Long trip - battery balancing question

[loop68]

Hi all

I've arrived in Spain from the UK en route to Portugal (great timing).

Thursday was London - Tours, France
Friday was Tours - Madrid.

I used superchargers heavily on the way down, and destination charging in Madrid and Tours.

The question is... after multiple short snd long SuC visits, what is the best way to rebalance the battery pack over night and while standing? Destination charge to 90? 95? 100?

Bear in mind the next stint is another 600 km or so, so I dont mind going to 100%

Thank you

 

[DontBetAgtsEln]

90%, upolug and let your car sit there for (ideally) 4hrs after you reach that SOC. That's when the balancing happens.

 

[NorfolkMustard]

Honestly, don't worry about it, just add kWh when you need to and drive it Have a good trip.

 

[Jeeves]

Why might ‘rebalancing’ be important or desirable?

 

[loop68]

I've read that the battery cells can go out of whack a little bit if you supercharge or fast charge a lot, without doing any slow charges. The battery cells will start to give slightly unequal voltages as I understand. This can result in slight deviations in range and SoC prediction. It seems the car 's battery management system will balance each individual cell after a slow charge. Trying to ascertain the right behaviour to trigger this balancing process...

 

[pgkevet]

I don't know the honest answer but the following is speculation:
I doubt that tesla manages batteries to the individual cell but rather to the individual block. How they do it is likely to be by total voltage and by block resistance measurements and with other pack types I've had some time with (mostly lipoly's which i know are different) the balancing was by charging, measuring the comparative voltage across cells/blocks and then discharging those that are high to the level of those that are low and recharging a few repeat to get an overall average balanced charge hoping to push the lower ones higher. On something like a car they''ll doubtless check available discharge rates through those cycles too. It's why the top end of charging is slow because that's where the imbalance appears.

How that makes any difference to cell longevity between frequent fast charges to, say, 70-80% or slow charges is unknown. We do know that full charges aren't good if left at full charge for any length of time but if regular balancing was critical for longevity to pack then one could expect advice to be to always try to charge to that 100% just before departure

 

[PACEMD]

Run it down to 12%, charge to 67% on a supercharger, rub essential oils on the bottom of the battery pack (or if you are pressed for time you can just spray the oils on but try to get a uniform coat), let sit for 5 hours, then charge to 92% on a low voltge circuit. Works like nobodies business..........

 

[pgkevet]

Run it down to 12%, charge to 67% on a supercharger, rub essential oils on the bottom of the battery pack, let sit for 5 hours, then charge to 92% on a low volt circuit. Works like nobodies business..........

3.6V at 1mA takes a while...

 

[M3noob]

Run it down to 12%, charge to 67% on a supercharger, rub essential oils on the bottom of the battery pack (or if you are pressed for time you can just spray the oils on but try to get a uniform coat), let sit for 5 hours, then charge to 92% on a low voltge circuit. Works like nobodies business..........

Under a full moon? When I examined the entrails of a small bird, the answer was different

 

[NorfolkMustard]

Run it down to 12%, charge to 67% on a supercharger, rub essential oils on the bottom of the battery pack (or if you are pressed for time you can just spray the oils on but try to get a uniform coat), let sit for 5 hours, then charge to 92% on a low voltge circuit. Works like nobodies business..........

Dude, dangerous misinformation. It’s 67.4%

 

[PACEMD]

Dude, dangerous misinformation. It’s 67.4%

Only on the metric system..........

 

[bhav]

Run it down to 12%, charge to 67% on a supercharger, rub essential oils on the bottom of the battery pack (or if you are pressed for time you can just spray the oils on but try to get a uniform coat), let sit for 5 hours, then charge to 92% on a low voltge circuit. Works like nobodies business..........

Most informative post in a while.

Seriously, don't worry about balancing/rebalancing. Just enjoy using your car and charge it when you need to, even if that's supercharging repeatedly for a long trip. It's not going to make the slightest bit of difference! (Also, make sure you're on % battery not on miles/range as that will only serve to drive you to these kinds of obsessions! )

 

[Andy_T_73]

Euan McTurk - elecro chemist chap on YouTube - recommends going to 100% every now and again to allow BMS to balance cells. I've no idea if that applies to all cars or which charging method. Anyways, wouldn't do any harm to overnight AC charge to 100% if you're going to use it all the next day.

 

[UncleCreepy]

I went on a 9,000 km road trip this summer and frequently drained the battery to about 4% before supercharging at up to 250 kW. Whenever I charged at a hotel I set the slider to 90% overnight and then to 100% when I got up in the morning. That way I always left with close to 100% without the battery sitting at that SoC for hours.

Degradation? I had 403-406 km at 80% before and it hasn't changed one bit.