How many kWh of 8.8kWh battery is usable?

What is the latest info for recent model year Prius Primes regarding what portion of the 8.8kWh battery is usable? I read some Prius Chat threads from a number of years back, including those way back when it was the Plug-in Prius PIP. I'm predicting it appears maybe 75% of the battery is usable and thus 25% is buffer/protection for battery cells. But curious if some folks know more precisely and for recent model years. Thanks. Doug

 

Thanks for the prompt and helpful responses. It makes sense that Toyota would protect the traction battery with a good buffer. Chevrolet did the same for their Chevy Volt battery.

This also helps clarify that the movie (links to "The Car Care Nut" video from Fall 2020 peppered around posts on Prius Chat) of a mechanic sharing their experience with Prius Primes is, as one might expect, just one persons ideas. In the video he shares the point that one should rarely let the Prius Prime battery remain in a 100% state of charge (via the guess o meter on the MID display) because that would harm the battery ("charge to 100% in the morning and drive soon after charging..."). While the sentiment is valid for Lithium batteries and some EVs that provide the driver with access to nearly 100% of the battery (e.g. Tesla), it's good to know that in the case of the Prius Prime the customer is not permitted to actually charge the battery past ~85%. And 85% provides very generous protection for the battery longevity.

Related question, in the video this mechanic shared that he had customers who never ran the gasoline engine for over a year, simply used electric EV mode, which could certainly happen, and that stale gas (and the alcohol in the fuel in particular) really harmed the car and led to expensive repairs. In a similar car to the PP, the Chevy Volt, once and awhile the software would automatically alert the driver that it was going to turn on the gasoline engine to perform a "maintenance mode" to move fluids etc, does the Toyota Prius Prime do a similar automatic use of the HV system if months have passed without using the gasoline engine?

 

Thanks for that info, so at the very least the PP will alert you if it predicts the fuel is getting stale. Good to know. I think I only once saw a warning related to stale gasoline when owning my Gen 1 Chevy Volt. In the Spring of 2021 after the first winter of the pandemic. Since I live in Michigan I do not expect stale gasoline will frequently become a problem if for no reason other then heating the car in winter. But as the pandemic goes on, and if Omicron is an escape variant as it appears to be, might happen.

 

Wow, great experiment, much respect. Hmmm... I regularly saw alerts saying something like "Maintenance Mode, can we do it now?" on my Gen 1 Chevy Volt. It, of course had a 16kWh battery, which got me 50 electric miles each day and thus made it even easier to never use gas. So, the PP may not worry as much as the Volt did about Maintenance Mode, for me in Michigan, while in winter the heater will likely take care of circulating fluids and consuming gas, but in the late Spring-Summer-Fall stretch I should go on a few road trips to see family.