obviously being dense about this, thanks for the patience.

If I just consider the battery in isolation, is my use of I*I*R correct ?
That is, does an increase of R to R1 reduce the current to sqrt(R/R1) ?
Yes, for a short circuit test of the battery, i.e. you connect the two terminals of the battery together (no load) and the battery resistance
increased. Typically the resistance would decrease as it heated. Or you used to different external resistors and did that test.
:: light bulb ignites ::
I think I finally get it

(R1 - R) acts as a additional serial resistor in my simple circuit

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 12:21 am
by kovadam
Hi!

Strange thing happened in the last two days. From Saturday to Sunday the SOH dropped from 96.91% to 96.70%, then from Sunday to Monday the SOH dropped to 97.48%. Without any reason.
The car was not QC-d, the battery was not overheated, I charged using L1 charger (220V/10A) from Friday to Saturday to 92% SOC (from around 40-50%, used 8 hours of charging with the charge timer) and did not even use the car on the weekend, despite this, the SOH dropped 0.5%. Also Hx dropped from 114.58% to 114.23%.

Funny thing, that with a full charge I still get over 97% capacity, if I check the GIDs. I still can charge over 485 GIDS (488-490 some times, which is 97.6-97.8%, for a couple weeks ago I was able to charge till 38.1kWh capacity, which is way over 98%) which is 97.4% or above, and over 37kWh estimated capacity.

I think SOH & Hx are totally wrong with the new Leaf, and since the battery chemistry is totally different from the previous models, also the values mean totally different things, or are not even meaning anything regarding SOH, they are only some numerical data read from the CAN and interpreted as SOH, because it showed some correlation between bar lost and SOH value drop in the past, but only Nissan Engineers know what this values mean.

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 12:36 am
by LeftieBiker
Strange thing happened in the last two days. From Saturday to Sunday the SOH dropped from 96.91% to 96.70%, then from Sunday to Monday the SOH dropped to 97.48%. Without any reason.
That last number is higher, not lower...

I agree that Hx is now useless (if it was ever really useful) but SOH seems to still be valuable, at least if you don't count very small changes as significant. BTW, if the above increase with the last number isn't a typo, that would be, I think, the first rise in SOH for a 40kwh pack we've seen.

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 6:21 am
by DaveinOlyWA
kovadam wrote:Hi!

Strange thing happened in the last two days. From Saturday to Sunday the SOH dropped from 96.91% to 96.70%, then from Sunday to Monday the SOH dropped to 97.48%. Without any reason.
The car was not QC-d, the battery was not overheated, I charged using L1 charger (220V/10A) from Friday to Saturday to 92% SOC (from around 40-50%, used 8 hours of charging with the charge timer) and did not even use the car on the weekend, despite this, the SOH dropped 0.5%. Also Hx dropped from 114.58% to 114.23%.

Funny thing, that with a full charge I still get over 97% capacity, if I check the GIDs. I still can charge over 485 GIDS (488-490 some times, which is 97.6-97.8%, for a couple weeks ago I was able to charge till 38.1kWh capacity, which is way over 98%) which is 97.4% or above, and over 37kWh estimated capacity.

I think SOH & Hx are totally wrong with the new Leaf, and since the battery chemistry is totally different from the previous models, also the values mean totally different things, or are not even meaning anything regarding SOH, they are only some numerical data read from the CAN and interpreted as SOH, because it showed some correlation between bar lost and SOH value drop in the past, but only Nissan Engineers know what this values mean.
Well, when it happens again in approximately 90 days, it will be less strange. My Hx is over 120

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 6:54 am
by Jerryr
Just as a point of reference. My brand 2019 SL Plus w/62 kWh battery, manufacture date 2/19. 46 miles on odometer after driveling it home from dealership.

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Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 7:25 am
by kovadam
Sorry, it was a typo, 96.48, but after I left work in afternoon it was only 96.41%, so within 10 hours it dropped again 0.07% without any reason, the Hx dropped again a bit. Will see how this evolves, the car is 6 months old and has around 14000km on ODO.

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 1:59 pm
by LeftieBiker
Just as a point of reference. My brand 2019 SL Plus w/62 kWh battery, manufacture date 2/19. 46 miles on odometer after driveling it home from dealership.
The 98.96 SOH may be an indication that the 62kwh pack loses capacity at at least the same rate as the 40kwh pack. Where do you live, Jeryr?

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 3:12 pm
by Jerryr
LeftieBiker wrote:
Just as a point of reference. My brand 2019 SL Plus w/62 kWh battery, manufacture date 2/19. 46 miles on odometer after driveling it home from dealership.
The 98.96 SOH may be an indication that the 62kwh pack loses capacity at at least the same rate as the 40kwh pack. Where do you live, Jeryr?
Tampa Florida area.

Re: The 40KWH Battery Topic

Posted: Mon May 13, 2019 3:13 pm
by LeftieBiker
Thanks. That's helpful information.