Ever wondered how Hot your battery can reach and still be funtional?

[2k1Toaster]

<snip>
lol, never come to the west then. Interstate speed limit is 75mph, drivers go 80-100mph, even the 18-wheelers. And it is by a mountain going N/S and literally through the mountains going E/W. If a little stretch of the south scared you, there's no hope on the front range.

Most people drive as fast as feels safe to them if they think they can get away with it, regardless of the posted limit. Utah monitored speeds on I-80 west of SLC before and after they raised the speed limit from 75 to 80 mph, and they found that driving speeds didn't change after they raised it. The flow of traffic speed was 82-84 mph before and after. One of the means suggested for setting 'rational speed limits' is known as the 85th percentile method: http://www.lsp.org/pdf/troopc85thSpeed.pdf

Yes exactly. So when people are driving at those speeds in the mountains, someone who is terrified to drive 65mph in flat wide open land, shouldn't drive out here...

When it looks like this, the left lane is usually still going 50mph to 65mph...

 

[GetOffYourGas]

There is a lot of condescension around here, and "my roads are tougher than your roads". Before you guys pick on someone for being "terrified to drive a little stretch in the south", you should be aware that I-24 in Tennessee is considered one of the most dangerous roads in the U.S. This isn't just some simple country boy afraid of traveling faster than his tractor can take him.

For example, I did a google search of "most dangerous roads in us" and found this list: http://www.smashinglists.com/top-10-most-dangerous-highways-in-america/. Notice that 7 of 10 of them are in the south.

 

[jjeff]

There is a lot of condescension around here, and "my roads are tougher than your roads". Before you guys pick on someone for being "terrified to drive a little stretch in the south", you should be aware that I-24 in Tennessee is considered one of the most dangerous roads in the U.S. This isn't just some simple country boy afraid of traveling faster than his tractor can take him.

For example, I did a google search of "most dangerous roads in us" and found this list: http://www.smashinglists.com/top-10-most-dangerous-highways-in-america/. Notice that 7 of 10 of them are in the south.

Thank you, yes I have no problem going above the speed limit, if I feel its safe. Heck I remember as a youth testing out my new Fiat X-19 for top end on a very flat stretch of road somewhere between TX and CA and I think it topped out somewhere around 110+ mph(the Fiat was only a 4 cylinder, 1.5L I believe) but it was evening and I was the only one on the road. What I didn't like about I-24 was in TN was everyone going above the speed limit, with bumper to bumper traffic :shock: All I could think of was if one person had a blowout(I see cars in parking lots all the time with near flat tires or what if someone picked up a nail or such, or maybe blew a piston, things happen) and at that high rate of speed and cars not much more than one car length apart, well it made me terrified. And before anyone says, just go a safe speed, well I do that when the traffic is light and people can easily go around me. I drive an ICE several times/year to Duluth MN and beyond(on I-35) and it gets far better mileage at 60 or even 55 than 70+(like 2+ mpg worse/5 miles per hour over 50) so even though the posted speed is 70(and most do 75) I like to do 60, I've done 55 but I feel a bit worried when a semi comes up behind me going 70+ and isn't paying attention and needs to make a last minute swerve to the fast lane. I figure at 10 mph difference it isn't so bad but 15+ difference would be even worse. Anyway I have no problem doing this because cars are generally several hundred yards apart, people have time to get in the other lane. When cars are bumper to bumper like I experienced on I-24 in TN, trying to go at a speed much lower than the flowing traffic IMO isn't safe to me or the other drivers, I just don't belong there, others may feel differently but it's just my feeling.
On another stretch of my TN trip, heading into Nashville from the North, we saw a accident in the Northbound lanes of the divided interstate, it looked horrific and even though the crash was well out of Nashville the backup approached the outskirts of Nashville, it was over 15 miles I've never seen anything like that in my area, sure we get backups during rush hour and several mile backups with accidents but other than extremely high traffic I feel most of the blame for such horrific crashes is the rate of speed compounded by people only being a car length or so apart from each other. One person has a issue and it's a domino effect. Oh during the 15+ mile Nashville backup I bet there was a dozen or so ripple effect crashes, again due to rate of speed and close following distance, just nuts IMO!
Sorry to have gotten OT in this heat related thread and it wasn't my intention, it's just when the OP started talking about that particular stretch of road it brought back memories, which I really hope to never experience again. Not that the countryside around that area wasn't beautiful, but it's hard to concentrate on beautiful scenery when I'm holding onto the steering wheel with all my might and am afraid to take my eyes off the road or the person a car length ahead of me. Funny part was we purposely waited in Nashville until we thought the traffic should have subsided, we didn't realize it would go well into the evening and even dark.
More OT talk, the '07 Prius we drove for a bit over 3000 miles from MN to FL(and back) basically all interstate(60-65 when we could, 70+ when we were forced to in areas like TN, around STL or even ATL) and we averaged 50 MPG! And this was in a vehicle carrying 4 people packed to the gills, if one has to use an ICE you can't really beat the little Prius

 

[2k1Toaster]

There is a lot of condescension around here, and "my roads are tougher than your roads". Before you guys pick on someone for being "terrified to drive a little stretch in the south", you should be aware that I-24 in Tennessee is considered one of the most dangerous roads in the U.S. This isn't just some simple country boy afraid of traveling faster than his tractor can take him.

For example, I did a google search of "most dangerous roads in us" and found this list: http://www.smashinglists.com/top-10-most-dangerous-highways-in-america/. Notice that 7 of 10 of them are in the south.

Again I don't put any faith in populous lists. I've been on almost all those roads and there's no problem. Even the reasons mentioned in the article are silly.

A road on a mountain that has runaway truck ramps? How about the entire stretch of I-70... A steep gradient on a bridge? How about the steepest grade of interstate in the entire country, no longer even legal to construct. Or roads that climb to 14,000ft elevation with one lane each way and no guard rail, they are considered highways in most cases.

I travel quite a bit, and the problem with those roads is the drivers. That's why the seasoned drivers (truckers) just try to pass everyone. If the road is unsafe inherently they know about it and will not be flying past. As they say in the article, the one turn on the one interstate exit is known to be dangerous because people don't pay attention to the signs and go off the road hitting the bridge. Nothing dangerous about that road, just the people. I would say a road where your tire is hanging off the side of a cliff as you slowly let another vehicle pass that has folded their mirrors in to not hit the sheer cliff face next to them, is a touch more dangerous.

Anyways, yes this was off topic, and it started with a small comment. But that's what forums do oh, well.

More OT talk, the '07 Prius we drove for a bit over 3000 miles from MN to FL(and back) basically all interstate(60-65 when we could, 70+ when we were forced to in areas like TN, around STL or even ATL) and we averaged 50 MPG! And this was in a vehicle carrying 4 people packed to the gills, if one has to use an ICE you can't really beat the little Prius

Yep, my little 2006 still gets 45mpg with winter tires in the mountains packed with people and equipment going 100mph on the interstates. It is a really cool car that doubles as a hauler. If Toyota made a Leaf equivalent, I'd be there in a heartbeat. Prius-e?

 

[arnis]

Going after very low SOC will add heat more than going over 85%.
Two reasons:
1) charging over 85% takes a lot of time. Current is going down and therefore battery has time to cool more.
Leaf will not allow any cell to get over 4.13V which is still very safe voltage and doesn't stress cells a lot.
2) discharging a lot will lower the pack voltage. Therefore driving at the same speed will require more amps.
Leaf hardly limits discharge at very low state of charge (except turtle mode). Same with DC charging.
More-or-less maximum current as soon as you start DC charging at super low SOC.

Therefore to cook battery more one should discharge really deep (right before turtle is ideal) and rapid charge right after that.

Thanks for cooking data. I was waiting for that
I was expecting turtle mode at the 12th bar :|

 

[knightmb]

Going after very low SOC will add heat more than going over 85%.
Two reasons:
1) charging over 85% takes a lot of time. Current is going down and therefore battery has time to cool more.
Leaf will not allow any cell to get over 4.13V which is still very safe voltage and doesn't stress cells a lot.
2) discharging a lot will lower the pack voltage. Therefore driving at the same speed will require more amps.
Leaf hardly limits discharge at very low state of charge (except turtle mode). Same with DC charging.
More-or-less maximum current as soon as you start DC charging at super low SOC.

Therefore to cook battery more one should discharge really deep (right before turtle is ideal) and rapid charge right after that.

Thanks for cooking data. I was waiting for that
I was expecting turtle mode at the 12th bar :|

Was finally able to achieve all temperature bars (135F / 57C). It only took 5 charging stops and speeds of 94 MPH between each stop to accomplish this. :lol:
Yes, when you reach all temperature bars, it restricts power to "turtle" mode until the battery cools down at least 1 bar. On the Interstate, I could still reach 65 mph while in turtle mode at full charge, full battery temperature.

 

[GetOffYourGas]

On the Interstate, I could still reach 65 mph while in turtle mode at full charge, full battery temperature.

Wow! But how long did it take? To what is the power restricted in turtle mode?

I see you still have 11 capacity bars. I don't suspect that will last for long with this kind of abuse.

 

[knightmb]

On the Interstate, I could still reach 65 mph while in turtle mode at full charge, full battery temperature.

Wow! But how long did it take? To what is the power restricted in turtle mode?

Actually was quit normal all the way to 60 mph and then took a while to tick up to 65 mph as I was going uphill slightly. It was interesting to drive on a full charge in turtle mode as everything else worked fine (AC going, etc.) I only had 3 acceleration bubbles, but only 2 of them could be used, so I was limited to about +20 kW of power. I set the cruise for 70 mph once I started going downhill slightly so at turtle mode power, my speed would flux between 60 mph and 70 mph depending on if I was going downhill or uphill. After about 10 miles, the battery had cooled enough to take away the last temperature bar and power returned to 6 acceleration bubbles. By the end of the trip, I had lost both 2 top, red temperature bars and all acceleration power had returned.

I see you still have 11 capacity bars. I don't suspect that will last for long with this kind of abuse.

It's been going on weekly before and since I made my first post about this here. I've been doing a lot of LeafSpy data gathering for the trip to see how much degradation I am getting. Every trip I do like this always raises the SOH up about 1% to 2%, so it does get a little confusing for me. I have to wait a few days of no DCFC to DCFC constant charging to get an idea of how much degradation is going on.

For this trip, I wanted to push it to the limit. I was driving at near max speed (+94 MPH) for all trips between charge locations, only thanks to other drivers also going this speed as well. I didn't tailgate anyone for drafting reasons at these speeds, but it was more convenient to use them as leaders in case the police was waiting up ahead, good ticket early warning system. :mrgreen:
If not for those drivers, I would have just kept the speed limit on cruise control like I usually do (+70 mph) but I didn't want to pass up a good opportunity to continually push the batteries to max.

 

[knightmb]

On another note, I did keep track of how much power is "reduced" when charging in the battery red zone.

The first 1 temperature bar limits your charging to 60 amps at the DCFC and 2 red temperature bars further reduces charging to 30 amps. So my last charging stop took a long time to reach full charge.

 

[arnis]

Some questions!

1) Are you absolutely sure you could charge at full speed (120A) with 10 bars? So pretty much no limitation up to that? :?

2) How much regen was available with 1 red and how much with 2 red bars?

3) Does QC limitations switch on/off with bars or they smootly change with each degree?

Awesome data.

 

[knightmb]

Some questions!

1) Are you absolutely sure you could charge at full speed (120A) with 10 bars? So pretty much no limitation up to that? :?

2) How much regen was available with 1 red and how much with 2 red bars?

3) Does QC limitations switch on/off with bars or they smootly change with each degree?

Awesome data.

Glad to answer

1) I remember at 10 bars that charging seemed to be limited to 115A, but I didn't know if that was a limitation of the charging station (It was a Blink station). As the battery charges, the taper off started again when nearing 80%, not sure if it was directly temperature related or just normal for that charging station. My guess it was temperature related, so it is probably possible to get full charging at 10 temperature bars, but the battery is already hot so some kind of thermal protection is probably going to kick in right away once the battery starts to warm up more.

2) At the first 1 red, regen was identical to regular charge state, only acceleration power was limited. I was only charging to 90% SOC max at each station (if I had the time or needed it to reach the next) At 2 red temperature bars, again, the acceleration power was limited (turtle mode) but the regen appeared to be unaffected. I never charged the vehicle to anywhere close to 100%, so regen did not seem to be affected, only acceleration was being limited the closer you go to maximum battery temperature. It was odd to drive in turtle mode with limited acceleration power but normal regen ability. I was also surprised as to how fast you can drive in turtle mode, LOL. Once the battery dropped the 12th temperature bar, turtle mode went away and acceleration bubbles slowly returned one by one.

3) It appears to me to based on temperature and a smooth change. For example, the last charge stop where the battery was at max temperature bars. The charging started at max and had a fast, but smooth change from 115A down to 30A (such as 115,114,113, etc) The last charge stop didn't start at 30A, that is just where it ended up after a few minutes of charging.

More to add this topic, after doing this so many times myself, it appears that maxing out your battery temperature then giving a few days of "normal" temperature for the car computer to recalculate battery capacity, it appears this eats about 1% off the battery SOH every time you do this.

 

[arnis]

I've tried to promote to hot climate users who try to keep battery temp down to keep their
acceleration and regen at minimum (up to 3 bubbles for example).
As not only will driving consumption go down also discharging battery at lower current will
result in higher discharge efficiency. So accelerating 5 seconds at 40kW will produce more
heat than accelerating 10 seconds at 20kW. And accelerating 2.5 seconds at 80kW will
produce more heat than 5sec@40kW and much more than 10sec@20kW.
Leaf engineers know that limiting acceleration to 2-3 bubbles almost totally resolves battery
heating up even more and that driving at 50+mph will help cool the battery. But not limiting REGEN
is a mystery, at least for me. Maybe it will happen if temperature rises few more degrees :lol:

 

[2k1Toaster]

I've tried to promote to hot climate users who try to keep battery temp down to keep their
acceleration and regen at minimum (up to 3 bubbles for example).
As not only will driving consumption go down also discharging battery at lower current will
result in higher discharge efficiency. So accelerating 5 seconds at 40kW will produce more
heat than accelerating 10 seconds at 20kW. And accelerating 2.5 seconds at 80kW will
produce more heat than 5sec@40kW and much more than 10sec@20kW.
Leaf engineers know that limiting acceleration to 2-3 bubbles almost totally resolves battery
heating up even more and that driving at 50+mph will help cool the battery. But not limiting REGEN
is a mystery, at least for me. Maybe it will happen if temperature rises few more degrees :lol:

If the Leaf is accelerating, it's using 80kW

Drive it like you stole it