2005 Prius 165k - Purple bars all of a sudden

My gen 2 could get to puple bars just waiting in line at a drive through. The battery is not that large.

If your new commute spends more time at very low speeds, I think it is normal.

 

Roughly how many minutes are you stopped at a time? Also, if the aircond is on while you're stopped it makes the SOC drop faster.

 

Your HV battery could be losing capacity, it's definitely possible.

The time to go down to 2 bars (purple) will depend on what electrical loads are on, and of course where the SOC originally started from. There was a test here that several people performed, where we left the prius in "D" with the park-brake applied and timed how long it took to drain SOC bars (all other electrical loads off). From memory it was about 10 to 11 minutes to drain the 6th bar and about 4 minutes to drain the 5th bar. You may like to try that test, I'll try to dig up a link for you.

 

BTW. One "unseen" electrical load is the charging current for the 12V battery (which comes from the main HV battery through a DC to DC converter). It could be worthwhile having your 12V battery health checked out to see if this is an issue. There are numerous 12V battery self test procedures linked in these forums if you want to search some out.

 

As uart said a failing 12volt battery can cause such a problem by requiring continuous charging.

If the HV battery is discharging steadily and recharging in a similar manor (not showing full charge at one moment and empty the next) I do not think you have a real problem with it, but another give away is hearing the rear cooling fan (vent on the rear seat) running at speed showing that the battery is overheating, combined with the rapid fluctuations in displayed charge levels.

John (Britprius)

 

ditto with checking the aux 12v battery first.

what's your avg mpg before moving to your new place and
what are you averaging now when you noticed the purple bars?

if the 12v is healthy, no need to worry about the purple bars for now even if you use the
AC or get stuck in traffic for long periods. It will get back up to blue quickly when the engine
kicks in when you start to move. Do worry if it stays in purple for a long time even when you're already
moving for a long time.

 

I think the battery ECU is pretty smart, and does change its strategy from time to time. I make the same trip often, and the battery levels will be different from trip to trip. Sometimes the ECU seems to do a deep cycle on purpose, as a way to equalize and recalibrate. Maybe someone can confirm if that is indeed the case.

 

last summer my car deep cycled. but all winter long ive been in the green and blue marks. granted with summer driving and the ac running i would quickly deplete to 2 bars *purple* but when the engine started it was right up to blue in a matter of a minute or so. i currently have a little over 93k miles on mine. i do not think it is something to worry about. but i would get the transaxle fluid replaced which ive heard helps the MG2 with regenerating power as well as protecting it from wear. im just going on what my toyota mechanic told me. but the software is good at managing the battery pack and sometimes they do need a deep discharge and recharge to keep them optimal. my battery seems to be just fine. and usually like i stated is always in green and blue. only twice have i seen it fill up all bars and that is usually after a long coast down exiting off a off ramp from the freeway.