Battery heat meter and 30kw leaf

BoatMad

I offer up this example

Left Gorey for Dublin yesterday , wth 5 bars of heat , overnight charge to 100%, ambient 10degrees C , top speed 100 kmph

Slow charge @ 6kw 1hour dunlaoghaire 5 bars of heat , ambient 14 degrees

Fast charge Lucan to 85% 6 bars of heat , ambient 15 degrees
Arrive Athlone , top speed 95 kmph , 6 bars of heat ambient 15 degrees
Fast charged to 45% , Athlone 6 bars of heat , covered 30km locally

Car sits off for 3.5 hours , on restart still shows 6 bars of heat

Fast charge Athlone to 90% , 8 bars of heat , ambient 13 degrees

Arrive FCP Carlow , 8 bars of heat , top speed 90 kmph

On multiple switch on and off, heat drops to 7 bars ( I noticed the gauge often only changes on switch on )

Recharge to 55% , 7 to 8 bar added at 50 % , ambient 10 degrees

Arrive Gorey , 8 bars

What is strange , is that there is no apparent cooling due to driving , I've never seen the bars drop underway , even at modest speeds

The change down in temperature ( not up) always seems to occur on switch on never underway

Considerable rest time has to pass before any noticeable drop in bars occurs on switch on ( >6 hours imho )

Speculation on mynissanleaf, suggests the temp gauge is a computer model , rather then a simple battery temperature reading , it certainly seems rather odd behaviour

KCross

Leafspy shows 3 battery temp sensors on mine. That wouldn't jive with the idea of it being a computer model

Why would you expect it to drop while driving? Wouldn't using the battery as well as charging it cause heat to be given off?

I would have expected the only way for temp drop is while the car is idle and even then it would be a slow drop.

BoatMad

KCross wrote: »

Leafspy shows 3 battery temp sensors on mine. That wouldn't jive with the idea of it being a computer model

Why would you expect it to drop while driving? Wouldn't using the battery as well as charging it cause heat to be given off?

I would have expected the only way for temp drop is while the car is idle and even then it would be a slow drop.

But there must be some cooling while the car is in operation , there are three states the temperature could be in in relation to cooling

1. heat being drawn away in excess of battery heat production , results in temperature drop

2. Heat being drawn away in less quantities then being produced , results in a rise in battery temp

3. Heat drawn away equal to heat production , results temp remains at static value

I would suggest that without active thermal management it's unlikely that scenario three is applicable to the leaf ( which for example is why an ice remains at its operating temp )

Hence I would expect to see a slow reduction in temp as you drive around , or conversely a rise in temp, but not a static value over long periods of driving ,

Yet I've never seen any reduction in bars while travelling , even quite slowly

The battery will warm up just from driving alone and also if you go mad with the brakes , all that 30 kw regen will warm it up too. Charging at 6.6 Kw will also warm it up a bit. Handy in winter. Unbelievably there is not even forced air cooling for the Leaf battery.

This is the battery range for the MK I which I presume is identical to the MK 1.5 + and most likely for the 30 Kwh. These battery temp bars range varies considerably.

BoatMad

That's the wiki table , but it's been widely discredited on mynissanleaf

The issue is why you don't see gain or loss while driving , that's the strange thing , I have seen temp gain under sustained 110kmh motorway driving

But I've never seen temp loss under slow speed driving , which doesn't make sense , as I said the steady state could only be maintained by active means.

KCross

As you said, probably only calculated/updated on power on

A drive with leafspy on and a rapid charge would answer that quick enough.

BoatMad

KCross wrote: »

As you said, probably only calculated/updated on power on

A drive with leafspy on and a rapid charge would answer that quick enough.

Yes , I have all the bits , will set it up later today

I wouldn't worry about it all because by the time any of our leafs need a new battery our lease will have expired.

A new battery will cost about 2k-2,500 k in 5-8 years, now it costs 5,500 installed.

KCross

I did a bit of LeafSpy monitoring today.

Started on 5 bars and LeafSpy said the battery was at 16C. Drove about 4-5 miles and and was stationary for an hour while waiting for one of the kids to finish training. I had the radio on and nothing much else. The battery temp actually went up a few fractions of a degree while I was waiting for that hour

Then did another 20 mile round trip with a rapid charge in the middle from ~30-80% and the temp went to about 24C. Still "stuck" on 5 bars.

Here's the kicker... at exactly 26C the bars went up to 6 while I was driving. So it does update while driving and the figures seem to roughly match what Mad_Lad has posted above (5 bars above 15C and 6 bars above 27C)

When I got home I checked the temp and it was 26.9 and 6 bars and I checked it an hour later and it was 25.6 and it had dropped back to 5 bars.

I'd say the algorithm is fairly simple. If you exceed the max temp for the bar it goes up a bar accordingly.

Driving doesnt seem to increase battery temp anything near as much as charging it does.
The temp drops quite slowly when the car is idle and I'd say the time immediately after driving it may even go up a bit while the BMS is balancing as I saw some cells changing color(blue-->red-->blue) in LeafSpy while I was sitting in it for the hour.

The range between bars is wide enough that you wont see alot of changes in the bars while driving. I'd say you would almost never see it decrease while driving unless it was freezing outside.

Edit: Just to clarify, since the title of the thread is 30kWh LEAF, mine is a 24kWh LEAF

BoatMad

Thanks, interesting

September1

I have only encountered once temperature change when driving and in this case it went from 4 to 5 bars. I did not use FCP on that day.

It's no surprise that the battery temp might climb a little while parked and not driving because there is a large thermal mass and just as the battery will take time to cool down it will take time to warm up and while parked it could still be getting warmer just after driving.

A good idea to park in the shade in warm weather.

KCross

Deleted User wrote: »

It's no surprise that the battery temp might climb a little while parked and not driving because there is a large thermal mass and just as the battery will take time to cool down it will take time to warm up and while parked it could still be getting warmer just after driving.

A good idea to park in the shade in warm weather.

Park in the shade! Really?!

I cant see how it would matter in our climate. It might add a few degrees to the battery but surely not enough to drive you into the red or damage a battery.

September1

I think in Irish climate it is very unlikely to heat significantly from ambient air and in fact sun is only environmental source of heat that could make impact.

KCross

KCross wrote: »

Park in the shade! Really?!

I cant see how it would matter in our climate. It might add a few degrees to the battery but surely not enough to drive you into the red or damage a battery.

It's not hard to warm the battery in Summer in Ireland when it's warm and then driving and fast charging can get it pretty toasty.

So yeah parking in the shade, the cooler the better, regardless of fast charging or not.

KCross

Deleted User wrote: »

It's not hard to warm the battery in Summer in Ireland when it's warm and then driving and fast charging can get it pretty toasty.

So yeah parking in the shade, the cooler the better, regardless of fast charging or not.

I agree that driving it and rapid charging heats it up quickly but I dont think parking in the shade would affect it in any noticeable way in Ireland.

The manual says that it is most efficient on the 6th bar, I think, so having it heated some bit is good. Its only when you hit red that you have issues and the BMS will kick-in to stop it doing damage.... or so the manual says.... given our climate I wouldnt pay any attention to parking in the shade.... unfortunately this isnt California!

KCross

KCross wrote: »

I agree that driving it and rapid charging heats it up quickly but I dont think parking in the shade would affect it in any noticeable way in Ireland.

The manual says that it is most efficient on the 6th bar, I think, so having it heated some bit is good. Its only when you hit red that you have issues and the BMS will kick-in to stop it doing damage.... or so the manual says.... given our climate I wouldnt pay any attention to parking in the shade.... unfortunately this isnt California!

The manual shows faster charge times from the 6th bar but it will also warm up faster if you're starting from an already warm battery.

The BMS will only limit power so as not to "destroy" the battery but it's too hot in the red zone and not something I'd frequently do or try do even once.

The manual also states how many bars to let it cool to before charging again be it fast or normal. That would be the minimum to let it cool to. A hot battery and high states of charge cause the fastest degradation.

If the BMS was so good why did all the leaf batteries in the hot climates in the U.S die early ? It just happens slower in less warm climates.

Why do GM, Tesla and BMW cool the battery ? one simple reason, because they are far better engineered.

The MK 1.5 battery is a lot better granted but If I wanted to keep the Leaf more than the 3 years I'd be doing everything I could to make sure I don't have to pay for a new battery for as long as possible.

Even the Zoe has a fan, simple and as basic as you get but it still has some form of heat control.

If you don't intend driving and doing more than one fast charge I wouldn't be bothered but if intending to drive long distance with a couple of fast charges then I'd start out with the battery as cool as possible.

You don't have to live in California to get the battery hot.

I'm not keeping the Leaf anyway so I couldn't care less.

Just remember , Nissan stated originally that the Leaf battery didn't need to be cooled in any climate. So they lied or didn't test it properly or NEC over rated their battery cells as battery makers often do and by the time Nissan discovered it they couldn't stand the humiliation of admitting defeat, they wanted to be the first to release a fully electric affordable car.

I can picture Nissan bosses meeting in the conference room all saying to themselves, ok now what do we do ? and they probably said well, we've spent the money so lets pray that people don't want to drive more than 5K Kms in such a low range car that they will never notice it and we can blame the degradation all on age and we won't have to pay for warranty !

KCross

I don't disagree with much if any of that. It's the "park in the shade" bit I'd question. I don't think the battery temp would increase much by being parked in the open relative to the shade in this country.

BoatMad

Mad_lad virtually everything you state is unfounded or hearsay

Nissan had an issue with the battery in high ambient conditions where ambient temperatures can approach 100 degrees F

The degradation was not universal and in fact was not related to charging at all. ( since most early US leafs only had L1 and even optional L2 and no DCQC

Even today on myNissanLeaf there is no concensus that cyclic heat is causing any degradation. There even a survey at the moment on the blog to try and arrive at a consistent perspective

The only fact we know is a "known Unknown" , that is that we know that under certain circumstances Li degrades under " extreme " heat conditions. It's chemistry dependant

What we don't know is really what set of usage conditions are leading to " premature " ( as opposed to normal battery degradation from usage ) , we have various anecdotes but no significant statistical evident one way or the other.

While Nissan obviously erred in relation to high ambient usage , it's easy to do so because there is no realistic accelerated test for Li life cycles.

Equally we should not second guess Nissan engineers. If they show a valid range of battery operating temperatures , then we should accept that until we have valid conclusive evidence to suggest otherwise.

What we do know is that many people are getting between 60-100k km before loosing a bar.

To compare Tesla is to mis-understand the engineering decisions.

Tesla decided to use 18650 form factor cells. These are poor conductors of heat compared to pouch cells , secondly Tesla needed their batteries to provide current draw way way in excess of the leaf. ( 700 Hp compared to 100 Hp)

Given the poor thermal performance of 18650 firm factor and thd power requirements ,Tesla had no option but to thermally manage the pack. It's wasn't a design decision , it's was mandatory.

Nissan , are using pouch cells that are better thermally , and they are packed less densely and current draw is far far less

Hence the design decision to omit any active thermL management ( which is slightly misleading as they do provide battery hearing in certain markets )

Whether Nissan can remain with no thermal management as power and density grows remains to be seen , I suspect not.

Finally parking under the shade in Ireland is just laughable. The thermal mass of the car and the typical ambients in Ireland mean that such temperatures have little effect on battery internal temperatures.

I suspect I will be a test case for the 30 kw given the mileage I'm doing

We shall see.

Tesla had to cool the battery because the cells will actually catch fire if they get too hot, Nissan's cells won't this doesn't mean that heat has no adverse effects on battery life, it just means Nissan could "get away" with not cooling them.

"Equally we should not second guess Nissan engineers. If they show a valid range of battery operating temperatures , then we should accept that until we have valid conclusive evidence to suggest otherwise."

^^^^^Funny!!!^^^^^^^^^ Spoken like a true Engineer, the company knows best, the company designed the product with the buyers interests in mind, the engineers know better, don't question the Engineers !

Remember the decision not to cool the battery was Nissan being pig headed, even Elon Musk had said when the Leaf was released that this was a mistake.

The MK 1.5 battery is definitely better however we don't know what the actual changes were, improved cycling, temperature resistance, C rate ? unlikely , it still gets quiet warm under charge/discharge. So probably better temperature resistance ( but not temperature resistant) and improved cycling.

GM cool their cells also and these are automotive specific cells which usually don't catch fire, BMW also and if heat has no adverse effects then I hardly think they'd bother with the complexity and extra expense of AC cooling the battery.

"While Nissan obviously erred in relation to high ambient usage , it's easy to do so because there is no realistic accelerated test for Li life cycles. "

Complete BS even Nasa know what heat does to Li cells, it's well documented.

Nissan chose no cooling because did not want to add cost and extra complexity and probably because their original cells were below spec a common issue with battery manufacturers over rating their cells.

Nissan didn't test the cells properly and / or didn't have time to do anything about it by the time the car was due to enter production, they never thought the Leaf would be driven such mileage that's seemingly very uncommon in Japan and probably hoped by the time it became an issue that the battery would be out of warranty. They were hoping no one would want to drive a battery car the distances they're driven in the U.S or Europe.

Remember they said the Leaf needed 0 cooling in all climates, so this is obvious their cells were seriously underrated.

BoatMad

If you stopped ranting and raving , I'd have more time for your logic

Deleted User wrote: »

Tesla had to cool the battery because the cells will actually catch fire if they get too hot, Nissan's cells won't this doesn't mean that heat has no adverse effects on battery life, it just means Nissan could "get away" with not cooling them.

I never said heat doesn't affect cell life, I said the opposite, really stop mis directing

What I said was that we do not know to any degree of statistical accuracy , the effect on cyclic heating ( as opposed to ambient ) on Li cells , specifically as fitted to a leaf. We have no real data , hence you or I cannot go off spouting " conclusions " . I merely say " we don't know what actual real life factors affect degradation and to what extent that degradation is normL or abnormal

^^^^^Funny!!!^^^^^^^^^ Spoken like a true Engineer, the company knows best, the company designed the product with the buyers interests in mind, the engineers know better, don't question the Engineers !

Perhaps 5 year old kids should design EVs , or Internet " know-all " pundits should , serously , these are the experts, I mean who else is there

Remember the decision not to cool the battery was Nissan being pig headed, even Elon Musk had said when the Leaf was released that this was a mistake.

given teslas use of standard Li technology ( 18650 cells from Panasonic ) , and musks background , he's no expert on Li tech.

There is no evidence to suggest that outside excessive ambients, ( coupled with a heat sensitive chemistry ) , that Nissans concept is flawed , one could equally argue that teslas is over engineered

The MK 1.5 battery is definitely better however we don't know what the actual changes were, improved cycling, temperature resistance, C rate ? unlikely , it still gets quiet warm under charge/discharge. So probably better temperature resistance ( but not temperature resistant) and improved cycling.

GM cool their cells also and these are automotive specific cells which usually don't catch fire, BMW also and if heat has no adverse effects then I hardly think they'd bother with the complexity and extra expense of AC cooling the battery.

Ps the conclusion on mynissanleaf is that the lizard battery isn't significantly better over the gen 1 battery, however the usual internet punditry warnings apply

BMW like tesla , seek to extract considerable more performance from their packs , once you get heat gain from that performance that cannot be handled passively , you must go to " forced " thermal management , any basic electronics engineer designing power electronics knows exactly the trade offs. In fact in embedded design , fan less ( ie passive ) cooling is considered better engineering then active thermal management

Simply because you cool because you have to does not make that science better.

The answers is in the data , if bmw batteries last materially longer then leafs , that's the key metric. , that data is not available so no conclusion can be made

Complete BS even Nasa know what heat does to Li cells, it's well documented.

Nissan chose no cooling because did not want to add cost and extra complexity and probably because their original cells were below spec a common issue with battery manufacturers over rating their cells.

It's quite obvious you are not an engineer with knowledge in this area

Added cost and complexity is bad engineering , removing costs and complexity is good engineering . The answer is in the results , Nissan are able to warrant their batteries and there are no statistically relevant data to suggest that cells are failing prematurely ( outside the original high ambient issue )

Nissan didn't test the cells properly and / or didn't have time to do anything about it by the time the car was due to enter production, they never thought the Leaf would be driven such mileage that's seemingly very uncommon in Japan and probably hoped by the time it became an issue that the battery would be out of warranty. They were hoping no one would want to drive a battery car the distances they're driven in the U.S or Europe.

Remember they said the Leaf needed 0 cooling in all climates, so this is obvious their cells were seriously underrated.

I'd like you to point out a car manufacturer that hasn't made a mistake , even Tesla has received recently a very bad reliability report , only saved by very quick repair action. their cars have problems , all cars do

Li cells cannot be tested reliably under accelerated testing typically of automotive testing cycles , because Li tech has properties that are a function of elapsed time and no one, not even tesla has found a way to accelerate time.

Nissan undestimated the sensitivity of their chosen Li chemistry to prolonged exposure to high ambient temperatures, that's a very difficult scenario to test , yes they made a design error. No ones denying that and it maybe that passive cooling is not universally suited to all climates.

That does not invalidate the general decision to use passively cooled cells. It merely means either reducing the operating envelope or changing to a more resilient chemistry.

Your nasa comment is bizzare and without logic , the issue is the specific Li chemistry used in a specific way , NASA know nothing about Nissans specific issues

If passive cooling shows that that abnormal cell degradation is not a material factor , then Nissans design decisions , for that leaf n that circumstances will be shown to be valid , despite the man that founded a payments companys opinion

If it's proven false , it will be a design decision failure and Nissan will follow the herd.

So Nissan decided to cool the ENv 200 van battery, I wonder why ! Because they didn't need to I bed yeah ? And that's not even sold in the USA.

Tesla have stated quiet clearly that they do not use a standard 18650 Li Cell, it's heavily altered to Tesla's specs. The only thing common with the 18650 cell is the 18650 format.

Anyway By the time most Gen 1.5 owners need a battery the cost should have halved from 5,500 to 2,500 Euro's ! I expect the majority of us leasing won't keep it anyway so I couldn't give a stuff but I do try not to abuse it.

BoatMad

[Deleted User] wrote: »

So Nissan decided to cool the ENv 200 van battery, I wonder why ! Because they didn't need to I bed yeah ? And that's not even sold in the USA.

Tesla have stated quiet clearly that they do not use a standard 18650 Li Cell, it's heavily altered to Tesla's specs. The only thing common with the 18650 cell is the 18650 format.

Anyway By the time most Gen 1.5 owners need a battery the cost should have halved from 5,500 to 2,500 Euro's ! I expect the majority of us leasing won't keep it anyway so I couldn't give a stuff but I do try not to abuse it.

There is no such thing as a standard 18650 cell. 18650 is a packaging format , that's all

Tesla , in effect , Panasonic , produce a variant of Li Po in the same vein as many large producers of Li tweak the chemistry.

The comments I stated remain , tesla had no option but to actively thermally manage their packs. 18650 has a poor thermal profile compared to other packaging formats. Coupled with their designed power requirements mean there was no design decision, that hadn't any other option

Nissan have ducted the van air con primarily because they expect the van to be repeatedly fast charged, many multiple times a day. ( you get a DCQC if you buy multiple vans)

As is clear DCQC results in hest gain and once you reach 8 bars , Nissan restricts the charge rate. ( and hence charge time) Presumably this was felt to be too limiting in the commercial market

This is not a comment on the design decision in the leaf. It's a design decision appropriate to the market intended for the vehicle

So it's ok then for a Leaf owner to roast their battery but not the Van owner , Nice !

BoatMad

Deleted User wrote: »

So it's ok then for a Leaf owner to roast their battery but not the Van owner , Nice !

I think you deliberately distract to make points

the van is cooled , because nissan determined that van users are more sensitive to the effects of reducing the DCQC charge time when the battery gets hot because they are likely to have more DCQC cycles per day

the purpose of the cooling is to allow DCQC to continue at full rate for more cycles then a non commercial user

in both cases the batteries get hot

Right so it's the Charge time not the damage to the battery they were concerned about ? give me a break !

KCross

Deleted User wrote: »

Right so it's the Charge time not the damage to the battery they were concerned about ? give me a break !

We're gone off topic a bit but I think the idea is that in general a van user is going to be driving much further on a daily basis than a "typical" car driver. Therefore the van could require 5,6,7 rapid charges in a day.... out for a delivery, back to office to charge, load up, out for another delivery etc.

A company is going to be more sensitive to increases in charge time than an EV car user as they are more time limited (in general).

Its not a case that they are more concerned about charge time at the expense of damaging the battery. In all cases the the battery damage is limited by the BMS but the EV van will be able to do more than the car on a daily basis because of the cooling.

Its about usage pattern not charge time vs battery damage.

BoatMad

Whatever the engineering merits , it's clearly the case that under temperate ambients and normal driving and slow charging , Nissan decision to passively cool was the right one. There is no noticeable heat gain and the passive cooling clearly stabilises the battery temperature

The issue arises with DCQC and particularly with the 30 kW , yesterday charging to 87 % , I saw two bars added. ( from 5 to 7 ). As Bar 8 is the onset of charge restrictions , it is remarkably easy to result in a situation where the stated fast charge advantages of the 30 kWh are completely mitigated by the extension of charging times because charge power is being reduced

It does suggest that Nissan have an issue with DCQC and the 30kwh that is not adequately addressed by the passive cooling

KCross

BoatMad wrote: »

Whatever the engineering merits , it's clearly the case that under temperate ambients and normal driving and slow charging , Nissan decision to passively cool was the right one. There is no noticeable heat gain and the passive cooling clearly stabilises the battery temperature

The issue arises with DCQC and particularly with the 30 kW , yesterday charging to 87 % , I saw two bars added. ( from 5 to 7 ). As Bar 8 is the onset of charge restrictions , it is remarkably easy to result in a situation where the stated fast charge advantages of the 30 kWh are completely mitigated by the extension of charging times because charge power is being reduced

It does suggest that Nissan have an issue with DCQC and the 30kwh that is not adequately addressed by the passive cooling

hmm. not sure this is specific to 30kWh. I've seen the 24kWh add 2 bars while charging. It happened on long journeys where I was doing multiple charges.

In one case it went from 6-8 and the other time from 7-9. See the tables I added here:
http://www.boards.ie/vbulletin/showpost.php?p=99372631&postcount=1
http://www.boards.ie/vbulletin/showpost.php?p=99509620&postcount=12

The temp difference between bars gets closer as you go up and if you are close to the max of a bar when you start charging it is easier for it to cross two boundaries.

So, I dont think the 30kWh has a systemic flaw there.

BoatMad

KCross wrote: »

hmm. not sure this is specific to 30kWh. I've seen the 24kWh add 2 bars while charging. It happened on long journeys where I was doing multiple charges.

In one case it went from 6-8 and the other time from 7-9. See the tables I added here:
http://www.boards.ie/vbulletin/showpost.php?p=99372631&postcount=1
http://www.boards.ie/vbulletin/showpost.php?p=99509620&postcount=12

The temp difference between bars gets closer as you go up and if you are close to the max of a bar when you start charging it is easier for it to cross two boundaries.

So, I dont think the 30kWh has a systemic flaw there.

reading Speakev, comment was made about two scottish guys that did a 4 session DCQC run , seemingly the temp gauge doesnt get above 8 as the BMS restricts the DCQC enough to prevent further heat gain

intersting

So, I dont think the 30kWh has a systemic flaw there

you could be right, after all I better no second guess design engineers, in the absence of any evidence to suggest anything is wrong

KCross

BoatMad wrote: »

reading Speakev, comment was made about two scottish guys that did a 4 session DCQC run , seemingly the temp gauge doesnt get above 8 as the BMS restricts the DCQC enough to prevent further heat gain

intersting

Not true. I saw mine go to 9!