Is this guy the expert he claims ?

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This guy is a bit of an ass but anyway I would greatly appreciate if someone for the sake of proper information could tell me if this guy is the battery expert he claims to be ?

Look at post 22 here, then read on. You really need to see the original post and read on.

http://www.boards.ie/vbulletin/showthread.php?t=2057511837&page=2

Quote
low temperatures i.e. above about 5% but less the 15% have no effect on Li charge rates, the graph isn't linear. in fact it can improve charge rates as the heating generated near the end of the charge taper phase can be carried away by the lower ambient temperature

where the electrolyte is in danger of freezing and even at slighter higher temperature, the mobility of Li ions is degraded only slightly, at electrolyte freezing then a careful low C " pre-qualifying charge" has to be applied , extending charge times significantly ( or the battery externally warmed)End Quote
 
the guy looks like he is looking for an argument to me tbh.
He keeps saying he has debunked peoples observations during use of their leaf which is a bit stupid.

Obviously as battery's age the internal resistance goes up reducing the rate they can be charged and discharged. When they get cold the internal resistance also goes up and to protect the battery the charger will reduce the charge rate to protect the battery.
 
Does increasing internal resistance in the cold mean that the battery itself won't accept or demand the full charge current or is this controlled by the charger ?
 
The battery is temperature sensitive. People with the Model S have found that charging in low temperatures takes a lot longer than in higher temperatures - an effect that is increased with low charging rates. Some people have also reported that regenerative braking will not work in extreme cold without the battery being warmed up first.

I'm pretty confident that electric car manufacturers wouldn't needless place those restrictions on their car if what the 'expert' says was correct. Luke or dnum would probably have the answers to your questions.

I knew you had to be Mad Lad. :mrgreen:

A family member is thinking about getting the 2016 LEAF (30KW/hr version). Do you mind if I ask what sort of range are you getting in the summer and does it deviate much in the winter? I'm guessing somewhere around 150km and 100km?
 
Joseph C. said:
The battery is temperature sensitive. People with the Model S have found that charging in low temperatures takes a lot longer than in higher temperatures - an effect that is increased with low charging rates. Some people have also reported that regenerative braking will not work in extreme cold without the battery being warmed up first.

I'm pretty confident that electric car manufacturers wouldn't needless place those restrictions on their car if what the 'expert' says was correct. Luke or dnum would probably have the answers to your questions.

I knew you had to be Mad Lad. :mrgreen:

A family member is thinking about getting the 2016 LEAF (30KW/hr version). Do you mind if I ask what sort of range are you getting in the summer and does it deviate much in the winter? I'm guessing somewhere around 150km and 100km?

Ye got me Joseph ! :mrgreen:

Boat mad is seriously driving me nuts, he's hijacking every thread.

He seems to think internal resistance doesn't change through the life of the battery and he thinks that I'm mad because I say charge times increase in the cold due to the rising internal resistance due to cold. He claims this is the charger controlling all this ! :shock:

I drive about 100-110 Kph most of the time and probably drive faster now that I have the work charge point. :mrgreen:

I would say in Winter to be at a charge point after 110 Kms max in winter and about 120-130 Kph in Summer at the same speed.

On our usual crap back roads you could get 140-160 Kph at 60-80 Kph in Summer.

So the 30 Kwh should get 140-160 Kms Winter to 140-180 Kms Summer. Give or take.
 
The thermal kinetics of the system determine the ion diffusion rate of lithium ions to migrate into the anode (ideally in an even distribution throughout the coating of active material) to intercalte into the carbons structure while charging.

Temperature dependant thermal kinetics of ions and molecules colliding in the electrolytes solvent are ultimately how Lithium ions get from cathode to anode in all liquid electrolyte LIBs. As a result, the ions move slower as they get colder. If you charge at a rate the drives ions towards the surface of the anode at a higher rate than the solvent channels into the structure of the anode layer can accept, ions can stick to ions, and unfortunately they tend to make crystalline metallic lithium metal when that happens. This causes other reactions that ultimately result in cell gas production, local irreversible capacity loss, and in an extreme situation using cells that dont have overtemp protection safety seperators could potentially undergo hard shorting from metallic lithium crystal growth leading to a thermal event or fire.

I didn't bother to read more than your quotes from that guy. He commutes with a LEAF, so his breadth of battery wisdom is beyond my humble scope of comprehension.

ATB,
-Luke
 
liveforphysics said:
The thermal kinetics of the system determine the ion diffusion rate of lithium ions to migrate into the anode (ideally in an even distribution throughout the coating of active material) to intercalte into the carbons structure while charging.

Temperature dependant thermal kinetics of ions and molecules colliding in the electrolytes solvent are ultimately how Lithium ions get from cathode to anode in all liquid electrolyte LIBs. As a result, the ions move slower as they get colder. If you charge at a rate the drives ions towards the surface of the anode at a higher rate than the solvent channels into the structure of the anode layer can accept, ions can stick to ions, and unfortunately they tend to make crystalline metallic lithium metal when that happens. This causes other reactions that ultimately result in cell gas production, local irreversible capacity loss, and in an extreme situation using cells that dont have overtemp protection safety seperators could potentially undergo hard shorting from metallic lithium crystal growth leading to a thermal event or fire.

I didn't bother to read more than your quotes from that guy. He commutes with a LEAF, so his breadth of battery wisdom is beyond my humble scope of comprehension.

ATB,
-Luke

Hi Luke ,

Which guy are you referring to , boat mad Or mad lad ?

I'm mad lad and I'm the one commuting if you were referring to me lol. The other guy doesn't have a leaf yet.

So what I would like to know is what causes the reduced charge current when the battery is cold, is it what you said above, and is this what causes internal resistance to rise and is the internal resistance the cause or is the ChaDeMo charger solely responsible for reducing the current or the battery itself simply won't demand it.

I noticed it's my LiPo I couldn't get the same amounts of amps in the cold and there was nothing connected such as bus or anything so this tells me the current just couldn't get out of the battery.
 
My apologies for the confusion, like I mentioned before, I didn't bother to read that thread.

The charger is always capable of whatever current it can deliver. When you plug into a cold pack, the BMS tells the CHAdeMO to not exceed some current value that is appropriate for that temperatures packs capacity to safely intercalate charge.
 
liveforphysics said:
My apologies for the confusion, like I mentioned before, I didn't bother to read that thread.

The charger is always capable of whatever current it can deliver. When you plug into a cold pack, the BMS tells the CHAdeMO to not exceed some current value that is appropriate for that temperatures packs capacity to safely intercalate charge.

Is it the BMS that decides the current sent to the pack when it's cold or is it because of the higher internal resistance that the pack only can accept a lower current, meaning it won;t pull any more regardless ?

Like I assumed the reduced regen on older packs was due to higher internal resistance meaning the battery can't or won't take the current ?
 
o00scorpion00o said:
he thinks that I'm mad because I say charge times increase in the cold due to the rising internal resistance due to cold. He claims this is the charger controlling all this ! :shock:

For the most part he is right and you are wrong. A battery having higher internal resistance will still charge at the constant current rate of the charger. A 5A charger will put 5A into a battery with low internal resistance just as it will in one with high internal resistance. Where you are slightly correct is at the very end of charging in the constant voltage region. A pack with higher internal resistance will have a higher terminal voltage during charging, and will hit the constant voltage 'taper' portion of the charge earlier on, and will then sit in the constant voltage taper zone for a longer period of time to fully top up.
Play around with this tool for a bit:
http://www.ebikes.ca/tools/charge-simulator.html
You can use the custom battery option and set lead + tab resistance to a higher value in order to quantify exactly what a given increase in internal resistance will do to the charge curve and final charge time. For instance, here is a stock pack:
Charge Times, stock pack.jpg

Then say at a given cold temperature you know that the internal resistance is 120mOhm higher. Just add this to the lead+tab resistance (now 150mOhm total) and you can get a first order look at what cold weather charging wold look like:
Charge Times, highe rinternal resistance.jpg

To the original discussion with the EV. If the bulk charge current is reduced in cold temperatures, or the regen is being limited, then that has nothing whatsoever to do with the higher internal pack resistance. That is external control electronics (either the charger or motor controller) recognizing that the battery is cold and then adjusting its operating parameters for lower currents, likely at the suggestion and recommendation of the battery manufacturer, who presumably knows best about what to do for the long term health of the cells.
 
Thanks for that Justin,

How then do you notice a lot less amps can be drawn from a cold LiPo pack with no BMS doing any monitoring ?

And so if the ramp down current on the Nissan Leaf At the chaDeMo chargerfor instance starts at about 60% for the sake of arguing that by 60 % it's pulling 35 Kw from the charger and started at 45 Kw then this is controlled solely by the charger or BMS and not as a general part of how Li batteries charge ?
 
My, likely wrong, idea of it was that the very cold pack simply wasted some of its watt hours warming itself when you start discharging it.
 
Read this form .

University of Wisconsin Milwaukee
UWM Digital Commons

It's not the only reference I can find on the subject either in relation to internal resistance, which is I presume related to the effects of cold on the chemistry itself.


http://dc.uwm.edu/cgi/viewcontent.cg...46&context=etd

Quote

We also know that with the rise in internal resistance, the battery performance deviates
and degrades. This results in a rise in the charging time and degraded performance of the
battery pack during the driving cycle.

The charge process from grid for all batteries in the group is shown as in Fig. 4.6. The
charging time increases as the internal resistance of the battery increase. EndQuote
 
If Internal resistance goes up enough when cold, then discharging it in that condition results in the resistance warming the battery. There went some watt hours. That was the way I understood it.

If the battery is in a situation where it cannot warm up, then the high resistance continues for the entire discharge.

It seemed like this was the case for my ping lifepo4 batteries. They'd sag like mad till they warmed up. So I assumed at that moment, resistance had increased. At one point I tried taking the bus half way on the coldest mornings. That was a disaster, since the battery chilled riding on the front of the bus.

Back when I did commute on freezing days, I found a metal battery box and no insulation was not the way. Just some thin insulation inside the box in winter would allow the ping battery to warm itself up, or if warm already, keep warm during the ride vs getting colder after leaving the house.
 
Hi Dogman,

Exactly my observations with LiPo, can't remember the effects of cold on my old Ping.

So I would assume the same thing going on with LiPo is the same observed when "charging" the Leaf on the ChADeMo fast charger ? as well as people suffering increased charge times which was observed in the paper in the above link form the University of Wisconsin which isn't the only reference I can find to this.

Also regarding the ramp down phase from constant current to constant voltage , we were discussing why the 2016 30 Kwh Leaf charges in the same time from low battery warning to 80% as the 24 Kwh, Boat_Mad insists this is solely controlled by the charger or instructions from the BMS to tell the charger to allow the Leaf longer in this constant current stage.

My interpretation of this was that because the battery is larger that it "can" stay in this constant stage for longer before the charger ramps down the power meaning it charges in the same time to 80% as the smaller 24 Kwh and it's not because of the different chemistry or instructions or Nissan reprogramming the BMS to tell the charger to do so.
 
As a CHAdeMO can deliver constant full current all the way to 500vdc, anytime you see current less than maximum from the CHAdeMO, you can rest assured its because the BMS told the charge station over its CAN connection to behave the way its behaving.

When you connect to a CHAdeMO, it just becomes a slave controlled power supply that your vehicle gets to determine what voltage and current its delivering at each moment.
 
So what If Dogman and I experience a sluggish LiPo pack for instance and there is no BMS in between what's causing the reduced performance ? and does the same not apply to the Leaf chemistry ? and I've never charged LiPo at high rates so probably never noticed any difference in charging but I'm guessing if cold reduces LiPo and LiFeP04 performance when discharging should the same not apply to charging ?

There are several reports on the web about this being the cause of increased internal resistance and a paper from the University Of Wisconsin I linked to.
 
It's difficult to find real test results for the effects of temp on lipo, but there was a interesting ser of data from Samsung on the 25R introduction PDFs...https://endless-sphere.com/forums/download/file.php?id=130053
It's a set of 10 amp discharge curves for temperatures 0deg to -20 deg which clearly show the effects on voltage, which could be interpreted as change in DCIR of the magnitude of ~20mohm ( in effect trippling of the standard cell DCIR, from 23mOhm to 60+ mohm )
Is it fair to assume that same change in IR would present during charging, but as we know chargers are CC regulated as mentioned before.
vxvPV1.png
 
o00scorpion00o said:
So what If Dogman and I experience a sluggish LiPo pack for instance and there is no BMS in between what's causing the reduced performance ? and does the same not apply to the Leaf chemistry ? and I've never charged LiPo at high rates so probably never noticed any difference in charging but I'm guessing if cold reduces LiPo and LiFeP04 performance when discharging should the same not apply to charging ?

There are several reports on the web about this being the cause of increased internal resistance and a paper from the University Of Wisconsin I linked to.


If you re-read my above responses it answers this question quite thoroughly.
 
liveforphysics said:
o00scorpion00o said:
So what If Dogman and I experience a sluggish LiPo pack for instance and there is no BMS in between what's causing the reduced performance ? .

If you re-read my above responses it answers this question quite thoroughly.

To be more specific, what you describe as a sluggish performance does not mean that your battery is not able to put out the same number of amps. If you have a 25A controller, it will pull 25A from a hot pack just as it will pull it from a freezing cold pack. But the cold pack will have higher internal resistance so the terminal voltage at 25A will be less than the warm pack. Less voltage at a given current means less power, and less power can be interpreted as feeling sluggish.

In a more extreme case the voltage sag could be such that the pack terminal voltage is at the controller's low voltage rollback, and in that case you will actually have less amps under load with the freezing battery, but it's the controller doing that erroneously trying to prevent overdischarge of the cells because the pack looks flat when there is so much sag. In no case here is the cold battery itself unable to "put out" a certain number of amps.
 
Sorry if my comment just confused the discussion.

I did not mean the battery could not put out the same amps when cold. It sags voltage when close to 0c/32f. Less volts x whatever amps the motor will pull at the moment = less watts. Less watts can't go as fast, so you will see less amps at cruise speed because cruise just got 5-10 mph slower.

But I only assumed the effect was a result of high resistance in the battery. I assumed that since the battery is ice cold, and appears to be resisting a lot, that some of the potential capacity was lost into warming the pack.

Cold battery, old battery, from the saddle they act very similar. Lots of sag, low capacity. So I made the assumption the cause was similar, high resistance.

On the charging side, I have no idea about anything. Nor would I assume anything to do with discharging would have an effect on charging.

Do cold batteries charge a lot like old batteries? Do they slow down as if full, before the normal target voltage like old cells? What appears to happen with old lipo, is they think they are full at 4v, then charging slows to a trickle which is mostly eaten up by resistance. So getting that last ah into really old lipo packs can take hours. Coldest I've run chargers is about 40F. Typically I don't charge in a cold garage.
 
Well , in the case of the Nissan leaf, charging does slow down noticeably even with a colder weather can see a 10-15 min increase in fast/DC charge times.

Regen also weakens as the battery ages.

And battery charge times increase on the DC charger also when the battery ages.
 
Seems Nissan themselves varied that the chemistry and internal resistance is what allows the 30 Kwh to charge faster . I'm sure ye read the info on it and no need to link to it here.
 
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