Best way to charge for battery health?

[Dragon]

Tesla recommends plugging it in every night so that is what I do. If that was detrimental to the battery, they probably wouldn't recommend it.

Most probably you could optimize the charging by plugging it in and taking consideration of a lot of parameters (ambient temperature, battery temperature, state of charge, driving needs next day, etc.). But is it worth the effort? If you do that for 5 years just to have 5-10 miles more on your ideal range, probably not.

[dsm363]

That's kind of how I look at it too. I'm sure it's possible to outsmart Tesla's engineers but I'd imagine the savings will be very small as you said. It also takes one of the EV advantages away which is leaving home with a full 'tank' each day, even if you rarely need it.

[vfx]

... I'm sure it's possible to outsmart Tesla's engineers ....

Hmmm....

[dsm363]

Hmmm....

I meant more in the theoretical sense. If you took all factors into account you might be able to come up with a charge method that was slightly better than simply plugging in every night but I doubt it and it probably wouldn't be worth all the effort to save a very small change in ideal miles over 5+ years. It's safer and easier to simply plug in each night.

I didn't mean to imply that the Tesla engineers weren't doing an amazing job. I think the Roadster has been great and the Model S looks to be even better.

[Raffy.Roma]

The cathode in Li ion batteries forms defects (microcracks) due to stress caused by expansion and contraction relative to neighboring materials. It is simply bigger or smaller depending on whether it's charged or discharged. The more you discharge it, the more it changes size. And the more it changes size, the more microcracks it gets. These microscopic cracks lower the battery's capacity. That's one reason why smaller cycles, more often, contribute to longer battery life. That's why you should plug it in every night.

Heat aggravates the microcracking process, so keeping your battery cool contributes to longer battery life. And guess what? Your battery heats up more when used at a lower SOC because it requires more amps to keep your car going 65mph than it does at a higher SOC. That's why you should charge it every night.

Capacity fade also comes from the build-up of non-soluble deposits on the anode and cathode. This chemical process happens faster when the battery is warmer. It also happens faster when at a high SOC. But the process slows to a crawl when you drop the SOC to 80 or 90%, and slows only a tiny bit more at 50%. So if you are going to drive your car, keeping it charged in std mode has less impact on battery life (lower amps, less heat) than driving at a lower SOC. But if you're not going to drive your car for a few days, there are no amps or heat to worry about. That's when Tesla recommends putting it in storage mode, which keeps it at a lower SOC.

end of science lesson.

Can I ask you by taking these precautions after eight years what is the efficiency of the batteries?

[wiztecy]

>Can I ask you by taking these precautions after eight years what is the efficiency of the batteries?

hcsharp reported in the battery log thread that he still gets 245 miles in range mode, so I think his charging practice is working for him


>Heat aggravates the microcracking process, so keeping your battery cool contributes to longer battery life.

@hcsharp to contradict that for sake of argument, if you don't need to charge then why charge it? Ignoring the fact of emergency miles... Since heating will result in heating the pack up. So wouldn't be better to not charge it if you don't need to and are over 50%? I think its also key to charge at a lower ambient temperature if possible.

I don't want the SOCs to be sitting higher than 50% with nothing to do (if you know you're not driving the roadster til the morning). So for me I have the Roadster begin its charge so that its completed 1 hour before I leave for work. The one hour gives time for the pack to equalize and cool. Anytime you can allow the pack to cool is a good thing. Then I drive 35 miles to work, for which I pull the SOC down from 185 ideal miles to 150 (81% SOC). The roadster sits unplugged all day, I then commute back home another 35 miles and my ideal miles is at 115 miles (62% SOC). I then plug the roadster, where charge is not initiated until the next morning, in where the cycle starts again where my charge initiates 1hr before I need to depart for work. Over the weekend I don't do too much driving since I live in Santa Cruz and its a resort for me, beaches, bike rides, sun and kayaking in the ocean I leave the roadster unplugged typically over the weekend holding the 60-62% SOC. So my working SOC is between 60% and 81% give or take a few %'s A SOC range the battery pack should like. The one thing I would need to do every so often is to rebalance / equalize the battery pack. The best way to do this is to leave it sitting in Standard Mode for a long duration. If you're going on a trip for a week it is most likely adventurous to use this down time of the EV to equalize. I'd let it sit the week in Std. mode. I was told the battery pack begins this equalization process of the battery pack whenever the SOC is over 80%.

I know the LiPo battery packs tested in consumer electronics favor the 50% SOC in longevity tests I've seen and reviewed with a battery engineer I work with (who's also an EV enthusiast).

[Doug_G]

The thing about leaving the battery at lower SOC is that the cell voltage slumps a bit. That means that the car has to draw more current to maintain the same power level, which would mean more heating and stress on the battery. So storing the car at lower SOC is better for the battery, but operating the car at lower SOC is not.

[wiztecy]

Thanks Doug and for the background on the battery science technology Henry. Makes sense and very good points to keep in mind. Another thing to consider is AMPs to charge. I believe Tom did an analysis on what Amps are the most efficient to charge at and his curves showed 30Amps ( I need to revisit it if that was the exact Amps, I believe so). Any lower and its inefficient in terms of cost to push the amps across the line. I believe above 30 Amps you start building up heat and heating up the battery packs more than necessary. When I charged at Tesla down in Santa Row they had the 70amp quick charger. I wasn't in a hurry and my charge not too low so I dialed it down to 30Amps in the Roadster.

[Raffy.Roma]

>Can I ask you by taking these precautions after eight years what is the efficiency of the batteries?

hcsharp reported in the battery log thread that he still gets 245 miles in range mode, so I think his charging practice is working for him


>Heat aggravates the microcracking process, so keeping your battery cool contributes to longer battery life.

@hcsharp to contradict that for sake of argument, if you don't need to charge then why charge it? Ignoring the fact of emergency miles... Since heating will result in heating the pack up. So wouldn't be better to not charge it if you don't need to and are over 50%? I think its also key to charge at a lower ambient temperature if possible.

I don't want the SOCs to be sitting higher than 50% with nothing to do (if you know you're not driving the roadster til the morning). So for me I have the Roadster begin its charge so that its completed 1 hour before I leave for work. The one hour gives time for the pack to equalize and cool. Anytime you can allow the pack to cool is a good thing. Then I drive 35 miles to work, for which I pull the SOC down from 185 ideal miles to 150 (81% SOC). The roadster sits unplugged all day, I then commute back home another 35 miles and my ideal miles is at 115 miles (62% SOC). I then plug the roadster, where charge is not initiated until the next morning, in where the cycle starts again where my charge initiates 1hr before I need to depart for work. Over the weekend I don't do too much driving since I live in Santa Cruz and its a resort for me, beaches, bike rides, sun and kayaking in the ocean I leave the roadster unplugged typically over the weekend holding the 60-62% SOC. So my working SOC is between 60% and 81% give or take a few %'s A SOC range the battery pack should like. The one thing I would need to do every so often is to rebalance / equalize the battery pack. The best way to do this is to leave it sitting in Standard Mode for a long duration. If you're going on a trip for a week it is most likely adventurous to use this down time of the EV to equalize. I'd let it sit the week in Std. mode. I was told the battery pack begins this equalization process of the battery pack whenever the SOC is over 80%.

I know the LiPo battery packs tested in consumer electronics favor the 50% SOC in longevity tests I've seen and reviewed with a battery engineer I work with (who's also an EV enthusiast).

Does it mean that by treating carefully the batteries of a Tesla Model you could still have an efficiency of almost 100% after eight years?

[wiztecy]

There's the factor of time that batteries have a constant shelf life. But it does mean your battery should be more reliable and healthier if you understand the battery technology as well as the physical and electrical principals that are tied to it. The battery logs research is a big part of this and I encourage all to participate. I know every time I stop at Tesla to have anything done they pull my logs. I'm sure they're doing the same and much more analysis on this data as we are to understand battery and charging characteristics based on multiple variables.