I had my 2005 Prius sitting idle for three days and when I last used the car it had 6 bars of battery (blue). Today I turn it on and it has only 2 bars of battery (purple) and the engine stayed on about 10 minutes to charge the battery. After about 10 minutes it went all the way to 7 bars (green) and the engine did its normal idle stop. Is it normal for the battery to drain that much in only a few days? Thanks!
Have you replaced your 12 volt battery? Strange things happen when the 12v battery is weak. Five to six years is about when it needs replacement.
Even on my 2011, I've had situations where the SOC was 1-2 bars lower after parking the car overnight.
It is not unusual for the displayed SoC to change after sitting overnight. The displayed SoC is calculated, as there is no direct way to measure. Because of this, external factors such as temperature can create differing results for the same real SoC. People also post this question when their SoC hasn't changed over night, but changes quickly once the car is powered up. A rapid loss of SoC when starting is common, as your Prius runs mostly from the battery during the first few seconds. A failing 12V battery can aggravate this situation. The engine running until full green bars is more troubling. This is not normal behavior, unless the outside temperature is cold. In that case the engine is forced to run to make heat, and while it is running it might as well charge the battery. When and how did you take this measurement? This reading is low for a fully charged unloaded 12V battery, but not bad for one under load. Tom
