Battery Indicator

It will never show all bars or completely charged unless you go down a really steep downgrade for a fairly long distance. The HV battery management ECU maintains the HV battery between 40 to 80% State of Charge (SOC). With normal driving on relatively flat terrain the screen will normally show about two bars below the top which is about 60% SOC, which is the battery sweet spot the ECU tries to maintain.

 

Building on jdcollins' comments, there's a whole world of knowledge around (all kinds of) batteries. For brevity's sake, it's enough to know that a Prius traction battery's life is prolonged by managing the preferred 40% - 80% state of charge (SOC).

 

The display shows the state of the High Voltage (HV) battery. The state of the low voltage battery is not displayed, but is, none the less, critical to starting the car.

 

Just so that the OP doesn't get alarmed: that situation is exactly the same as in every conventional car. You don't have to pay any special attention to the 12V battery in a Prius.

 

Well, to add to it, most people with a conventional car don't know how bad off their battery is until they try to turn over the engine. I should know, as my old Nissan Sentra, when the battery was pretty much dead, I had enough power to see the dash instrumentation, but could not get my car started until I had a plug in charger help recharge the battery enough to see about getting my car up and going. The car's indicators, lacked any information though on low battery.

 

My Jeep has a voltmeter on the dash which shows the state of the battery, to a point, and also verifies charging.

The reason I know about the Low Voltage battery in a Prius is that I encountered one on a test drive overnight. The salesman had to drive to my home with a booster box so I could get the car started. That battery would not hold a charge. To verify that battery as discharged, I used a simple $15 voltmeter. That tool also showed that the car was trying to charge the LV batt.

Below 9 volts LV, the Prius will not go to "ready" mode.

Given the level of sophistication of the Prius, including a simple voltage reading capability available to the driver or, better yet, tracking the idle voltage to predict a failure would be good.

 

Well, mind you, a basic volt meter will also draw power as well. Most cars are again not a Jeep and even then, not all cars really have a battery volt meter on their dash, just like you don't see many cars with an RPM indicator, only a few of them have that. Heck, not many cars also have an Oil, or Brake, or Steering fluid meters also. That use to be true on some old cars, but nowadays, not even that.

 

If you get a Scangauge II, Voltage is one meter you can track.

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