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Re: The 40KWH Battery Topic

Posted: Wed Sep 09, 2020 10:21 am
by danrjones
DougWantsALeaf wrote:
Tue Sep 08, 2020 8:06 pm
Congrats. The BMS taketh..but every once in a while giveth.
It certainly is a strange system that Nissan coded. Taking it away only to give it back, assuming we are looking at data that's actually useful and valid in the first place.

Still going up as of this AM. Will post again when the 3 month adjustment is complete.

Re: The 40KWH Battery Topic

Posted: Wed Sep 09, 2020 12:35 pm
by WetEV
danrjones wrote:
Wed Sep 09, 2020 10:21 am
DougWantsALeaf wrote:
Tue Sep 08, 2020 8:06 pm
Congrats. The BMS taketh..but every once in a while giveth.
It certainly is a strange system that Nissan coded. Taking it away only to give it back, assuming we are looking at data that's actually useful and valid in the first place.

Still going up as of this AM. Will post again when the 3 month adjustment is complete.
Nothing real was taken away. The estimate changed, that's all.

SOC is an estimate. Accurate to a couple of percent at best, readout to 4 significant digits is misleading at best.

Re: The 40KWH Battery Topic

Posted: Wed Sep 09, 2020 1:18 pm
by lorenfb
WetEV wrote:
Wed Sep 09, 2020 12:35 pm
danrjones wrote:
Wed Sep 09, 2020 10:21 am
DougWantsALeaf wrote:
Tue Sep 08, 2020 8:06 pm
Congrats. The BMS taketh..but every once in a while giveth.
It certainly is a strange system that Nissan coded. Taking it away only to give it back, assuming we are looking at data that's actually useful and valid in the first place.

Still going up as of this AM. Will post again when the 3 month adjustment is complete.
Nothing real was taken away. The estimate changed, that's all.
Right!
WetEV wrote:
Wed Sep 09, 2020 12:35 pm
SOC is an estimate. Accurate to a couple of percent at best, readout to 4 significant digits is misleading at best.
All this preoccupation with very minor anecdotal changes in SOH/SOC has little value, and any inference results in a non sequitur.

Re: The 40KWH Battery Topic

Posted: Wed Sep 09, 2020 1:45 pm
by danrjones
WetEV wrote:
Wed Sep 09, 2020 12:35 pm
danrjones wrote:
Wed Sep 09, 2020 10:21 am
DougWantsALeaf wrote:
Tue Sep 08, 2020 8:06 pm
Congrats. The BMS taketh..but every once in a while giveth.
It certainly is a strange system that Nissan coded. Taking it away only to give it back, assuming we are looking at data that's actually useful and valid in the first place.

Still going up as of this AM. Will post again when the 3 month adjustment is complete.
Nothing real was taken away. The estimate changed, that's all.

SOC is an estimate. Accurate to a couple of percent at best, readout to 4 significant digits is misleading at best.
I understand that, its Nissan's system I find wonky. Why bother to sit there day by day and nibble away at it then run a algorithm every 3 months to adjust up or down. The daily nibbles can contradict the algorithm and vice versa. Those daily nibbles seem a pointless maneuver if the 3 month adjustment is going to go and overrule them.

Re: The 40KWH Battery Topic

Posted: Fri Sep 11, 2020 11:04 am
by jmurtagh13
Image

22,186 Miles 30 months old. Last month's drop .12%, SOH 90.60

Charge only with level2 to a max of 65%. Charge early morning when it's cooler and the battery get's a chance to cool some. I don't drive aggressively so the battery temp stays below 85 deg most of the time, never above 90 deg. I feel like a I really baby the battery, yet the BMS shows about the same as others who have many more miles and do DC charging. I'm into ebikes and do the same by only charging to 65-70% and that definitely makes those batteries last a lot longer. I'm just not sure I believe the BMS, I guess more time will tell.

Re: The 40KWH Battery Topic

Posted: Fri Sep 11, 2020 11:26 am
by DougWantsALeaf
Nice graph. Have your miles been put on fairly consistently over the past 2 1/2 years?

Re: The 40KWH Battery Topic

Posted: Fri Sep 11, 2020 11:59 am
by SageBrush
jmurtagh13 wrote:
Fri Sep 11, 2020 11:04 am
the battery temp stays below 85 deg most of the time, never above 90 deg.
Ouch

If you can improve (decrease) the average battery temp it will last longer.

Re: The 40KWH Battery Topic

Posted: Fri Sep 11, 2020 3:04 pm
by jmurtagh13
DougWantsALeaf wrote:
Fri Sep 11, 2020 11:26 am
Nice graph. Have your miles been put on fairly consistently over the past 2 1/2 years?
Thanks.

Yes for the most part, this last month was a rare exception, we put on an additional 300 miles to our normal 700 a month.

Re: The 40KWH Battery Topic

Posted: Fri Sep 11, 2020 3:17 pm
by jmurtagh13
SageBrush wrote:
Fri Sep 11, 2020 11:59 am
jmurtagh13 wrote:
Fri Sep 11, 2020 11:04 am
the battery temp stays below 85 deg most of the time, never above 90 deg.
Ouch

If you can improve (decrease) the average battery temp it will last longer.
That would be hard to do in Atlanta's summers. By the time the charging starts about 3:00am the battery is down to between 75 and 80. and that is just during the hottest 4 months of the year. The other 8 months it's 70 or below. I really thought that those temperatures were reasonable. My understanding is that EV's with battery thermal management don't start cooling until the batteries reach around 110 degrees.

Re: The 40KWH Battery Topic

Posted: Fri Sep 11, 2020 3:27 pm
by SageBrush
jmurtagh13 wrote:
Fri Sep 11, 2020 3:17 pm
SageBrush wrote:
Fri Sep 11, 2020 11:59 am
jmurtagh13 wrote:
Fri Sep 11, 2020 11:04 am
the battery temp stays below 85 deg most of the time, never above 90 deg.
Ouch

If you can improve (decrease) the average battery temp it will last longer.
That would be hard to do in Atlanta's summers. By the time the charging starts about 3:00am the battery is down to between 75 and 80. and that is just during the hottest 4 months of the year. The other 8 months it's 70 or below. I really thought that those temperatures were reasonable. My understanding is that EV's with battery thermal management don't start cooling until the batteries reach around 110 degrees.
Reasonable for driving -- sure.
Reasonable for degradation -- No

I can only speak about my Tesla -- temp management is waay lower than 110F. You can watch youtube videos by Bjorn Nyland when he monitors pack temps after supercharging. IIRC the battery is cooled down into the 80s F immediately after DC charging but the car is still being driven, and once the car is parked the battery is cooled into the 70s F within an hour or two. That is the pack chemistry of the Model 3, which I gather prefers life at a warmer temperature than prior Tesla cell chemistries.

If you keep the car in a poorly ventilated garage, consider instead leaving it outside during the hot months when ambient is less than your garage. You are otherwise managing the car wisely, but battery temp is THE issue with these cars. The more you can do for the LEAF battery, the longer it lasts. My 2013 LEAF still has 11.5 battery capacity bars but I start fretting when the temp bars goes over 5. That is unfortunately what it takes to get long(er) life from these cars.