Posted by Michael Dobony on June 16, 2012, 5:45 pm
2007 Prius: While checking the error code I noticed that the engine was
charging the drive battery in park, per the info screen, but the charge
went from 4 bars down to 3. I also noticed that many times the charge when
I start seems quite low. When I check the voltage per the info screen it
says 12.3-12.5 volts. Going from On to Accessory mode and turn on the
lights it drops to 11.3. There seems to be a lot of conflicting info on
this as to whether or not the 12 v is good under these conditions. I'm not
sure if this is a new or OEM battery as bought used a few months ago.
Posted by Daniel who wants to know on June 18, 2012, 8:06 am
The battery bars on the energy monitor screen have nothing to do with the
12v battery, they only show the HV battery state, and 1 pink bar is actually
~40% state of charge, all green bars are actually ~80% SoC.
Posted by Michael Dobony on June 18, 2012, 4:45 pm
On Mon, 18 Jun 2012 03:06:20 -0500, Daniel who wants to know wrote:
DUH! But the HV battery charges the 12V. When the vehicle is off it can
still drain the HV battery, trying to charge a bad 12v.
Posted by Pat on June 18, 2012, 6:35 pm
On Mon, 18 Jun 2012 11:45:53 -0500, Michael Dobony
I don't believe that is true. When the vehicle is off, the HV
battery is effectively disconnected for safety reasons. It will not
charge the 12v when the vehicle is off.
Posted by Elmo P. Shagnasty on June 18, 2012, 11:33 pm
When the vehicle is off, the vehicle is OFF--just like with any other
The ONLY power usage would be from the accessories that draw from the
The traction battery is NOT in play when the car is off. Period. When
you turn the car on, just like with any other car, the car will then
charge the 12v battery--to the best of its ability. If the 12v battery
is faulty in some way, it may not take the charge properly.
But none of that has anything to do with the traction battery.