Since the start of the pandemic, we've been doing very little driving. I haven't kept track but it is on the rough order of 20 miles per week. I've only filled the tank about three times and each time it has really been just a "top-up" of three gallons or so. The last sustained bit of highway driving was a 60 mile round trip a week ago. Everything seems fine and e.g. the 12-volt battery is staying charged (I have a voltage-reading gadget plugged into the 12V power outlet). But I've noticed that the main batter charge indicator has never been above five bars, most commonly at three. I have the AC on usually, and when the charge gets low for any reason the engine starts and brings it up quickly, just about "as usual." The main thing I've noticed is that I can't ever go into EV mode because the charge level is never high enough. (It's not something I do very often but I do use it occasionally--for example, when reparking when I've done a bad parking job!) Is this "normal" for a very lightly driven car? Have other people seen it?
it's hard to say, because until now, there haven't been a whole lot of lightly driven gen4's. 5-6 bars is typically more normal for a prius, so unless someone with experience eases your concerns, you may want to invest in dr. prius if it works on gen 4, to monitor your cell voltages and do a health test. i'm not comfortable with those gadget 12v monitors. it may be possible that your 12v health is dragging down the hybrid battery
Take it for a really good drive making sure to go down hills and applying the brakes lightly while coasting. You should see the battery charge up one or two bars away from being full. Posted via the PriusChat mobile app.
How many miles per trip on average? Typically the Prius will maintain a charge level of about 60-64% for a highway trip (about 3/4 full on the indicator), a bit more variation for country road, city driving. Although fairly expensive I use a ScanGauge to monitor critical systems on my 2017 Prius 2 and also used on my earlier 2008 Gen 2. The advantage of a ScanGauge is that it can be left connected without depleting your 12v aux battery. In this situation you can display the State of Charge, Main battery voltage and current, even temperatures. For now, if after the above recommendations it doesn't seem to be charging right, have the dealer check it.
^^^+1 to AzusaPrius' post. I'll bet you're just not getting enough momentum. Do you have experience with hybrid driving, "pulse and glide" driving? Depending on your locale, you might not have enough opportunity to do the "glide" part. Hybrids/EVs benefit from attentive throttle input. A sustained drive will determine if your car is having issues with the charging system.
Does this include that longer highway trip? If so, then I'd become concerned. Short city drives can give plenty of opportunity to lower the traction battery, but little to charge it up, so behavior there is more difficult to decipher without additional details.
