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Discussion Starter #21 (Edited)
rkw: Correct. I try to avoid fully charging (or discharging) any Li-ion device.

Greg: Thanks for reminding me to specify that immediate discharge is optimal ONLY with an actively cooled battery such as 500e WITH A/C manually selected. If you manually select A/C before or immediately after full charge, the batt will experience MUCH less time at the high temp caused by charging without A/C.

I will try to find references & post them here. In the mean time, consider the well-known fact that high or low voltage (State Of Charge) is not optimal, so it stands to reason that it is preferable to spend as little time as possible at either extreme, just as it is for extremes of temperature & current (amps or watts)
 

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Finally got our car :)
While l1 charging it last night I could hear a fan come on with regularity. Maybe every 2 min or so, and it lasted a few secs each time so that makes me feel like the car is programmed to take care if its cooling needs automatically? I don't think I heard the compressor come in, just a fan.
 

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Discussion Starter #24 (Edited)
Yes, cooling NEEDS (to avoid serious damage), but apparently not ideal cooling for maximum battery life.

Our battery's cycle life was tested at 77F to achieve this thread's subject line. As you know from feeling your cell phone after charging, it gets hotter than that.

The fan you heard only comes on when its radiator temp is well above ambient. That does help, but only the A/C compressor can keep the batt cooled to ambient temp while driving or charging.
 

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Yes, cooling NEEDS (to avoid serious damage), but apparently not ideal cooling for maximum battery life.

Our battery's cycle life was tested at 77F to achieve this thread's subject line. As you know from feeling your cell phone after charging, it gets hotter than that.

The fan you heard only comes on when its radiator temp is well above ambient. That does help, but only the A/C compressor can keep the batt cooled to ambient temp while driving or charging.
Understood.

Where is this study you mention? And if temp is say 70F, then....
 

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Discussion Starter #26
I haven't been able to find my original source again yet, only the one at the bottom for the the newer 68Ah model, not our older 64s, for which the test results weren't as great, but you can see they tested at 77F, presumably to get the best results for the sales pitch.

64Ah (500e):
20% range loss after
3200 cycles from
100% to
20% at
1C drain rate
0.5C charge rate
25 degrees C (77F).

68Ah (link below):
20% range loss after
6000 cycles from
100% to
00% at
1C drain rate
1C charge rate
25 degrees C (77F).

https://drive.google.com/file/d/0BzzOLtL0HXj4UURWOW16T3JqaVk/view
 

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You say presumably, and that's a big gap. You need to know what the wear rate is at 67, 87, etc degrees. It might be better, marginally worse, or the same, for all you know.
 

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As a soon to be new owner and new forum poster, I'm totally now confused as to when the battery gets cooled.

I even made a thread to get some answers to the question of just when the car will cool the battery.

It's a very sensitive topic for me as:

1. I live in AZ with 100°+ temps quite frequently

2. I'm trading in my Leaf that has absolutely zero TMS for the battery, not even a fan. Jeesh

3. I've already experienced loss of SOC on that Leaf solely from our heat and my precautions of proper charging, storage not at 100% SOC, etc really don't help.

3. I'm grateful we have this forum and I hope I get to understand how exactly this car cools the battery cause I'm giving up my Leaf for it, however I drove them before and the Fiat blows away the Leaf in so many ways and it's WAY cooler looking

4. Thnx all! :)
 

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Discussion Starter #29 (Edited)
Ideal battery temp is similar to the ideal human environment: Freezing or 100F are tolerable but not preferable. Below is a link to details of another Samsung SDI test, showing VERY greatly reduced cycle life at 113F (45C).

You can try this yourselves: Plug into L2 charger with A/C on ("LO" temp & fan, vents closed). After 10 or 15 minutes feel how close to body temp the coolant pipe is*. Turn off A/C for 10 or 15 & when you turn it back on CAREFULLY feel how the pipe is now about 150F! Leave A/C on a few more minutes & feel how much closer it is to body temp again, now that the batt isn't so hot, even though it's still charging.

*Pic attached of where A/C refrigerant exits the batt coolant heat exchanger. You can remove the motor cover & follow the tubes yourself, to the batt coolant reservoir labeled on page 65 of the manual shown.

https://pushevs.com/2018/04/05/samsung-sdi-94-ah-battery-cell-full-specifications/
 

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Discussion Starter #31
Yes, NCM.

Note that there are many different alloys of those 3 elements, with different characteristics. For example, one of the most recent versions is 811 (80% nickel, 10% cobalt, 10% manganese) with much more capacity per weight, per volume & per dollar than ours which I think are 622 or something.

Also even within the same alloy there are different electrode surface finishes & coatings that also alter the characteristics, including cycle life. Hey! How bout that: I actually circled back to the subject line!
 

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Yes, NCM.

Note that there are many different alloys of those 3 elements, with different characteristics. For example, one of the most recent versions is 811 (80% nickel, 10% cobalt, 10% manganese) with much more capacity per weight, per volume & per dollar than ours which I think are 622 or something.

Also even within the same alloy there are different electrode surface finishes & coatings that also alter the characteristics, including cycle life. Hey! How bout that: I actually circled back to the subject line!
Cool, thx!
 

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I will be reading this thread carefully, but, for the moment:
  • Is there consensus that for best battery life, it's best to end charging shortly before driving the car?
    I'm trying to keep my charges between 20% and 80%. Two nights ago, I went from an initial onboard meter reader report of 22% to 78% during a 9-hour charge at 120v, ending at 10 pm. I then left the car unplugged until 6:30 am, when I made a 10-mile round trip to the gym and back. I drove on various work-related, fairly short, trips later in the day. That would be fairly typical for me. I
    Will leaving the car for several hours at 78% charge appreciably hurt the battery in the next decade?
  • With my second lease, I got spooked by the sharp drops I saw in range when I turned on the AC. They were significantly sharper than with the first car.
    So with this recent purchase, I've stayed away from AC, and sometimes sweltered a little. I'm the type who might turn on the air conditioning if it were 65 degrees outside. I'd rather be comfortable if I'm not injuring the car. Now I see assertions that turning on the AC helps cool the battery. And I think to myself, gee, even if I were to charge every day (I don't) I could go through several years before seeing any cost to the battery.
Thoughts?
 

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Can't comment on the AC as I haven't had to use it much and didn't pay attention to the guess-o-meter when it's on. Leaving the car charged at ~80% for a prolonged period is probably ideal. I think I read somewhere in the FIAT literature to do the same when storing the car for a prolonged period.
 

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Ignore the sharp drops when you turn on the AC. Those initial drops seem to be based on a worst case scenario assumption. After you drive for 5 to 10 miles you'll see the GOM figures things out and gives you a more reasonable estimate.
 

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Thanks. The GOM is aptly named, I know. But while it did tend to exaggerate, I'm also pretty sure I saw more impact from using the ventilation system (heat, fan, or AC) than I really liked. Anybody else know anything more about the link between running the AC and cooling the battery?
And also, if it is better practice to charge until right before driving, how come?
 

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Thanks. The GOM is aptly named, I know. But while it did tend to exaggerate, I'm also pretty sure I saw more impact from using the ventilation system (heat, fan, or AC) than I really liked. Anybody else know anything more about the link between running the AC and cooling the battery?
And also, if it is better practice to charge until right before driving, how come?
The air conditioning compressor will turn on only if it needs to when the HV battery pack gets too hot. This will typically be on very hot days when driving hard and fast.

It is best practice to finish charging to 100% just before driving. The longer a Li-on battery sits at full charge, the more degradation takes place. In cold temperatures, the act of charging warms the battery which increases range. Apple even changed their charging algorithm to finish topping up the battery shortly before needing it in the morning.
 

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Discussion Starter #38
Since starting this thread I've learned two very important facts:

1) You can't charge a Fiat to 100%. Only to around 85%, at which time it stops charging. The gauge is for USABLE capacity, so it reads "100%" at 85% of the battery's actual capacity.

2) As Abe just noted, A/C cools the battery ONLY when it SELF-activates. It only does that at a pretty high temperature, since mine hasn't ever come on, even when the speedo read 113F. Turning on A/C manually makes NO difference to batt temp.



On point #1, consider typical use of 90% of drivers, not by us overly-cautious forum members, but rather the average 9-5 worker with a leased car they're NEVER going to buy*: Full charge when leaving at 8am, drive 20 miles to work, sitting 8 hours at "80%" (really under 65%), drive home, plug into L2**, fully recharged before 8pm, sitting fully charged for 12 hours (literally half its life). HOWEVER, sufficiently detailed reports (a few mph headwind will throw off your test results) of true range loss are virtually non-existent, even for second owners with over 50k mi.

As for sweltering without A/C, you can reduce the need with full use of true fresh vent air (all left-side lights off) with the fan cranked & passenger vents closed. Then when you really do need A/C, moderate use often makes a surprisingly small difference in range, since the batt is much more efficient at higher temperatures. It takes much less power than driving a bit faster because you're so hot you need to get out to cool down.

*Due to the ridiculous buy-out cost. Yes, there's a work-around, but hardly anyone does it, since even when they know (like my friend), the dealer says "NO WAY!" & they give up.

**Because even though the average US daily drive is fully recharged in 8 hours of sleep (or work) from a heavy-duty extension cord in a standard wall outlet :) all the sales people & even Plug In America website STILL say "everyone" needs it :rolleyes:
 

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Discussion Starter #39
Leaving the car charged at ~80% for a prolonged period is probably ideal. I think I read somewhere in the FIAT literature to do the same when storing the car for a prolonged period

Pretty close. It's actually 85%:

Page 314 of the digital 2013 Fiat manual says:
"VEHICLE STORAGE
The preferred way of storing your vehicle for a long period of time is to leave it attached to a Level 1 or Level 2 charger. The vehicle has a wake-up feature that will wake the system every 3 weeks and do a maintenance charge on the 12 Volt battery and also top off the high voltage battery if necessary."

That would keep it at about 85% of its true capacity.
 

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Discussion Starter #40 (Edited)
The GOM is aptly named, I know. But ... I saw more impact from using the ventilation system (heat, fan, or AC) than I really liked.
My 2013 GOM is actually quite accurate UNLESS I'm at either end of a hill or speed zone change (city to highway, or vice-versa), or JUST turned on HVAC for the first time in ... I'm not sure how long it takes to reset to "assume-worst-case".

HVAC makes a HUGE difference HOW you set it:

  • VENT air flows quite well (except when stopped) using NO power. Push whichever button is lit on the left HVAC cluster, until they're all off (including the "off" button).
  • FAN takes MUCH less than A/C, so keep turning up the fan until it's maxed out, before turning on A/C, but THEN back it off:
  • A/C reportedly only uses 1/4 or 1/2kW* to maintain temperature, after the cabin has cooled from parking temperature. I saw NO range difference on MODERATE settings (76, or I can usually even handle 80 for a short drive if I bring an ice-cold drink) with passenger vents closed & recirculate on (unless you want it colder inside than out: keep an eye on the speedo's temp gauge). On that note, make SURE you unplug the extremely false-positive-prone humidity sensor, since it deactivates recirculate, & activates the A/C compressor (without even lighting the "A/C" light!).
  • HEAT uses more than A/C, but make SURE your humidity sensor is off so you can run recirc, so when it's literally freezing it reportedly only takes 8kW for 10 minutes to heat the cabin, & then backs off to around 1kW* just to keep it warm, without wasting power heating outside air. Like A/C, with moderate settings & dressed warm with a hot drink that's still less power wasted than driving just a few mph faster to get there before you freeze.
*Compare those to over 17kW to go 60mph, & under 15 to go 55. Taking longer at lower speed means more time with HVAC on, so you actually have to go 55 instead of 60 in order to maintain the same range with 1kW of heat running.
 
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