Does a weak 12v battery affect the Hybrid battery system?

Yes. If the 12V battery is perpetually low, the car will keep running the ICE to attempt to charge it. Others have reported that replacing their bad 12V battery gave them an increase in fuel efficiency by 5-10 MPG.

 

I just changed mine today, so we'll see if I notice a difference.

 

yes, the 12v boots the ecu's and closes relays. turning it off and on when it is going south can get enough juice to make ready

 

If you go to any car parts store, they'll load test the battery for free. If it tests as bad, you should replace it promptly. Of course, they'll hope that you'll buy it from them, but you don't have to.

Incidentally, I did this recently, and the lady insisted that she had to test it under the hood. I told her repeatedly that, "the battery is right here, I've even exposed it, you can just clamp right on to the battery itself." Finally, she agreed.

 

Including the 12 volt? They typically have a pro-level electronic load tester, the kind with a small printer, that prints out something about the size of a grocery store receipt. See anything like that? How old's the battery btw?

New tires can also impact mpg. What did you get, and what did you have before?

 

Got 5mpg decrease after installing Michelin Cross Climate 2

 

Sounds like I'm not the only one, I got a Prius V, just installed Cross Climate2, mpg down from ~36mpg to ~30mpg. So it's probably my tires. How long have you had the cross climates? I imagine after a certain amount of miles the mpg would recover (or maybe just wishful thinking)

 

part of it may be a larger circumference as well.

 

installed in late summer and since then getting lower mpg, right now we are in the cold season of 30s here in Indiana, and gets around 40. Expecting better performance compared to its own tires during winter in terms of mpg. Btw, it has really soft threads so I tried 37 psi and gains about 2 mpg

 

my MPG just bumped back to normal range after replacing rear brake pads and rotors. Caliper pistons were stuck so caused uneven worn and extra friction. check others things as well

 

This rear brake drag can be caused by misoriented piston: it has a cross pattern on the face that MUST be oriented like an X, and well seated thus.

To check it’s done right this time: raise the rear and verify wheels are now relatively free spinning.

more info in attachment:

 

Exactly!, I personally paid extra attention to leaving the piston in the X position to match the little notch on pads. I don't how much this affects traction battery but the performance really mattered in terms of MPG, driving smoothness, the car's kinda unleashed

 

I think you're able to judge just by seat-of-pants, but if you want to double check, try the wheel spin test. It should be pretty much last step, in any rear brake job in particular. The drill:

1. Disconnect 12 volt neg cable.
2. Do the brake job, taking particular care with the piston orientation, to have it X oriented on assembly. Do NOT apply parking brake.
3. Push brake pedal multiple times, to seat the reassembled brake components.
4. Reconnect 12 volt neg cable, and take for a short test drive. Use brakes gently.
5. On your return, apply/release parking brake several times, gently at first.
6. Raise rear and check wheel spin. Slight drag is normal, but wheel should free-spin 2~3 revolutions with a good push.