SoH dropping fast

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pyromancy5

Well-known member
Joined
Apr 3, 2017
Messages
113
So I've owned my car since the beginning of April. I've driven roughly 1700 miles and since I first checked my SoH at 82% now I am down to 80%. Should I be concerned about this fast of a drop in batt health?
 
I know this is a short period of time to track data. But if one looks at 35k miles and a drop of 18% batt health, it works out to 1,944 miles per 1% drop in SoH.

Since I've owned the car, it seems to have accelerated to twice that. Will batt degradation speed up as the car ages?

(2014 SL)
 
pyromancy5 said:
I know this is a short period of time to track data. But if one looks at 35k miles and a drop of 18% batt health, it works out to 1,944 miles per 1% drop in SoH.

Since I've owned the car, it seems to have accelerated to twice that. Will batt degradation speed up as the car ages?

(2014 SL)

Yes. lower SOH means more charge cycles per mile driven, greater resistance to current flow, etc.
 
Battery stats seem to be very dependent on driving / charging cycles. Short commutes and irregular / small charges seem to be detrimental to statistics. Long driving and full charging seem to be beneficial to statistics.

I used to have an 16 mile round commute and charged to 80% every 2nd night. Then swapped cars with my wife whose 32 mile + decent lunch trips resulted in a fairly regular 20% - 80% daily charging cycle. My battery gained over 2Ahr in a month.

Whether these statistics actually represent underlying conditions is unknown and I would suggest unlikely.
 
Thanks for that Aussie, I have a 7mi round trip commute and we run most errands in my car as well. I charge twice a week. Maybe one top off in there as well but I do my best to run it down to at least 20% before charging again thought not always. I also charge to 100%. With a 2014, I don't believe I have the ability to limit the charge consistantly to 80%.
 
pyromancy5 said:
I know this is a short period of time to track data. But if one looks at 35k miles and a drop of 18% batt health, it works out to 1,944 miles per 1% drop in SoH.

Since I've owned the car, it seems to have accelerated to twice that. Will batt degradation speed up as the car ages?

(2014 SL)

A somewhat related comment to your situation...

http://daveinolywa.blogspot.com/2017/07/death-by-thousand-cuts.html
 
So, with an in-service date of 5/2014, 38K mi on the clock, and 78% SOH, I have 18+ months left on the battery warranty. In 6 months/ 4k miles i have dropped from 82% to 78%. Still have 11 bars.

This car lived it's first 30k miles/ 3 years in GA.

What do you think my chances of dropping 3 more bars in a year and a half?
 
Your 11th bar should drop any day now. The next two bars are worth about 13%
Will you lose 13% in 18 months ? Maybe. Depends a lot on your locale.
 
I have always heard that the batteries like to be at 50 % charge. I have also always thought that draining down to 20% before charging results in a greater strain than recharging at 40-50%????
 
powersurge said:
I have always heard that the batteries like to be at 50 % charge. I have also always thought that draining down to 20% before charging results in a greater strain than recharging at 40-50%????

I don't think this is accurate. I don't know if this is true now, but with older Li batteries, if they weren't fully discharged, the would lose their zero point. Something to do with migration of free radicals and dendrite formation... not sure I understand it all, but I believe migration happens more under full charge , not when empty.
 
SageBrush said:
Your 11th bar should drop any day now. The next two bars are worth about 13%
Will you lose 13% in 18 months ? Maybe. Depends a lot on your locale.


I'm in Ohio. We get plenty hot in the summer, but I only have one summer left and I now park at work in a covered garage, instead of a surface lot. I don't plan on abusing it to run it down, but it's tempting to keep it at 100%, QC next summer when I can. There is a free QC near my grocery store, but it always stops at like 92%
 
pyromancy5 said:
powersurge said:
I have always heard that the batteries like to be at 50 % charge. I have also always thought that draining down to 20% before charging results in a greater strain than recharging at 40-50%????

I don't think this is accurate. I don't know if this is true now, but with older Li batteries, if they weren't fully discharged, the would lose their zero point. Something to do with migration of free radicals and dendrite formation... not sure I understand it all, but I believe migration happens more under full charge , not when empty.

It is very likely true. The battery's best charge capacity is dependent upon having as near a perfect balance of the two compounds that represent the anode and cathode. As the compounds swap back and forth, the ability to regenerate back to a balanced level is reduced. Now this is a VERY simplified answer but the ideology remains the same.

Obviously leaving SOC near 50% all the time is not beneficial to range unless you have a LOT of charging opportunities and very short drives. So the question becomes is it better to go deeper into discharge or recharge?

Well, since we want the battery to be recharged, I have to say the higher the SOC the better as long as

You drive it daily, One way commute reduces SOC to 80% or less.

Another thing to keep in mind; I charge fully nearly every day due to the amount of driving I have to do and experience little as far as abnormal degradation. Now we can talk about the weather but if ONLY comparing cars IN MY LOCAL AREA, the facts remain the same.

Point 2; You car makes a big deal of letting you know that you should charge when SOC is low. Do not ignore your battery warnings.

ALWAYS PLUG IN IMMEDIATELY TO GAIN ENOUGH CHARGE TO TURN OFF THOSE WARNINGS ASAP.

Does this mean stopping 10 miles from your house to plug in when LBW comes on? Well, since I don't do that, I am not going to recommend that anyone else do that either but I do plug in for an hour or two when I get home no matter what time of day it is...
 
DaveinOlyWA, you make some interesting points. I'm under the assumption that there are all these warnings because it's a serious PITA if you get stranded without any juice in the Bat. I'm sure there is some extra capacity that we cannot access for anti-bricking, but I don't think it has anything to do with battery chemistry. It's all about driver behavior, concerns for stranded customers, and I really think they went over board on the warnings. The red light, like an ICE car, you always wonder how long that thing has been on. The initial message is nice to have, but that thing will really start to get annoying if I am on that last 10 miles home and I have 20% left. Without knowing what kind of damage an empty Li battery is inflicting on itself, I'm inclined to think it's all babysitting.
 
pyromancy5 said:
DaveinOlyWA, you make some interesting points. I'm under the assumption that there are all these warnings because it's a serious PITA if you get stranded without any juice in the Bat. I'm sure there is some extra capacity that we cannot access for anti-bricking, but I don't think it has anything to do with battery chemistry. It's all about driver behavior, concerns for stranded customers, and I really think they went over board on the warnings. The red light, like an ICE car, you always wonder how long that thing has been on. The initial message is nice to have, but that thing will really start to get annoying if I am on that last 10 miles home and I have 20% left. Without knowing what kind of damage an empty Li battery is inflicting on itself, I'm inclined to think it's all babysitting.

I notice there is no warning when you park it with 85% SOC

Why is there not a "Please drive another 5 miles if you plan to be here for an extended period of time"

The reality is much more likely to be engineers using the mindset of a lifelong gasser who ran the gas tank down because in their mind, the only risk was running out of gas. Anyone who can drive a car without noticing the gas gauge is someone I do not want to share the road with.

Since this is an EV and there are other repercussions besides being stranded, they decided the extra warning was warranted...or in our case, the extra 3 warnings.
 
pyromancy5 said:
Yup, mfg in 03/14, so it couldn't have sat too long.
Knowing the name of the dealer from Carfax, you could look up the actual weather history for that town in April, May and June of 2014 and see exactly how warm the weather was while it was on the lot, if that level of trivia interests you.

I like Weather Underground (wunderground.com) for this. For any location, you can scroll down to the "almanac" link and choose your dates. For example, in the week before your car was sold, Athens GA had temps in the mid-90s:

https://www.wunderground.com/history/airport/KAHN/2014/6/16/MonthlyHistory.html?req_city=&req_state=&req_statename=&reqdb.zip=&reqdb.magic=&reqdb.wmo=
 
Interesting... In winter, my SoH climbed by 1.5% points, and now that we're seeing 80 degree+ days, It's back down to 78% and I'm @10 bars now. I have 12 months and 21 days left under warranty... Looks unlikely that my SoH will drop fast enough to qualify for replacement.
 
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