Ye got me Joseph !Joseph C. wrote: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.
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?
Hi Luke ,liveforphysics wrote: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.
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 ?liveforphysics wrote: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.
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.o00scorpion00o wrote: 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 !
o00scorpion00o wrote: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.
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.liveforphysics wrote:If you re-read my above responses it answers this question quite thoroughly.o00scorpion00o wrote: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 ? .