Toyota Prius Prime 2021 LE Battery Maintenance and Other Things you Need to Know to Enjoy the Hybrid

Some of this from the Car Care Nut on YouTube:

Under the backseat is the onboard traction battery charger which is air cooled. There are three vents at the bottom of the backseat that are used to cool the charger. Never block these air intake vents when charging the battery. However, these vents can be blocked when driving and NOT charging the battery. I load up the back floor board with camping equipment.

1) The OTBC communicates with the computer in the battery to determine whether to charge it or not. It takes the AC Voltage from your 120 home outlet and converts it to DC.

2) It also converts the AC to DC 12 Volts and uses that to power up the Prime electronics. This keeps you from draining the 12 Volt battery under the hood. The Car Care Nut says it also charges the 12 Volt battery.

When you set a charging schedule the car will automatically perform a PRE-CHARGING routine to condition the battery for optimal charging. For example, it will heat it up or cool it down as needed. When you use the charging schedule there are a lots of steps the car performs that at beneficial to the battery.

Behind the scenes

Under the backseat is the onboard charger which is air cooled. There are two vents at the bottom of the backseat that are used to cool the charger.
1) It communicates with the computer in the battery to determine whether to charge or not. It take the AC Voltage from your 120 home outlet and converts it to DC.
2) It also converts the AC to DC 12 Volts and uses that to power up the Prime electronics. This keeps you from drainng the 12 Volt battery under the hood. The Car Care Nut says it also charges the 12 Volt battery.

When you set a charging schedule the car will automatically perform a PRE-CHARGING routime to condition the battery for optimal charging. For example, it will heat it up or cool it down as needed. When you use the charging schedule there are a lots of steps the car performs that at beneficial to the battery.

Page 145 -- Charging -- Prius Prime 2021

Onboard traction battery charger cooling air intake vents

The grilles under the rear seats are the cooling air intake vents for the onboard traction battery charger installed under the seats.

Make sure to observe the following precautions regarding the cooling air intake vents.

- Do not block the air intake vents with seat covers or luggage
- If the air intake vents are clogged with dust, clean them with a vacuum cleaner

Multi information display with ask if you want to run the air conditioner.

Page 143 of the 2021 Prius Prime manual reads leave a low level of charge in the hybrid battery (traction battery) with leaving the vehicle undriven for a long period of time.

How do you charge the Prius Prime battery to 50% when you plan to park the car for a few days or weeks? You recommend using the charging schedule because it PREPs the battery but I don't see a way to stop charging at 50% to maintain the Lithium Ion battery. I do it by manually plugging in and watch the time to charge for 2 to 3 hours of charge time remaining and pull the plug then.