Long Descents

The car limits battery charging to around 30 kW IIRC, which is ballpark L2: 240V * 15 Amps

 

Toyota's fairly protective of the pack, so I wouldn't worry too much about long descents. They start at ~30kW at low SOCs, but as that increases its's throttled back to ~10kW.

http://energy.gov/sites/prod/files/2014/03/f13/vss110_rask_2013_o.pdf

 

If the HV battery is full, it won't charge. The Prius will even turn the engine using MG1, thereby using electricity and braking the car. If you have adaptive cruisecontrol engaged it will do that automatically to keep the desired speed (normal CC will only brake a bit but will let the speed increase).

 

I discharge my full battery in 15 minutes twice a day on my drive to and from work, and range has not decreased in two years, so if the pack can take such a quick discharge, it can probably take a quick charge as well.

 

I cannot understand your post because you do not say what the capacity is of your battery or the fractional discharge, but a PiP battery that goes from 80% to 40% capacity in 15 minutes is averaging a discharge rate of 2/0.25 = 8 kW. That is less than L1 charging.

 

The condition of the electrodes is mainly the condition of the battery. If the charge state goes too low or two high, permanent damage can result to the structure of the electrodes. That's why Toyota's battery is protected from cycling too deeply.

 

That may not be entirely accurate according to the latest research:

New Light Shed On Why Batteries Go Bad - Technology News - redOrbit

Apparently heavy charging and discharging cause far less damage than realized and may even be beneficial over being "nice" to the battery.

 

When I was deep-cycling my lithium phone batteries; charging them once a day, they barely lasted a year. Since I started plugging in my phone everywhere I can; in the car, at work, and back at home, I seem to be getting much longer life out of them.

Go figure...

 

Yeah I do a lot of "opportunistic charging" for most of my electronics. And yes, they seem to last much, much longer. I think that has something to do with better heat dissipation more than the amount of charge. Most of their research also appears around single cells which would have much better heat dissipation.

 

Assuming you have a PiP. On a PiP you can discharge all usable battery capacity at near freeway/highway speeds in less than 15 minutes. It may not be the most efficient use of EV, but certainly there are many commuters who have to do this routinely.

On long mountain descents the opposite is roughly true regarding regeneration. I can confirm that the PiP will protect itself and hold regeneration if this is happening too fast for more than a few minutes at a time.

This is faster than level 2 charging in the PiP (3.3 kW) or even the more robust 6.6 kW charging level 2 limit of other plug-ins. So far, I am not aware of Toyota documenting any concerns about rapid discharge and regeneration as noted.

 

There is a fellow PC'er from Santa Fe NM who set up a business reconditioning batteries for the folks with early battery problems. His main clientele were commuters to Los Alamos who deeply discharged their cars daily going up the mountain.

 

I'm not sure what IIRC means but 240 volts * 15 amps = 3.6 kW. At that rate it will take just under 50 minutes to charge the battery from 20% SOC to 85% SOC. It doesn't actually charge at the full 15 amp capacity and slows down near full charge so it would be more like 1.2 hours for full charge. Its about 2.4 hours at 120 volts.

The car will charge 150 Wh in 1 minute on a good 50 mph downhill with the appropriate amount of regeneration braking as seen on the energy display. That will provide 3 kWh in 20 minutes. I'm not sure the car will allow that rate of charge for that long (if you can find the right hill) but you could probably get a full charge in 30 minutes or so.

 

Right you are -- my calc was off by a decimal.
Thanks for the correction

 

So you say you rented a Subaru Outback huh?
Hey, I'm fine with that.
Even if you PiP could of handled everything fine, you probably saved it some wear and tear. Even wear and tear that falls under acceptable normal parameters of operation.
Plus sometimes it's fun to drive something different once in a while.
Avoiding a debate over the minutia of battery charge/discharge and long mountaneous descents, I'd say you rented a good tool for the job. And now your Prius is ready for the work week.

 

Wrong. If the car will let you do it then it is okay. If the charge rate is too fast for too long the ICE will come on and take over enough braking to limit the charge rate. If its still too fast and long (unlikely) then it will add friction braking. You can always use the B mode but you will may lose some of the available regeneration charging. As they say "just drive it" the car will take care of itself.

 

You said we can all agree "that a long descent is bad on the battery". Wrong, we don't all agree. The PiP is a fine car for mountain driving and provides great mileage due to its super regeneration capability.