Capacity vs Hx (Health)

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I believe you are actually seeing two effects.

First, the battery is an electro-chemical device. Lower temperatures actually cause a slow down in the chemical to electrical conversion process within the battery. When batteries are cold they can give the appearance of a high internal resistance because of the slower ability to convert chemical energy into electrical energy. So most types will show higher IR.. no way to get around this except fancy Nissan gimmicky programming... it just happens..

On the other side of the equation, heat has a different effect. Heat will typically increase the internal resistance of a battery therefore limiting the current the battery can provide. If you continue raising the temperature of the battery the chemical process works better however the higher resistance limits the current the battery can supply. This is NOT "C" rating..

Ideally, you want to use the battery in it's sweet spot or recommended operating temperature, not too cold or not too hot. Also the reason you should let your batteries cool down after you use them prior to recharging. This is also why on very cold days, a battery will actually start to perform better as you drive because the heat created from the discharge process warms up the chemicals and the conversion process improves.

I've noticed now on mine that the sweet spot is 22-28*c and they are kicking!

I hope that makes sense....
 
14jx3d1.png

I figured it would be time to post some data here again after a bit of a hiatus.
Above is a plot of CAP (and HX) vs time for my 2012 LEAF. The P3227 update was done on 4/26/14.
It seems that pre-update there were some roller coaster hills, and post update not so much.

The green line is just a line I put in to see how the CAP data fits a linear decay vs time.

Ignoring the tetons sticking up, it looks like a fairly linear decay of capacity. HX does seem to mostly follow the CAP if you scale it right.

Comments?
 
Yeah. Looks like they track more closely post update. I am curious what scalars you applied. Here is a graph from my 2011 - all post-update. For Hx, all I did was add 21. For Ah, all I did was multiply by 1.52. Also, is what you are calling CAP the same thing as SOH?
 

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CAP in this case is the raw AmpHour capacity group 79b index 5, bytes 2-4. Same as your Ah I suspect. I didn't do any math, I just plotted the raw data on their own axis and lined them up. Ah scale on left, hx scale on right.
 
TickTock said:
A data point from my new battery (after a week of "settling in")

SOH: 100%
Hx: 100.1
Ah: 66.14

nice. what are your plans for monitoring degradation? I think you would be a great benchmark for acid test on new Lizard pack
 
Not sure if this is the right place to post this, correct me if i'm wrong please.

With regards to hx value: I have noticed that if i drive my Leaf in B-mode arround 50-60 mph on the highway, and i drive the car for 2 seconds with full throttle, then 2 seconds no throttle, again 2 seconds full throttle, then 2 seconds no throttle and so on for half a 'tank' of power, the hx value increases a lot (from 97% to 102,5%).

Anybody knows what that means?
 
plieshout said:
Not sure if this is the right place to post this, correct me if i'm wrong please.

With regards to hx value: I have noticed that if i drive my Leaf in B-mode arround 50-60 mph on the highway, and i drive the car for 2 seconds with full throttle, then 2 seconds no throttle, again 2 seconds full throttle, then 2 seconds no throttle and so on for half a 'tank' of power, the hx value increases a lot (from 97% to 102,5%).

Anybody knows what that means?

what you are doing is simply running a lot of current thru your pack in a very short period of time. no different than the boost in numbers seen when you fast charge... not sure I would recommend your actions on a regular basis.

in the general scheme of things; there is only ONE guaranteed way of insuring greater longevity of your pack and this driving efficiently.

1937177_10208617195095230_6932344811969537857_n.jpg


no saying that anyone else can match me but if I am averaging 4.8 miles per kwh and someone else is averaging 3.8 miles per kwh, then it stands to reason that my pack will last longer due to less cycling but that is only the beginning. Gentler driving means a less stressful battery life. now how extreme is the damage done from this type of driving? minimal I think but in your case, you are artificially increasing your cycle count for no real benefit.

This is another reason I am a fan of neutral driving. it is stress free miles
 
For your info:

2 days ago the data was:
AHr: 63,15
SOH:96%
Hx: 97,04%

Now after a night of charging with the standard Nissan charger to 100% the numbers are:
AHr: 66,66
SOH:100%
Hx 102,35%

car milage is about 10.000 miles now. We drive the car every day for about 100 miles.
 
Can someone please explain what SOH is? Is it a raw value from the CAN bus, or is it derived somehow? Is it the same as what was referred to as Capacity/CAP earlier in this thread, and if so, what was the rationale for renaming it SOH? How does it relate to the ratio of Ah(now)/Ah(new) and the ratio of GIDS(now)/GIDS(new)?

Thanks.
 
Hi,

Edited on 5May16 to remove irrelevant ...

There are 4 metrics used in LeafSPy:
- Ah
- SOC
- SOH
- Hx

Have those being defined?
 
SparkyEV said:
Can someone please explain what SOH is? Is it a raw value from the CAN bus, or is it derived somehow? Is it the same as what was referred to as Capacity/CAP earlier in this thread, and if so, what was the rationale for renaming it SOH? How does it relate to the ratio of Ah(now)/Ah(new) and the ratio of GIDS(now)/GIDS(new)?

Thanks.
Reading the Help that comes with the app will explain the values.
 
I've been looking at SOH and Hx values for a year. I've noticed that Hx fluctuations are happening more often
and usually result in SOH changing its value after a short period of time.
If Hx value is going down SOH value will round down to Hx almost immediately (1-2 trips). Usually only 1%.
If Hx value gets up (next whole number) SOH value will follow but more slowly (usually at least a day or two).

Hx value can be raised with heavy usage (acceleration or DC charging).
Sometimes Hx/SOH values go wild, especially if constantly charging to 80% with only shallow discharges.
Doing so for a month and then going below VLBW might result in surprise turtle (whole pack gets really
unbalanced and weakest cell dictates turtle). Happened to me twice.

3-4 month per year my battery temperature is between 2 and 4 bars. This year Hx/SOH values froze and never
updated during winter period. I managed to get a small update during one longer trip with DC charges
(battery got to around 5 bars) a month before spring. Update was modest (less than 0,5% Hx and no SOH)
Most likely BMS is unable to calculate precise capacity if chemistry is cold - therefore it doesn't even try.

I've noticed that at ideal temperatures Hx updates quite often. I've seen updates every few minutes during driving.
My rare occurrences of 100% charge usually encourage Hx updates. Same with deep discharges. 100% charge
often results in BMS balancing the pack (i believe?) as most shunts are red during whole trip after 100% charge.

2014 UK Leaf, 61500km, 91% SOH 90,9-91,7Hx. Normal cycle between 80% and LBW.
Never seen less than 5 regen bubbles below 90% SOC.
 
I feel my experience may be useful here at this point in the thread :)

Hx very definitively seems to be a measure of internal resistance. That is, how difficult it is for energy to enter or leave the battery, relative to a new battery. At 100%, it performs just like a new battery. It's hard to tell what 0% is, but I have a good dang impression...

I saw a Leaf a short while ago that had 6/12 bars -- 50% degradation! :shock: Yeah, half its battery capacity. https://goo.gl/photos/vZ3D252e7gNyU77r7 -- and it had 29.38% Hx.

The result of Hx? It could not quick-charge at all, basically. I think it only took in about 25 amps, max -- or, what is that, about 10 kW, out of 50 -- at just below 50% SOC. As it approached 66%-70% SOC, it slowed to about 7 kW, and eventually got below 6.6kW, then charging on a quick charger even slower than my 6.6kW Leaf's onboard charger.

So, the correlation between Hx and apparent internal resistance is very strong.

OTOH, the SOH figure precisely matched the bars on the dash - he'd just lost his 6th bar (which is what got our attention and came in to get a Leaf Spy report pulled from his car), and it showed 50% SOH, exactly half (6 of 12 bars remain, 6 of 12 bars lost).

So, SOH is clearly "capacity remaining" and Hx is "internal resistance". The lower your Hx, the less regen and slower quick charges you get -- also, the more sensitive it is to heavy acceleration. Accelerating hard on a low Hx will dramatically reduce your range (and heat the battery).

Hope this helps clear any remaining fog up. :mrgreen:
 
^^^
Very interesting, esp. how crappy QCing became for that 6 BL. Those are terrible rates.

Over at http://www.mynissanleaf.com/viewtopic.php?p=472551#p472551, I pointed to what appears to be a 7 bar loser, assuming his car was fully booted. That poster is confused.
 
cwerdna said:
^^^
Very interesting, esp. how crappy QCing became for that 6 BL. Those are terrible rates.

Over at http://www.mynissanleaf.com/viewtopic.php?p=472551#p472551, I pointed to what appears to be a 7 bar loser, assuming his car was fully booted. That poster is confused.

yep but not due to degradation so much as the charging profile Nissan used in earlier models. My 2013 with 43,500 miles with 12 bars charges at 40 amps at 50% SOC.

The other day, I was charging when a 30 kwh 2016 SV pulled up and plugged in. He wasn't that low but was going home to Bellevue and wanted to top off. We talked while the cars were charging and I happened to look over and he was charging at 97 (max is 100 amps on EVGO station) amps at 85%! At the same time, I was charging at 30 amps at 72%....

SUCKS!

Can't wait to dump this LEAF and get a one with a real fast charge option!
 
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