Battery life/charging strategy

I live in so.cal. and have gotten in the (bad?) habit of keeping everything in "evacuation" mode. My house burned to the ground in 2003 and ive had some very close calls since then. Evacuation mode means (in case of the Prime) always keeping the battery fully charged no matter what; even a 1 or 2 mile drive. Also keeping at least 1/2 a tank of gas in it.

Then there's the argument of "bulletproof" reputation of toyota. They already figured out what's best for the battery in the long run so you, the consumer, dont have to worry about it. Just let the computers handle it.

 

My philosophy: I bought and paid for the entire battery so I use the entire battery. To me not using the battery is the same as permanent degradation in the end: less EV miles driven overall.

Other things to ponder: Why "protect" a battery so that it makes it beyond the warranty period before it fails? Why not use it and "hope" it fails under warranty? What if there's a wreck or it's sold a few years down the road?

Basically the only thing I don't do is fast charge (level II) in the sun during our hot parts of the year (majority) and set up my garage charge timer to end in the morning about an hour before departure (also gives time for cabin heat preconditioning on the handful of mornings we actually use that wonderful feature). Otherwise, we just enjoy the vehicle and the benefits it provides.

 

The traction battery heater is not for keeping the battery warm to prolong its longevity. It is used to prevent damage to the battery by letting it charge under freezing conditions. The battery stays fine under very cold temperatures as long as it is not being charged. If you don't need the battery charged, then keeping the EVSE plugged in will do more harm than good. For one thing, having the EVSE plugged in after the charge is complete, it drains the 12v battery quicker. Plus you are now keeping the fully charged, despite it is really at 84% SoC, for a prolonged time which is detrimental to the longevity of the traction battery. If I were you, use as much of charge scheduling as possible for weekdays to use the traction battery as soon as the charge is completed. And for the weekend, I would not worry too much about charging the car and charge it as soon as you know you are going to drive the car. With an L2 EVSE, it's only 2 hours notice you will need to get the battery full.

 

i typically leave my pip at half charge when idk if or when i'll be going anywhere.

toyota warns against leaving the battery full, and recommends draining it all the way down to hv level for any extended periods of time.
they do not specify how long that is.

 

If you go strictly by what the manual suggests to do, then you are supposed to leave the SoC at 0% EV (which is approximately 11-14% real SoC) for any long period of unuse. However, from what I have read about lithium battery, leaving the traction battery SoC at 35-45% is the most stable. This corresponds to the displayed SoC of 30-40%. That's where I have been keeping my traction battery for most of the time now since I don't do daily drive anymore due to COVID-19 restriction. I fully charge the traction battery only if I know I will be driving immediately after the charge is completed.

 

i have read that different chemistry batteries have different requirements, and that the medium level long term storage is not a 'one size fits all'.
i trust toyota's advice, seeing that i know zip about batteries

 

You'll need to look at your specific hybrid warranty for that (usually in glovebox); different manufacturers use different methods and CARB vs non-CARB states.

Yes. A battery that you used. Batteries degrade over time whether you use them or not.

 

Kudos to Toyota for not doing that CARB distinction. All of their hybrids (including plug-ins) carry the same longer warranty in all 50 states now.

 

For the 2020 model and newer, Toyota warrants the traction battery with 10 years/150k miles for all vehicles. Pre 2019 models had 10yr/150k only for CARB states, and 8yr/100K for non-CARB states.

See my comment and the manual excerpt above. Toyota recommends leaving the traction battery at 0% for a long period of non-use.

 

Saw it!

 

That "when leaving the vehicle undriven for a long period of time" really throws people and has been a good source of misconceptions.

But when you dig into details of how real-world driving actually plays out, intentionally leaving it vague makes sense. There's simply too many variables at play to draw a line anywhere. The demand & stress on battery-packs varies far too much. That's why all the experience Toyota has had with reliability from their hybrid offerings never increased any detail on the dashboard. It still resembles what it did way back in the late 90's. There's more available, if you want it. But you have to be smart enough (a critical thinker) to understand what the data tells you, so the process to retrieve it is left for the better informed.

The best example I have found to define "long" came from my electric lawnmower manufacturer, EGO. Built into their batteries is a protective system that will cause the battery to self-discharge down to 50% if it hasn't been used for 30 days. That is their storage strategy. It resembles what we have been saying all along (since 2012) for Toyota PHV. If you are going on a "long" vacation, it is best to not leave the battery with a "full" charge.

Realistically, how many owners don't touch their vehicle at all for an entire month? You run into other maintenance steps being neglected beyond that anyway. Engine fluids need to be circulated and tires lose pressure. Gas obviously ages too. Using the vehicle from time to time is part of ownership responsibility. There are consequences if you don't. This isn't rocket science.

It's like leaving your car out to cook in the sun day after day. Use some critical thinking to find out how "long" extended exposure to extreme heat is tolerable before it has an big impact. Engineering is filled with tradeoffs. It won't destroy the battery, but it will accelerate aging.