Overnight Charging Question

Back before phones and computers, that was often true of rechargeable batteries on 'dumb' (manually controlled) chargers.

Chargers are vastly smarter these days. There is no battery problem leaving them plugged in.

The modern issue with phones and computers is the waste of energy when the charger is idling. And even that has been sharply reduced by EnergyStar and other efficiency regulations.

 

Nothing to worry about here. The charger stops charging when you have a full charge. Notice the orange charging indicator light inside the the power door goes out when the charge is complete. Sporadic charging, such as charging when you still have EV miles left over should never be a problem either. It's just like if you ran out of juice on the road and the engine gives you a partial charge while you keep driving. As for phones and laptops, I think the main problem there is when the batteries are allowed to drain very low they may never quite recover. Toyota already thought of that, and they take appropriate measures in the Prius to prevent draining the battery down to zero.

 

the manual staes not to leave the battery full for long periods of time. unfortunately, they don't get any more specific, so it's up to each owner to decide what is best. i leave mine between empty and half full, depending on the situation, but sometimes i get caught with my pants down and no charge.
even trying to do this, i have seen about 15% degradation since new.

 

Long periods of time would be weeks, like when you go on vacation. Shorter, it's just fine. Simply leaving it partially depleted is an easy way to avoid that. You still have a 15% buffer regardless, since "full" is really just 85%. Exceeding it would only come from routinely drive downhill for many miles at a time, those who live in areas with mountains or deep valleys.

More likely is not allowing the battery to rest before recharging. That's called a "cold soak". The timer feature helps make that easier. Chemicals inside benefit from the opportunity to settle and cool down. If you plug in right away after driving EV or expose the car to extreme heat, it will shorten battery-life.

As for your 15% degradation, that doesn't tell us much. Some owners never see levels other owners do anyway. With mine, I haven't noticed any real loss after 4.5 years. It's still delivering 13 miles of consecutive EV on good days. That's more than the 11-mile rating. How should measurements be made years later? We don't have a method available.

 

leaving it plugged in after it charges doesn't matter because the charger shuts off, and will not come back on, even as the battery slowly loses charge, you have to pull it out, and push it back in to reinstate charging.

leaving the battery full for long periods of time falls into the 'some say' category, with no official word from toyota. ask the dealer for guidance.

 

I've seen at least 10% degradation as well, but I bang the hell out of my battery with a high-speed commute with hills, discharging it within 15 minutes every day. I DO, however, follow the advice in the manual about setting the timer to charge in the early-morning hours just before I use the car at 9am. The problem is not "overcharge", it's leaving the battery fully charged that supposedly degrades it a bit.

 

exactly. mine has been driven by a little old lady, so perhaps driving style doesn't affect battery degradation much.

 

I routinely merge onto the highway in EV mode. The engine would start upon a high-draw request anyway. So, I wouldn't think driving style falls into play either.

 

I've been doing this for the past 2 weeks since owning my Prime. After driving for an hour commute to work (using EV miles for the last 10 miles to my destination), I usually stop to a free charging station at the mall to charge for 30 mins to 1 hr.
Maybe I should stop doing this and save my battery life.

 

The occasional charge is just fine under normal operating conditions. Unless you just experienced an extreme (high heat or high speed), it's no big deal.