Jeff Dahn's recommendation on long term battery preservation

[Tam]

...quest...

The old and long youtube from professor Jeff Dahn seems to imply that shorten the charging time is good, prolonging the charging time is bad. It's just like taking off a band-aid: Do you want to suffer so quickly that you can't hardly feel or do you want to take it off real slowly?

However, Tesla would decrease your peak-charging rate if you use too many DC-DC fast charging.

 

[jsmay311]

A bit off topic, but in Jeff Dahn's TedX talk he makes a very sobering observation about using batteries for grid storage:

If Nova Scotia (with a population of under 1 million) wanted to have 100% renewable power with enough battery storage to cover just a single day's worth of electricity demand, it would require more than 1.5 years worth of the Gigafactory's projected production of battery cells. (55 GWh/day vs the Gigafactory's 35 GWh/yr)

Making Batteries Better | Jeff Dahn | TEDxDalhousieU

 

[jsmay311]

The old and long youtube from professor Jeff Dahn seems to imply that shorten the charging time is good, prolonging the charging time is bad. It's just like taking off a band-aid: Do you want to suffer so quickly that you can't hardly feel or do you want to take it off real slowly?

However, Tesla would decrease your peak-charging rate if you use too many DC-DC fast charging.

I think you need be a bit more cautious in how broadly you interpret that presentation and extrapolate its findings to real-world charging of Tesla vehicles.

1. He's discussing LiFePO4 cells, which are a very different chemistry than what Tesla and pretty much everyone else uses.
2. He's specifically discussing A123 cells, which were specifically designed for very high charge and discharge rates.
3. He's comparing 2 very extreme examples: 1.5C charge and 2.5C discharge vs 0.018C charge and discharge.
4. The tests he's comparing took place at 60C (140F), which is well above the maximum recommended temperature for LiFePO4 cells.

For all of these reasons, I wouldn't automatically assume that his findings are applicable to charging Tesla battery packs in realistic conditions.

 

[Science->Truth]

A couple of decades? Nice... I'm quite interested to see how that evolves.

Jeff

Yes, life (wishes/wants etc) change. I, oh so close, almost traded by 2013 S85 for a 100D last year, but at the end, I found I couldn't let go of this fantastic amazing vehicle. My (folding) bike is always with me in the (largishj) fronk, And, I love the "classic" style of the front end. But, 20 years? Very unlikely, unless they stop selling 'em. Maybe this is a "problem" (for Tesla), since I'm at the point where traditionally I'd trade. But, my classic continues with its wonderful amazing performance, problem free, unabated by the years.... On the flip side, in the aftermarket, anyone buying a 4-5 year old Tesla is getting a deal.

 

[Tam]

...wouldn't automatically assume that his findings are applicable to charging Tesla battery packs in realistic conditions.

I guess Freedom101 needs to get the professor to clarify which is better for battery longevity: slow or fast charging?

 

[Science->Truth]

This is a great question and I'm on a quest to find the answer to this as well. Would love insight from anyone knowledgeable on the topic.

I don't believe the speed of a level 2 charge matters but I don't know this. There is alot of info regarding supercharging and overdoing it so I wouldn't install a level 3 charger at home until I understood it better and there was more information on it.

I'm having my panel upgraded tomorrow and the Tesla wall mount installed on a 100amp circuit. I can only charge at a max of 48 amps but figure why not do it at the higher capacity (cost is essentially the same). The beauty of going higher on a level 2 charger with a Tesla is you can always slow the overnight charge down if you find info that it is beneficial to do so.

If you are in US: My experience is the key to cost of install is length of the copper (wire) to where the HPWC or the NEMA-14-50 outlet is. IF your car location is close to your main breaker box, I'd install very heavy wire and set the HPWC to run at max of 100 amps, or the max of whatever your incoming service allows. But, if you have to run a line hundreds of feet, the cost of the copper wire will mount up. So, if that is too high cost, I'd drop to a 60 amp breaker line, which allows max charge on current Teslas with a single charger. Aside from the technicals, if you never need a faster charge (e.g., always have entire overnight to charge), a 50-amp breaker line is fully adequate.

 

[seclinton]

Ohh this is so much fun. But no one is asking the underlying question. Why is 40-60% SOC the best?

I'm no "expert" or published professor, and a little study of Li-ion leads to some interesting observations. Indulge me if you will:

- lithium batteries operate by let's call it shuttling Li ions between the anode and cathode.
- yeah yeah, in this case the anode is Graphite and the cathode is a NMC, NCM, the A123 kind with phosphorus
- well lithium ions are kinda big (as in a beach ball being lithium and Oxygen being a basketball.
- so when you charge your battery, the Li ions are moved from the cathode reservoir ( the cathode to anode raitio always has > cathode reserve capacity)
- carbon can form how many bonds? You can look it up. (Hint it's 4)
- so when we shuttle the Li ion, it absorbs into the carbon graphite matrix
- these "fat" ions cause the anode to swell (ala like a sponge)
- charge to 100% and your sponge is saturated (leave it there and the Carbon-carbon spacing is stretched too much (I.e. Under tension like a balloon at maximum inflation
- when you discharge these LI ions break free and are pushed back to the cathode
- doing this breaks carbon-carbon bonds ( yes they can self repair, the wonder of modern chemistry understanding)
- broken bonds increase resistance and the sponge collapses (I.e permanent capacity loss)
- charging in the mid % range minimizes these swell and contraction excursions and a half full sponge can accept more if needed as it allows those fatty li ions room to move in; (we call this coulombic efficiency). (I.e.2. The raitio of power in vs power out)


I like to dumb this down some, but think of lithium cells that swell and contract when charged and discharged. Weird and bad stuff happens at 100% SOC and <20% SOC. Side reactions occur, god forbid a Lithum crystal forms a dentrire > the separator thickness at high SOC. Too low and you lose catholic protection (google IS your friend), and the base foils become exposed and ions start to migrate and copper starts to dissolve, hello dying battery.

Long story short, be nice to your battery, don't stay at too high or low a SOC, and if you want longer life, reduce your Wh/mile. Flooding the cathode during discharge can lead to a traffic jam; lithium ions squeeze together and that next charge anything behind that blockage might create a temporary dead end and a pocket of space blocking one li ion from squeezing in.

40-60% is ideal, and so on. The 90/20% rule from tesla is sort of the limits to avoid the obvious known immediate degradation paths.

Whew...let me know what you think.
18+ years making batteries (meaning career) and still doing it...if I'm wrong in anything above, please let me know, I'll correct it.

 

[seclinton]

I guess Freedom101 needs to get the professor to clarify which is better for battery longevity: slow or fast charging?

Slow is better

 

[Freedom101]

If you are in US: My experience is the key to cost of install is length of the copper (wire) to where the HPWC or the NEMA-14-50 outlet is. IF your car location is close to your main breaker box, I'd install very heavy wire and set the HPWC to run at max of 100 amps, or the max of whatever your incoming service allows. But, if you have to run a line hundreds of feet, the cost of the copper wire will mount up. So, if that is too high cost, I'd drop to a 60 amp breaker line, which allows max charge on current Teslas with a single charger. Aside from the technicals, if you never need a faster charge (e.g., always have entire overnight to charge), a 50-amp breaker line is fully adequate.

Thanks for the input. I'm in Canada but it is very similar I believe.

I'm upgrading my panel from 100amps to 200amps (have a suite so basically no choice - I could get a switch installed but wasn't liking that option). I'm installing the Tesla wall charger and that will literally be beside the electrical panel in my garage so the wire will run about 1-2 feet only so very heavy wire it will be! My plan is to have a 100amp circuit breaker put in as I don't need the extra amperage for anything else (even though my car X will only accept 48amps).

I've already shot the first half of this video and will hopefully shoot the rest tomorrow when the electrician finishes up (hoping he doesn't leave too much of a mess).

If there are any electricians on here please let me know if my plan is at all flawed. The electrician I'm using seems to be on board with the plan and has done several EV charger installations.

Excited to not have to plug into the wall outlet anymore!

 

[AWDtsla]

The old and long youtube from professor Jeff Dahn seems to imply that shorten the charging time is good, prolonging the charging time is bad.

You're misinterpreting what he's saying. The point of that section is that the degradation is time dependant not cycle dependant.

 

[22522]

Lots of good information here.

As I understand it,
1) Overcharging creates an oxide film on one of the 'nodes.
2) This film reduces capacity (is bad).
3) Deep discharges should be avoided.

I would charge to a value that leaves the car at 28% charge at the end of the day.

 

[J X 3]

Once full autonomy is legal, car as a service ramps fast and that leads to a collapse of the used cars market - the market is flooded with offers while demand drops hard.
So ideally you want to sell your car before autonomy becomes legal in major jurisdictions or you are gonna take a substantial financial hit.

 

[BartJ]

I had set my car to 70% the last days as per recommendation.
since then , I noticed that the car starts charging every two to three hours , just to top of to 70%.
if set and stored at 90%, this only occurs every one to two days.

 

[Chickenlittle]

Once full autonomy is legal, car as a service ramps fast and that leads to a collapse of the used cars market - the market is flooded with offers while demand drops hard.
So ideally you want to sell your car before autonomy becomes legal in major jurisdictions or you are gonna take a substantial financial hit.

Yes and sell stock at all time high 5 minutes before it drops. Don't forget to buy back at lows 5 minutes before it goes up. It's really quite easy

 

[scaesare]

We have just bought a house (try to settle down?!) in Blacksburg VA. I asked electrician to install a Tesla Charger he suggested that the wiring difference between 40Amp (available) and 80A is around $150. I wasn't going to spend the extra as overnight charging would be the same.....

Does anyone know if it is better to charge more slowly? If I had the faster charger, I could keep the charge limit lower and have the option to top it off quickly. Any thoughts?

Unless otherwise specified, it's usually safe to charge Li-ion batteries at a "1C" rate (with 1C being equal to the battery begin fully recharged in one hour). And typically batteries that specify otherwise allow for faster charging, seldom are they required to charge more slowly.

So, for the size of the currently available packs, a 1C charge rate would be anywhere from 75-100KW. That means that any of the available home charging options (up to ~20KW for a 240V/80A circuit) are a fraction of 1C. There's going to be practically negligible impact from charging at any of those rates.

 

[Freedom101]

I had set my car to 70% the last days as per recommendation.
since then , I noticed that the car starts charging every two to three hours , just to top of to 70%.
if set and stored at 90%, this only occurs every one to two days.

Interesting... Mine is not doing this. I have it set at 70 percent and once it reaches 70 percent it doesn't charge again (I've monitored and noticed the vampire drain overnight). I haven't left my X without driving it dor more than about 12-15 hours since setting the charge rate to 70 percent.

I wonder why the discrepancy. Maybe temperature?

 

[RCardona68]

We have just bought a house (try to settle down?!) in Blacksburg VA. I asked electrician to install a Tesla Charger he suggested that the wiring difference between 40Amp (available) and 80A is around $150. I wasn't going to spend the extra as overnight charging would be the same.....

Does anyone know if it is better to charge more slowly? If I had the faster charger, I could keep the charge limit lower and have the option to top it off quickly. Any thoughts?

 

[Roadster2010]

I'm more interested in how FAST to charge my 2010 Roadster.
I've seen all kinds of comments, but I'm still unsure if it's better to charge slowly or quickly (i.e., lower or higher amperage).
Are there expert opinions on charging rate?

 

[BartJ]

I'm more interested in how FAST to charge my 2010 Roadster.
I've seen all kinds of comments, but I'm still unsure if it's better to charge slowly or quickly (i.e., lower or higher amperage).
Are there expert opinions on charging rate?

slower is better on a roadster. less heat produced which is better for the battery life.

 

[BartJ]

slower is better on a roadster. less heat produced which is better for the battery life.

but make sure to maintain at least 3kw (e.g. 13A @ 220v ) , otherwise there is not enough power for the HVAC to come on in order to cool the battery during the charge.