New to Prius Prime - Battery Questions

I'm new to the Prime but this is my 4th Prius so I'm not new to the brand or the car. That said, I have been relentlessly holding off buying a plug-in or full EV because the pending battery technology breakthrough (low-valence nano-fractal peace dividend electrode substrate technology) we are all waiting for hasn't happened yet. Back in 2010 I guessed it would have broken through by 2015 or so but we're still waiting. I avoided lithium-ion for safety reasons (they tend to overheat easily when under high discharge rate or worse get shorted) and lack of wide climate and temperature range performance, but the temptation this year to get a 2020 Prime got the best of me so I sold my 2014 to a friend and got one. No regrets, no remorse. The car is everything I expected.

That said, I have read everything in these forums that I could regarding traction battery hygiene and I see a lot of vagueness and inference but no real definitive scientific opinion based on research into the chemistry and physics of keeping lithium-ion batteries healthy. Is there any basic research published? I am sure there are patent filings and scientific papers out there but I haven't had time to search for them.

There are some common sense ideas that can be safely inferred like avoiding cold and heat when possible but very little research-based opinion regarding charge/discharge speed, optimal capacity management and general sound guidelines which are backed by research and science.

One thing that I'm curious about is Level 1 vs Level 2 charging. I currently use L-1 at home and L-2 where I can get it for free. My intuition tells me that -L1 is less stressful but others here have said L-2 is not a problem. I know for a fact that L-2 generates more heat than L-1 which cannot be a good thing. With shelter-in-place orders here in NorCal I haven't had much opportunity to commute to work or take the car on the road (spare tire arriving in a few days from eBay, thanks to forum articles here about which tire size to order, etc.) but I have driven quite a bit locally here and getting 34-38 miles on a charge (I have experience hypermiling my previous 2014 Prius to 74MPH for a full tank). I don't see a need to invest adding a 50A circuit since I'm plenty comfortable using gas if necessary (I don't think I've spent more than a few miles out of 600 total in hybrid mode, BTW). I really don't see the need if the L-2 charger is going to degrade the batteries, even minimally, over the life of the car. Will it degrade the batteries more than L-1 would?

Anyway, thank you for the wonderful forums. I've learned a lot here.

 

Thanks. I drive my daily driver like an old grandmother. I have a 400HP Focus RS on the weekends and drive like a madman. I lead two lives, driver wise. LOL.

 

I tend to agree with you in full. Inference can be less than optimal, especially when scientific method is not applied to something like battery life which requires it. I'll start doing some searches to see what comes out.

 

Excellent article. This is the type of data I was looking for. There is quite a bit of generalization but it is backed up by data.

 

I'm new to Prime and EV, less than a month new, but I have been reading up on the battery topic for a long time. I'm not really concerned as much as just curious about best practices based on scientific research vs anecdotal or inferred opinion.

The only exception I take to inferred opinions regarding charge rates, ambient temperature and capacity guidelines based on logical thinking is that batteries, especially lithium-based ones have non-linear behavior in state-of-charge and wear and charge/discharge characteristics.

Here are some points I ponder with respect to this subject.

• EV vehicles use an array of 18650 cylindrical cells. The capacity is determined by the number of 18650 cells. One point lost is the number of cells also determines the amount of charge and discharge current that is loaded to each individual cell. Tesla uses a huge array of cells for the Model S and enables and disables them according to the feature you pay for when you buy the car. Lower range means lower capacity allowed but it is for the same number of cells for the same SOC capacity. It sounds counter-intuitive but if I owned a Tesla I would try to find the S-model 60 (lowest, I think) because it is going to have the best conditioned battery. Again, this is just a logical inference, perhaps a misguided inference.
• Discharge and charge rates are independent in terms of battery wear. There is much conventional wisdom inference that they are the same. It could be valid, no dispute of this. I would just like to read some scientific reasoning to back up this inference.
• L1 and L2 are arbitrary standards based on input current limits but as I understand things the charge control unit in the car determines the actual charge current and resulting charge rate. As I understand things charge rates are very non-linear based on the overall SOC. Again, a lot of inference here but it is short on data.
• I bring up linearity and equivalence because much inference is based on it. I just found the batteryuniversity website and it has a wealth of scientific data and reasoning which I am digesting now. It is overwhelming, BTW.
• Lastly, I hope this doesn't evolve into something like this thread: Full state of charge vs 80% | PriusChat which I found informative and amusing but very difficult to pull wheat from chaff. I remember lurking in this thread when it happened and I learned a lot but there were too many hard feelings and gotcha's for my taste.