Best way to do Long Term Storage?

At first I was seriously doubting this whole "Different Chemistry" thing....

BUT then I had that, duh your not very bright moment feeling....about myself.

I've personally enjoyed R/C cars & planes that use Li-polymer batteries & have built multiple large battery packs that use 18650 & my favorite 26650 Li-ion batteries.

Moral of the story: they're certainly different chemistry Li-ion batteries that can be bought right now, some are designed to have slow discharge rates & some are designed to have fast discharge rates.

Toyota certainly has the resources to custom develop a "chemistry cocktail" for their Li-Ion batteries that would allow the best charge & discharge rates as they see it.


Rob43

 

I tried some online searching yesterday to see if I could find any info about possible differences (other than size & capacity) between Prime, PiP, & Prius Li-ion batteries. I came up empty. It's like it's beyond top secret from all I could learn.

 

Are all Gen4 regular Prius using Li-ion? I remember eAWD models are NiMH. Was there any Li-ion battery used on earlier Prius beside PiP?

 

As of 2020, only the eAWD is NiMH from what I gather on Toyota's website. In 2016, the trim 2 had NiMH according to the brochure I have. I haven't looked up what year they made the change but if I had to guess, I'd guess it was when they went from nice linear model numbers to cryptic arbitrary model letters.

 

I thought the AWD used NiMH? Maybe due to them being more popular in cold regions? Or I'm dreamiing?

 

PRIUS+! This is the first time I've ever heard of it. Only in the EU market?

 

Wait, Prius Alpha... Isn't it the same as Prius V in the US?

 

I see. I did not know they made 7 seaters of V in other countries. The third-row seats have to be for kids only.

 

Nice catch. I think @Tideland Prius meant the opposite of what he wrote for the 2019 MY.

 

Yeah that's what I'm thinking too, his 2019 statement is just flipped. In other words, lower levels have NiMH, the rest have Li-Ion, except AWD which stick with NiMH. I added a quote now, to alert him.

 

The nice thing is that he has a super power. I'm pretty sure he can edit any post any time whether the time limit for editing has passed or not.

 

I think I'm going to have to disagree with Toyota on this one.

Specifically, I'm thinking about this line from BU-1003a: Battery Aging in an Electric Vehicle (EV) – Battery University

In my experience, the actual SoC ranges from 12%-88% so at the very least you don't want to leave your Prime at full "charge" or full "discharge" states for long periods. I don't know how the Li-ion chemistry for Prime's differ, but this site also suggests a storage charge of 30-40% BU-702: How to Store Batteries – Battery University

In short, I'd shoot for a little less than half of the charge level before extended storage.

 

Same for me. I'm annoyed as well. Somewhere in the past I ran across a reference that RAV4 Prime would be introducing an improved lithium chemistry. No detail was provided though. But even a basic reference is nice when the entire industry is stalled and we're all trapped at home.

 

I get the sense the only way to achieve any state-of-charge is to overcharge a bit, then drive around some, scrub off charge? Seems a little funky? Or no big deal?

 

So "0-20%" HV charge range is really on top of the 12% untouchable "real bottom end. The "100%" EV top end is really at the 87% limit. That means the "20%" HV top-end is really 27% of total battery capacity. Still a bit low for for 30-40% - but close.

So, I wonder what else happens as the car switches from EV to HV mode, to make the outcome of long term storage better? The manual:
"
●Leave a low level of charge in the hybrid battery (traction battery) when leaving the vehicle undriven for a long period of time.
After confirming that EV mode has switched to HV mode, turn the power switch off.

●Use the charging timer function as much as possible in order to fully charge the hybrid battery (traction battery) immediately before starting off. (P. 157)"

That second bullet - don't charge the battery up unless you're going to use it pretty soon. Doing that over multiple charge/discharge cycles means parasitic self-discharge really starts to add-up.

The self-discharge rate will be higher for higher charge level (I=V/Rparasitic, and higher charge => somewhat higher voltage so higher discharge current), so perhaps the Manual recommended charge level keeps the self-discharge rate lower. Which is probably better for the battery's long term capacity saving. Weigh that against finally heading down into the 0-12% after some amount of time, that also ends up causing reduced battery capacity.

It's probably a balance between the capacity reduction due to long term parasitic self-discharge, weighed against the capacity reduction that occurs when the charge drops too low. What level of charge maximizes the time before capacity reduction effects start to increase? Answer: probably that EV to HV cross-over charge level.

Interesting. But it does seem like the manual's recommended store at HV to EV cross-over charge level is relatively close to that 30-40% recommended by "Battery University."