Prime Prime - understanding kWh

The latest upgrade from that aftermarket app (called "Hybrid Assistant") I use to create Prius Prime drive videos with has added a very informative new meter. You can now see the electricity being consumed & regenerated.

That display of kWh is real-world data we've never had access to on this level. It's a great learning tool to really understand what the plug-in hybrid technology is really delivering.

Here's my first video using it, featuring a 30-mile drive of all EV with kWh data the entire way:

I'm quite curious what others will have to say after observing that collection of content compiled into a single contiguous video. Feel free to sound off on whatever information catches your interest.

 

I'm working on a cheat-sheet. Posts like this are how I collect feedback about the content for it. In this instance, the topic is kWh.

kWh is the amount of actual electricity consumed by the vehicle. This is a big deal, since some plug-ins are more efficient than others. In fact, some are outright guzzlers of electricity. That's why drawing attention to how well Prius Prime uses its supply available will help endorse Toyota's well thought out design.

Think about kWh. That's the unit of electricity your provider bills you for. Requiring less to travel the same distance is a better return on your vehicle purchase. Your monthly statement will be lower. It also means you'll spend less time at the charger. So, knowing the actual efficiency rate is very important. Understanding of that starts with observation of how kWh is used.

Prius Prime has a 8.79 kWh capacity battery-pack. Part of that is reserved for longevity, never touched for the sake of avoiding stress on the cells. Extremes accelerate aging. There's also a portion of it reserved for HV travel. The portion allocated for EV travel is noted on the dashboard as the percent value from 100 to 0, when the numeric display option is selected. On that secondary display (to the right), it is the range from 87% to 12%. In other words, the dashboard shows "usable" capacity and the phone app for that aftermarket gauge connected to the ODB-II port shows "actual" charge level.

Watching the video, you'll see the Total kWh value go up & down. That's because it is showing the net result of using plug-supplied electricity and some of what it recovered when braking (known as "regeneration" of electricity). For that 30-mile drive, it states a 5.2 kWh as the transition point, where EV capacity is depleted entirely and HV mode engages. At that point, the gas-engine joins in to supply power for both propulsion & electricity.

The next step in understanding kWh is to look at what happens when you plug in. There are conversion losses going from household AC to the battery DC. There are efficiency differences from the charging speed as well.

 

Since I recharge at work, most of driving is totally electric... which means not actually depleting the battery-pack to 0% that often. So, I don't have that data available.

We cannot account for every aspect of battery design & capacity; however, we can monitor inputs & outputs. A full recharge for me registers as 5.75 kWh via the charger. The observed 5.2 kWh from driving would account for that rather well when we factor in conversion losses.

Since it is all plug-supplied electricity being tracked, no. Seeing the flow in both directions makes it difficult to follow, especially when recovery is only partial, but it's the same quantity in the end.

The best analogy for that is to envision a pitcher of water being the energy source. You may pour a little back when a glass is filled too full. You may also spill a little in the process. But there is never any more water added beyond what you started with.

 

That 167° is temperature of the traction motor, not much of an influence on anything related to the drive itself.

That red/yellow/green ball going up & down and white circle is an efficiency meter, a feature of the app designed for those who don't have a handy hybrid display like we do in Prius.

That 0.0 on the left is the kW (power) meter for the gas engine, which is never used in this particular video.

That 15 on the right is the kW (power) meter for the electric output (both motors combined) showing traction energy sent to the tires. It's what many of us find most important, since it indicates EV power. Each generation of Prius has offered more, to the point where we see everyday need is covered just fine.